Guyton and Hall Physiology 03
25. In which conditions is alveolar PO 2
increased and alveolar PCO 2
decreased?
A) Increased Va and unchanged metabolism
B) Decreased Va and unchanged metabolism
C) Increased metabolism and unchanged Va
D) Proportional increase in metabolism and VA
26. The O2
-CO2
diagram above shows a ventilation-perfusion ( )
ratio line for the normal lung. Which of the following best
describes the effect of decreasing ratio on the alveolar PO 2
and
PCO 2?
CO2 Tension O2 Tension
A) Decrease Decrease
B) Decrease Increase
C) Decrease No change
D)
Increase Decrease
E)
Increase Increase
Questions 27 and 28
27. A 67-year-old man has a solid tumor that pushes against an
airway, partially obstructing air flow to the distal alveoli. Which
point on the line of the O2
-CO2
diagram above corresponds to
the alveolar gas of these distal alveoli?
A) A
B) B
C) C
D) D
E) E
28. A 55-year-old man has a pulmonary embolism that completely
blocks the blood flow to his right lung. Which point on the line
of the O2
-CO2
diagram above corresponds to the alveolar gas of his
right lung?
A) A
B) B
C) C
D) D
E) E
29. The figure above shows a lung with a large shunt in which mixed
venous blood bypasses the O2
exchange areas of the lung.
Breathing room air produces the O2
partial pressures shown on the
diagram. What is the O2
tension of the arterial blood (in mm Hg)
when the person breathes 100% O2
and the inspired O2
tension is
greater than 600 mm Hg?
A) 40
B) 55
C) 60
D) 175
E) 200
F) 400
G) 600
30. A 32-year-old medical student has a 4-fold increase in cardiac
output during strenuous exercise. Which curve on the above figure
most likely represents the changes in O2
tension that occur as blood
flows from the arterial end to the venous end of the pulmonary
capillaries in this student?
A) A
B) B
C) C
D) D
E) E
31. The above figure shows changes in the partial pressures of O2
and
CO2
as blood flows from the arterial (Art) end to the venous (Ven)
end of the pulmonary capillaries. Which diagram best depicts the
normal relationship between PO 2
(red line) and PCO 2
(green line)
during resting conditions?
A) A
B) B
C) C
D) D
E) E
32. Which of the following would be true if the blood lacked red
blood cells and just had plasma and the lungs were functioning
normally?
A) The arterial PO 2
would be normal
B) The O2
content of arterial blood would be normal
C) Both A and B
D) Neither A nor B
33. The above figure shows a normal O2
-Hb dissociation curve. What
are the approximate values of Hb saturation (% Hb-O2
), PO 2
, and
O2
content for oxygenated blood leaving the lungs and reduced
blood returning to the lungs from the tissues?
Oxygenated Blood Reduced Blood
% Hb-O2 PO 2 O2 Content % Hb-O2 PO 2 O2 Content
A) 100 104 15 80 42 16
B) 100 104 20 30 20 6
C) 100 104 20 75 40 15
D) 90 100 16 60 30 12
E) 98 140 20 75 40 15
34. A person with anemia has an Hb concentration of 12 g/dl. He
starts exercising and uses 12 ml O2
/dl. What is the mixed venous
PO 2?
A) 0 mm Hg
B) 10 mm Hg
C) 20 mm Hg
D) 40 mm Hg
E) 100 mm Hg
35. Which points on the above figure represent arterial blood in a
severely anemic person?
Top Graph Boom Graph
A) D D
B) E E
C) D E
D) E D
36. A stroke that destroys the respiratory area of the medulla would
be expected to lead to which of the following?
A) Immediate cessation of breathing
B) Apneustic breathing
C) Ataxic breathing
D) Rapid breathing (hyperpnea)
E) None of the above (breathing would remain normal)
Questions 37 and 38
37. Which of the below O2
-Hb dissociation curves corresponds to
normal blood (red line) and blood containing CO (green line)?
A) A
B) B
C) C
D) D
E) E
F) F
38. Which of the above O2
-Hb dissociation curves corresponds to
blood from an adult (red line) and blood from a fetus (green line)?
A) A
B) B
C) C
D) D
E) E
F) F
39. What is the most important pathway for the respiratory response to
systemic arterial CO2
(PCO 2
)?
A) CO2
activation of the carotid bodies
B) Hydrogen ion (H+) activation of the carotid bodies
C) CO2
activation of the chemosensitive area of the medulla
D) H+
activation of the chemosensitive area of the medulla
E) CO2
activation of receptors in the lungs
40. The basic rhythm of respiration is generated by neurons located in
the medulla. What limits the duration of inspiration and increases
respiratory rate?
A) Apneustic center
B) Dorsal respiratory group
C) Nucleus of the tractus solitarius
D) Pneumotaxic center
E) Ventral respiratory group
41. When the respiratory drive for increased pulmonary ventilation
becomes greater than normal, a special set of respiratory neurons
that are inactive during normal quiet breathing becomes active,
contributing to the respiratory drive. These neurons are located in
which structure?
A) Apneustic center
B) Dorsal respiratory group
C) Nucleus of the tractus solitarius
D) Pneumotaxic center
E) Ventral respiratory group
42. CO2
is transported from the tissues to the lungs predominantly in
the form of bicarbonate ion. Compared with arterial red blood
cells, which of the following options best describes venous red
blood cells?
Intracellular Chloride Concentration Cell Volume
A) Decreased Decreased
B) Decreased Increased
C) Decreased No change
D)
Increased Decreased
E)
Increased No change
F)
Increased Increased
G) No change Decreased
H) No change Increased
I) No change No change
43. An anesthetized man is breathing with no assistance. He then
undergoes artificial ventilation for 10 minutes at his normal VT but
at twice his normal frequency. He undergoes ventilation with a gas
mixture of 60% O2
and 40% nitrogen. The artificial ventilation is
stopped, and he fails to breathe for several minutes. This apneic
episode is due to which of the following?
A) High arterial Po2
suppressing the activity of the peripheral
chemoreceptors
B) Decrease in arterial pH suppressing the activity of the
peripheral chemoreceptors
C) Low arterial Pco2
suppressing the activity of the medullary
chemoreceptors
D) High arterial Pco2
suppressing the activity of the medullary
chemoreceptors
E) Low arterial Pco2
suppressing the activity of the peripheral
chemoreceptors
44. Which of the following describes a patient with constricted lungs
compared with a normal patient?
TLC RV Maximum Expiratory Flow
A) Normal Normal Normal
B) Normal Normal Reduced
C) Normal Reduced Reduced
D) Reduced Normal Normal
E) Reduced Reduced Normal
F) Reduced Reduced Reduced
45. Which diagram in the above figure best describes the relationship
between VA and arterial CO2
tension (PCO 2
) when the PCO 2
is
changed acutely over a range of 35 to 75 mm Hg?
A) A
B) B
C) C
D) D
E) E
F) F
46. Which diagram in the above figure best describes the relationship
between VA and arterial O2
tension (PO 2
) when the PO 2
is changed
acutely over a range of 0 to 160 mm Hg and the arterial PCO 2
and
H+
concentration remain normal?
A) A
B) B
C) C
D) D
E) E
F) F
47. VA increases severalfold during strenuous exercise. Which factor
is most likely to stimulate ventilation during strenuous exercise?
A) Collateral impulses from higher brain centers
B) Decreased mean arterial pH
C) Decreased mean arterial Po2
D) Decreased mean venous Po2
E) Increased mean arterial Pco2
48. During strenuous exercise, O2
consumption and CO2
formation
can increase as much as 20-fold. VA increases almost exactly in step
with the increase in O2
consumption. Which option best describes
what happens to the mean arterial O2
tension (PO 2
), CO2
tension
(PCO 2
), and pH in a healthy athlete during strenuous exercise?
Arterial Po2 Arterial Pco2 Arterial pH
A) Decreases Decreases Decreases
B) Decreases Increases Decreases
C)
Increases Decreases Increases
D)
Increases Increases Increases
E) No change No change No change
49. Cheyne-Stokes breathing is an abnormal breathing paern
characterized by a gradual increase in the depth of breathing,
followed by a progressive decrease in the depth of breathing that
occurs again and again approximately every minute. Which time
points on the above figure (V-Z) are associated with the highest
PCO 2
of lung blood and highest PCO 2
of the neurons in the
respiratory center?
Lung Blood Respiratory Center
A) V V
B) V W
C) W W
D) X Z
E) Y Z
50. A 45-year-old man inhaled as much air as possible and then
expired with a maximum effort until no more air could be expired.
This action produced the maximum expiratory flow-volume
(MEFV) curve shown in the below figure. What is the forced vital
capacity (FVC) of this man (in liters)?
A) 1.5
B) 2.5
C) 3.5
D) 4.5
E) 5.5
F) 6.5
51. The MEFV curve shown in the above figure is used as a diagnostic
tool for identifying obstructive and restrictive lung diseases. At
which point on the curve does airway collapse limit maximum
expiratory air flow?
A) A
B) B
C) C
D) D
E) E
52. The MEFV curves shown in the above figure were obtained from a
healthy person (red curve) and a 57-year-old man with shortness of
breath (green curve). The man with shortness of breath likely has
which disorder?
A) Asbestosis
B) Emphysema
C) Kyphosis
D) Scoliosis
E) Silicosis
F) Tuberculosis
53. A 62-year-old man reports difficulty breathing. The above figure
shows an MEFV curve from the patient (green line) and from a
typical healthy individual (red curve). Which of the following best
explains the MEFV curve of the patient?
A) Asbestosis
B) Asthma
C) Bronchospasm
D) Emphysema
E) Old age
54. The MEFV curve shown in the above figure (red line) was
obtained from a 75-year-old man who smoked 40 cigarees per day
for 60 years. The green flow-volume curve was obtained from the
man during resting conditions. Which set of changes is most likely
to apply to this man?
Exercise Tolerance TLC RV
A) Decreased Decreased Decreased
B) Decreased Increased Increased
C) Decreased Normal Normal
D)
Increased Increased Increased
E) Normal Decreased Decreased
55. The above figure shows a forced expiration for a healthy person
(curve X) and a person with a pulmonary disease (curve Z). What
is the forced expiratory volume in the first second of expiration
(FEV1
)/forced vital capacity (FVC) ratio (as a percent) in these
persons?
Person X Person Z
A) 80 50
B) 80 40
C) 100 80
D) 100 60
E) 90 50
F) 90 60
56. The above figure shows forced expirations from a person with
healthy lungs (curve X) and from a patient (curve Z). The patient
most likely has which condition?
A) Asthma
B) Bronchospasm
C) Emphysema
D) Old age
E) Silicosis
57. Which of the following describes blood gases during consolidated
pneumonia?
Arterial PO 2 Arterial O2 Content Arterial PCO 2
A) Normal Normal Normal
B) Normal Normal Increased
C) Decreased Normal Normal
D) Decreased Decreased Increased
E) Decreased Decreased Decreased
F) Decreased Decreased Normal
58. Which of the following occurs during atelectasis of one lung?
A) Increase in arterial Pco2
B) A 40% decrease in Po2
C) Normal blood flow in the lung with atelectasis
D) Slight decrease in arterial content
59. The volume–pressure curves in the above figure were obtained
from a normal subject and patient with a pulmonary disease.
Which abnormality is most likely present in the patient?
A) Asbestosis
B) Emphysema
C) Mitral obstruction
D) Rheumatic heart disease
E) Silicosis
F) Tuberculosis
60. A 34-year-old medical student generates the flow-volume curves
shown in the above figure. Curve W is a normal MEFV curve
generated when the student was healthy. Which of the following
best explains curve X?
A) Asthma aack
B) Aspiration of meat into the trachea
C) Heavy exercise
D) Light exercise
E) Normal breathing at rest
F) Pneumonia
G) Tuberculosis
61. Which of the following best describes comparison of the lung
compliance and surfactant levels in a premature infant with
respiratory distress syndrome versus a normal full-term infant?
Lung Compliance (Premature vs. Full-Term
Infant)
Surfactant Levels (Premature vs. Full-Term Infant)
A) ↑ ↓
B) ↑ ↑
C) ↓ ↓
D) ↓ ↑
E) ↔ ↑
F) ↔ ↓
62. Compared with a normal healthy person, how do total lung
capactiy (TLC) and maximum expiratory flow (MEF) change with
restrictive lung disease?
TLC MEF
A) ↑ ↓
B) ↓ ↓
C) ↑ ↑
D) ↓ ↑
63. A 78-year-old man who smoked 60 cigarees per day for 55 years
reports shortness of breath. The patient is diagnosed with chronic
pulmonary emphysema. Which set of changes is present in this
man compared with a healthy nonsmoker?
Pulmonary Compliance Lung Elastic Recoil TLC
A) Decreased Decreased Decreased
B) Decreased Decreased Increased
C) Decreased Increased Increased
D)
Increased Decreased Decreased
E)
Increased Decreased Increased
F)
Increased Increased Increased
64. While breathing room air, a patient with chronic obstructive
pulmonary disease has a systemic arterial PCO 2
of 65 mm Hg and a
PO 2
of 40 mm Hg. Supplemental oxygen is administered at a 40%
fractional concentration of oxygen in inspired gas (FIO 2
), which
resulted in an increase of PO 2
to 55 mm Hg and PCO 2
to 70 mm Hg.
Which of the following describes the supplemental O2?
A) Restored arterial dissolved O2
to normal
B) Did not change breathing
C) Reduced the hypoxic stimulation of breathing
D) Increased the pulmonary excretion of CO2
65. When he was in his early 40s, a 75-year-old man worked for 5
years in a factory where asbestos was used as an insulator. The
man is diagnosed with asbestosis. Which set of changes is present
in this man compared with a person with healthy lungs?
Pulmonary Compliance Lung Elastic Recoil TLC
A) Decreased Decreased Decreased
B) Decreased Increased Increased
C) Decreased Increased Decreased
D)
Increased Decreased Decreased
E)
Increased Decreased Increased
F)
Increased Increased Increased
66. Relative to atmospheric pressure the pleural pressure at rest is −5
cm H2O. What would alveolar pressure be at the end of an
inhalation?
A) −5 cm H2O
B) −2 cm H2O
C) 0 cm H2O
D) +2 cm H2O
E) 5 cm H2O
67. Compared with normal conditions, which of the following
conditions will be present in a healthy individual who is running a
half marathon?
Blood Flow at the Top
of the Lung
Pulmonary Vascular
Conductance
Pulmonary Airway
Conductance
Pulmonary
Venous Po2
Mixed
Venous Po2
A) ↔ ↓ ↓ ↔ ↔
B) ↔ ↑ ↓ ↔ ↑
C) ↑ ↑ ↑ ↑ ↔
D) ↑ ↑ ↑ ↑ ↓
E) ↑ ↑ ↓ ↑ ↓
F) ↔ ↑ ↓ ↔ ↑
68. Which of the following would be increase airway conductance?
A) Stimulation of parasympathetic nerves to the lungs
B) Low lung volumes
C) Release of histamine by mast cells
D) Inhalation to TLC
69. With the development of congestive heart failure and no other
pathologies, which of the following mechanism is most important
in preventing pulmonary edema?
A) Retention of salt and water by the kidneys.
B) Increase alveolar pressure due to forceful ventilation
C) Increase in surfactant
D) Washout of interstitial proteins due to increase in fluid
filtration from capillaries
70. A person is lying at rest on a bed with a catheter in the femoral
artery and vein. Arterial PO 2
is 95 mm Hg, and arterial PCO 2
is 38
mm Hg. Total blood flow to the muscles of the right leg is 350
ml/min. As a test, acetylcholine, a vasodilator, is infused into the
right femoral artery. Which of the following will happen in the
venous blood from the right leg?
Venous PO 2 Venous PCO 2
A) ↑ ↓
B) ↓ ↑
C) ↓ ↔
D) ↔ ↑
E) ↑ ↑
F) ↓ ↓
G) ↔ ↔
71. A 54-year-old woman with COPD is admied to the hospital for
shortness of breath. Her arterial blood gases are
PO 2
= 75 mm Hg
PCO 2
= 45 mm Hg
pH = 7.29
What are some of the pulmonary changes occurring in this woman?
A) Decreased ventilator drive leading to abnormal blood gases
B) Decreased airway resistance
C) Trapping of air in alveoli
D) Normalization of ratio throughout the lungs.
72. After 40 years of smoking, a woman is diagnosed with COPD.
Which set of changes is present in this woman compared with a
person with healthy lungs?
Forced Vital Capacity FEV1 TLC
A) Decreased Decreased Decreased
B) Decreased Increased Increased
C) Decreased Increased Decreased
D)
Increased Decreased Decreased
E) Decreased Decreased Increased
F)
Increased Increased Increased
73. If the mean pulmonary arterial and left atrial pressures are 25 and
5 mm Hg, respectively, and total blood flow is 5 l/min, what is the
pulmonary vascular resistance?
A) 0.001 mm Hg/ml/min
B) 0.002 mm Hg/ml/min
g
C) 0.004 mm Hg/ml/min
D) 0.005 mm Hg/ml/min
74. Which of the following is true?
A) Exhaled gases are equal to alveolar gases
B) Exhaled PO 2
is higher than alveolar PO 2
C) Exhaled PCO 2
is higher than alveolar PCO 2
D) Exhaled PCO 2
is lower than atmospheric PCO 2
E) Exhaled PO 2
is lower than alveolar PCO 2
75. A patient with no respiratory problems and normal blood gases is
given a 500-ml blood transfusion consisting of 90% red cells. Which
of the following will occur?
A) Arterial PO 2
will increase
B) Arterial PCO 2
will decrease
C) Arterial saturation will increase
D) Arterial oxygen content will decrease
E) Arterial oxygen content will increase
76. A patient has nerve damage to the nerve that innervates the
external intercostals. Which of the following would be affected?
A) Normal inhalation
B) Normal exhalation
C) Forced inhalation
D) Forced exhalation
77. George is a 55-year-old banker who started having chest
discomfort 3 years ago. He did not see a doctor. He recently had an
aack of severe chest pain and was admied to the hospital. He
became short of breath and started coughing up a frothy fluid. His
chest radiograph showed an elevated ST segment. His arterial PO 2
is 59 mm Hg, PCO 2
is 35 mm Hg, and pH is 7.35. He is given 100%
PO 2
to breathe, resulting in an increase in arterial PO 2
to 150 mm
Hg. How does dead space and shunt blood flow in George’s lungs
compare with normal blood flow?
Dead Space Shunted Blood Flow
A) ↑ ↑
B) ↑ ↔
C) ↓ ↓
D) ↔ ↑
E) ↓ ↑
78. In a normal subject at sea level breathing 50% O2
, which
compartment has the lowest CO2
partial pressure?
A) Pulmonary vein in the basal region of lung
B) Alveolar air in zone II
C) Pulmonary arterial blood
D) Anatomic dead space at the end of inspiration
79. Compared with a normal O2
dissociation curve a right- shifted
curve
A) Allows more O2
to be unloaded from the blood for a given PO
2
B) Allows less CO2
to be unloaded from the blood for a given fall
in PO 2
C) Allows a greater degree of oxygen loading of the blood within
the lungs
D) Reduces the amount of oxygen that can be maximally carried
by the blood
80. In an anemic person with normal lungs,
A) Systemic arterial CO2
is normal
B) Systemic venous O2
is normal
C) Systemic arterial O2
is above normal
D) Systemic venous CO2
is below normal
81. A long-time smoker is referred to you by a colleague who has
already ordered PFTs. The results are as follows (∗ indicates value
outside the 95% CI):
Predicted Measured % Predicted
FVC (L) 6.0 3.8 63∗
FEV1
(L) 5.0 2.2 44∗
FEV1
/ FVC (%) 83 58∗ 67∗
VC 6.0 4.0 67∗
TLC 7.5 8.8 117∗
RV 1.8 2.2 122∗
FRC 3.5 3.9 111
What is the diagnosis?
A) Obstructed lung disease
B) Constricted lungs
C) Combined obstruction and constriction
D) Pulmonary vascular disease
82. The peripheral chemoreceptors would produce the greatest
increase in ventilation in replaced to which of the following?
A) Breathing 30% oxygen
B) Anemia that decrease hematocrit to 30%
C) Moderate poisoning with carbon monoxide
D) An infusion of lactic acid
83. In patients with a chronic hypercapnia (elevated PCO 2
), the normal
__?___ drive to breathe is replaced with a ___?____ drive.
A) hypoxic; hypercapnic
B) hypercapnic; hypoxic
C) apneustic; pneumotaxic
D) pneumotaxic; apneustic
84. Which of the following changes in PO 2
would have the greatest
effect on the O2
saturation in the blood?
A) from 0 mm Hg to 20 mm Hg
B) from 20 mm Hg to 40 mm Hg
C) from 40 mm Hg to 70 mm Hg
D) from 80 mm Hg to 100 mm Hg
85. A(n) __?___ in the cerebrospinal fluid concentration of __?___ is
considered to be the direct stimulus for the increase alveolar
ventilation via the central chemoreceptors.
A) increase; CO2
B) decrease; CO2
C) decrease; H+
D) increase; H+
86. Acute hemorrhage causes a reduction of Hb concentration to 60%
of normal in an otherwise health individual. If the alveolar
ventilation and oxygen consumption rates remain the same as
before the hemorrhage, which of the following will occur after the
hemorrhage?
A) Normal arterial PO 2
, normal venous PO 2
.
B) Low arterial PO 2
, normal venous PO 2
.
C) Low arterial PO 2
, low venous PO 2
.
D) Normal arterial PO 2
, low venous PO 2
.
E) High arterial PO 2
, normal venous PO 2
.
87. When a pneumothorax is induced, the chest wall__________, and
the lungs____
A) collapses in, expand out
B) expands out, collapse in
C) does not change, do not change
D) collapses, collapse
Answers
1. D) Contraction of the internal intercostals and abdominal recti pulls the
rib cage downward during expiration. The abdominal recti and other
abdominal muscles compress the abdominal contents upward toward
the diaphragm, which also helps to eliminate air from the lungs. The
diaphragm relaxes during expiration. The external intercostals,
sternocleidomastoid muscles, and scaleni increase the diameter of the
chest cavity during exercise and thus assist with inspiration, but only
the diaphragm is necessary for inspiration during quiet breathing.
TMP14 pp. 491–492
2. D) The diaphragm and external intercostals are used for inhalation. The
sternocleidomastoid is a muscle in the neck and is not used for
inhalation or exhalation. The rectus abdominis and internal intercostals
are used for exhalation. The majority of the force for exhalation is
generated by the rectus abdominis.
TMP14 p. 491
3. E) Compliance (C) is the change in lung volume (ΔV) that occurs for a
given change in the transpulmonary pressure (ΔP): that is, (The
transpulmonary pressure is the difference between the alveolar pressure
and pleural pressure.) Because compliance is equal to the slope of the
volume–pressure relationship, it should be clear that curve S represents
the highest compliance and that curve U represents the lowest
compliance.
TMP14 p. 493
4. E) Minute ventilation is VT × respiratory rate. VT from the graph is 500
ml. Therefore, minute ventilation = 500 × 12 = 6 l/min.
TMP14 p. 497
5. C) The FRC equals the ERV (2 liters) plus the RV (1.0 liter). This is the
amount of air that remains in the lungs at the end of a normal
expiration. FRC is considered to be the resting volume of the lungs
because none of the respiratory muscles is contracted at FRC. This
problem illustrates an important point: a spirogram can measure
changes in lung volume but not absolute lung volumes. Thus, a
spirogram alone cannot be used to determine RV, FRC, or TLC.
TMP14 pp. 495–497
6. D) Because the compliance is 0.2 l/cm H2O, it should be clear that a 1.0-l
increase in volume will cause a 5 cm H2O decrease in pleural pressure
(1.0 l/0.2 l/cm H2O = 5.0 cm H2O), and because the initial pleural
pressure was −4 cm H2O before inhalation, the pressure is reduced by 5
cm H2O (to −9 cm H2O) when 1.0 liter of air is inhaled.
TMP14 p. 493
7. D) Surfactant is formed relatively late in fetal life. Premature babies born
without adequate amounts of surfactant can develop pulmonary failure
and die. Surfactant is a surface-active agent that greatly reduces the
surface tension of the water lining the alveoli. Water is normally
aracted to itself, which is why raindrops are round. By reducing the
surface tension of the water lining the alveoli (and thus reducing the
tendency of water molecules to coalesce), the surfactant reduces the
work of breathing—that is, less transpulmonary pressure is required to
inhale a given volume of air. Because compliance is equal to the change
in lung volume for a given change in transpulmonary pressure, it
should be clear that pulmonary compliance is decreased in the absence
of surfactant.
TMP14 pp. 493–494, 1063–1064
8. C) Residual volume = FRC − ERV = 3 l − 1.5 l = 1.5 l
TMP14 pp. 495–496
9. B) A spirometer can be used to measure changes in lung volume, but it
cannot determine absolute volume. It consists of a drum filled with air
inverted over a chamber of water. When the person breathes in and out,
the drum moves up and down, recording the changes in lung volume.
The spirometer cannot be used to measure RV because the RV of air in
the lungs cannot be exhaled into the spirometer. The FRC is the amount
of air left in the lungs after a normal expiration. FRC cannot be
measured using a spirometer because it contains the RV. The TLC is the
total amount of air that the lungs can hold after a maximum inspiration.
Because the TLC includes the RV, it cannot be measured using a
spirometer. TLC, FRC, and RV can be determined using the helium
dilution method or a body plethysmograph.
TMP14 pp. 495–496
10. B) Both the lung and thoracic cage are elastic. Under normal
conditions, the elastic tendency of the lungs to collapse is exactly
balanced by the elastic tendency of the thoracic cage to expand. When
air is introduced into the pleural space, the pleural pressure becomes
equal to atmospheric pressure—the chest wall springs outward, and the
lungs collapse.
TMP14 pp. 491–492
11. D) The lower zones of the lung ventilate beer than the upper zones,
and the middle zones have intermediate ventilation. These differences in
regional ventilation can be explained by regional differences in pleural
pressure. The pleural pressure is typically about −10 cm H2O in the
upper regions and about −2.5 cm H2O in the lower regions. A less
negative pleural pressure in the lower regions of the chest cavity causes
less expansion of the lower zones of the lung during resting conditions.
Therefore, the boom of the lung is relatively compressed during rest
but expands beer during inspiration compared with the apex.
TMP14 pp. 518–519
12. E) Total ventilation is equal to the tidal volume (VT
) times the
ventilation frequency. VA = (VT − VD) × Frequency, where VD is the dead
space volume. Both persons have the same total ventilation: subject T,
1000 × 10 = 10 l/min; subject V, 500 × 20 = 10 l/min. However, subject T
has a VA of 18 l (i.e., (2000 − 200) × 10), whereas subject V has a VA of
only 12 l (i.e., (500 − 200) × 40). This problem further illustrates that the
most effective means of increasing VA is to increase the VT
, not the
respiratory frequency.
TMP14 pp. 497–498
13. B) Arterial content = 15 g/dl × 1.34 ml O2
/g Hb = 20 ml O2
/dl (1 dl = 100
ml).Venous saturation is 25%, so venous content is 20 ml O2
/dl × 0.25 = 5
ml O2
/dl. Fick’s principle is O2
consumption = cardiac output (arterial
content − venous content).750 ml O2
/min = cardiac output × (20 ml O2
/dl
− 5 ml O2
/dl). Cardiac output = (750 ml O2
/min)/(15 ml O2
/dl) = 5000
ml/min
TMP14 pp. 256, 522–524
14. D) Ductus arteriosus is present in a fetus, not a healthy adult, in the
segment that connects the pulmonary artery to the aorta. Either this is
not present in an adult or the pressures would be higher than measured
because this is connected to the aorta. The foramen ovale is a cardiac
shunt in the fetal heart from right atrium to left atrium, so pressures
would be very low. The left atrial pressure should be between 1 and 5
mm Hg. The pulmonary artery pressure ranges from 25 systolic to ∼12
to 14 mm Hg diastolic. The right atrial pressure is ∼0 to 2 mm Hg.
TMP14 p. 504
15. A) It is usually not feasible to measure the left atrial pressure directly in
a normal human being because it is difficult to pass a catheter through
the heart chambers into the left atrium. The balloon-tipped, flowdirected catheter (Swan-Ganz catheter) was developed nearly 30 years
ago to estimate left atrial pressure for the management of acute
myocardial infarction. When the balloon is inflated on a Swan-Ganz
catheter, the pressure measured through the catheter, called the wedge
pressure, approximates the left atrial pressure for the following reason:
blood flow distal to the catheter tip has been stopped all the way to the
left atrium, which allows left atrial pressure to be estimated. The wedge
pressure is actually a few mm Hg higher than the left atrial pressure,
depending on where the catheter is wedged, but this still allows changes
in left atrial pressure to be monitored in patients with left ventricular
failure.
TMP14 pp. 504, 507
16. A) The pulmonary blood flow can increase severalfold without causing
an excessive increase in pulmonary artery pressure for the following
two reasons: previously closed vessels open up (recruitment), and the
vessels enlarge (distension). Recruitment and distension of the
pulmonary blood vessels both serve to lower the pulmonary vascular
resistance (and thus to maintain low pulmonary blood pressures) when
the cardiac output has increased.
TMP14 pp. 505–506
17. C) A P. aeruginosa infection can increase the capillary permeability in
the lungs and elsewhere in the body, which leads to excess loss of
plasma proteins into the interstitial spaces. This leakage of plasma
proteins from the vasculature caused the plasma colloid osmotic
pressure to decrease from a normal value of about 28 mm Hg to 19 mm
Hg. The capillary hydrostatic pressure remained at a normal value of 7
mm Hg, but it can sometimes increase to higher levels, exacerbating the
formation of edema. The interstitial fluid hydrostatic pressure has
increased from a normal value of about −5 mm Hg to 1 mm Hg, which
tends to decrease fluid loss from the capillaries. Excess fluid in the
interstitial spaces (edema) causes lymph flow to increase.
TMP14 pp. 507–509
18. D) With a PO 2
of 95 and a content of 19 ml O2
/dl on room air, the
patient has no issues with ratio or pulmonary edema. An arterial
content of 19 ml O2
/dl and a PO 2
of 95 suggest a normal Hb
concentration. A low cardiac output would require a greater extraction
of O2
from the blood to supply O2
to the tissue, resulting in a decreased
mixed venous content.
TMP14 pp. 514, 522–523
19. B) Arterial content = 12 g Hb/dl × 1.34 ml O2
/dl = 16 ml O2
/dl.Venous
saturation = 20%, so venous content = 16 ml O2
/dl × 0.2 = 3.2 ml O2
/dl.
TMP14 pp. 524–525
20. B) When a person performs the Valsalva maneuver (forcing air against
a closed glois), high pressure builds up in the lungs that can force as
much as 250 ml of blood from the pulmonary circulation into the
systemic circulation. The lungs have an important blood reservoir
function, automatically shifting blood to the systemic circulation as a
compensatory response to hemorrhage and other conditions in which
the systemic blood volume is too low.
TMP14 p. 504
21. E) When an airway is blocked, no movement of fresh air occurs.
Therefore, the air in the alveoli reaches an equilibration with pulmonary
arterial blood. Therefore, PO 2
will decrease from 100 to 40, PCO 2
will
increase from 40 to 45, and systemic PO 2
will decrease because there is a
decrease in O2
uptake from the alveoli and thus decreased O2
diffusion
from the alveoli.
TMP14 pp. 517–519
22. E) Fick’s law of diffusion states that the rate of diffusion (D) of a gas
through a biological membrane is proportional to ΔP, A, and S and
inversely proportional to d and the square root of the MW of the gas
(i.e., D α (ΔP × A × S) / (d × MW−
2
). The greater the pressure gradient,
the faster the diffusion. The larger the cross-sectional area of the
membrane, the higher will be the total number of molecules that can
diffuse through the membrane. The higher the solubility of the gas, the
higher will be the number of gas molecules available to diffuse for a
given difference in pressure. When the distance of the diffusion pathway
is shorter, it will take less time for the molecules to diffuse the entire
distance. When the MW of the gas molecule is decreased, the velocity of
kinetic movement of the molecule will be higher, which also increases
the rate of diffusion.
TMP14 pp. 516–517
23. B) Normal alveolar PCO 2
is 40 mm Hg. Normal VA for this person is 3.6
l/min. On the ventilator the VA is 7.2 l/min. A doubling of VA results in a
decrease in alveolar PCO 2
by one-half. Thus, alveolar PCO 2
would be 20.
TMP14 pp. 498, 513–514
24. B) Alveolar air normally equilibrates with the mixed venous blood that
perfuses them; thus, the gas composition of alveolar air and pulmonary
capillary blood are identical. When a group of alveoli are not perfused,
the composition of the alveolar air becomes equal to the inspired gas
composition, which has an O2
tension of 149 mm Hg and CO2
tension of
about 0 mm Hg.
TMP14 pp. 514–515, 518–519
25. A) Alveolar PO 2
depends on inspired gas and alveolar PCO 2
. Alveolar
PCO 2
is a balance between VA and CO2
production. To decrease alveolar
PCO 2
, there must be increased VA in relation to metabolism. Low PO 2
will not directly affect PCO 2
, but it can stimulate respiration (if PO 2
is
sufficiently low), which would then reduce PCO 2
. An increased
metabolism with unchanged VA will increase PCO 2
. A doubling in
metabolism with a doubling in VA will have no effect on PCO 2
.
TMP14 p. 514
26. D) A decrease in the VA/Q is depicted by moving to the left along the
normal ventilation-perfusion line shown in the figure. Whenever the
VA/Q is below normal, there is inadequate ventilation to provide the O2
needed to fully oxygenate the blood flowing through the alveolar
capillaries (i.e., alveolar PO 2
is low). Therefore, a certain fraction of the
venous blood passing through the pulmonary capillaries does not
become oxygenated. Poorly ventilated areas of the lung also accumulate
CO2
diffusing into the alveoli from the mixed venous blood. The result
of decreasing VA/Q (moving to the left along the VA/Q line) on alveolar
PO 2
and PCO 2
is shown in the figure; that is, PO 2
decreases, and PCO 2
increases.
TMP14 pp. 518–519
27. B) When the ventilation is reduced to zero (VA/Q = 0), alveolar air
equilibrates with the mixed venous blood entering the lung, which
causes the gas composition of the alveolar air to become identical to that
of the blood. This occurs at point A, where the alveolar PO 2
is 40 mm
Hg and the alveolar PCO 2
is 45 mm Hg, as shown in the figure. A
reduction in VA/Q (caused by the partially obstructed airway in this
problem) causes the alveolar PO 2
and PCO 2
to approach the values
achieved when VA/Q = 0.
TMP14 pp. 518–519
28. E) A pulmonary embolism decreases blood flow to the affected lung,
causing ventilation to exceed blood flow. When the embolism
completely blocks all blood flow to an area of the lung, the gas
composition of the inspired air entering the alveoli equilibrates with
blood trapped in the alveolar capillaries so that within a short time, the
gas composition of the alveolar air is identical to that of inspired air. An
increase in VA/Q caused by the partially obstructed blood flow in this
problem causes the alveolar PO 2
and PCO 2
to approach the values
achieved when VA/Q = ∞. The point at which VA/Q is equal to infinity
corresponds to point E in the figure (inspired gas).
TMP14 pp. 518–519
29. C) Breathing 100% O2
has a limited effect on the arterial PO 2
when the
cause of arterial hypoxemia is a vascular shunt. However, breathing
100% O2
raises the arterial PO 2
to more than 600 mm Hg in a normal
subject. With a vascular shunt, the arterial PO 2
is determined by (a)
highly oxygenated end-capillary blood (PO 2
> 600 mm Hg) that has
passed through ventilated portions of the lung and (b) shunted blood
that has bypassed the ventilated portions of the lungs and thus has an
O2
partial pressure equal to that of mixed venous blood (PO 2
= 40 mm
Hg). A mixture of the two bloods causes a large fall in PO 2
because the
O2
dissociation curve is so flat in its upper range.
TMP14 p. 519
30. E) The PO 2
of mixed venous blood entering the pulmonary capillaries
is normally about 40 mm Hg, and the PO 2
at the venous end of the
capillaries is normally equal to that of the alveolar gas (104 mm Hg). The
PO 2
of the pulmonary blood normally rises to equal that of the alveolar
air by the time the blood has moved a third of the distance through the
capillaries, becoming almost 104 mm Hg. Thus, curve B represents the
normal resting state. During exercise, the cardiac output can increase
severalfold, but the pulmonary capillary blood still becomes almost
saturated with O2
during its transit through the lungs. However,
because of the faster flow of blood through the lungs during exercise,
the O2
has less time to diffuse into the pulmonary capillary blood, and
therefore the PO 2
of the capillary blood does not reach its maximum
value until it reaches the venous end of the pulmonary capillaries.
Although curves D and E both show that O2
saturation of blood occurs
near the venous end, note that only curve E shows a low PO 2
of 25 mm
Hg at the arterial end of the pulmonary capillaries, which is typical of
mixed venous blood during strenuous exercise.
TMP14 pp. 517, 521–522
31. A) The PO 2
of mixed venous blood entering the pulmonary capillaries
increases during its transit through the pulmonary capillaries (from 40
mm Hg to 104 mm Hg), and the PCO 2
decreases simultaneously from 45
mm Hg to 40 mm Hg. Thus, PO 2
is represented by the red lines, and PCO
2
is represented by the green lines in the various diagrams. During
resting conditions, O2
has a 64 mm Hg pressure gradient (104 − 64 = 64
mm Hg), and CO2
has a 5 mm Hg pressure gradient (45 − 40 = 5 mm Hg)
between the blood at the arterial end of the capillaries and the alveolar
air. Despite this large difference in pressure gradients between O2
and
CO2
, both gases equilibrate with the alveolar air by the time the blood
has moved a third of the distance through the capillaries in the normal
resting state (choice A). This is possible because CO2
can diffuse about
20 times as rapidly as O2
.
TMP14 pp. 522–523
32. A) O2
diffuses from the lung into the blood and is both dissolved and
bound to Hb. Despite having no red blood cells, the PO 2
would be
normal as the O2
is dissolved in the plasma. The content would be
minimal, just due to the dissolved O2
in the plasma.
TMP14 pp. 514, 524
33. C) Pulmonary venous blood is nearly 100% saturated with O2
and has a
PO 2
of about 104 mm Hg, and each 100 ml of blood carries about 20 ml
of O2
(i.e., O2
content is about 20 vol%). Approximately 25% of the O2
carried in the arterial blood is used by the tissues under resting
conditions. Thus, reduced blood returning to the lungs is about 75%
saturated with O2
, has a PO 2
of about 40 mm Hg, and has an O2
content
of about 15 vol%. Note that it necessary to know only one value for
oxygenated and reduced blood and that the other two values requested
in the question can be read from the O2
-Hb dissociation curve.
TMP14 pp. 524–525
34. C) Each gram of Hb can normally carry 1.34 ml of O2
. Hb = 12 g/dl.
Arterial oxygen content = 12 × 1.34 = 16 ml O2
/dl. Using 12 ml O2
/dl
yields a mixed venous saturation of 25%. With a saturation of 25%, the
venous PO 2
should be close to 20 mm Hg.
TMP14 p. 524
35. D) When a person is anemic, there is a decrease in O2
content. The O2
saturation of Hb in the arterial blood and the arterial O2
partial pressure
are not affected by the Hb concentration of the blood.
TMP14 pp. 524–525, 527
36. A) The respiratory area of the medulla controls all aspects of
respiration, so a destruction of this area would cause a cessation of
breathing.
TMP14 pp. 531–532
37. E) CO combines with Hb at the same point on the Hb molecule as O2
and therefore can displace O2
from the Hb, reducing the O2
saturation of
Hb. Because CO binds with Hb (to form carboxyhemoglobin) with about
250 times as much tenacity as O2
, even small amounts of CO in the
blood can severely limit the O2
-carrying capacity of the blood. The
presence of carboxyhemoglobin also shifts the O2
dissociation curve to
the left (which means that O2
binds more tightly to Hb), which further
limits the transfer of O2
to the tissues.
TMP14 pp. 527–528
38. C) Structural differences between fetal Hb and adult Hb make fetal Hb
unable to react with 2,3 diphosphoglycerate (2,3-DPG) and thus to have
a higher affinity for O2
at a given PO 2
. The fetal dissociation curve is
thus shifted to the left relative to the adult curve. Typically, fetal arterial
O2
pressures are low, and hence the leftward shift enhances the
placental uptake of O2
.
TMP14 p. 1048
39. D) CO2
is the major controller of respiration as a result of a direct effect
of H+
on the chemosensitive area of the medulla. H+
do not cross the
blood-brain barrier. Thus, CO2
diffuses across the blood-brain barrier
and then is converted to H+
, which acts on the chemosensitive area. CO2
and H+
activation of carotid bodies is minimal under normal conditions.
TMP14 p. 533
40. D) The pneumotaxic center transmits signals to the dorsal respiratory
group that “switch off” inspiratory signals, thus controlling the duration
of the filling phase of the lung cycle. This has a secondary effect of
increasing the rate of breathing because limitation of inspiration also
shortens expiration and the entire period of respiration.
TMP14 p. 532
41. E) The basic rhythm of respiration is generated in the dorsal respiratory
group of neurons, which is located almost entirely within the nucleus of
the tractus solitarius. When the respiratory drive for increased
pulmonary ventilation becomes greater than normal, respiratory signals
spill over into the ventral respiratory neurons, causing the ventral
respiratory area to contribute to the respiratory drive. However,
neurons of the ventral respiratory group remain almost totally inactive
during normal quiet breathing.
TMP14 p. 532
42. F) Dissolved CO2
combines with water in red blood cells to form
carbonic acid, which dissociates to form bicarbonate and H+
. Many of
the bicarbonate ions diffuse out of the red blood cells, whereas chloride
ions diffuse into the red blood cells to maintain electrical neutrality. The
phenomenon, called the chloride shift, is made possible by a special
bicarbonate-chloride carrier protein in the red blood cell membrane that
shules the ions in opposite directions. Water moves into the red blood
cells to maintain osmotic equilibrium, which results in a slight swelling
of the red blood cells in the venous blood.
TMP14 pp. 528–530
43. C) This patient would have increased VA, therefore resulting in a
decrease in arterial PCO 2
. The effect of this decrease in PCO 2
would be an
inhibition of the chemosensitive area and a decrease in ventilation until
PCO 2
was back to normal. Breathing high O2
does not decrease nerve
activity sufficient to decrease respiration. The response of peripheral
chemoreceptors to CO2
and pH is mild and does not play a major role in
the control of respiration.
TMP14 pp. 498, 514, 533–534
44. F) A person with constricted lungs has a reduced TLC and RV. Because
the lung cannot expand to a normal size, the MEF cannot equal normal
values.
TMP14 p. 542
45. F) VA can increase by more than 8-fold when the arterial CO2
tension is
increased over a physiological range from about 35 to 75 mm Hg. This
demonstrates the tremendous effect that CO2
changes have in
controlling respiration. By contrast, the change in respiration caused by
changing the blood pH over a normal range from 7.3 to 7.5 is more than
10 times less effective.
TMP14 p. 534
46. D) The arterial O2
tension has essentially no effect on VA when it is
higher than about 100 mm Hg, but ventilation approximately doubles
when the arterial O2
tension falls to 60 mm Hg and can increase as much
as 5-fold at very low O2
tensions. This quantitative relationship between
arterial O2
tension and VA was established in an experimental seing in
which the arterial CO2
tension and pH were held constant. The student
can imagine that the ventilatory response to hypoxia would be blunted
if the CO2
tension were permied to decrease.
TMP14 p. 536
47. A) Because strenuous exercise does not significantly change the mean
arterial PO 2
, PCO 2
, or pH, it is unlikely that these play an important role
in stimulating the immense increase in ventilation. Although the mean
venous PO 2
decreases during exercise, the venous vasculature does not
contain chemoreceptors that can sense PO 2
. The brain, upon
transmiing motor impulses to the contracting muscles, is believed to
transmit collateral impulses to the brain stem to excite the respiratory
center. Also, the movement of body parts during exercise is believed to
excite joint and muscle proprioceptors that then transmit excitatory
impulses to the respiratory center.
TMP14 pp. 536–538
48. E) It is remarkable that the arterial PO 2
, PCO 2
, and pH remain almost
exactly normal in a healthy athlete during strenuous exercise despite the
20-fold increase in O2
consumption and CO2
formation. This interesting
phenomenon begs the question: What is it during exercise that causes
the intense ventilation?
TMP14 pp. 537–538
49. B) The basic mechanism of Cheyne-Stokes breathing can be aributed
to a buildup of CO2
that stimulates overventilation, followed by a
depression of the respiratory center because of a low PCO 2
of the
respiratory neurons. It should be clear that the greatest depth of
breathing occurs when the neurons of the respiratory center are exposed
to the highest levels of CO2
(point W). This increase in breathing causes
CO2
to be blown off, and thus the PCO 2
of the lung blood is at its lowest
value at about point Y in the figure. The PCO 2
of the pulmonary blood
gradually increases from point Y to point Z, reaching its maximum
value at point V. Thus, it is the phase lag between the PCO 2
at the
respiratory center and the PCO 2
of the pulmonary blood that leads to
this type of breathing. The phase lag often occurs with left heart failure
due to enlargement of the left ventricle, which increases the time
required for blood to reach the respiratory center. Another cause of
Cheyne-Stokes breathing is increased negative feedback gain in the
respiratory control areas, which can be caused by head trauma, stroke,
and other types of brain damage.
TMP14 pp. 538–539
50. D) The FVC is equal to the difference between the TLC and the RV. The
TLC and RV are the points of intersection between the abscissa and
flow-volume curve; that is, TLC = 5.5 l and RV = 1.0 l. Therefore, FVC =
5.5 − 1.0 = 4.5 l.
TMP14 p. 543
51. D) The MEFV curve is created when a person inhales as much air as
possible (point A, total lung capacity = 5.5 liters) and then expires the air
with a maximum effort until no more air can be expired (point E,
residual volume = 1.0 l). The descending portion of the curve indicated
by the downward pointing arrow represents the MEF at each lung
volume. This descending portion of the curve is sometimes referred to
as the “effort-independent” portion of the curve because the patient
cannot increase expiratory flow rate to a higher level even when a
greater expiratory effort is expended.
TMP14 p. 542
52. B) In obstructive diseases such as emphysema and asthma, the MEFV
curve begins and ends at abnormally high lung volumes, and the flow
rates are lower than normal at any given lung volume. The curve may
also have a scooped-out appearance, as shown in the figure. The other
diseases listed as answer choices are constricted lung diseases (often
called restrictive lung diseases). Lung volumes are lower than normal in
constricted lung diseases.
TMP14 pp. 542–543
53. A) Asbestosis is a constricted lung disease characterized by diffuse
interstitial fibrosis. In constricted lung disease (more commonly called
restrictive lung disease), the MEFV curve begins and ends at abnormally
low lung volumes, and the flow rates are often higher than normal at
any given lung volume, as shown in the figure. Lung volumes are
expected to be higher than normal in asthma, bronchospasm,
emphysema, old age, and in other instances in which the airways are
narrowed or radial traction of the airways is reduced, allowing them to
close more easily.
TMP14 p. 542
54. B) The figure shows that a maximum respiratory effort is needed
during resting conditions because the MEF rate is achieved during
resting conditions. It should be clear that his ability to exercise is greatly
diminished. The man has smoked for 60 years and is likely to have
emphysema. Therefore, the student can surmise that the TLC, FRC, and
RV are greater than normal. The VC is only about 3.4 l, as shown in the
figure.
TMP14 pp. 542, 544
55. A) The FVC is the VC measured with a forced expiration. The FEV1
is
the amount of air that can be expelled from the lungs during the first
second of a forced expiration. The FEV1
/FVC for the normal individual
(curve X) is 4 l/5 l = 80% and 2 l/4 l = 50% for the patient (curve Z). The
FEV1
/FVC ratio has diagnostic value for differentiating between normal,
obstructive, and constricted paerns of a forced expiration.
TMP14 p. 543
56. E) The FVC is the VC measured with a forced expiration. The FEV1
is
the amount of air that can be expelled from the lungs during the first
second of a forced expiration. The FEV1
/FVC ratio for the healthy
individual (X) is 4 l/5 l = 80%; FEV1
/FVC for patient Z is 3.0/3.5 = 86%.
FEV1
/FVC is often increased in silicosis and other diseases characterized
by interstitial fibrosis because of increased radial traction of the airways;
that is, the airways are held open to a greater extent at any given lung
volume, reducing their resistance to air flow. Airway resistance is
increased (and therefore FEV1
/FVC is decreased) in asthma,
bronchospasm, emphysema, and old age.
TMP14 pp. 542–543
57. D) With consolidated pneumonia, the lung is filled with fluid and
cellular debris, which results in a decreased area for diffusion. In
addition, the ratio is decreased, which will lead to hypoxia
(decreased PO 2
and content) and hypercapnia (increased PCO 2
).
TMP14 pp. 544–545
58. D) With atelectasis of one lung, a collapse of the lung tissue occurs,
which increases the resistance to blood flow. In addition, the hypoxia in
the collapsed lung causes an additional vasoconstriction. The net effect
is to shift blood to the opposite, ventilated lung, resulting in the majority
of flow in the ventilated lung. A slight compromise in ratio will
occur. With minimal changes in the ratio, there will be minimal
changes in PO 2
and PCO 2
. Thus, there should be a slight decrease in
arterial PO 2
and a slight decrease in saturation and content.
TMP14 pp. 518–519, 545
59. B) The loss of alveolar walls with destruction of associated capillary
beds in the emphysematous lung reduces the elastic recoil and increases
the compliance. The student should recall that compliance is equal to the
change in lung volume for a given change in transpulmonary pressure;
that is, compliance is equal to the slopes of the volume-pressure
relationships shown in the figure. Asbestosis, silicosis, and tuberculosis
are associated with deposition of fibrous tissue in the lungs, which
decreases the compliance. Mitral obstruction and rheumatic heart
disease can cause pulmonary edema, which also decreases the
pulmonary compliance.
TMP14 pp. 493, 542–543
60. C) Curve X represents heavy exercise with a VT of about 3 l. Note that
the expiratory flow rate has reached a maximum value of nearly 4.5 l/sec
during the heavy exercise. This effect occurred because a maximum
expiratory air flow is required to move the air through the airways with
the high ventilatory frequency associated with heavy exercise. Normal
breathing at rest is represented by curve Z; note that the VT is less than
1 l during resting conditions. Curve Y was recorded during mild
exercise. An asthma aack or aspiration of meat would increase the
resistance to air flow from the lungs, making it unlikely that expiratory
air flow rate could approach its maximum value at a given lung volume.
The VT should not increase greatly with pneumonia or tuberculosis, and
it should not be possible to achieve a maximum expiratory air flow at a
given lung volume with these diseases.
TMP14 pp. 542–543
61. C) A premature infant with respiratory distress syndrome has absent or
reduced levels of surfactant. Loss of surfactant creates a greater surface
tension. Because surface tension accounts for a large portion of lung
elasticity, increasing surface tension will increase lung elasticity, making
the lung stiffer and less compliant.
TMP14 pp. 535–536, 547
62. B) Total lung capacity and MEF are reduced in restrictive lung disease.
TMP14 pp. 542–543
63. E) Loss of lung tissue in emphysema leads to an increase in the
compliance of the lungs and a decrease in the elastic recoil of the lungs.
Pulmonary compliance and elastic recoil always change in opposite
directions; that is, compliance is proportional to 1/elastic recoil. The
TLC, RV, and FRC are increased in emphysema, but the VC is decreased.
TMP14 p. 543
64. C) There was an increase in PO 2
but not to normal levels. The increase
in PCO 2
means that the VA decreased. In this patient, the VA was driven
by the decreased O2
levels. If PCO 2
increased, there is no increased
pulmonary excretion of CO2
.
TMP14 pp. 493–494, 545
65. C) Asbestosis is associated with deposition of fibrous material in the
lungs, which causes the pulmonary compliance (i.e., distensibility) to
decrease and the elastic recoil to increase. Pulmonary compliance and
elastic recoil change in opposite directions because compliance is
proportional to 1/elastic recoil. It is somewhat surprising to learn that
the elastic recoil of a rock is greater than the elastic recoil of a rubber
band; that is, the more difficult it is to deform an object, the greater the
elastic recoil of the object. The TLC, FRC, RV, and VC are decreased in
all types of fibrotic lung disease.
TMP14 pp. 542–543
66. C) At the end of inspiration, there is no airflow, so the pressure
gradient is 0. Therefore, alveolar pressure has to be 0 cm H2O, relative to
atmospheric pressure.
TMP14 p. 492
67. D) With exercise, there is an increased cardiac output, thus decreasing
zone 1 areas of the lung. There is still greater flow at the base of the
lungs but also more flow at the apex to improve gas exchange. With the
increased flow, there is an increase in pulmonary blood vessel diameter,
leading to an increased vascular conductance. With the increased
ventilation, there is a greater negative pressure in the pleural space, thus
opening airways and increasing airway conductance. Pulmonary venous
PO 2
is blood after passing through the lungs. With exercise, there is a
beer ratio, so pulmonary venous PO 2
is elevated. Mixed venous PO
2
is blood coming from tissue, so this will fall due to increased
metabolism.
TMP14 pp. 506–507, 517, 524–525
68. D) Stimulation of parasympathetic nerves to the lung decreases the
airway diameter, leading to a decrease in conductance and an increase
in resistance. With low lung volumes the airways collapse, decreasing
conductance. Histamine directly decreases airway diameter, decreasing
conductance. Inhalation to TLC results in a negative thoracic pressure,
which helps to open airways and increases conductance, decreasing
resistance.
TMP14 pp. 492, 499
69. D) As pulmonary capillary pressure increases, there is fluid filtration
into the interstitial spaces. This fluid is removed by the lymphatics along
with protein, thus decreasing interstitial osmotic pressure and
minimizing fluid filtration from the capillaries.
TMP14 pp. 507–509
70. A) Venous oxygen in a tissue is dependent on the balance between flow
and metabolism. If flow goes up, then venous PO 2
increases. If flow goes
down the venous PO 2
decreases. Venous PCO 2
is a balance between
tissue metabolism and flow. With a resting tissue metabolism, a
decrease in flow results in increases in venous PCO 2
and less washout of
CO2
. If flow increases, then there is a greater washout of PCO 2
, resulting
in decreases in venous PCO 2
.
TMP14 pp. 524–526
71. C) COPD means excessive air in the lungs. This is due to a chronic
infection that includes mucus plugging the airways leading to increased
airway resistance, along with destruction of alveolar walls. The
abnormal blood gases are due to diffusion and abnormalities. There
is a decrease in diffusing capacity in the lungs. Some portions of the
lung have low ratio, a shunt, and others have high ratio, dead
space.
TMP14 p. 543
72. E) A person with COPD has airway obstruction leading to air trapping
and an increased TLC. A person with airway obstruction exhales less air
in the first second, FEV1
due to greater resistance. The Forced Vital
Capacity is slightly less in a person with COPD compared with a person
without COPD.
TMP 542–543
73. C) Flow = ΔPressure/Resistance 5 l/min = 5000 ml/min = (25 − 5 = 20 mm
Hg)/R R = 20 mm Hg/5000 ml/min = 4 mm Hg/1000 ml/min = 0.004 mm
Hg/ml/min
TMP14 pp. 503–504
74. B) Exhaled air is a combination of ∼150 ml of dead space, high PO 2
(150 mm Hg) and low CO2
(1 mm Hg), and 350 ml of alveolar air, PO 2=
100 and PCO 2
= 40. Therefore, exhaled PO 2
is higher than alveolar PO 2
,
and exhaled PCO 2
is lower than alveolar PCO 2
.
TMP14 p. 513
75. E) Arterial PO 2
and PCO 2
are a measure of what is dissolved in the
plasma and do not change, with hematocrit. An anemic person with
normal lungs will have normal blood gases. If PO 2
does not change,
then saturation does not change. Adding just red cells will increase the
hematocrit, which will increase the arterial oxygen content. Content = g
Hb/100 ml x 1.34 ml O2
/g Hb.
TMP14 pp. 524–525
76. C) External intercostal are used for inspiration when there is a need for
an active respiration. Therefore, this patient would have a problem with
a forced inhalation.
TMP14 p. 491
77. D) The normal PCO 2
suggests that his ventilatory control is normal. If
the addition of 100% PO 2
does not increase arterial PO 2
, this shows that
there is blood that is not able to uptake the oxygen because of some
problem with diffusion. His condition suggests severe pulmonary
edema and inadequate diffusion across the lungs. Thus blood flowing
by alveoli filled with fluid, pneumonia, are acting as a shunt, thus no
diffusion of oxygen.
TMP14 pp. 512, 516, 518–519
78. D) Even breathing 50% O2
the CO2
levels in the pulmonary artery (45
mm Hg), vein (40 mm Hg), and alveoli (40 mm Hg) will not change.
Anatomic dead space at the end of inhalation would be similar to
atmospheric air and have less than 1 mm Hg CO2
.
TMP14 pp. 506, 513, 522
79. A) A shift in the curve results in a decreased affinity of hemoglobin to
bind oxygen. A shift in the curve occurs in response to increased
temperature, hydrogen ion, and CO2
. These increases normally occur
within a metabolically active tissue. The shift in the curve maintains a
gradient for diffusion but off loads more O2
to tissue, a beneficial effect.
TMP14 pp. 525–526
80. A) In an anemic person, CO2
values will be normal. Arterial and venous
oxygen content will be decreased.
TMP14 pp. 524–525, 528–530
81. A) A decrease in FVC and FEV1
with an increase in TLC is classified as
airway obstruction.
TMP14 pp. 542–543
82. D) An increase in ventilation driven by the peripheral chemoreceptor is
due to, in order of importance, a decrease in PO 2
, an increase in PCO 2
or
an increase in H+
ion concentration, and decreased pH. With 30% O2
, the
PO 2
does not decrease. In anemia, there is no decrease in arterial PO 2
.
Breathing CO results in a decrease in oxygen bound to hemoglobin and
decreased content, but arterial PO 2
will not decrease. A decrease in pH,
and increased H+
ion following a lactic acid infusion will activate
peripheral chemoreceptors to increase ventilation.
TMP14 pp. 534–535
83. B) Normally, the drive to breathe is through the pH changes at the
central chemoreceptor. However, if PCO2 increases due to severe lung
disease, then the peripheral chemoreceptor hypoxic drive becomes more
important.
TMP14 pp. 533–535
84. B) One looks at the hemoglobin dissociation curve and sees that at 0
mm Hg PO 2
, the saturation is 0, and at 20 mm Hg, the saturation is 25%
(25% increase in saturation). At 40 mm Hg, the saturation is 75%, a 50%
increase in saturation from 20 mm Hg.
TMP14 p. 524
85. D) Central chemoreceptors respond directly to changes in H+
in
response to increases in blood PCO 2
.
TMP14 p. 533
86. D) A hemorrhage will cause a refilling of fluid from the interstitial
space to maintain blood volume. This results in a reduction in
hematocrit. With a reduction in hematocrit, there will be a decrease in
arterial content. However, arterial PO 2
will remain normal. Because the
tissue metabolism remains the same, the tissues will use, on average, 5
ml O2
/100 ml blood. Starting from a lower arterial content caused by the
hemorrhage, the venous oxygen content will be less, resulting in a lower
venous PO 2
.
TMP14 pp. 524–525
87. B) The negative pressure in the pleural space tends to pull the chest
wall in and expands the lungs. When there is a hole in the chest wall and
the pleural pressure is atmospheric, the chest wall will expand outward,
and the lungs will collapse. For a healthy person during normal
breathing, inspiration is generally considered to be passive because of
the natural tendency of the chest cage to expand.
TMP14 pp. 491–492
Unit VIII: Aviation, Space, and
Deep-Sea Diving Physiology
1. A diver is breathing 21% oxygen (O2
) at a depth of 132 feet.
The diver’s body temperature is 37°C, and partial pressure of
carbon dioxide (PCO 2
) = 40 mm Hg. What is the alveolar
partial pressure of oxygen (PO 2
)?
A) 149 mm Hg
B) 380 mm Hg
C) 578 mm Hg
D) 738 mm Hg
E) 3703 mm Hg
2. A man is planning to leave Miami (at sea level) and travel to
Colorado to climb Mount Wilson (14,500 feet, barometric
pressure = 450 mm Hg). Before his trip he takes
acetazolamide, a carbonic anhydrase inhibitor that forces the
kidneys to excrete bicarbonate. What response would be
expected before he makes the trip?
A) Alkalotic blood
B) Normal ventilation
C) Elevated ventilation
D) Normal arterial blood gases
3. Which set of changes best describes a Himalayan native living
in the Himalayas, compared with a sea-level native living at
sea level?
Hematocrit Arterial Po2 Arterial O2 Content
A) Decreased Decreased Decreased
B) Decreased Decreased No difference
C) Decreased Increased Decreased
D) Decreased Increased No difference
E)
Increased Decreased Decreased
F)
Increased Increased Decreased
G)
Increased Increased No difference
H)
Increased Decreased No difference
4. A pilot is flying a commercial, pressurized (730 mm Hg)
airplane at 30,000 feet; the barometric pressure is 226 mm Hg.
If the pilot’s body temperature is normal and the alveolar PO
2
is 90 mm Hg, which of the following is true?
A) Arterial PCO 2
is 40 mm Hg
B) Alveolar ventilation will be increased
C) Arterial pH will be 7.6
D) Alveolar PCO 2
will be 45 mm Hg
E) The pilot will be polycythemic
5. Which of the following arterial gases and pH were obtained
from a healthy person 1 hour after arriving at an altitude of
10,000 ft? (Barometric pressure = 523 mm Hg.)
PO 2 PCO 2 pH
A) 55 36 7.42
B) 70 20 7.42
C) 33 50 7.28
D) 70 15 7.53
E) 55 25 7.53
6. A scuba diver at a depth of 90 feet would be expected to
A) have a smaller tidal volume than normal
B) have a normal arterial PCO 2
C) have a decreased hemoglobin saturation
D) have a decreased arterial oxygen content
7. During acclimation to altitude
A) the sensitivity of carotid bodies to hypoxia increases
B) the sensitivity of central chemoreceptors to hypoxia
increases
C) the sensitivity of carotid sinuses to hypoxia increases
D) the concentration in the blood increases
E) the concentration in the brain decreases
Answers
1. D) 132 feet is equivalent to 5 atmospheres of pressure (4 of water
and 1 of air). The total barometric pressure is 760 × 5 = 3800.
Alveolar PCO 2
would be normal at 40. Alveolar PO 2
= (3800 − 47) ×
0.21 − (40/0.8) = 738 mm Hg.
TMP14 pp. 561–562
2. C) Acetazolamide is a medication that that forces the kidneys to
excrete bicarbonate, the base form of CO2
. This excretion
reacidifies the blood, balancing the effects of the hyperventilation
that occurs at altitude in an aempt to get O2
. Such reacidification
acts as a respiratory stimulant, particularly at night, reducing or
eliminating the periodic breathing paern common at altitude.
This would increase ventilation, resulting in a decreased PCO 2
.
TMP14 pp. 554–555
3. H) Acclimatization to hypoxia includes an increase in pulmonary
ventilation, an increase in red blood cells, an increase in diffusion
capacity of the lungs, an increase in vascularity of the tissues, and
an increase in the ability of the cells to use available O2
. The
increase in hematocrit of high-altitude natives allows normal
amounts of O2
(or even greater than normal amounts of O2
) to be
carried in the blood despite lower than normal arterial O2
tension.
For example, those native to elevations of 15,000 feet have an
arterial O2
tension of only 40 mm Hg, but because of greater
amounts of hemoglobin in the blood, the quantity of O2
carried in
the blood is often greater than that in the blood of sea-level
natives.
TMP14 pp. 554–556
4. A) Since the airline cabin is pressurized the pilot is not exposed to
a decreased barometric pressure. Blood gases would be normal
TMP14 p 554
5. A) Note that there is an increase in ventilation upon arriving at
high altitude. This will result in a decrease in PCO 2
. However,
remember that H+
ion at the central chemoreceptor is the major
stimulus for the control of ventilation. The peripheral
chemoreceptors will respond to the decreased PO 2
by wanting to
increase ventilation, but the fall in H+
ion will limit increase in
ventilation. Therefore, there will be a small fall in PCO 2
.
Additionally, you could use the following equation.
Alveolar PO 2
= (Barometric pressure–Water vapor pressure) ∗ %
O2
inhaled –(Blood PCO 2
/0.8)
= (523–47) ∗ 0.21–(Blood PCO 2
/0.8)
= 100–(Blood PCO 2
/0.8)
Predicted Po2 based on PCO 2
PO 2 PCO 2 pH Predicted PO 2
A) 55 36 7.42 55
B) 70 20 7.42 75
C) 33 50 7.28 37.5
D) 70 15 7.53 81
E) 55 25 7.53 69
TMP14 p. 554
6. B) A scuba diver is breathing in gases at higher partial pressures,
resulting in elevated systemic Po2
. Therefore, hemoglobin will be
100% saturated and arterial oxygen content will be increased (due
to increased dissolved oxygen levels). To remove the normal
amount of CO2
produced, the tidal volume has to be normal. PCO 2
has to be normal, or ventilation would change.
TMP14 pp. 561–563, 565
7. E) Upon going to high altitude and low barometric pressure, there
is a decrease in atmospheric PO 2
. This leads to an increase in
ventilation, resulting in a decrease in PCO 2
and thus alkalosis. The
alkalosis results in a decrease in H+ ions at the central
chemoreceptor, thus preventing an increase in ventilation to
increase PO 2
. To bring pH back to normal, the kidney excretes
, thus returning pH back toward normal, which allows the
decreased PO 2
to have a greater stimulatory effect through the
peripheral chemoreceptors.
TMP14 p. 555
Unit IX: The Nervous System
A. General Principles and Sensory Physiology
1. A pool of presynaptic neurons innervates the dendrites of a
postsynaptic neuron. Postsynaptic potentials are then transferred
from the dendrites to the soma of the postsynaptic neuron by
which of the following processes?
A) Action potential
B) Active transport
C) Capacitive discharge
D) Diffusion
E) Electrotonic conduction
2. A transmier substance released from a presynaptic neuron causes
the membrane potential of a postsynaptic neuron to change from
−60 millivolts to −62 millivolts. Which of the following best
describes this change in membrane potential (in millivolts)?
A) Excitatory postsynaptic potential = +2
B) Excitatory postsynaptic potential = −2
C) Inhibitory postsynaptic potential = +2
D) Inhibitory postsynaptic potential = −2
3. All the following neurotransmiers are released from vesicles
EXCEPT one. Which one is the EXCEPTION?
A) Acetylcholine
B) Glutamate
C) Glycine
D. Nitric oxide
E) Norepinephrine
4. Which of the following best describes the main inhibitory
neurotransmier in the spinal cord?
A) Acetylcholine
B) Glutamate
C) Glycine
D) Histamine
E) Norepinephrine
5. Which of the following best describes the type of neurologic circuit
shown?
A) Converging circuit
B) Diverging circuit
C) Inhibitory circuit
D) Reverberatory circuit
6. Which of the following best describes the chief inhibitory
transmier in the brain?
A) Acetylcholine
B) Gamma-aminobutyric acid (GABA)
C) Norepinephrine
D) Glutamate
E) Serotonin
7. Inhibitory postsynaptic potentials (IPSPs) are most likely caused by
opening of which of the following types of membrane channels?
A) Ligand-gated calcium channels
B) Ligand-gated potassium channels
C) Ligand-gated sodium channels
D) Voltage-gated calcium channels
E) Voltage-gated potassium channels
F) Voltage-gated sodium channels
8. Fatigue of synaptic transmission can result from all the following
EXCEPT one. Which one is the EXCEPTION?
A) Abnormal ion concentrations
B) Diminished electrotonic potentials
C) Receptor inactivation
D) Transmier depletion
9. Referred pain results from an intermingling of visceral and skin
pain fibers in which of the following structures?
A) Anterolateral system
B). Dorsal horn of spinal cord
C) Midbrain periaqueductal gray
D) Primary somatosensory cortex
E) Ralph nuclei
10. Which of the following serves to improve the two-point
discrimination threshold in the tips of the fingers of a typical
human being?
A) Lateral inhibition
B) Action potential
C) Spatial resolution
D) Pain
E) Damage
11. Which of the following best describes a disorder of the trigeminal
nerve that leads to paroxysmal facial pain triggered by touch or
cold?
A) Brown-Sequard syndrome
B) Hyperalgesia
C) Tic Douloureux
D) Hemineglect
E) Astereognosis
F) Agraphesthesia
12. A 32-year-old woman involved in a motor vehicle collision
received an injury to the spine at C5 that transected the left half of
the spinal cord. On which side of the patient would you expect
pain and temperature sensations to be absent?
A) Left side
B) Right side
C) Neither side
D) Both sides
13. Hyperventilation is most likely to have which of the following
effects on a typical neuron in the central nervous system?
A) Decreased neuronal activity
B) Increased neuronal activity
C) Increased synaptic delay
D) Decreased synaptic delay
14. All the following factors contribute to synaptic delay EXCEPT one.
Which one is the EXCEPTIOIN?
A) Action of receptor to increase sodium conductance
B) Action of transmier on membrane receptor
C) Diffusion of transmier to postsynaptic membrane
p y p
D) Outward diffusion of sodium to cause EPSP
E) Transmier discharge from presynaptic terminal
15. Signal amplification can be achieved by which of the following
neuronal pools?
A) Divergence in the same tract
B) Convergence from multiple sources
C) Lateral inhibition
D) Reverberating circuit
16. Which ion has the greatest electrochemical driving force in a
typical neuron with a resting membrane potential of −65 millivolts?
A) Chloride
B) Potassium
C) Sodium
17. A 10-year-old girl with fever is hyperventilating. Which of the
following is most likely to occur in this girl?
A) Decreased brain oxygenation only
B) Decreased brain oxygenation and increased neuronal activity
C) Decreased neuronal activity only
D) Increased brain oxygenation only
E) Increased brain oxygenation and decreased neuronal activity
F) Increased neuronal activity only
18. Pain receptors in the skin are typically classified as which of the
following?
A) Encapsulated nerve endings
B) A single class of morphologically specialized receptors
C) The same type of receptor that detects position sense
D) Free nerve endings
19. Which of the following best describes an expanded tip tactile
receptor found in the dermis of hairy skin that is specialized to
detect continuously applied touch sensation?
A) Free nerve endings
B) Merkel disc
C) Pacinian corpuscle
D) Ruffini endings
20. The release of neurotransmier at a chemical synapse in the
central nervous system is dependent on which of the following?
A) Synthesis of acetylcholinesterase
B) Hyperpolarization of the synaptic terminal
C) Opening of ligand-gated ion calcium channels
p g g g
D) Influx of calcium into the presynaptic terminal
21. A transmier substance released from a presynaptic neuron
activates a second messenger G-protein system in the postsynaptic
neuron. Which one of the following postsynaptic responses to the
transmier substance is NOT a possible outcome?
A) Activation of cyclic adenosine monophosphate (cAMP)
B) Activation of cyclic guanosine monophosphate (cGMP)
C) Activation of gene transcription
D) Closing an ion channel
E) Opening an ion channel
22. A 75-year-old man sustained a lower back injury that causes
severe chronic pain. His physician prescribes benzodiazepine
sedation medications to help him sleep. Which response best
describes why this man has difficulty sleeping without medication?
A) Depression of the amygdala
B) Depression of reticular formation
C) Excitation of the amygdala
D) Excitation of reticular formation
E) Loss of somatic sensations
F) Loss of visceral sensations
23. A 13-year-old girl with epilepsy visits a physician for testing. The
physician uses electroencephalography to study her brain waves
during various activities. Which of the following is most likely to
stimulate the greatest increase in brain activity in this girl?
A) Hyperventilation
B) Hypoventilation
C) Hyperventilation plus flashing lights
D) Hypoventilation plus flashing lights
24. Which of the following best describes the concept of specificity in
sensory nerve fibers that transmit only one modality of sensation?
A) Frequency coding principle
B) Concept of specific nerve energy
C) Singularity principle
D) Labeled line principle
25. Which of the following is an encapsulated receptor found deep in
the skin throughout the body, as well as in fascial layers, where it
detects indentation of the skin (pressure) and movement across the
surface (vibration)?
A) Pacinian corpuscle
p
B) Meissner’s corpuscle
C) Free nerve endings
D) Ruffini endings
26. The excitatory or inhibitory action of a neurotransmier is
determined by which of the following?
A) The function of its postsynaptic receptor
B). Its molecular composition
C) The shape of the synaptic vesicle in which it is contained
D) The distance between the pre- and postsynaptic membranes
27. A 54-year-old neurosurgeon picks up a scalpel, which activates
numerous sensory receptors in her hand. An increase in which of
the following best describes the basis for transduction of the
sensory stimuli into nerve impulses?
A) Activation of G protein
B) Decreased ion permeability
C) Decreased transmier release
D) Increased ion permeability
E) Increased transmier release
F) Inhibition of G protein
28. A physiology experiment is conducted in which a glass
microelectrode in inserted into a Pacinian corpuscle to record
receptor potentials during different levels of stimulation (from 0%
to 100%). Increasing stimulus strength from 10% of maximum to
30% of maximum causes a 40% increase in the amplitude of the
receptor potential. Increasing the stimulus potential from 70% of
maximum to 90% of maximum is most likely to cause which
increase in the amplitude of the receptor potential (in %)?
A) 10
B) 40
C) 60
D) 80
29. Interneurons that use the neurotransmier enkephalin to inhibit
afferent pain signals are most likely found in which region of the
central nervous system?
A) Dorsal horn of spinal cord
B) Postcentral gyrus
C) Precentral gyrus
D) δ-type A
E) Type C fiber
F) Ventral horn of spinal cord
30. Which system transmits somatosensory information with the
highest degree of temporal and spatial fidelity?
A) Anterolateral system
B) Dorsal column–medial lemniscal system
C) Corticospinal system
D) Spinocerebellar system
31. The pathway of which system crosses in the ventral white
commissure of the spinal cord within a few segments of entry and
then courses to the thalamus contralateral to the side of the body
from which the signal originated?
A) Anterolateral system
B) Dorsal column–medial lemniscal system
C) Corticospinal system
D) Spinocerebellar system
32. Neurons located in which area release serotonin as their
neurotransmier?
A) Periaqueductal gray area
B) Interneurons of the spinal cord
C) Periventricular area
D) Nucleus raphe magnus
33. Which system conveys information concerning highly localized
touch sensation and body position (proprioceptive) sensation?
A) Anterolateral
B) Dorsal column–medial lemniscal
C) Corticospinal
D) Spinocerebellar
34. The first order (primary afferent) cell bodies of the dorsal column–
medial lemniscal system are found in which structure?
A) Spinal cord dorsal horn
B) Spinal cord ventral horn
C) Dorsal root ganglia
D) Nucleus cuneatus
35. Which structure carries axons from the nucleus gracilis to the
thalamus?
A) Fasciculus gracilis
B) Fasciculus lemniscus
C) Lateral spinothalamic tract
p
D) Medial lemniscus
36. A 12-year-old boy cuts his finger with a pocketknife and
immediately applies pressure to the damaged area with his other
hand to partially alleviate the pain. Inhibition of pain signals by
tactile stimulation of the skin is mediated by which type of afferent
neurons from mechanoreceptors?
A) α-type A
B) β-type A
C) δ-type A
D) Type C
37. A pool of presynaptic neurons innervates the dendrites of a
postsynaptic neuron. Electrical signals are transferred from the
dendrites to the soma of the postsynaptic neuron by which
process?
A) Action potential
B) Active transport
C) Capacitive discharge
D) Diffusion
E) Electrotonic conduction
38. Which structure carries axons from neurons in the ventral
posterolateral nucleus of the thalamus to the primary
somatosensory cortex?
A) Medial lemniscus
B) External capsule
C) Internal capsule
D) Extreme capsule
39. Which of the following is characteristic of the events occurring at
an excitatory synapse?
A) There is a massive efflux of calcium from the presynaptic
terminal
B) Synaptic vesicles bind to the postsynaptic membrane
C) Voltage-gated potassium channels are closed
D) Ligand-gated channels are opened to allow sodium entry into
the postsynaptic neuron
40. Stimulation of which brain area can modulate the sensation of
pain?
A) Superior olivary complex
B) Locus coeruleus
C) Periaqueductal gray area
q g y
D) Amygdala
41. Which body part is represented superiorly and medially within
the postcentral gyrus?
A) Upper limb
B) Lower limb
C) Abdomen
D) Genitalia
42. Which of the following is a group of neurons in the pain
suppression pathway that uses enkephalin as a neurotransmier?
A) Postcentral gyrus
B) Nucleus raphe magnus
C) Periaqueductal gray area
D) Type AB sensory fibers
Questions 43 and 44
A 19-year-old man has an automobile accident that eliminates all nerve
traffic in the right half of the spinal cord at C2. Use this information to
answer the next two questions.
43. Loss of which function is most likely in the right hand of this man?
A) Crude touch and pain sensation
B) Crude touch and temperature sensation
C) Motor function and temperature sensation
D) Motor function and vibration sense
E) Vibration sense and crude touch
F) Vibration sense and pain sensation
44. Loss of which function is most likely in the left hand of this man?
A) Crude touch and pain sensation
B) Crude touch and vibration sense
C) Motor function and temperature sensation
D) Motor function and vibration sense
E) Vibration sense and pain sensation
F) Vibration sense and crude touch
45. The highest degree of pain localization comes from which of the
following?
A) Simultaneous stimulation of free nerve endings and tactile
fibers
B) Stimulation of free nerve endings by bradykinin
C) Nerve fibers traveling to the thalamus by way of the
paleospinothalamic tract
D) Stimulation of δ-type A fibers
46. Posetanic facilitation is thought to result from which of the
following?
A) Opening of voltage-gated sodium channels
B) Opening of transmier-gated potassium channels
C) A buildup of calcium in the presynaptic terminal
D) Electrotonic conduction
47. Within the primary somatosensory cortex, the various parts of the
contralateral body surface are represented in areas of varying size
that reflect which of the following?
A) The relative size of the body parts
B) The density of the specialized peripheral receptors
C) The size of the muscles in that body part
D) The conduction velocity of the primary afferent fibers
48. The gray maer of the primary somatosensory cortex contains six
layers of cells. Which layer(s) receive the bulk of incoming signals
from the somatosensory nuclei of the thalamus?
A) I
B) II and III
C) III only
D) IV
Questions 49 and 50
Each of the disorders in the next two questions is characterized either by
the production of excessive pain (hyperalgesia) or the loss of pain
sensation.
49. Which disorder is characterized by excessive pain in a skin
dermatomal distribution resulting from a viral infection of a dorsal
root ganglion?
A) Tic douloureux
B) Thalamic pain syndrome
C) Brown-Séquard syndrome
D) Herpes zoster
50. Which disorder involves a loss of pain sensation on one side of the
body coupled with the loss of proprioception, precise tactile
localization, and vibratory sensations on the contralateral side of
the body?
A) Herpes zoster
B) Thalamic pain syndrome
C) Lateral medullary syndrome
D) Brown-Séquard syndrome
51. Which disorder is characterized by the loss of pain sensation
throughout one entire side of the body and the opposite side of the
face?
A) Brown-Séquard syndrome
B) Thalamic pain syndrome
C) Herpes zoster
D) Lateral medullary syndrome
52. Stimulation by touching or pulling on which structure is least
likely to cause a painful sensation?
A) Postcentral gyrus
B) Dura overlying the postcentral gyrus
C) Branches of middle meningeal artery that lie superficial to the
dura over the postcentral gyrus
D) Branches of middle cerebral artery that supply the postcentral
gyrus
53. Vibratory sensation depends on the detection of rapidly changing,
repetitive sensations. The high-frequency end of the repetitive
stimulation scale is detected by which structure?
A) Merkel discs
B) Meissner corpuscles
C) Pacinian corpuscles
D) Free nerve endings
54. A 23-year-old gymnast lifts her right leg above her head while in
the standing position. Activation of a single pyramidal cell in the
motor cortex leads to stimulation of 2000 muscle fibers in her right
quadriceps muscle. Which of the following best describes the type
of neuronal circuitry activated in this woman when she lifts her
leg?
A) Converging
B) Diverging
C) Inhibitory
D) Reverberatory
55. An input neuron to a diverging circuit causes the membrane
potential of a target neuron to change from −65 millivolts to −55
millivolts. Which of the following best describes this change in
membrane potential (in millivolts)?
A) Excitatory postsynaptic potential = +10
B) Excitatory postsynaptic potential = −10
C) Inhibitory postsynaptic potential = +10
D) Inhibitory postsynaptic potential = −10
56. Prolonged changes in neuronal activity are usually achieved
through the activation of which of the following?
A) Voltage-gated chloride channels
B) Transmier-gated sodium channels
C) G-protein–coupled channels
D) Voltage-gated potassium channels
57. Position sense, or more commonly proprioceptive sensation,
involves muscle spindles and which of the following?
A) Skin tactile receptors
B) Deep receptors in joint capsules
C) Both tactile and joint capsule receptors
D) Pacinian corpuscles
58. Migraine headaches often begin with a prodromal symptom such
as nausea, loss of vision, visual aura, or other sensory
hallucinations. Which of the following is believed to be the cause of
such prodromes?
A) Increased blood flow to brain tissue in visual or other sensory
cortex
B) A selective loss of gamma-aminobutyric acid neurons in
various sensory areas of cortex
C) Constipation
D) Vasospasm leading to ischemia and disruption of neuronal
activity in relevant sensory areas of cortex
59. For a sensory nerve fiber that is connected to a Pacinian corpuscle
located on palmar surface of the right hand, the synaptic
connection with the subsequent neuron in the corresponding
sensory pathway is located in which of the following?
A) Right dorsal column nucleus
B) Left dorsal column nucleus
C) Dorsal horn of right side of spinal cord
D) Dorsal horn of left side of spinal cord
p
60. The sensation of temperature is signaled mainly by warm and cold
receptors whose sensory fibers travel in association with the
sensory fibers carrying pain signals. Which statement best
characterizes the transmission of signals from warm receptors?
A) Warm receptors are well characterized histologically
B) Signals from warm receptors are mainly transmied along
slow-conducting type C sensory fibers
C) Warm receptors are located well below the surface of the skin
in the subcutaneous connective tissue
D) There are 3 to 10 times more warm receptors than cold
receptors in most areas of the body
Answers
1. E) Most dendrites fail to transmit action potentials because their
membranes have relatively few voltage-gated sodium channels, and
their thresholds for excitation are too high for action potentials to occur.
Yet they do transmit electrotonic current along the dendrites to the soma.
Transmission of electrotonic current means direct spread of electrical
current by ion conduction in the fluids of the dendrites but without
generation of action potentials.
TMP14 p. 583
2. D) The decrease in membrane potential to a more negative value is
called the inhibitory postsynaptic potential (IPSP). Because the resting
membrane potential is −60 millivolts and the final membrane potential is
−62 millivolts, the IPSP is -2 millivolts. IPSPs are always negative.
Excitatory postsynaptic potentials (EPSPs) are always positive because
the membrane potential is increased to a less negative value.
TMP14 pp. 580–581
3. D) Nitric oxide is different from other small-molecule transmiers in its
mechanism of formation in the presynaptic terminal and in its actions
on the postsynaptic neuron. It is not preformed and stored in vesicles in
the presynaptic terminal as are other transmiers. Instead, it is
synthesized almost instantly as needed and then diffuses out of the
presynaptic terminals over a period of seconds rather than being
released in vesicular packets.
TMP14 pp. 576–577
4. C) Glycine is an inhibitory neurotransmier secreted primarily at
synapses in the spinal cord. When glycine receptors are activated,
chloride ions enter the neuron by way of ionotropic receptors, causing
an inhibitory postsynaptic potential.
TMP14 pp. 577–578
5. D) One of the most important of all circuits in the entire nervous system
is the reverberatory or oscillatory circuit. Such circuits are caused by
positive feedback within the neuronal circuit that feeds back to re-excite
the input of the same circuit. Consequently, once stimulated, the circuit
may discharge repetitively for a long time. The simplest oscillatory
circuit involves only a single neuron shown. In this case, the output
neuron sends a collateral nerve fiber back to its own dendrites or soma
to restimulate itself.
TMP14 p. 595
6. B) GABA (gamma-aminobutyric acid) is secreted by nerve terminals in
the spinal cord, cerebellum, basal ganglia, and many areas of the cortex.
GABA is an inhibitory neurotransmier because it blocks, or inhibits,
certain brain signals and decreases activity in the nervous system.
TMP14 p. 578
7. B) Both excitatory and inhibitory postsynaptic potentials are caused by
chemical transmiers (ligands) released from presynaptic neurons that
bind to ligand-gated receptors; this eliminates choices D–F). Opening of
calcium or sodium channels would cause the membrane potential to
move closer to the equilibrium potentials of the ions, which is positive
for both ions, so opening sodium or calcium channels would cause an
EPSP. Increasing the conductance to potassium channels (i.e., opening
potassium channels) would cause the membrane potential to move
closer to the equilibrium potential of potassium, which is usually about
−94 mV. Hence, opening potassium channels causes an IPSP.
TMP14 pp. 576, 581–582
8. B) When excitatory synapses are repetitively stimulated at a rapid rate,
the number of discharges by the postsynaptic neuron is at first very
great, but the firing rate becomes progressively less in succeeding
milliseconds or seconds. This phenomenon is called fatigue of synaptic
transmission. The mechanism of fatigue is mainly exhaustion or partial
exhaustion of the stores of transmier substance in the presynaptic
terminals. The excitatory terminals on many neurons can store enough
excitatory transmier to cause only about 10,000 action potentials, and
the transmier can be exhausted in only a few seconds to a few minutes
of rapid stimulation. Part of the fatigue process probably results from
two other factors as well: (1) progressive inactivation of many of the
postsynaptic membrane receptors and (2) slow development of
abnormal concentrations of ions. Diminished electrotonic potentials
(choice B) can be a result of fatigue, not a cause of fatigue.
TMP14 p. 584
9. B) Often a person feels pain in a part of the body that is fairly remote
from the tissue causing the pain. This phenomenon is called referred pain.
For instance, pain in one of the visceral organs often is referred to an
area on the body surface. Referred pain occurs when visceral pain fibers
are stimulated and are conducted through at least some of the same
neurons that conduct pain signals from the skin; this causes the person
to feel that pain sensations originate in the skin. The intermingling of
visceral and skin pain fibers occurs in the dorsal horn of the spinal cord.
TMP14 p. 618
10. A) A method frequently used to test tactile discrimination is to
determine a person’s so-called “two-point” discriminatory ability. In
this test, two needles are pressed lightly against the skin at the same
time, and the person determines whether one point or two points of
stimulus is/are felt. On the tips of the fingers, a person can normally
distinguish two separate points even when the needles are as close
together as 1 to 2 mm. The capability to distinguish two points of
stimulation is strongly influenced by lateral inhibition. Excitation of
virtually every sensory pathway gives rise to lateral inhibitory signals;
these inhibitory signals spread to the sides of the excitatory signal and
inhibit adjacent neurons. The importance of lateral inhibition is that it
blocks lateral spread of the excitatory signals and, therefore, increases
the degree of contrast in the sensory paern perceived in the cerebral
cortex.
TMP14 p. 606
11. C) A lancinating or stabbing type of pain occasionally occurs in some
people over one side of the face in the sensory distribution area (or part
of the area) of the fifth or ninth cranial nerves; this phenomenon is called
tic douloureux (or trigeminal neuralgia or glossopharyngeal neuralgia). The
pain feels like sudden (i.e., paroxysmal) electrical shocks, and it may
appear for only a few seconds at a time or may be almost continuous.
Often it is set off by exceedingly sensitive trigger areas on the surface of
the face, in the mouth, or inside the throat—almost always by a
mechanoreceptive stimulus such as touch or cold rather than a pain
stimulus.
TMP14 p. 620
12. B) Nerve fibers that transmit pain and temperature sensations enter the
spinal cord and terminate in the dorsal horns; here they excite secondorder neurons that give rise to long fibers that cross immediately to the
opposite side of the cord through the anterior commissure and then turn
upward, passing to the brain in the anterolateral columns. So, the left
side of the spinal cord transmits pain information from the right side of
the body.
TMP14 pp. 614–615
13. B) Most neurons are highly responsive to changes in pH of the
surrounding interstitial fluids. Normally, alkalosis (caused by
hyperventilation) greatly increases neuronal excitability. For instance, a
rise in arterial blood pH from the 7.4 norm to 7.8 to 8.0 often causes
cerebral epileptic seizures because of increased excitability of some or all
the cerebral neurons. Conversely, acidosis greatly depresses neuronal
activity; a fall in pH from 7.4 to below 7.0 usually causes a comatose
state. For instance, in very severe diabetic or uremic acidosis, coma
almost always develops.
TMP14 p. 584
14. D) Increasing membrane conductance to sodium leads to inward
diffusion of sodium to cause an EPSP, not an outward diffusion.
Opening sodium channels in the membrane allows sodium ions to move
down the sodium electrochemical gradient that is directed from the
extracellular fluid to the intracellular fluid.
TMP14 pp. 580–581
15. A) Amplifying divergence means simply that an input signal spreads to
an increasing number of neurons as it passes through successive orders
of neurons in its path. This type of divergence is characteristic of the
corticospinal pathway in its control of skeletal muscles, with a single
large pyramidal cell in the motor cortex capable, under highly facilitated
conditions, of exciting as many as 10,000 muscle fibers.
TMP14 pp. 593–594
16. C) The electrochemical driving force (VDF) for an ion can be calculated
as follows: VDF = Vm − Veq, where V m is the membrane potential and V
eq is the equilibrium potential of the ion. A positive value indicates
outward flux of the ion, and a negative value indicates inward flux of
the ion. A typical equilibrium potential for sodium (calculated using the
Nernst equation) is +62 millivolts, so the electrochemical driving force
for sodium is −65 − 62 = −127 millivolts. This means that a 127-millivolt
force aempts to drive sodium into the cell. The equilibrium potential is
about −86 millivolts for potassium and about −70 millivolts for chloride;
hence, the electrochemical driving forces for these two ions are +21 and
+5 millivolts, respectively (and both ions tend to be driven out of the
cell).
TMP14 pp. 64–65, 576
17. B) Hyperventilation lowers the carbon dioxide tension of the blood,
which leads to increases in the pH of the body tissues, including the
brain. Alkalinity increases neuronal activity in the brain. Carbon dioxide
also has the potent effect of increasing cerebral blood flow; thus,
hyperventilation can lead to decreased cerebral blood flow with a
subsequent decrease in oxygenation of the brain.
TMP14 p. 584
18. D) Pain receptors in the skin are free nerve endings.
TMP14 p. 613
19. B) Merkel discs are found in the dermis of hairy skin and signal
continuous touch.
TMP14 pp. 599–600
20. D) The release of neurotransmier depends on the influx of calcium
through voltage-gated channels. When this influx occurs, synaptic
vesicles fuse with the presynaptic membrane and release the transmier
agent into the synaptic cleft.
TMP14 p. 579
21. D) A so-called second messenger system can be activated by a
transmier substance released from an initial neuron by first causing the
release of a G protein into the second neuron’s cytoplasm.
Neurotransmier activation of G proteins is not known to cause closure
of an ion channel. G proteins can activate G-protein–gated ion channels
for both sodium and potassium, as well as gene transcription, and
cAMP and cGMP. G proteins also can activate intracellular enzymes that
have a variety of different functions.
TMP14 p. 575
22. D) Individuals experiencing severe chronic pain have difficulty
sleeping because the ascending pain pathways provide excitatory input
to reticular formation elements that constitute the reticular activating
system; this system maintains the alert, waking state. The overall
function of the amygdala is thought to make the person’s behavioral
response appropriate for each occasion; it does not play a major role in
establishing the awake state. Loss of visceral sensations or somatic
sensations would likely help the man sleep.
TMP14 pp. 615–616
23. C) Hyperventilation plus flashing lights can sometimes initiate an
epileptic seizure in a susceptible person who is poorly medicated.
Flashing lights alone activate neurons in the occipital cortex that can
sometimes lead to increases in electrical activity throughout the brain.
Hyperventilation (taking long, deep breaths) lowers carbon dioxide
levels in the blood, causing the brain to become alkalotic; this activation
method is commonly used to increase brain activity during
electroencephalography.
TMP14 pp. 584, 779
24. D) The association of one sensory modality with one type of nerve fiber
is the basis for the labeled line theory.
TMP14 p. 587
25. A) Pacinian corpuscles detect pressure and movement across the skin
surface and are encapsulated receptors found deep in the skin
throughout the body.
TMP14 pp. 588–589
26. A) The function of a transmier agent is solely dependent on the
postsynaptic receptor to which it binds.
TMP14 p. 574
27. D) Virtually all mechanical stimuli cause an increase in ion
permeability (usually to sodium) in mechanoreceptors. If the membrane
potential of the mechanoreceptor reaches a critical threshold value, an
action potential is initiated. The G-protein “second messenger” system is
typically involved with prolonged postsynaptic neuronal excitation or
inhibition; transduction in mechanoreceptors is rapid and transient.
Transmier release does not occur at the level of the mechanoreceptor,
but if a mechanoreceptor is activated, afferent nerve impulses do
stimulate transmier release at the nerve terminal in the central nervous
system.
TMP14 p. 588
28. A) The amplitude of the receptor potential from a Pacinian corpuscle
increases greatly with a step increase in stimulus intensity at lower
levels of stimulus strength and to a lesser extent with a similar step
increase at higher levels of stimulus strength, as shown. This
relationship between stimulus strength and amplitude of receptor
potential allows the Pacinian corpuscle to discern small changes in
stimulus strength at low levels of stimulation and yet still respond to
changes in stimulus strength when the intensity of stimulation is high.
TMP14 p. 589
Relation of amplitude of receptor potential to strength of a mechanical
stimulus applied to a Pacinian corpuscle. Data from Loëwenstein WR:
Excitation and inactivation in a receptor membrane. Ann N Y Acad Sci
94:510, 1961.
29. A) Interneurons in the dorsal horn of the spinal cord use enkephalin as
a transmier substance that effectively inhibits pain transmission from
tissues of the body. The somatosensory cortex is located in the
postcentral gyrus, and the primary motor cortex is located in the
precentral gyrus; neither is thought to use enkephalin to inhibit pain
transmission. Myelinated δ-type A fibers and unmyelinated type C
fibers are not interneurons. Interneurons are physically short neurons
that form a connection between other neurons that are usually close
together. There are distinguished from “projection” neurons that project
to more distant regions of the brain or spinal cord.
TMP14 p. 617
30. B) Temporal and spatial fidelity is enhanced in the dorsal column–
medial lemniscal system compared with the anterolateral system.
TMP14 p. 602
31. A) Fibers in the anterolateral system cross in the anterior white
commissure within a few segments of their entry before ascending on
the contralateral side. Signals ascending in the dorsal column–medial
lemniscal system do not cross until they reach the dorsal column nuclei
in the medulla.
TMP14 pp. 614–615
32. D) Neurons of the nucleus raphe magnus release serotonin at their
nerve endings. In the endogenous pain suppression system, the
termination of these neurons is in the spinal cord on interneurons that in
turn release enkephalin and block the incoming signals from the pain
fibers.
TMP14 p. 617
33. B) The sensations of highly localized touch and body position are
carried in the dorsal column–medial lemniscal system.
TMP14 p. 602
34. C) Primary afferent neuronal cell bodies are found in the dorsal root
ganglia.
TMP14 p. 602
35. D) The medial lemniscus conveys axons from the nucleus gracilis and
cuneatus to the thalamus (see figure ).
TMP14 p. 602
Dorsal column–medial lemniscal pathway for transmitting critical types of
tactile signals.
36. B) Stimulation of β-type A fibers from peripheral tactile receptors can
decrease transmission of pain signals by a type of lateral inhibition; this
process is mediated by inhibitory interneurons in the dorsal column of
the spinal cord. α-Type A neurons project to skeletal muscles, causing
them to contract. δ-Type A fibers and type C fibers conduct pain signals
to the dorsal column of the spinal cord.
TMP14 pp. 617–618
37. E) Transmission of electrical signals in dendrites occurs by electrotonic
conduction. Dendrites have few voltage-gated sodium channels, which
makes it impossible for action potentials to be initiated in this portion of
a typical neuron. A neuron can be considered as a type of capacitor that
discharges during an action potential, but this occurs in the axon, not
the dendrites. Electrotonic conduction does not occur by diffusion or
active transport.
TMP14 p. 574
38. C) The internal capsule conveys axons from the ventral posterolateral
thalamic nucleus to the primary somatosensory cortex.
TMP14 p. 602
39. D) Ligand-gated channels open and allow entry of sodium. This entry
is accompanied by the influx of calcium, binding of synaptic vesicles to
the presynaptic membrane, and electrical changes in the postsynaptic
membrane.
TMP14 pp. 572–574
40. C) The periaqueductal gray area in the midbrain contains neurons that
contribute to the descending pain suppression system.
TMP14 pp. 616–617
41. B) The lower limb representation is found in the superior and medial
portion of the postcentral gyrus (see figure).
TMP14 p. 604
Representation of the different areas of the body in somatosensory area I of
the cortex. From Penfield W, Rasmussen T: Cerebral Cortex of Man: A
Clinical Study of Localization of Function. New York: Hafner, 1968.
42. C) Neurons in the periaqueductal gray area use enkephalin as a
transmier agent.
TMP14 p. 617
43. D) Most motor neurons cross to the contralateral side in the pyramidal
decussation of the medulla oblongata, which is proximal to the
damaged area. Fine sensory sensations (vibration sense, fine touch,
proprioception, and two-point discrimination) transmied in the dorsalcolumn medial lemniscal pathway cross to the contralateral side in the
medulla. Therefore, both motor function and vibration sense are lost on
the same side (ipsilateral) as the cord lesion.
TMP14 pp. 602, 699
44. A) Crude touch, pain sensations, and temperature sensations travel in
the anterolateral pathway of the spinal cord; the afferent neurons from
the receptor organs decussate in the spinal cord close to the point of
entry. Hence, these sensations are lost on the side opposite of the lesion.
TMP14 pp. 614–615
45. A) In general, the sensation of pain is poorly localized. However, when
a tactile receptor and a pain receptor are stimulated simultaneously, the
pain sensation is localized with greater accuracy.
TMP14 p. 615
46. C) Posetanic facilitation is the neuronal phenomenon in which a
neuron is more easily excited after a brief period of activity. This
phenomenon is thought to be due to the buildup of calcium in the
presynaptic membrane caused by the prior neuronal activity.
Subsequent neuronal impulses release neurotransmier more readily as
a result of this preplaced calcium from the prior stimulus.
TMP14 p. 574
47. B) The size of the representation of various body parts in the primary
somatosensory cortex is correlated with the density of cutaneous
receptors in that body part.
TMP14 p. 604
48. D) Layer IV of the somatosensory cortex receives the bulk of the input
from the somatosensory nuclei of the thalamus.
TMP14 pp. 604–605
49. D) Herpes zoster is a disorder characterized by excessive pain in a
dermatomal distribution that results from a viral infection of a dorsal
root ganglion.
TMP14 p. 620
50. D) Brown-Séquard syndrome is characterized by a loss of pain
sensation on one side of the body coupled with a loss of discriminative
sensations, such as proprioception and vibratory sensation, on the
opposite side of the body.
TMP14 pp. 620–621
51. D) The lateral medullary syndrome exhibits one of the most
characteristic paerns of sensory loss in clinical neurology; pain
sensation is lost over one side of the body from feet to neck and on the
opposite side of the face. Moreover, the side of facial pain loss indicates
the side of the lesion.
TMP14 p. 620
52. A) Touching or pulling on the postcentral gyrus is least likely to evoke
a painful sensation because brain tissue lacks pain receptors.
TMP14 p. 621
53. C) High-frequency repetitive stimulation (indentation/pressure) of the
skin is sensed by Pacinian corpuscles.
TMP14 pp. 588–589
54. B) A diverging neuronal pathway amplifies nerve signals; activation of
a single pyramidal cell in motor cortex can stimulate as many as 10,000
muscle fibers. In a converging circuit, multiple input fibers converge
upon a single postsynaptic neuron, which allows summation of
information from multiple sources. An inhibitory circuit often has
inhibitory interneurons that stop the spread of a nerve signal.
Reverberatory circuits have positive feedback elements that allow a
nerve impulse to continue for a prolonged time.
TMP14 pp. 593–594
55. A) The positive increase in membrane potential to a less negative value
is called the excitatory postsynaptic potential (EPSP). Because the
resting membrane potential is −65 millivolts and the final membrane
potential is −55 millivolts, the EPSP is +10 millivolts. EPSPs are always
positive. Inhibitory postsynaptic potentials are always negative because
the membrane potential is lowered to a more negative value.
TMP14 pp. 580–581
56. C) Activation of G proteins usually changes the long-term response
characteristics of the neuron.
TMP14 pp. 575–576
57. C) Proprioceptive sensation depends on tactile and joint capsule
receptors.
TMP14 p. 608
58. D) Vasospasm and eventually ischemia in a sensory area of cortex is
thought to be the basis for the prodromal symptoms experienced by
patients with migraines.
TMP14 p. 621
59. A) The Pacinian corpuscle transmits a modality of sensation (vibration)
that is transmied in the dorsal column–medial lemniscal system. The
first synaptic connection in this sensory pathway is in the dorsal column
nuclei on the ipsilateral side of the body.
TMP14 p. 602
60. B) Warm receptors mainly transmit signals along relatively slowconducting type C fibers.
TMP14 p. 622
Unit X: The Nervous System
B. The Special Senses
1. Which of the following best describes the refractive power of a lens
that focuses incoming parallel light rays at a point that is two
meters from the refractive center of the lens (in diopters)?
A) 0.5
B) 1.0
C) 2.0
D) 10.0
E) 20.0
2. A 62-year-old man visits his physician because of difficulty seeing
while driving at night. The man has frequent, foul smelling stools.
Stool analyses reveal a high content of digested fat. A decrease in
retinal levels of which of the following is the most likely cause of
his night blindness?
A) 2-Monoglycerides
B) Amino acids
C) Free fay acids
D) Glucose
E) Vitamin A
F) Vitamin C
Questions 3 and 4
A 42-year-old woman visits an ophthalmologist because of difficulty
seeing. Tests show that her right eye has an intraocular pressure of 34 mm
Hg, and her left eye has an intraocular pressure of 38 mm Hg (reference
range, 12–20 mm Hg).
3. Which of the following is the most likely cause of this increase in
intraocular pressure of both eyes?
A) Decreased hydraulic resistance of trabecular spaces
B) Decreased production of aqueous humor
C) Increased hydraulic resistance of trabecular spaces
D) Increased production of aqueous humor
4. All the following are likely to occur in the eyes of this patient
EXCEPT one. Which one is the EXCEPTION?
A) Axonal compression
B) Blockade of axonal flow of cytoplasm
C) Decreased nutrition of neuronal cell bodies
D) Decreased retinal nutrition
E) Lens hypertrophy
F) Retinal ischemia
5. A 14-year-old girl sits in a dark movie theater for 2 hours and then
walks outside. Which of the following best describes the
permeability to sodium and potassium ions in rod cells in response
to the onset of photopic conditions?
A) Decreased sodium permeability, decreased potassium
permeability
B) Decreased sodium permeability, increased potassium
permeability
C) Decreased sodium permeability, no change in potassium
permeability
D) Increased sodium permeability, decreased potassium
permeability
E) Increased sodium permeability, increased potassium
permeability
F) Increased sodium permeability, no change in potassium
permeability
6. A 32-year-old student with 20/20 vision redirects her gaze from a
distant building back to her computer screen. Which of the
following best describes the lens, ciliary muscle, and
parasympathetic responses to changing her gaze to the computer
screen?
A) Thicker lens, contraction of ciliary muscle, increased
parasympathetic stimulation
B) Thicker lens, contraction of ciliary muscle, decreased
parasympathetic stimulation
C) Thicker lens, relaxation of ciliary muscle, increased
parasympathetic stimulation
D) Thicker lens, relaxation of ciliary muscle, decreased
parasympathetic stimulation
E) Thinner lens, contraction of ciliary muscle, increased
parasympathetic stimulation
F) Thinner lens, contraction of ciliary muscle, decreased
parasympathetic stimulation
G) Thinner lens, relaxation of ciliary muscle, increased
parasympathetic stimulation
H) Thinner lens, contraction of ciliary muscle, decreased
parasympathetic stimulation
7. The human tongue typically has about how many taste buds?
A) 30–100
B) 100–3,000
C) 3,000–10,000
D) 10,000–30,000
E) 30,000–100,000
8. A 25-year-old factory worker develops a noise-induced hearing loss
over a period of 6 months because of repeated, prolonged
exposures to loud sounds. The physical loss of which of the
following structures is most likely to contribute to the hearing
deficit?
A) Cochlea
B) Hair cells
C) Organ of Corti
D) Scala vestibuli
E) Aenuation reflex
9. Which of the following structures provides a gating function for
transmission of the visual signal from the retina to the central
nervous system?
A) Lateral geniculate nucleus
B) Optic radiation
C) Optic chiasm
D) Optic nerve
E) Visual cortex
10. Which of the following best describes the electrical response of
rods in the retina to photopic conditions?
A) Action potential
B) Capacitive discharge
C) Depolarization
D) Hyperpolarization
11. A 43-year-old man wakes up at night and turns on a light. Which
of the following substances is most likely to increase in the rods of
the retina when the man is exposed to photopic conditions?
A) cAMP
B) cGMP
C) Metarhodopsin II
D) Rhodopsin
E) Vitamin A
12. A 30-year-old woman is admied as an emergency to University
Hospital because of sudden, severe pain in the right eye. Tests
show an intraocular pressure of 60 mm Hg in her right eye; the
intraocular pressure of her left eye is 15 mm Hg (reference range:
12–20 mm Hg). Which of the following is the most likely cause of
acute eye pain in this woman?
A) Closed-angle glaucoma
B) Chronic glaucoma
C) Conjunctivitis
D) Corneal abrasion
E) Open-angle glaucoma
F) Optic neuritis
13. A 90-year-old woman visits the ophthalmologist because of
difficulty seeing. The patient is given an eye exam, and bifocal
lenses are prescribed. The woman sees well with her new
prescription glasses. Which of the following is the most likely
vision problem in this woman?
A) Cataracts
B) Emmetropia
C) Glaucoma
D) Hyperopia
E) Myopia
F) Presbyopia
14. Which of the following cell types is most likely to play a central
role in lateral inhibition to enhance visual contrast?
A) Amacrine cells
B) Bipolar cells
C) Cones
D) Ganglion cells
E) Horizontal cells
F) Rods
15. Ganglion cells aached to rods or cones located on the nasal
portion of each retina terminate (or synapse) in which of the
following structures?
A) Calcarine fissure of occipital cortex
B) Contralateral lateral geniculate nucleus
C) Contralateral visual cortex
D) Ipsilateral lateral geniculate nucleus
E) Ipsilateral visual cortex
16. Which of the following is the leading cause of blindness
worldwide?
A) Albinism
B) Cataracts
C) Glaucoma
D) Presbyopia
17. Topical application of atropine in the eye has which of the
following effects?
A) Miosis, inhibition of accommodation
B) Miosis, stimulation of accommodation
C) Mydriasis, inhibition of accommodation
D) Mydriasis, stimulation of accommodation
18. Which of the following best describes myopia and hyperopia?
A) Myopia: long eyeball, farsightedness; hyperopia: short
eyeball, nearsightedness
B) Myopia: long eyeball, nearsightedness; hyperopia: short
eyeball, farsightedness
C) Myopia: short eyeball, farsightedness; hyperopia: long
eyeball, nearsightedness
D) Myopia: short eyeball, nearsightedness; hyperopia: long
eyeball, farsightedness
19. Low-frequency sound causes which portion of the basilar
membrane to vibrate to the greatest extent?
A) Near oval window
B) Middle portion
C) Along entire length
D) Near helicotrema
20. A 9-year-old girl looks at a flower through a magnifying glass. She
finds that the flower must be 10 cm from the convex lens to be in
focus. Which value best describes the refractive power of the lens
(in diopters)?
p
A) 0.1
B) 1.0
C) 10
D) 100
E) 1000
21. Which of the following best describes the “blind spot” of the eye?
A) Located 5 degrees lateral to central point of vision
B) Exit point of the optic nerve
C) Contains only rods and thus has monochromatic vision
D) Contains no blood vessels
E) Area where chromatic aberration of lens is greatest
22. A 10-year-old girl with albinism is taken to the ophthalmologist
because of difficulty seeing. Testing shows that her visual acuity is
reduced. Which of the following is the most likely cause of the
decrease in visual acuity in this girl?
A) Cataracts
B) Hyperopia
C) Myopia
D) Photophobia
E) Presbyopia
23. Which substance is most likely to elicit the sensation of bier taste?
A) Aldehydes
B) Alkaloids
C) Amino acids
D) Hydrogen ions
E) Ketones
24. Damage to the sixth cranial nerve is most likely to produce which
deficit in eye movement?
A) Inability to move eyes in a vertical up-and-down motion
B) Inability to rotate eyes within the eye socket
C) Inability to move eyes laterally toward the midline
D) Inability to move the laterally away from the midline
E) Vertical strabismus
25. The condition of cataracts is usually the result of which process or
condition?
A) Denaturation of the proteins in lens of eye
B) Elongated eye globe
C) Unresponsive and dilated pupil
D) Coagulation of proteins in lens of the eye
g p y
E) Increase in intraocular pressure
26. Which substance is most likely to elicit the sensation of sour taste?
A) Aldehydes
B) Alkaloids
C) Amino acids
D) Hydrogen ions
E) Ketones
27. Which taste sensation is most likely to be the most sensitive (i.e.,
has the lowest stimulation threshold)?
A) Acid
B) Bier
C) Salty
D) Sour
E) Sweet
28. Which of the following best describes the middle ear ossicle that is
aached to the tympanic membrane?
A) Columella
B) Incus
C) Malleus
D) Modiolus
E) Stapes
29. Light entering the eye passes through which retinal layer first?
A) Inner nuclear layer
B) Outer nuclear layer
C) Outer plexiform layer
D) Photoreceptor layer
E) Retinal ganglion layer
30. Ganglion cells aached to photoreceptors located on the temporal
portion of the retina project to which structure?
A) Contralateral lateral geniculate nucleus
B) Ipsilateral lateral geniculate nucleus
C) Ipsilateral medial geniculate nucleus
D) Calcarine fissure
E) Contralateral medial geniculate nucleus
31. Which of the following is most likely to occur when parallel light
rays pass through a concave lens?
A) Rays converge toward each other
B) Rays diverge away from each other
C) Rays maintain a parallel relationship
y p p
D) Rays reflect back in the direction from where they came
E) Rays refract to one focal point
32. Which compartment of the cochlea contains the organ of Corti?
A) Ampulla
B) Saccule
C) Scala media
D) Scala tympani
E) Scala vestibuli
33. Which molecules combine to form rhodopsin?
A) Bathorhodopsin and 11-cis-retinal
B) Bathorhodopsin and all-trans-retinal
C) Bathorhodopsin and scotopsin
D) Scotopsin and 11-cis-retinal
E) Scotopsin and all-trans-retinal
34. Analysis of visual detail occurs in which secondary visual area?
A) Brodmann’s area 18
B) Inferior ventral and medial regions of the occipital and
temporal cortex
C) Frontal lobe
D) Occipitoparietal cortex
E) Posterior midtemporal area
35. Which substance is most likely to stimulate the umami taste
sensation?
A) Acetic acid
B) Potassium tartrate
C) Long-chained organic substances containing nitrogen
D) Fructose
E) Glutamate
36. Which cell type(s) have action potentials in the retina of the human
eye?
A) Bipolar cells and ganglion cells
B) Bipolar cells only
C) Bipolar cells, horizontal cells, and ganglion cells
D) Ganglion cells and horizontal cells
E) Ganglion cells only
F) Horizontal cells only
37. Olfactory receptor cells belong to which group of cells?
A) Bipolar neurons
B) Fibroblasts
C) Modified epithelial cells
D) Multipolar neurons
E) Pseudounipolar neurons
38. Under low or reduced light conditions, which chemical compound
is responsible for the inward-directed sodium current in the outer
segments of the photoreceptors?
A) Metarhodopsin II
B) cGMP
C) 11-cis retinal
D) cAMP
E) 11-trans retinal
39. Which cells in layer IV of the primary visual cortex detect
orientation of lines and borders?
A) Border cells
B) Complex cells
C) Ganglion cells
D) Hypercomplex cells
E) Simple cells
40. Which event occurs in photoreceptors during phototransduction in
response to light?
A) Phosphodiesterase activity decreases
B) Transducin activity decreases
C) Hydrolysis of cGMP increases
D) Neurotransmier release increases
E) The number of open voltage-gated calcium channels increases
Questions 41 and 42
A 50-year-old woman visits an otolaryngologist for sudden bouts of
dizziness that subside after about 20 minutes. She also has temporary
hearing losses and a feeling of fullness in her right ear; low-pitched
buzzing sounds occur intermiently in her right ear. Physical examination
shows nystagmus during a dizzy spell. Use this information to answer the
next two questions.
41. Which of the following is the most likely diagnosis?
A) Acoustic neuroma
B) Aural polyp
C) Exostosis
D) Incus erosion
E) Meniere’s disease
42. An increase in which of the following is the most likely cause of
this patient’s condition?
A) Endolymph pressure only
B) Endolymph volume only
C) Endolymph volume and pressure
D) Perilymph pressure only
E) Perilymph volume only
F) Perilymph volume and pressure
43. The condition of myopia is usually corrected by which type of
lens?
A) Compound lens
B) Convex lens
C) Spherical lens
D) Concave lens
E) Cylindrical lens
44. Which lobe of the cerebral cortex contains the small bilateral
cortical area that controls voluntary fixation movements?
A) Frontal
B) Limbic
C) Occipital
D) Parietal
E) Temporal
45. Which sensory system is most likely to have the smallest range of
intensity discrimination?
A) Auditory
B) Gustatory
C) Olfactory
D) Somatosensory
E) Visual
46. Which molecules move from the endolymph into the stereocilia
and depolarize the hair cell?
A) Calcium ions
B) Chloride ions
C) Hydrogen ions
D) Potassium ions
E) Sodium ions
47. The stereocilia of hair cells are embedded in which membrane?
A) Basilar
B) Reissner’s
C) Tectorial
D) Tympanic
E) Vestibular
48. Which cranial nerve is correctly paired with the extraocular
muscle it innervates?
A) Abducens nerve–medial rectus
B) Oculomotor nerve–inferior oblique
C) Oculomotor nerve–lateral rectus
D) Oculomotor nerve–superior oblique
E) Trochlear nerve–superior rectus
49. After olfactory receptor cells bind odor molecules, a sequence of
intracellular events occurs that culminates in the entrance of
specific ions that depolarize the olfactory receptor cell. Which ions
are most likely to be involved?
A) Calcium
B) Chloride
C) Hydrogen
D) Potassium
E) Sodium
50. Which of the following is most likely to occur when the eye adapts
to intense light?
A) Bipolar cells will continuously transmit signals at the
maximum rate possible
B) Photochemicals in both rods and cones will be reduced to
retinal and opsins
C) The levels of rhodopsin will be very high
D) The size of the pupil will increase
E) Vitamin A will convert into retinal
51. In the central auditory pathway, which option represents the
correct sequence of structures in the pathway?
A) Cochlear nuclei–superior olive–inferior colliculus via the
lateral lemniscus–medial geniculate–auditory cortex
B) Cochlear nuclei–inferior olive–inferior colliculus via the
medial lemniscus–medial geniculate–auditory cortex
C) Cochlear nuclei–superior olive–superior colliculus via the
lateral lemniscus–lateral geniculate–auditory cortex
D) Cochlear nuclei–inferior olive–inferior colliculus via the
lateral lemniscus–lateral geniculate–auditory cortex
g y
E) Cochlear nuclei–trapezoid body–dorsal acoustic stria–inferior
colliculus via the lateral lemniscus–medial geniculate–auditory
cortex
52. Which event prompts the auditory system to interpret a sound as
loud?
A) A decreased number of inner hair cells become stimulated
B) A decreased number of outer hair cells become stimulated
C) Hair cells excite nerve endings at a diminished rate
D) The amplitude of vibration of the basilar membrane decreases
E) The amplitude of vibration of the basilar membrane increases
53. The condition of hyperopia is usually caused by which anomaly of
the eye?
A) Decreased production of melanin
B) Uneven curvature of the cornea
C) An eyeball that is shorter than normal
D) An eyeball that is longer than normal
E) A lens system that is too powerful and focuses the object in
front of the retina
54. When a person turns the head to the left about the axis of the neck,
the motion begins when the chin is directly over the right shoulder
and ends with the chin directly over the left shoulder. Which
option best describes the eye movements associated with this type
of head rotation in a normal person?
A) While the head is turning, the eyes will be moving to the right
and saccadic eye motion will be to the left
B) While the head is turning, the eyes will be moving in the same
direction as the head rotation and the saccadic eye motion will
be to the left
C) While the head is turning, the eyes will be moving to the right
and the saccadic eye motion will be to the right
D) While the head is turning, the eyes will remain stationary
within the orbits and the saccadic eye motion will be to the
right
E) While the head is turning, the eyes will be moving to the left
and the saccadic eye motion will be to the right
55. Olfactory information transmied to the orbitofrontal cortex
passes through which thalamic nucleus?
A) Dorsomedial
B) Lateral geniculate
g
C) Medial geniculate
D) Ventral posterolateral
E) Ventral posteromedial
56. A 29-year-old student with 20/20 vision looks at a beautiful scene.
The axons of ganglion cells transmiing visual signals in the form
of action potentials to the primary visual cortex are most likely to
synapse in which structure?
A) Lateral geniculate nucleus
B) Medial geniculate nucleus
C) Optic chiasm
D) Optic radiation
E) Superior cervical ganglion
F) Superior colliculus
57. Which muscle is contracted as part of the pupillary light reflex?
A) Ciliary muscle
B) Pupillary dilator muscle
C) Pupillary sphincter muscle
D) Radial fibers of the iris
E) Superior oblique muscle
Questions 58 and 59
A 24-year-old woman sustains a laceration on the right side of the neck
in a motor vehicle accident. Physical examination shows that her right
pupil is constricted, her right eyelid droops, the skin is dry on the right
side of her face, and the conjunctiva of her right eye is red. Use this
information to answer the next two questions.
58. What is the most likely diagnosis?
A) Cone-rod dystrophy
B) Horner’s syndrome
C) Iris heterochromia
D) Retinoblastoma
E) Xerophthalmia
59. Which test result shown in the boom of left column figure is
most likely after topical treatment with cocaine in both eyes?
A) A
B) B
C) C
D) D
60. Which neurotransmier is released by both rods and cones at their
synapses with bipolar cells?
A) Acetylcholine
B) Dopamine
C) Glutamate
D) Glycine
E) Serotonin
61. Which of the following allows the visual apparatus to accurately
determine the distance of an object from the eye (depth
perception)?
A) Monocular vision
B) The location of the retinal image on the retina
C) The phenomenon of stationary parallax
D) The phenomenon of stereopsis
E) The size of the retinal image if the object is of unknown size
62. Which of the following provides about two thirds of the 59
diopters of refractive power of the eye?
A) Anterior surface of the cornea
B) Anterior surface of the lens
C) Iris
D) Posterior surface of the cornea
E) Posterior surface of the lens
63. Which photoreceptor responds to the broadest spectrum of
wavelengths of light?
A) Rod receptors
B) Green cone receptors
C) Blue cone receptors
D) Red cone receptors
E) Cells containing melanin in the pigment layer
64. Which structure secretes the intraocular fluid of the eye?
A) Ciliary processes
B) Cornea
C) Iris
D) Lens
E) Trabeculae
65. Which type of papillae is in the posterior part of the tongue?
A) Circumvallate
B) Foliate
C) Fungiform
D) Fungiform and circumvallate
E) Papilla of Vater
66. Auditory information is relayed through which thalamic nucleus?
y y g
A) Dorsomedial
B) Lateral geniculate
C) Medial geniculate
D) Ventral posterolateral
E) Ventral posteromedial
67. Which of the following describes the phenomenon of taste
preference?
A) A central nervous system process
B) The result of neonatal stimulation of circumvallate papilla
C) A learned behavior in animals
D) A result of taste bud maturation
E) A result of taste bud proliferation after exposure to glutamic
acid
68. The primary auditory cortex lies primarily in which lobe of the
cerebral cortex?
A) Frontal
B) Limbic
C) Occipital
D) Parietal
E) Temporal
69. The first central synapse for neurons transmiing the sweet taste
sensation is in which structure?
A) Dorsal sensory nucleus of vagus nerve
B) Nucleus of solitary tract
C) Nucleus of olfactory nerve
D) Nucleus of hypoglossal nerve
E) Nucleus of facial nerve
70. Which structure functions to ensure that each of the three sets of
extraocular muscles is reciprocally innervated so that one muscle
of the pair relaxes while the other contracts?
A) Edinger-Westphal nucleus
B) Medial longitudinal fasciculus
C) Pretectal nucleus
D) Superior colliculus
E) Suprachiasmatic nucleus
71. The intraocular fluid of the eye flows from the canal of Schlemm
into which location?
A) Anterior chamber
B) Aqueous veins
q
C) Lens
D) Posterior chamber
E) Trabeculae
72. Which retinal cells are most likely to have action potentials?
A) Bipolar cells
B) Ganglion cells
C) Horizontal cells
D) Photoreceptors
73. Which brain stem structure plays a major role in determining the
direction from which a sound originates?
A) Cochlear nucleus
B) Inferior colliculus
C) Lateral lemniscus
D) Superior olivary nucleus
E) Trapezoid
74. A 25-year-old student studies for a test in medical physiology. The
visual contrast of the subject maer is enhanced due to lateral
inhibition of the visual input by which cell type in the retina?
A) Amacrine cells
B) Bipolar cells
C) Ganglion cells
D) Horizontal cells
75. Which type of papillae is located in the folds along the lateral
surfaces of the tongue?
A) Circumvallate
B) Foliate
C) Fungiform
D) Fungiform and circumvallate
E) Papilla of Vater
Answers
1. A) The refractive power of a lens is measured in terms of diopters. The
refractive power in diopters of a convex lens is equal to 1 m divided by
its focal length. Thus, a spherical lens that converges parallel light rays
to a focal point 1 m beyond the lens has a refractive power of 1.0 diopter.
If the lens focuses parallel light rays at a point 2 m from the refractive
center of the lens, the lens has a refractive power of 0.5 diopters (choice
A). In addition, a lens capable of converging parallel light rays to a focal
point only 10 cm (0.10 m) beyond the lens has a refractive power of +10
diopters.
TMP14 pp. 629–630
2. E) Night blindness occurs in persons with severe vitamin A deficiency
because without vitamin A, the amounts of retinal and rhodopsin that
can be formed are severely depressed. This condition is called night
blindness because the amount of light available at night is too lile to
permit adequate vision in vitamin A–deficient persons. The man is
losing fat in his feces, and vitamin A is a fat-soluble vitamin that is also
lost in the feces.
TMP14 p. 642
3. C) Glaucoma, one of the most common causes of blindness, is a disease
of the eye in which the intraocular pressure becomes pathologically
high, sometimes rising acutely to 60 to 70 mm Hg. Pressures above 25 to
30 mm Hg can cause loss of vision when maintained for long periods. In
most cases of glaucoma, the abnormally high pressure results from
increased resistance to fluid outflow through the trabecular spaces
(choice C) into the canal of Schlemm at the iridocorneal junction. For
instance, in acute eye inflammation, white blood cells and tissue debris
can block these trabecular spaces and cause an acute increase in
intraocular pressure. In chronic conditions, especially in older persons,
fibrous occlusion of the trabecular spaces appears to be the likely culprit.
TMP14 p. 637
4. E) Extremely high intraocular pressures can cause blindness within days
or even hours. As the pressure rises, the axons of the optic nerve are
compressed where they leave the eyeball at the optic disc. This
compression is believed to block axonal flow of cytoplasm from the
retinal neuronal cell bodies into the optic nerve fibers leading to the
brain. The result is lack of appropriate nutrition of the fibers, which
eventually causes death of the involved fibers. It is possible that
compression of the retinal artery, which enters the eyeball at the optic
disc, also adds to the neuronal damage by reducing nutrition to the
retina (i.e., retinal ischemia occurs). There is no reason to expect lens
hypertrophy (choice E) in this patient with glaucoma.
TMP14 p. 637
5. C) When rhodopsin in the outer segment of the rod is exposed to light, it
is activated and begins to decompose. The cGMP-gated sodium
channels are then closed, causing sodium permeability to decrease
(choice C). The potassium channels are not gated, and therefore remain
open in both photopic and scotopic conditions.
TMP14 pp. 642–643
6. A) The ciliary muscle is controlled almost entirely by parasympathetic
nerve signals transmied to the eye through the third cranial nerve from
the third nerve nucleus in the brain stem, as explained in Chapter 52.
Stimulation of the parasympathetic nerves contracts both sets of ciliary
muscle fibers, which relaxes the lens ligaments, thus allowing the lens to
become thicker and increase its refractive power. With this increased
refractive power, the eye focuses on objects nearer than when the eye
has less refractive power.
TMP14 pp. 631, 660–661
7. C) Adults have 3000 to 10,000 taste buds, and children have a few more.
Beyond the age of 45 years, many taste buds degenerate, causing taste
sensitivity to decrease in old age.
TMP14 p. 677
8. B) Minute hairs, or stereocilia, project upward from the hair cells (choice
B) and either touch or are embedded in the surface gel coating of the
tectorial membrane, which lies above the stereocilia in the scala media.
Bending of the hairs in one direction depolarizes the hair cells, and
bending in the opposite direction hyperpolarizes them. This in turn
excites the auditory nerve fibers synapsing with their bases. These hair
cells are damaged when they are exposed to prolonged, loud sounds;
the loss is permanent.
TMP14 p. 667
9. A) The optic nerve fibers of the visual system terminate in the dorsal
lateral geniculate nucleus (choice A), located at the dorsal end of the
thalamus. The dorsal lateral geniculate nucleus serves two principal
functions: First, it relays visual information from the optic tract to the
visual cortex by way of the optic radiation. The second major function of
the dorsal lateral geniculate nucleus is to “gate” the transmission of
signals to the visual cortex—that is, to control how much of the signal
can pass to the cortex.
TMP14 pp. 653–654
10. D) The rod receptor potential is hyperpolarizing, not depolarizing.
When the rod is exposed to photopic conditions (light), the resulting
receptor potential is different from the receptor potentials in almost all
other sensory receptors because excitation of the rod causes increased
negativity of the intrarod membrane potential, which is a state of
hyperpolarization. This is exactly opposite to the decreased negativity (the
process of “depolarization”) that occurs in almost all other sensory
receptors.
TMP14 pp. 642–643
11. C) When the rhodopsin in the outer segment of the rod is exposed to
light, it is activated to become metarhodopsin II (choice C), also called
activated rhodopsin. The activated rhodopsin stimulates a G protein
called transducin, which then activates cGMP phosphodiesterase, an
enzyme that catalyzes the breakdown of cGMP to 5′-cGMP; the
reduction in cGMP closes the cGMP-gated sodium channels and reduces
the inward sodium current.
TMP14 pp. 641–642
12. A) In closed-angle glaucoma, the iridocorneal angle is completely
closed because of forward displacement of iris against the cornea,
resulting in the inability of the aqueous fluid to flow from the posterior
to the anterior chamber and then out through the trabecular meshwork.
The rapid accumulation of aqueous humor in closed-angle glaucoma
causes an acute increase in pressure and pain. Closed-angle glaucoma is
a medical emergency; blindness can occur rapidly if not treated.
TMP14 p. 637
13. F) As a person grows older, the lens grows larger and thicker and
becomes far less elastic, partly because of progressive denaturation of
the lens proteins. The ability of the lens to change shape decreases with
age. The power of accommodation decreases from about 14 diopters in a
child to less than 2 diopters by the time a person reaches 45 to 50 years
and to essentially 0 diopters at age 70 years. Thereafter, the lens remains
almost totally nonaccommodating, a condition known as presbyopia
(choice F).
TMP14 p. 631
14. E) The horizontal cells connect laterally between the synaptic bodies of
the rods and cones and also connect with the dendrites of the bipolar
cells. The outputs of the horizontal cells are always inhibitory.
Therefore, this lateral connection provides the same phenomenon of
lateral inhibition that is important in other sensory systems—that is,
helping to ensure transmission of visual paerns with proper visual
contrast.
TMP14 pp. 639, 646–647
15. B) The visual nerve signals leave the retinas through the optic nerves.
At the optic chiasm, the optic nerve fibers from the nasal halves of the
retinas cross to the opposite sides, where they join the fibers from the
opposite temporal retinas to form the optic tracts. The fibers of each
optic tract then synapse in the dorsal lateral geniculate nucleus of the
thalamus, and from there, geniculocalcarine fibers pass by way of the
optic radiation to the primary visual cortex in the calcarine fissure area
of the medial occipital lobe.
TMP14 p. 653
16. B) “Cataracts” are an especially common eye abnormality that occurs
mainly in older people. A cataract is a cloudy or opaque area or areas in
the lens. In the early stage of cataract formation, the proteins in some of
the lens fibers become denatured. Later, these same proteins coagulate
to form opaque areas in place of the normal transparent protein fibers.
When a cataract has obscured light transmission so greatly that it
seriously impairs vision, the condition can be corrected by surgical
removal of the lens. When the lens is removed, the eye loses a large
portion of its refractive power, which must be replaced by a convex
plastic lens implanted in front of the eye.
TMP14 p. 634
17. C) The accommodation mechanism—that is, the mechanism that
focuses the lens system of the eye—is controlled by the parasympathetic
nerves. Hence, accommodation is inhibited when the acetylcholine
muscarinic receptors are blocked by atropine. Stimulation of the
parasympathetic nerves also excites the pupillary sphincter muscle,
thereby decreasing the pupillary aperture; this process is called miosis.
So, when the acetylcholine receptors are blocked by atropine, pupillary
dilation occurs, a process called mydriasis.
TMP14 pp. 631, 660–661
18. B) Hyperopia, which is also known as “farsightedness,” is usually due
to either an eyeball that is too short or, occasionally, a lens system that is
too weak. In myopia, or “nearsightedness,” when the ciliary muscle is
completely relaxed, the light rays coming from distant objects are
focused in front of the retina. This condition is usually due to an eyeball
that is too long, but it also can result from too much refractive power in
the lens system of the eye.
TMP14 p. 632
19. D) High-frequency resonance of the basilar membrane occurs near the
base, where the sound waves enter the cochlea through the oval
window. However, low-frequency resonance occurs near the
helicotrema (choice D), mainly because of the less stiff fibers but also
because of increased “loading” with extra masses of fluid that must
vibrate along the cochlear tubules.
TMP14 p. 665
20. C) The refractive power of a lens (in diopters) = 1 m/focal length; if the
subject maer is in focus when a convex lens is 1 m from the subject
maer, the lens has a refractive power of 1 m/1 m = 1 diopter. Thus,
there is an inverse relationship between focal length and refractive
power; a thicker convex lens has a shorter focal length and a greater
refractive power. In this problem, the lens must be 10 cm from the
subject maer to be in focus (focal length = 100 mm); therefore, 1000
mm/100 mm = 10 diopters. Because the retina of the eye is about 17 mm
behind the lens, the refractive power of the lens of the eye is about 59
diopters.
TMP14 p. 629
21. B) The blind spot is located 15 degrees lateral to the central point of
vision. It is the location where fibers that make up the optic nerve exit
the globe of the eye. There are no photoreceptors in this location.
TMP14 p. 657
22. D) Photophobia is discomfort or pain to the eyes due to light exposure;
it is a medical condition, not a fear or phobia. The lack of melanin (black
pigment) in the irises of the eyes makes them somewhat translucent, so
they cannot block light effectively. The lack of melanin in the pigment
layer of the retina causes light to scaer inside the globe of the eye,
which decreases contrast and visual acuity.
TMP14 p. 641
23. B) The taste sensation of bier is caused by many organic substances
that contain nitrogen, as well as by alkaloids.
TMP14 p. 675
24. D) The sixth cranial nerve is also known as the abducens nerve. The
abducens nerve innervates the lateral rectus muscle, which is aached to
the lateral surface of the globe of the eye. Contraction of the lateral
rectus muscle results in movement of the eyeball laterally away from the
midline of the face in an abducting manner—thus the name abducens
nerve.
TMP14 pp. 657–658
25. D) The condition of cataracts causes the lens of the eye to become
opaque and resemble the look of water in a waterfall or rapids in a river,
thus the name, cataract. A cataract results from the progressive
coagulation of the proteins that make up the lens. One can think of this
coagulation as like the white of an egg turning opaque as it is cooked.
Heating the egg white results in coagulation of the proteins contained
within it.
TMP14 p. 634
26. D) The taste sensation of sour is proportional to the logarithm of the
hydrogen ion concentration caused by acids. The taste sensation of
sweet is caused by a long list of chemicals, including sugars, alcohols,
aldehydes, ketones, and amino acids.
TMP14 p. 675
27. B) The bier taste sense is much more sensitive than the other
sensations because it provides an important protective function against
many dangerous toxins in food.
TMP14 p. 676
28. C) The malleus is aached to the tympanic membrane, and the stapes is
aached to the oval window. The incus has articulations with both of
these bones.
TMP14 p. 663
29. E) Light passes through the eye to the retina in the posterior portion of
the eye. The most anterior layer of the retina, through which light passes
first, is the retinal ganglion layer. Light then passes through the other
cell layers of the retina until it reaches the photoreceptors in the
posterior region of the retina.
TMP14 p. 639
30. B) The axons of the ganglion cells make up the fibers of the optic nerve.
The first synapse in the visual system takes place in the lateral
geniculate nucleus. Ganglion cells aached to photoreceptors on the
temporal side of the retina project to the same-sided or ipsilateral lateral
geniculate nucleus. Fibers from the nasal side of the retina cross over to
the opposite or contralateral lateral geniculate nucleus in the optic
chiasm. The medial geniculate nucleus is a sensory relay for the
auditory system.
TMP14 p. 653
31. B) A concave lens diverges light rays; in contrast, a convex lens will
converge light rays toward each other. If a convex lens has the
appropriate curvature, parallel light rays will be bent so that all pass
through a single point, called the focal point.
TMP14 pp. 627–628
32. C) The ampulla and saccule are part of the vestibular apparatus, not the
cochlear apparatus. The cochlea has three main compartments, with
fluid movement occurring in the scala vestibuli and scala media in
response to sound vibrations. The organ of Corti is contained within the
scala media.
TMP14 p. 665
33. D) Rhodopsin is the light-sensitive chemical in rods. Scotopsin and alltrans retinal are the breakdown products of rhodopsin, which has
absorbed light energy. The all-trans retinal is converted into 11-cis
retinal, which can recombine with scotopsin to form rhodopsin.
TMP14 p. 642
34. B) Visual information from the primary visual cortex (Brodmann’s area
17) is relayed to Brodmann’s area 18 and then into other areas of the
cerebral cortex for further processing. Analysis of three-dimensional
position, gross form, and motion of objects occurs in the posterior
midtemporal area and occipitoparietal cortex. Analysis of visual detail
and color occurs in the inferior ventral and medial regions of the
occipital and temporal cortex.
TMP14 pp. 654–655
35. E) The term umami is derived from the Japanese word for savory or
delicious and is often described as similar to the taste of meat.
Glutamate is the chemical believed to elicit the umami taste sensation.
TMP14 pp. 675–676
36. E) Ganglion cells are the only cell type in the retina that have action
potentials. The axons of ganglion cells make up the optic nerve. Bipolar
cells, cones, rods, horizontal cells, and other cell types in the retina
signal information by electrotonic conduction, which allows a graded
response proportional to light intensity.
TMP14 p. 648
37. A) The receptor cells for the smell sensation are bipolar nerve cells
derived originally from the central nervous system itself.
TMP14 p. 679
38. B) In low light conditions, the level of cGMP is high. cGMP-dependent
sodium channels in the outer portions of the rods and cones allow
sodium ions to pass from the extracellular space to the intracellular
space of the photoreceptor. This passage results in a membrane potential
that is somewhat lower than the resting membrane potential of a typical
neuron. The movement of the sodium ions and resulting electrical
potential change as a result of this enhanced permeability is known as
the dark current.
TMP14 pp. 643–644
39. E) The simple cells of the primary visual cortex detect orientation of
lines and borders, whereas the complex cells detect lines oriented in the
same direction but are not position specific. That is, the line can be
displaced moderate distances laterally or vertically, and the same few
neurons will be stimulated as long as the line is the same direction.
TMP14 p. 656
40. C) In the dark state, cGMP helps maintain the open state of the sodium
channels in the outer membrane of the rod. Hydrolysis of cGMP by light
causes these sodium channels to close. Less sodium is able to enter the
rod outer segment, thus hyperpolarizing the rod.
TMP14 pp. 643–644
41. E) This woman has Meniere’s disease, which is a disorder of the inner
ear that affects hearing and balance. The disease results from excess
endolymph in the scala media and membranous labyrinth. The cause is
not known, but it appears to have a genetic component. Symptoms
include vertigo, nystagmus, low-pitched tinnitus, and sudden but
temporary hearing loss; hearing loss can become permanent. Acoustic
neuroma is a slow-growing benign tumor that develops on the auditory
nerve. An aural polyp is a growth in the auditory canal that may be
aached to the tympanic membrane, or it may grow from the middle
ear. An exostosis is the formation of new bone on the surface of an
existing bone; it sometimes occurs in the auditory canal of swimmers
after prolonged exposure to cold water and is sometimes called “surfer’s
ear.” The incus bone is anvil-shaped and is one of the three ossicles in
the middle ear.
TMP14 p. 672
42. C) Increases in both volume and pressure of endolymph in the
membranous labyrinth produce the symptoms of Meniere’s disease; the
reason for this buildup of endolymph is unknown. The membranous
labyrinth is composed mainly of the cochlea and balance organs
(semicircular canals, utricle, and saccule). Repeated rupturing and
healing of the endolymphatic sac of the membranous labyrinth can
account for the intermient symptoms of Meniere’s disease. The
endolymphatic sac is thought to regulate hydrostatic pressure of
endolymph by simple expansion or collapse; it may also have secretory
and absorption functions.
TMP14 p. 672
43. D) In myopia, the focal point of the lens system of the eye is in front of
the retina. A concave lens will diverge light rays. By placing the proper
concave lens in front of the eye, the divergence of light rays will move
the focal point from in front of the retina to a position on the retina.
TMP14 pp. 632–633
44. A) A bilateral premotor cortical region of the frontal lobes controls
voluntary fixation movements. A lesion of this region makes it difficult
for a person to “unlock” the eyes from one point of fixation and then
move them to another point.
TMP14 pp. 658–659
45. C) Concentrations that are only 10 to 50 times above threshold values
evoke maximum intensity of smell, which is in contrast to most other
sensory systems of the body, where the range of intensity discrimination
may reach 1 trillion to 1. This phenomenon can perhaps be explained by
the fact that smell is concerned more with detecting the presence or
absence of odors than with quantitative detection of their intensities.
TMP14 p. 681
46. D) Although most cells in the nervous system depolarize in response to
sodium entry, hair cells are one group of cells that depolarize in
response to potassium entry.
TMP14 p. 668
47. C) The scala media is bordered by the basilar membrane and Reissner’s
membrane and contains a tectorial membrane. The apical border of hair
cells has stereocilia that are embedded in the tectorial membrane.
TMP14 p. 667
48. B) The abducens nerve innervates the lateral rectus muscle. The
trochlear nerve innervates the superior oblique muscle. The oculomotor
nerve innervates the medial rectus, inferior oblique, superior rectus, and
inferior rectus muscles.
TMP14 pp. 657–658
49. E) Even the minutest concentration of a specific odorant initiates a
cascading effect that opens extremely large numbers of sodium
channels. This phenomenon accounts for the exquisite sensitivity of the
olfactory neurons to even the slightest amount of odorant.
TMP14 pp. 679–680
50. B) The reduction of rhodopsin and cone pigments by light reduces the
concentrations of photosensitive chemicals in rods and cones. Thus, the
sensitivity of the eye to light is correspondingly reduced. This
phenomenon is called light adaptation.
TMP14 pp. 644–645
51. A) Auditory fibers enter the cochlear nucleus. Fibers from the cochlear
nucleus pass to the inferior colliculus via the lateral lemniscus. Fibers
from the inferior colliculus travel to the medial geniculate nucleus and
from there to the primary auditory cortex.
TMP14 p. 670
52. E) The auditory system determines loudness in at least three ways.
First, the amplitude of vibration of the basilar membrane increases so
that hair cells excite nerve endings at more rapid rates. Second, more
and more hair cells on the fringes of the resonating portion of the basilar
membrane become stimulated. Third, outer hair cells become recruited
at a significant rate.
TMP14 pp. 668–669
53. C) In hyperopia, the focal point of the eye’s lens system is behind the
retina. This is usually the result of an eyeball that is too short in the
anterior to posterior direction.
TMP14 p. 632
54. A) In the situation described, the eyes fix on an object in the visual field
and remain on that object while the head is turning to the left, resulting
in eye movement to the right as the head is turned to the left. When the
object is no longer in the central field of vision, the eyes will exhibit a
quick jumping movement to the left (i.e., in the direction of the head
rotation) and fix on a new object in the visual field. This jump is called a
saccade. This process repeats until the head has turned all the way to the
left. During saccadic eye movement, vision is suppressed.
TMP14 p. 659
55. A) A newer olfactory pathway has been found that projects to the
dorsomedial thalamic nucleus and then to the orbitofrontal cortex.
However, the older olfactory pathways bypass the thalamus to reach the
cortex, in contrast to other sensory systems, which have thalamic relays.
TMP14 pp. 681–682
56. A) Ganglion cells of the retina have synaptic connections within the
lateral geniculate nucleus (LGN); from there the visual signals (action
potentials) are transmied to the primary visual cortex. Ganglion cells in
the nasal half of the retina synapse in the contralateral LGN, whereas
ganglion cells from the temporal half of the retina synapse in the
ipsilateral LGN. Decussation occurs in the optic chiasm. Postsynaptic
neurons in the LGN travel in the optic radiations and synapse in a fanshaped manner in the primary visual cortex.
TMP14 p. 653
57. C) In a normal individual, shining a light in either eye will result in
both pupils constricting due to contraction of the pupillary sphincter
muscles. In contrast, the pupillary dilator muscle dilates the pupil. The
ciliary muscle is involved in focusing the eye (accommodation).
TMP14 p. 662
58. B) This woman has Horner’s syndrome, which is not a disease but
rather a symptom of a disease or other problem. In this problem,
lacerations to the right side of the neck have damaged the sympathetic
nerves to the right eye and right side of the face. Other causes of
Horner’s syndrome include aortic dissection that compresses adjacent
tissues, carotid dissection, Pancoast lung tumor, and tuberculosis, and it
can also be congenital. Disruption of sympathetic nerves to the eye
causes ipsilateral miosis, ptosis, and dilated blood vessels in the
conjunctiva. Cone-rod dystrophy is a chronic disease in which the rods
and cones deteriorate over time. Iris heterochromia is a difference in the
color of the irises of the two eyes, which often occurs in persons with
Horner’s syndrome before the age of 2 years but not in adults, in whom
eye color has been established. Retinoblastoma is a cancer of the eye in
children. Xerophthalmia (also called dry eye syndrome) is a disease
caused by dryness of the eye.
TMP14 p. 662
59. C) Cocaine blocks the reuptake of norepinephrine, increasing its
concentration at the nerve terminal. Nor epinephrine relaxes the
pupillary dilator muscle (also called the pupillary sphincter), causing the
pupil to become larger. Failure of cocaine to cause pupillary dilation
indicates disruption of the sympathetic nerves to the pupillary dilator
muscle because norepinephrine is not being released at the nervemuscle junction. A more recent approach is to apply an α-adrenergic
agonist (such as apraclonidine) to both eyes. The pupillary dilator
muscle responds to denervation by increasing the number of its α-1
receptors. The weak α-1 adrenergic properties of apraclonidine have no
effect on the normal pupillary dilator muscle but cause extensive
dilation of the hypersensitive, denervated pupillary dilator muscle.
Thus, with application of apraclonidine, the correct answer would be C
because the right eye is denervated and thus hypersensitive to α-1
adrenergic stimulation.
TMP14 p. 662
60. C) At least eight types of neurotransmier substances have been
identified for amacrine cells. The neurotransmiers used for bipolar and
horizontal cells are unclear, but it is well established that rods and cones
release glutamate at their synapses with bipolar cells (see figure above).
TMP14 pp. 647–648
61. D) Because one eye is a lile more than 2 inches to the side of the other
eye, the images on the two retinas differ from one another. This
binocular parallax (stereopsis) allows a person with two eyes far greater
ability than a person with only one eye to judge relative distances when
objects are nearby.
TMP14 p. 635
62. A) The principal reason why the anterior surface of the cornea provides
most of the refractive power of the eye is that the refractive index of the
cornea is markedly different from that of air.
TMP14 p. 630
63. D) Intuitively, one might guess that the rod photoreceptor would have
the greatest range of spectral sensitivity. However, it is the red cone that
has the broadest spectral sensitivity, followed by the rods, the green
cones, and finally the blue cones, which have the narrowest range of
spectral sensitivity.
TMP14 pp. 645–646
64. A) Ciliary processes secrete all the aqueous humor of the intraocular
fluid at an average rate of 2 to 3 µl/min. These processes are linear folds
that project from the ciliary muscle into the space behind the iris. The
intraocular fluid flows from behind the iris through the pupil into the
anterior chamber of the eye.
TMP14 pp. 635–636
65. A) Circumvallate papillae are located in the posterior part of the
tongue, fungiform papillae in the anterior part of the tongue, and foliate
papillae on the lateral part of the tongue. The papilla of Vater empties
pancreatic secretions and bile into the duodenum.
TMP14 p. 676
66. C) The medial geniculate nucleus is the thalamic nucleus that conveys
auditory information from the brain stem to the primary auditory
cortex.
TMP14 p. 669
67. A) Taste preference, although not completely understood, is believed to
involve a central process.
TMP14 pp. 678–679
68. E) Most of the primary auditory cortex is in the temporal lobe, but the
association auditory cortices extend over much of the insular lobe and
even onto the lateral portion of the parietal lobe.
TMP14 pp. 669–670
69. B) The termination of taste fibers for all taste sensations is in the
nucleus of the solitary tract in the medulla.
TMP14 p. 678
70. B) The medial longitudinal fasciculus is a pathway for nerve fibers
entering and leaving the oculomotor, trochlear, and abducens nuclei of
the brain stem, thus allowing communication to coordinate the
contraction of the various extraocular eye muscles.
TMP14 p. 658
71. B) Intraocular fluid flows from the anterior chamber of the eye,
between the cornea and the iris through a meshwork of trabeculae into
the canal of Schlemm, which empties into extraocular aqueous veins (see
the figure above).
TMP14 pp. 635–636
72. B) Only ganglion cells have action potentials. Photoreceptors, bipolar
cells, and horizontal cells all appear to operate through graded
potentials.
TMP14 p. 648
73. D) The superior olivary nuclei (see figure on the right) receive auditory
information from both ears and begin the process of detecting the
direction from which a sound comes. The lateral part of the superior
olivary nucleus does so by comparing the difference in intensities of
sound reaching the two ears, whereas the medial part of the superior
olivary nucleus detects time lag between signals entering both ears.
TMP14 pp. 669–670
Auditory nervous pathways. N., Nerve.
74. D) The outputs of horizontal cells are always inhibitory; their lateral
connections with synaptic bodies of photoreceptors (rods and cones)
and dendrites of bipolar cells provide lateral inhibition to ensure
transmission of visual paerns with proper visual contrast. Lateral
inhibition is critical in all sensory systems to sharpen the sensory
signals. There are many types of amacrine cells with at least six types of
functions; they transmit signals both horizontally and vertically,
forming connections with many different cell types. Bipolar cells
transmit signals vertically from photoreceptors and horizontal cells to
ganglion cells and amacrine cells in the inner plexiform layer of the
retina. Ganglion cells transmit output signals from the retina through
the optic nerve to the brain.
TMP14 p. 648
75. B) Foliate papillae are located in the folds along the lateral surfaces of
the tongue, fungiform papillae are located in the anterior part of the
tongue, and circumvallate papillae are located in the posterior part of
the tongue. The papilla of Vater empties pancreatic secretions and bile
into the duodenum.
TMP14 pp. 669–670
Unit XI: The Nervous System
C. Motor and Integrative Neurophysiology
1. Which of the following best describes anterior motor neurons and
their innervation targets?
A) Alpha-extrafusal fibers; gamma-intrafusal fibers
B) Alpha-intrafusal fibers; gamma-extrafusal fibers
C) Alpha-extrafusal fibers; gamma-extrafusal fibers
D) Alpha-intrafusal fibers; gamma-intrafusal fibers
2. Which of the following best describes the transmier released from
Renshaw cells and the primary action of Renshaw cells under
normal physiological conditions?
A) Glycine—inhibitory
B) Glycine—excitatory
C) Acetylcholine—inhibitory
D) Acetylcholine—excitatory
E) Strychnine—excitatory
F) Strychnine—inhibitory
3. Which of the following best describes the reflex arc and muscle
response of the Golgi tendon organ?
A) Monosynaptic reflex arc; relaxation of muscle
B) Monosynaptic reflex arc; contraction of muscle
C) Disynaptic reflex arc; relaxation of muscle
D) Disynaptic reflex arc; contraction of muscle
E) Polysynaptic reflex arc; relaxation of muscle
F) Polysynaptic reflex arc; contraction of muscle
4. Which of the following best describes the sensory capabilities of the
muscle spindle under normal physiological conditions?
A) Length only
B) Tension only
C) Rate of change in length only
D) Length and tension only
E) Length and rate of change in length
F) Tension and rate of change in length
5. Which of the following types of muscle fibers is responsible for the
dynamic response in a muscle spindle receptor?
A) Extrafusal muscle fiber
B) Static nuclear bag fiber
C) Nuclear chain fiber
D) Nuclear bag fiber
E) Static nuclear chain fiber
6. Which of the following best describes the type of reflex arc and
sensory receptor for the flexor withdrawal reflex?
A) Reflex arc: disynaptic sensory receptor: Pacinian corpuscle
B) Reflex arc: disynaptic sensory receptor: nociceptor
C) Reflex arc: monosynaptic sensory receptor: Pacinian corpuscle
D) Reflex arc: monosynaptic sensory receptor: Golgi tendon
organ
E) Reflex arc: polysynaptic sensory receptor: nociceptor
F) Reflex arc: polysynaptic sensory receptor: muscle spindle
7. Which of the following has the greatest area of representation in the
primary motor cortex?
A) Hip
B) Knee
C) Thumb
D) Toes
E) Trunk
8. Afferent signals from the periphery of the body travel to the
cerebellum in which of the following nerve tracts?
A) Ventral spinocerebellar tract
B) Fastigioreticular tract
C) Vestibulocerebellar tract
D) Reticulocerebellar tract
9. Neurologic disease associated with the cerebellum produces which
of the following types of symptoms?
A) Resting tremor only
B) Athetosis and resting tremor
C) Rigidity and resting tremor
D) Ataxia and dysmetria
10. Which of the following best describes the Purkinje cell input to the
deep nuclear cells of the cerebellum?
A) Always stimulatory
B) Always inhibitory
y y
C) Stimulatory only if it originates from inferior olivary complex
D) Stimulatory only if it originates from mossy fibers
11. Neurologic disease associated with the globus pallidus produces
which of the following symptoms?
A) Rigidity
B) Chorea
C) Hemiballismus
D) Athetosis
12. All the following structures are part of the basal ganglia EXCEPT
one. Which one is this EXCEPTION?
A) Caudate nucleus
B) Red nucleus
C) Substantia nigra
D) Putamen
13. Hemiballismus is associated with damage or dysfunction of which
of the following structures?
A) Thalamus
B) Caudate nucleus
C) Subthalamus
D) Red nucleus
14. Retrograde amnesia is usually the result of damage to, or
dysfunction of which of the following structures?
A) Hippocampus
B) Subthalamus
C) Hypothalamus
D) Thalamus
15. Damage to Broca’s area on the dominant side of the brain results in
which of the following neurologic symptoms?
A) Anterograde amnesia
B) Intension tremor
C) Ataxia
D) Motor aphasia
16. Which of the following structures provides the connection between
Wernicke’s area and Broca’s area in the cerebral cortex?
A) Medial lemniscus
B) Medial forebrain bundle
C) Corpus callosum
D) Arcuate fasciculus
17. Weak stimulation of which area in the brain gives an animal a
sense of reward?
A) Amygdala
B) Dorsal raphe nucleus
C) Periaqueductal gray region
D) Tissue surrounding medial forebrain bundle
18. The neurons located in the substantia nigra release which of the
following neurotransmiers?
A) Norepinephrine
B) Serotonin
C) Dopamine
D) Acetylcholine
19. Which of the following statements best describes the changes in
sleep paerns that occur during the aging process from childhood
to old age?
A) Amount of time spent in stage 4 sleep increases
B) Amount of time spent in REM sleep increases
C) Amount of time one could record delta waves in an EEG
during sleep decreases
D) Incidence of nocturnal awakenings decrease
20. An excess of which of the following neurotransmiers is most
likely to cause mania?
A) Dopamine
B) Serotonin
C) GABA
D) Acetylcholine
21. Which of the following structures is innervated almost entirely by
the sympathetic division but not the parasympathetic division of
the autonomic nervous system?
A) Blood vessels
B) Gastrointestinal tract
C) Heart
D) Reproductive organs
E) Urinary bladder
22. Which of the following type of autonomic stimulation is correctly
paired with its function?
A) Sympathetic stimulation–ejaculation
B) Sympathetic stimulation–blood vessel dilation
C) Sympathetic stimulation–pupillary constriction
y p p p y
D) Parasympathetic stimulation–increased heart rate
E) Parasympathetic stimulation–constriction of coronary artery
F) Parasympathetic stimulation–dilation of bronchi
23. Selective destruction of the right superior cervical ganglion would
most likely result in which of the following?
A) Dilated pupil in right eye
B) Dilated pupil in left eye
C) Constricted pupil in left eye
D) Constricted pupil in right eye
24. Which of the following best describes the neurotransmier in both
sympathetic and parasympathetic autonomic ganglia?
A) Acetylcholine
B) Norepinephrine
C) Epinephrine
D) Dopamine
25. Physiological studies are conducted in mice to find new ways to
facilitate entry of methotrexate into brain tissues for tumor control.
Mice are infused with hypertonic mannitol via the internal carotid
artery at various rates. The optimal rate of mannitol infusion that
produced temporary blood-brain barrier disruption without
neurological sequelae was 0.25 ml.s-1.kg-1 for 20 s. The duration of
blood-brain barrier disruption was maximal for approximately 5
min and then rapidly reversed. Methotrexate levels in brain tissues
were four to five times higher in the mannitol-infused brains
compared with brain tissues of saline control mice. Which of the
following is the most likely effect of the optimal mannitol infusion
regimen on endothelial cell volume and brain capillary
permeability in this experiment?
A) Decreased endothelial cell volume; decreased capillary
permeability
B) Decreased endothelial cell volume; increased capillary
permeability
C) Decreased endothelial cell volume; no change in capillary
permeability
D) Increased endothelial cell volume; decreased capillary
permeability
E) Increased endothelial cell volume; increased capillary
permeability
F) Increased endothelial cell volume; no change in capillary
permeability
26. A 46-year-old man is admied to the emergency department after
falling off his porch and hiing his head on a cement step. His
Glasgow Coma Scale score is 10. The patient is intubated, and a CT
scan shows a large subdural hematoma. He has bilateral
papilledema. Which of the following best describes the most likely
intracranial pressure (ICP), brain capillary pressure (Pc), and
intracranial venous volume (ICVV) in this patient during a positive
feedback cycle involving all three variables?
A) Decreased ICP, decreased Pc, decreased ICVV
B) Decreased ICP, decreased Pc, increased ICVV
C) Decreased ICP, increased Pc, decreased ICVV
D) Decreased ICP, increased Pc, increased ICVV
E) Increased ICP, decreased Pc, decreased ICVV
F). Increased ICP, decreased Pc, increased ICVV
G) Increased ICP, increased Pc, decreased ICVV
H) Increased ICP, increased Pc, increased ICVV
27. Which of the following best describes brain blood flow at mean
arterial pressure levels between 140 mm Hg and 180 mm Hg in a
normotensive person?
A) Varies with level of arterial pressure
B) Constant and not dependent on pressure
C) Independent of arterial pressure
D) Inversely proportional to arterial pressure
28. Which of the following best describes the total volume of
cerebrospinal fluid in an adult human nervous system (in
milliliters)?
A) 150
B) 500
C) 50
D) 300
29. An increase in which of the following has a direct action to increase
cerebral blood flow?
A) Arterial carbon dioxide levels
B) Arterial hydrogen ion concentration
C) Brain interstitial carbon dioxide levels
D) Brain interstitial hydrogen ion concentration
30. Most strokes in the United States can be aributed to which of the
following?
A) Hemorrhage due to arterial rupture
B) Hemorrhage due to venular trauma
C) Ischemia due to systemic hypotension
D) Ischemia due to thromboembolism
31. Which of the following best describes the rate of formation of
cerebrospinal fluid in a normal adult human being (in milliliters
per day)?
A) 50
B) 100
C) 300
D) 500
E) 1000
32. A 98-year-old woman has a stroke that severely impairs her
speech. Which area of her brain is most likely damaged?
A) Primary motor cortex
B) Premotor area
C) Broca’s area
D) Cerebellum
33. A 23-year-old woman sustains serious head and neck trauma in a
motorcycle accident. Physical examination shows a positive
Babinski sign. What part of the brain has most likely been
damaged in this woman?
A) Anterior motor neurons
B) Cerebellum
C) Corticospinal tract
D) Premotor cortex
34. Which statement best describes a functional role for the lateral
hemispheres of the cerebellum?
A) Control and coordinate movements of axial muscles, as well
as shoulder and hip
B) Control movements that involve distal limb musculature
C) Function with cerebral cortex to plan movements
D) Stimulate motor neurons through their connections to spinal
cord
35. Which of the following would produce an increase in cerebral
blood flow?
A) Increase in carbon dioxide tension
B) Increase in oxygen tension
C) Decrease in the activity of cerebral cortex neurons
D) Decrease in carbon dioxide tension
E) Decrease in arterial blood pressure from 120 mm Hg to 90
mm Hg
36. As the axons of motor neurons leave the spinal cord and course
peripherally to skeletal muscle, they must pass through which
structure?
A) Posterior column
B) Posterior root
C) Ventral white commissure
D) Posterior horn
E) Anterior root
37. Which spinal cord level contains the entire population of
preganglionic sympathetic neurons?
A) C5–T1
B) C3–C5
C) S2–S4
D) T1–L2
E) T6–L1
Questions 38 and 39
A left-side subdural hematoma develops in a 23-year-old man after an
automobile accident. Physical examination shows papilledema 3 days after
the accident. Use this information to answer the next two questions.
38. Which of the following is most likely to be increased in this
patient?
A) Cerebral blood flow
B) Cerebrospinal fluid production
C) Cerebrospinal fluid volume
D) Intracranial pressure
E) Intracranial venous volume
39. Collapse of which of the following structures is most likely to lead
to a decrease in brain oxygenation in this patient?
A) Arteries
B) Capillaries
C) Lateral ventricles
D) Subarachnoid space
E) Veins
40. Preganglionic sympathetic axons pass through which of the
following structures?
A) Dorsal root
B) Dorsal primary rami
C) White rami
D) Gray rami
E) Ventral primary rami
41. The gigantocellular neurons of the reticular formation release
which neurotransmier?
A) Norepinephrine
B) Serotonin
C) Dopamine
D) Acetylcholine
E) Glutamate
42. Astrocytes participating in the metabolic control of cerebral blood
flow have the following three events associated with the process:
(1) prostaglandin release, (2) a calcium wave, and (3) glutamate
spillover. Which sequence best describes the correct temporal order
of these three events?
A) 2, 1, 3
B) 1, 2, 3
C) 3, 1, 2
D) 1, 3, 2
E) 3, 2, 1
F) 2, 3, 1
43. A 15-year-old girl is taken to see a physician because of a sore
throat. An antibiotic is prescribed that can enter most tissues of the
body but cannot penetrate the blood-brain barrier. The blood-brain
barrier can be aributed primarily to which cell type?
A) Astrocyte
B) Endothelial cell
C) Glial cell
D) Macrophage
E) Pericyte
F) Smooth muscle cell
44. In which type of neuron does the axon form synaptic junctions
with skeletal muscle cells (intrafusal fibers) within the muscle
spindles?
p
A) Alpha motor neuron
B) Pyramidal neuron
C) Gamma motor neuron
D) Granule cell
E) Purkinje cell
45. Which projection system is contained in the superior cerebellar
peduncle?
A) Pontocerebellar
B) Cerebellothalamic
C) Posterior spinocerebellar
D) Corticospinal
Questions 46 and 47
A 54-year-old man steps on a broken bole with his bare right foot. His
right leg immediately lifts while his left leg extends before he can
consciously react to the pain. Use this information to answer the next two
questions.
46. This action is aributable to which reflex?
A) Walking reflex
B) Stretch reflex
C) Patellar tendon reflex
D) Golgi tendon reflex
E) Flexor withdrawal reflex
47. Which of the following best describes the type of reflex arc and
sensory receptor for this reflex?
Reflex Arc Sensory Receptor
A) Disynaptic Pacinian corpuscle
B) Disynaptic Nociceptor
C) Monosynaptic Pacinian corpuscle
D) Monosynaptic Golgi tendon organ
E) Polysynaptic Nociceptor
F) Polysynaptic Muscle spindle
48. Which brain structure serves as the major controller of the limbic
system?
A) Hypothalamus
B) Hippocampus
C) Amygdala
D) Mammillary body
E) Fornix
49. A large portion of the cerebral cortex does not fit into the
conventional definition of motor or sensory cortex. Which term
refers to the type of cortex that receives input primarily from
several other regions of the cerebral cortex?
A) Cortex that is agranular
B) Secondary somatosensory cortex
C) Association cortex
D) Supplementary motor cortex
E) Secondary visual cortex
50. The two hemispheres of the brain are connected by which nerve
fibers or pathways?
A) Lateral lemniscus
B) Corticofugal fibers
C) Corpus callosum
D) Arcuate fasciculus
E) Medial longitudinal fasciculus
51. The fibers of the corticospinal tract pass through which structure?
A) Medial lemniscus
B) Medullary pyramid
C) Posterior funiculus
D) Medial longitudinal fasciculus
E) Anterior roots
52. The condition of prosopagnosia usually results from dysfunction
or damage to which area of the cerebral cortex?
A) Prefrontal area
B) Junction of the parietal and temporal lobe on the
nondominant side of the brain
C) Frontal eye fields
D) Underside of the medial occipital and temporal lobes
E) Limbic association areas of frontal and anterior temporal lobes
53. Lesions of which area of the brain would have the most
devastating effect on verbal and symbolic intelligence?
A) Hippocampus
B) Amygdala
yg
C) Wernicke’s area on the nondominant side of brain
D) Broca’s area
E) Wernicke’s area on the dominant side of brain
54. A stroke involving the middle cerebral artery on the left side is
likely to cause which symptom?
A) Paralysis of the left side of the face and left upper extremity
B) Paralysis of left lower extremity
C) Complete loss of vision in both eyes
D) Loss of ability to comprehend speech
E) Loss of vision in the left half of both eyes
55. The creation of memory can be interrupted by which activity?
A) Phosphorylation of a potassium channel to block activity
B) Activation of adenylate cyclase
C) Unnatural loss of consciousness
D) Increase in protein synthesis
E) Activation of cyclic guanosine monophosphate (cGMP)
phosphodiesterase
56. Which of the following structures is innervated almost entirely by
the sympathetic division but not the parasympathetic division of
the autonomic nervous system?
A) Blood vessels
B) Gastrointestinal tract
C) Heart
D) Lungs
E) Urinary bladder
57. Which projection system is contained in the inferior cerebellar
peduncle?
A) Pontocerebellar
B) Cerebellothalamic
C) Posterior spinocerebellar
D) Corticospinal
E) Dorsospinocerebellar
58. Signals from motor areas of the cortex reach the contralateral
cerebellum after first passing through which structure?
A) Thalamus
B) Caudate nucleus
C) Red nucleus
D) Basilar pontine nuclei
E) Dorsal column nuclei
59. Cerebrospinal fluid (CSF) provides a cushioning effect both inside
and outside the brain. Which space that lies outside the brain or
spinal cord contains CSF?
A) Lateral ventricle
B) Third ventricle
C) Cisterna magna
D) Epidural space
E) Aqueduct of Sylvius
Questions 60 and 61
A 34-year-old woman visits the physician because of uncontrolled
movements of her arms, legs, head, face, and upper body. These
symptoms have increased progressively during the past 12 months. She is
also depressed and irritable, and she repeats the same question six times
during the 30-minute office visit. Gene analyses show expansion of a CAG
triplet repeat on chromosome 4. Use this information to answer the next
two questions.
60. Which diagnosis is most likely?
A) Alzheimer disease
B) Bipolar disorder
C) Brain tumor
D) Huntington’s disease
E) Parkinson’s disease
61. Which of the following is most likely to be decreased in this
woman?
A) Acetylcholine neurons in the magnocellular forebrain nucleus
B) Dopamine neurons in the substantia nigra
C) γ-Aminobutyric acid (GABA) neurons in the caudate nucleus
and putamen
D) Serotonin neurons in the raphe nuclei
62. Which projection system is contained in the middle cerebellar
peduncle?
A) Pontocerebellar
B) Cerebellothalamic
C) Posterior spinocerebellar
D) Corticospinal
E) Ventrospinocerebellar
63. The peripheral sensory input that activates the ascending
excitatory elements of the reticular formation comes mainly from
which of the following?
A) Pain signals
B) Proprioceptive sensory information
C) Corticospinal system
D) Medial lemniscus
E) Input from Pacinian corpuscles
64. Cells of the adrenal medulla receive synaptic input from which
type of neuron?
A) Preganglionic sympathetic
B) Postganglionic sympathetic
C) Preganglionic parasympathetic
D) Postsynaptic parasympathetic
E) Presynaptic parasympathetic
65. Which activity will increase the sensitivity of the stretch reflex?
A) Cuing the dorsal root fibers associated with the muscle in
which the stretch reflex is being examined
B) Increasing the activity of the medullary reticular nuclei
C) Bending the head forward
D) Enhanced activity in the fusimotor (gamma motor neuron)
system
E) Stimulating the lateral hemispheres of the cerebellum
66. A complex spike paern in the Purkinje cells of the cerebellum can
be initiated by stimulation of which brain area?
A) Inferior olivary complex
B) Brain stem reticular nuclei
C) Neurons in red nucleus
D) Superior olivary complex
E) Dorsal vestibular nucleus
67. Which structure serves as an “alternative pathway” for signals
from the motor cortex to the spinal cord?
A) Red nucleus
B) Basilar pontine nuclei
C) Caudate nucleus
D) Thalamus
E) Dorsal column nuclei
68. The phenomenon of decerebrate rigidity can be explained, at least
in part, by which of the following?
p y g
A) Stimulation of type 1b sensory neurons
B) Loss of cerebellar inputs to the red nucleus
C) Overactivity of the medullary reticular nuclei involved in
motor control
D) Unopposed activity of the pontine reticular nuclei
E) Degeneration of the nigrostriatal pathway
69. The primary motor cortex is organized into vertical columns
composed of cells linked together throughout the six layers of the
cortex. The cells that contribute axons to the corticospinal tract are
concentrated in which cortical layer?
A) Layer I
B) Layer II
C) Layer III
D) Layer IV
E) Layer V
Questions 70 and 71
A 77-year-old man is taken to the physician because of a tremor in his
hands, trouble sleeping, constipation, and dizziness. Physical examination
shows a resting tremor, rigidity, and bradykinesia. The man is alert,
engaging, and optimistic. He speaks in a low, soft voice. Use this
information to answer the next two questions.
70. Which diagnosis is most likely?
A) Alzheimer disease
B) Bipolar disorder
C) Brain tumor
D) Huntington’s disease
E) Parkinson’s disease
71. Which of the following is most likely to be decreased in this man?
A) Serotonin neurons in the raphe nuclei
B) GABA neurons in the caudate nucleus and putamen
C) Dopamine neurons in the substantia nigra
D) Acetylcholine neurons in the magnocellular forebrain nucleus
72. Motor cortex neurons receive feedback from muscles activated by
the corticospinal system. This feedback arises from which of the
following structures?
A) Red nucleus
B) Spinocerebellar tracts
C) Skin surface of fingers used to grasp an object
D) Muscle spindles in muscles antagonistic to those used to
make the movement
E) Vestibular nuclei
73. The sweat glands and piloerector muscles of hairy skin are
innervated by which type of fibers?
A) Cholinergic postganglionic parasympathetic
B) Cholinergic postganglionic sympathetic
C) Adrenergic preganglionic parasympathetic
D) Adrenergic postganglionic sympathetic
E) Adrenergic preganglionic sympathetic
74. In a neurophysiology experiment conducted with monkeys, the
amygdalae are surgically ablated bilaterally. Which of the
following is most likely to be increased 6 months after ablation of
the amygdala?
A) Despondence
B) Memory
C) Paranoia
D) Sex drive
E) Tremors
75. In controlling the fine muscles of the hands and fingers,
corticospinal axons can synapse primarily with which of the
following?
A) Posterior horn neurons
B) Spinal cord interneurons
C) Spinal cord motor neurons
D) Purkinje cells
E) Renshaw cells
76. Which of the following foramina allows cerebrospinal fluid to pass
directly from the ventricular system into the subarachnoid space?
A) Foramen of Magendie
B) Aqueduct of Sylvius
C) Third ventricle
D) Lateral ventricle
E) Arachnoid villi
77. Which epileptic condition involves a postictal depression period
lasting from several minutes to several hours?
A) Generalized tonic-clonic seizure
B) Absence seizure
C) Jacksonian seizure
D) Phase-out clonic seizure
E) Temporal lobe seizure
78. Which cells receive direct synaptic input from Golgi tendon
organs?
A) Type Ia inhibitory interneurons
B) Dynamic gamma motor neurons
C) Alpha motor neurons
D) Type Ib inhibitory interneurons
E) Type II excitatory interneurons
79. Which neurotransmier is used by the axons of locus coeruleus
neurons that distribute throughout much of the brain?
A) Norepinephrine
B) Dopamine
C) Serotonin
D) Acetylcholine
Questions 80 and 81
A 41-year-old woman visits the physician because of difficulties
performing simple tasks that involve repetitive movements. The physician
asks the patient to turn one hand upward and downward at a rapid pace.
The woman quickly loses all perception of the instantaneous position of
the hand, which results in a series of stalled aempts and jumbled
movements. Use this information to answer the next two questions.
80. Which term best describes this patient’s movements?
A) Agraphesthesia
B) Astereognosis
C) Dysarthria
D) Dysdiadochokinesia
E) Hemineglect
81. Which area of her brain is most likely to have a lesion?
A) Cerebellum
B) Limbic system
C) Medulla oblongata
D) Premotor cortex
E) Primary motor cortex
82. The excitatory or inhibitory effect of a postganglionic sympathetic
fiber is determined by which feature or structure?
A) Function of the postsynaptic receptor to which it binds
B) Specific organ innervated
C) Ganglion where the postganglionic fiber originates
D) Ganglion containing the preganglionic fiber
E) Emotional state of the individual
83. A vascular lesion that causes degeneration of corticospinal axons
in the basilar pons will most likely lead to which condition?
A) Paralysis primarily involving muscles around the
contralateral shoulder and hip joints
B) Paralysis of the muscles of mastication
C) Loss of voluntary control of discrete movements of the
contralateral hand and fingers
D) Inability to speak clearly
E) Inability to convert short-term memory to long-term memory
84. Fine-motor movement of the middle finger can be elicited by
stimulation of which brain area?
A) Primary motor cortex
B) Lateral cerebellar hemisphere
C) Premotor cortex
D) Supplemental motor area
E) Red nucleus
85. Which type of cholinergic receptor is found at synapses between
preganglionic and postganglionic neurons of the sympathetic
system?
A) Muscarinic
B) Nicotinic
C) Alpha
D) Beta-1
E) Beta-2
86. A 32-year-old basketball player mentally rehearses free throw
shots while lying in bed. Which option best describes the area of
the brain that is involved in generating a motor image of this action
in the absence of actual movement?
A) Basal ganglia
B) Cerebellum
C) Limbic system
D) Premotor cortex
E) Primary motor cortex
87. The formation of cerebrospinal fluid by the choroid plexus
includes (1) osmosis of water, (2) active transport of sodium, and
(3) passive diffusion of chloride. Which sequence best describes the
correct temporal order of these processes?
A) 2, 3, 1
B) 3, 2, 1
C) 1, 3, 2
D) 3, 1, 2
E) 1, 2, 3
F) 2, 1, 3
Questions 88 and 89
A 12-year-old boy is taken to the physician because of difficulty walking.
Physical examination shows loss of tendon reflexes in the knees and ankles
and reduced two-point discrimination in the hands and feet. Repeat visits
to the physician show a progressive worsening of these symptoms during
the next 2 years. However, the boy is always alert and seems to have
normal reasoning abilities. His aunt had similar problems at age 12 years
and later developed scoliosis followed by loss of hearing and vision. Use
this information to answer the next two questions.
88. What is the most likely diagnosis?
A) Friedreich ataxia
B) Huntington disease
C) Multiple sclerosis
D) Parkinson’s disease
E) Poliomyelitis
89. What is the most likely cause of these symptoms in this boy?
A) A lesion in the premotor cortex
B) A lesion in the primary motor cortex
C) Malformation of the cerebellum
D) Malformation of the frontal lobe
E) Nerve degeneration
F) Nerve proliferation
90. Which neurotransmier is used by the axons of substantia nigra
neurons that project to the caudate and putamen?
A) Norepinephrine
B) Dopamine
C) Serotonin
D) Acetylcholine
E) GABA
91. Damage limited to the primary motor cortex (Brodmann area 4) is
thought to cause hypotonia in the affected muscles. However, most
cortical lesions, particularly those caused by vascular infarcts,
generally involve the primary motor cortex in addition to
surrounding areas of cortex or cortical efferent axons. The laer
type of cortical lesion will cause which of the following?
A) Spastic muscle paralysis
B) Flaccid muscle paralysis
C) No paralysis; only jerky, fast movements
D) Complete blindness in the contralateral eye
E) Loss of sensation in the contralateral foot
92. Which substance activates adrenergic alpha and beta receptors
equally well?
A) Acetylcholine
B) Norepinephrine
C) Epinephrine
D) Serotonin
E) Dopamine
93. The posterior and lateral hypothalamus, in combination with the
preoptic area, are involved in the control of which of the following
functions?
A) Cardiovascular functions involving blood pressure and heart
rate
B) Regulation of thirst and water intake
C) Stimulation of uterine contractility and milk ejection from the
breast
D) Signaling that food intake is sufficient (satiety)
E) Secretion of hormones from the anterior lobe of the pituitary
gland
94. In the patellar tendon reflex, which of the following items
synapses directly on alpha motor neurons that innervate the
muscle being stretched?
A) Ia sensory fiber
B) Ib sensory fiber
C) Excitatory interneurons
D) Gamma motor neurons
E) Inhibitory interneurons
y
95. Occlusion of which structure would lead to communicating
hydrocephalus?
A) Aqueduct of Sylvius
B) Lateral ventricle
C) Foramen of Luschka
D) Foramen of Magendie
E) Arachnoid villi
96. Evaluation of a patient reveals the following deficits: (1) decreased
aggressiveness, and ambition and inappropriate social responses,
(2) inability to process sequential thoughts in order to solve a
problem, and (3) inability to process multiple bits of information
that could then be recalled instantaneously to complete a thought
or solve a problem. Damage to which brain region could be
responsible for such deficits?
A) Premotor cortex
B) Parieto-occipital cortex in the nondominant hemisphere
C) Broca’s area
D) Limbic association cortex
E) Prefrontal association cortex
97. A 23-year-old woman is a right-handed musician of considerable
talent. Which brain structure is most likely to have been physically
larger in the dominant hemisphere compared with the
nondominant hemisphere at birth?
A) Anterior temporal lobe
B) Posterior temporal lobe
C) Premotor cortex
D) Primary motor cortex
E) Primary somatosensory area
F) Sensory association area
98. The neurons located in the locus coeruleus release which
neurotransmier at their synaptic terminals?
A) Norepinephrine
B) Dopamine
C) GABA
D) Acetylcholine
E) Serotonin
99. Which portion of the cerebellum functions in the planning of
sequential movement?
A) Vermis and fastigial nucleus
g
B) Intermediate zone and fastigial nucleus
C) Lateral hemisphere and interposed nucleus
D) Cerebrocerebellum and dentate nucleus
E) Spinocerebellum and interposed nucleus
100. Which reflex is correctly paired with the sensory structure that
mediates the reflex?
A) Autogenic inhibition—muscle spindle
B) Reciprocal inhibition—Golgi tendon organ
C) Reciprocal inhibition—Pacinian corpuscle
D) Stretch reflex—muscle spindle
E) Golgi tendon reflex—Meissner corpuscle
101. Damage to which brain area leads to the inability to comprehend
the wrien or the spoken word?
A) Insular cortex on dominant side of brain
B) Anterior occipital lobe
C) Junction of parietal, temporal, and occipital lobes
D) Medial portion of precentral gyrus
E) Most anterior portion of temporal lobe
102. A computed tomography scan of a newborn boy shows agenesis
of the corpus callosum. Which of the following is most likely to
occur in this child during the next 5 years as he matures?
A) Inability to form new memories
B) Inability to understand spoken words
C) Inability to verbally express words
D) Reduction in communication between the two hemispheres
E) Tameness and inability to recognize expressions of fear
103. A 32-year-old man has a stroke. One week later, he experiences
sudden and uncontrolled flailing, ballistic movements of his limbs.
Which part of the man’s brain is most likely to have been damaged
by the stroke?
A) Globus pallidus
B) Lateral hypothalamus
C) Red nucleus
D) Subthalamic nucleus
E) Ventrobasal complex of thalamus
104. In an otherwise normal person, dysfunction of which brain area
will lead to behavior that is not appropriate for the given social
occasion?
A) Ventromedial nuclei of hypothalamus
yp
B) Amygdala
C) Corpus callosum
D) Fornix
E) Uncus
105. Schizophrenia is thought to be caused in part by excessive
production and release of which of the following
neurotransmiers?
A) Norepinephrine
B) Serotonin
C) Acetylcholine
D) Substance P
E) Dopamine
106. Stimulation of which subcortical area can lead to contraction of a
single muscle or small groups of muscles?
A) Dentate nucleus of the cerebellum
B) Ventrobasal complex of the thalamus
C) Red nucleus
D) Subthalamic nucleus
E) Nucleus accumbens
107. Bilateral lesions involving the ventromedial hypothalamus is
most likely to cause which of the following deficits?
A) Decreased eating and drinking
B) Loss of sexual drive
C) Excessive eating, rage and aggression, hyperactivity
D) Uterine contractility, mammary gland enlargement
E) Obsessive compulsive disorder
108. Which of the following cerebellar structures has a topographical
representation of the body?
A) Dentate nucleus
B) Lateral hemispheres
C) Flocculonodular lobe
D) Vermis and intermediate hemisphere
E) Cerebellar peduncle
109. Which structure is an important pathway for communication
between the limbic system and the brain stem?
A) Mammillothalamic tract
B) Fornix
C) Anterior commissure
D) Indusium griseum
g
E) Medial forebrain bundle
110. A 77-year-old man is taken to the physician because of worsening
forgetfulness. He recently got lost during a walk in the
neighborhood where he has lived in for 35 years. Which substance
is most likely to be increased in the brain of this man?
A) Alpha-1 antitrypsin
B) Alpha-amylase
C) Beta-amyloid peptide
D) Beta-endorphin
E) Gamma-glutamyl hydrolase
F) Gamma-glutamyl transferase
111. Which of the following best describes the cerebellar deficit in
which there is a failure to perform rapid alternating movements
indicating a failure of “progression” from one part of the
movement to the next?
A) Past-pointing
B) Intention tremor
C) Dysarthria
D) Cerebellar nystagmus
E) Dysdiadochokinesia
112. Which structure in the vestibular apparatus is responsible for the
detection of angular acceleration?
A) Statoconia
B) Macula
C) Semicircular canals
D) Saccule
E) Ampullae
Questions 113 and 114
A 55-year-old man is taken to the psychiatrist because of delusional
behavior in the workplace. The man accused a coworker of scheming with
his neighbor to transplant poison ivy in his backyard. This plot was
revealed to the man by a voice in his head. Other examples of delusional
thinking and voices in the man’s head are abundant. Use this information
to answer the next two questions.
113. What is the most likely diagnosis?
A) Bipolar disorder
B) Dissociative identity disorder
C) Multiple personality disorder
D) Schizophrenia
114. A decrease in size of which brain structure is most likely in this
man?
A) Globus pallidus
B) Hippocampus
C) Lateral hypothalamus
D) Red nucleus
E) Subthalamic nucleus
115. Which structure is maximally sensitive to linear head movement
in the vertical plane?
A) Macula of the utricle
B) Macula of the saccule
C) Crista ampullaris of the anterior semicircular duct
D) Crista ampullaris of the horizontal semicircular duct
116. Retrograde amnesia is the inability to recall long-term memories.
Damage to which brain region leads to retrograde amnesia?
A) Hippocampus
B) Dentate gyrus
C) Amygdaloid complex
D) Thalamus
E) Mammillary nuclei of hypothalamus
117. Which component of the basal ganglia plays a major role in the
control of cognitive (memory-guided) motor activity?
A) Globus pallidus
B) Substantia nigra
C) Caudate nucleus
D) Putamen
E) Subthalamic nucleus
118. A 9-month-old boy is brought to the emergency department
because of irritability and vomiting. Magnetic resonance imaging
shows retinal hemorrhages in both eyes, a subdural hematoma,
and cerebral edema. Which of the following is most likely to be
increased in this infant?
A) Brain oxygenation
B) Cerebral venous volume
C) Intracranial pressure
D) Visual acuity
119. Stimulation of the punishment center can inhibit the reward
center, demonstrating that fear and punishment can take
precedence over pleasure and reward. Which of the following cell
groups is considered the punishment center?
A) Lateral and ventromedial hypothalamic nuclei
B) Periventricular hypothalamus and midbrain central gray area
C) Supraoptic nuclei of hypothalamus
D) Anterior hypothalamic nucleus
120. Although the sympathetic nervous system is often activated in
such a way that it leads to mass activation of sympathetic
responses throughout the body, it can also be activated or inhibited
to produce relatively discrete responses. Which option is an
example of a local or discrete sympathetic action?
A) Heating of a patch of skin causes a relatively restricted
vasodilation in the heated region
B) Food in the mouth causes salivation
C) Emptying of the bladder may cause reflexive emptying of the
bowel
D) Dust particles in the eye cause increased tear fluid release
E) Bright light introduced into one eye
121. An experimental drug is administered intravenously to six
healthy volunteers. A unanimous finding in all six volunteers is
decreased induction of sleep. A decrease in production of which
substance is most likely in these volunteers after treatment with the
experimental drug?
A) Acetylcholine
B) Dopamine
C) Glutamate
D) Norepinephrine
E) Serotonin
122. A 10-year-old boy jumps off the porch and lands on the balls of
his feet. The increase in muscle tension causes a sudden, complete
relaxation of the affected muscles. Which sensory receptor is most
likely to mediate this relaxation of muscles when tension is
increased?
A) Free nerve ending
B) Golgi tendon organ
C) Krause corpuscle
D) Muscle spindle
p
E) Pacinian corpuscle
123. A wide variety of neurotransmiers have been identified in the
cell bodies and afferent synaptic terminals in the basal ganglia. A
deficiency of which transmier is typically associated with
Parkinson’s disease?
A) Norepinephrine
B) Dopamine
C) Serotonin
D) GABA
E) Substance P
124. The condition of athetosis results when which area of the brain is
dysfunctional?
A) Globus pallidus
B) Substantia nigra
C) Putamen
D) Subthalamus
Answers
1. A) Alpha motor neurons innervate the extrafusal muscle fibers that
make up the primary muscle itself. Gamma motor neurons innervate the
smaller, intrafusal muscle fibers located in the muscle spindle.
TMP14 p. 687
2. A) Renshaw cells are inhibitory cells that transmit inhibitory signals to
the surrounding motor neurons by releasing glycine, an inhibitory
neurotransmier. Stimulation of each motor neuron tends to inhibit
adjacent motor neurons, an effect called lateral inhibition. This effect is
important for the following major reason: The motor system uses this
lateral inhibition to focus, or sharpen, its signals in the same way that
the sensory system uses the same principle to allow unabated
transmission of the primary signal in the desired direction while
suppressing the tendency for signals to spread laterally.
TMP14 p. 686
3. C) Signals from the tendon organ are transmied to the spinal cord
through large, rapidly conducting type Ib nerve fibers. These fibers
synapse with a single inhibitory interneuron that inhibits the anterior
motor neuron through a second synapse (disynaptic reflex arc). This
local circuit directly inhibits the individual muscle without affecting
adjacent muscles.
TMP14 pp. 690–691
4. E) When the receptor portion of the muscle spindle is stretched slowly,
the number of impulses transmied from both the primary and the
secondary endings increases almost directly in proportion to the degree
of stretching and the endings continue to transmit these impulses for
several minutes. This effect, called the static response of the spindle
receptor, estimates muscle length. When the length of the spindle
receptor increases rapidly, the primary ending (but not the secondary
ending) is stimulated powerfully. This stimulus of the primary ending is
called the dynamic response, which means that the primary ending
responds extremely actively to a rapid rate of change in length.
TMP14 p. 688
5. D) There are two types of muscle spindle intrafusal fibers: (1) nuclear bag
muscle fibers and (2) nuclear chain fibers. The nuclear bag fibers are
responsible for the dynamic response of a muscle spindle receptor. The
nuclear chain fibers are responsible for the static response of a muscle
spindle receptor. Extrafusal muscle fibers make up the bulk of a skeletal
muscle and are not part of the muscle spindle.
TMP14 pp. 687–688
6. E) The flexor reflex is elicited most powerfully by stimulation of pain
endings, for which reason it is also called a nociceptive reflex, or simply a
pain reflex. A painful stimulus applied to the hand causes the flexor
muscles of the upper arm to become excited, thus withdrawing the hand
from the painful stimulus. The pathways for eliciting the flexor reflex do
not pass directly to the anterior motor neurons but instead pass first into
a pool of interneurons within the spinal cord and only secondarily to the
motor neurons. The shortest possible circuit is a three- or four-neuron
pathway with multiple synapses (polysynaptic) as shown in the figure
below.
TMP14 p. 692
Flexor reflex, crossed extensor reflex, and reciprocal inhibition.
7. C) The topographical representations of the different muscle areas of the
body in the primary motor cortex shows that more than one half of the
entire primary motor cortex is concerned with controlling the muscles of
the hands and the muscles of speech; the thumb is particularly wellrepresented in the primary motor cortex.
TMP14 p. 698
8. A) The cerebellum receives sensory signals directly from the peripheral
parts of the body, mainly through four tracts on each side, two of which
are located dorsally in the cord and two ventrally. The two most
important of these tracts are the dorsal spinocerebellar tract and the ventral
spinocerebellar tract (choice A). The dorsal tract enters the cerebellum
through the inferior cerebellar peduncle and terminates in the vermis
and intermediate zones of the cerebellum on the same side as its origin.
The ventral tract enters the cerebellum through the superior cerebellar
peduncle, but it terminates in both sides of the cerebellum.
TMP14 p. 713
9. D) Two of the most important symptoms of cerebellar disease are
dysmetria and ataxia. In the absence of the cerebellum, the subconscious
motor control system cannot predict how far movements will go.
Therefore, the movements ordinarily overshoot their intended mark;
then the conscious portion of the brain overcompensates in the opposite
direction for the succeeding compensatory movement. This effect is
called dysmetria, and it results in uncoordinated movements that are
called ataxia.
TMP14 p. 719
10. B) One characteristic of both Purkinje cells and deep nuclear cells is
that normally both of them fire continuously; the Purkinje cell fires at
about 50 to 100 action potentials per second, and the deep nuclear cells
fire at much higher rates. Purkinje cells send inhibitory input to deep
nuclear cells.
TMP14 p. 714
11. D) Lesions in the globus pallidus frequently lead to spontaneous and
often continuous writhing movements of a hand, an arm, the neck, or
the face. These movements are called athetosis.
TMP14 pp. 721–722
12. B) The basal ganglia are located on each side of the brain mainly lateral
to and surrounding the thalamus; they consist of the caudate nucleus,
putamen, globus pallidus, substantia nigra, and subthalamic nucleus.
The red nucleus is located in the rostral midbrain and is involved in
motor coordination.
TMP14 pp. 720–721
13. C) A lesion in the subthalamus often leads to sudden flailing
movements of an entire limb, a condition called hemiballismus.
TMP14 p. 722
14. D) Damage in some thalamic areas may lead specifically to retrograde
amnesia without causing significant anterograde amnesia. A possible
explanation of this is that the thalamus may play a role in helping the
person “search” the memory storehouses and thus “read out” the
memories. That is, the memory process not only requires the storing of
memories but also an ability to search and find the memory later.
TMP14 p. 739
15. D) Sometimes a person is capable of deciding what he or she wants to
say but cannot make the vocal system emit words; instead, the person
emits unintelligible noises. This effect, called motor aphasia, results from
damage to Broca’s speech area, which lies in the prefrontal and premotor
facial region of the cerebral cortex—about 95% of the time in the left
hemisphere.
TMP14 p. 734
16. D) Transmission of signals from Wernicke’s area to Broca’s area occurs
by way of the arcuate fasciculus.
TMP14 p. 734
17. D) The major reward centers have been found to be located along the
course of the medial forebrain bundle, especially in the lateral and
ventromedial nuclei of the hypothalamus.
TMP14 p. 749
18. C) The substantia nigra lies anteriorly in the superior mesencephalon; it
sends dopamine secreting neurons mainly to the caudate nucleus and
putamen.
TMP14 p. 723
19. C) Delta waves include all the waves of the EEG with frequencies less
than 3.5 cycles/sec, and they often have voltages two to four times
greater than most other types of brain waves. They occur in very deep
sleep, in infancy, and in persons with serious organic brain disease.
TMP14 p. 756
20. B) Some patients with mental depression alternate between depression
and mania, which is called either bipolar disorder or manic-depressive
psychosis, and fewer patients exhibit only mania without the depressive
episodes. Drugs that diminish the formation or action of norepinephrine
and serotonin, such as lithium compounds, can be effective in treating
the manic phase of the condition.
TMP14 p. 760
21. A) Most systemic blood vessels, especially those of the abdominal
viscera and skin of the limbs, are constricted by sympathetic
stimulation. Parasympathetic stimulation has almost no effect on most
blood vessels.
TMP14 p. 765
22. A) Sexual reflexes are initiated both by psychic stimuli from the brain
and by stimuli from the sexual organs. Impulses from these sources
converge on the sacral cord and, in men, result first in erection, mainly a
parasympathetic function, and then ejaculation, partially a sympathetic
function.
TMP14 pp. 765, 772
23. D) Stimulation of sympathetic fibers in the right superior cervical
ganglion leads to contraction of the meridional fibers of the iris that
dilate the pupil. Hence, destruction of the right superior cervical
ganglion would cause construction of the pupil of the eye on the same
side.
TMP14 p. 768
24. A) All preganglionic neurons are cholinergic in both the sympathetic
and the parasympathetic nervous systems. Acetylcholine or
acetylcholine-like substances, when applied to the ganglia, will excite
both sympathetic and parasympathetic postganglionic neurons.
TMP14 p. 765
25. B) The cause of the low permeability of the blood-brain barrier is the
manner in which the endothelial cells of the brain tissue capillaries are
joined to one another. They are joined by so-called tight junctions. That
is, the membranes of the adjacent endothelial cells are tightly fused
rather than having large slit pores between them, as is the case for most
other capillaries of the body. Hypertonic solutions of mannitol cause
brain endothelial cells to shrink (decreased endothelial cell volume),
which, in turn, pulls adjacent endothelial cells apart thus increasing
endothelial permeability.
TMP14 p. 783
26. G) One of the most serious complications of abnormal cerebral fluid
dynamics is the development of brain edema. Because the brain is
encased in a solid cranial vault, accumulation of extra edema fluid
compresses the blood vessels, often causing seriously decreased blood
flow and destruction of brain tissue. A common cause is a serious blow
to the head, leading to brain concussion, in which the brain tissues and
capillaries are traumatized and capillary fluid leaks into the traumatized
tissues. When brain edema begins, the veins are compressed (reducing
venous volume). The venous compression leads to increased capillary
pressure, which further increases the formation of edema, and thus
further increases the intracranial pressure.
TMP14 p. 783
27. A) During normal daily activities, arterial pressure can fluctuate
widely, rising to high levels during states of excitement or strenuous
activity and falling to low levels during sleep. However, cerebral blood
flow is “autoregulated” extremely well between arterial pressure limits
of 60 and 140 mm Hg. That is, mean arterial pressure can be decreased
acutely to as low as 60 mm Hg or increased to as high as 140 mm Hg
without significant change in cerebral blood flow. When the arterial
pressure rises above about 140 mm Hg in a normotensive person, the
blood flow to the brain then varies with the level of arterial pressure
because this exceeds the autoregulatory limits of the brain vasculature.
TMP14 p. 779
28. A) The entire cerebral cavity enclosing the brain and spinal cord has a
capacity of about 1600 to 1700 ml. About 150 ml (choice A) of this
capacity is occupied by cerebrospinal fluid and the remainder by the
brain and cord.
TMP14 p. 780
29. D) Carbon dioxide is believed to increase cerebral blood flow by
combining first with water in the body fluids to form carbonic acid, with
subsequent dissociation of this acid to form hydrogen ions. The
hydrogen ions then cause vasodilation of the cerebral vessels, with the
dilation being almost directly proportional to the increase in hydrogen
ion concentration up to a blood flow limit of about twice normal. Hence,
hydrogen ions have a direct action to increase cerebral blood flow;
carbon dioxide has an indirect action to do the same.
TMP14 pp. 777–778
30. D) Most strokes are caused by arteriosclerotic plaques that occur in one
or more of the feeder arteries to the brain. The plaques can activate the
cloing mechanism of the blood, causing a blood clot to occur which can
block blood flow in the artery (i.e., ischemia), thereby leading to acute
loss of brain function in a localized area. Thromboembolism is
obstruction of a blood vessel by a blood clot that has become dislodged
from another site in the circulation.
TMP14 p. 780
31. D) Cerebrospinal fluid is formed at a rate of about 500 ml each day.
TMP14 p. 781
32. C) Broca’s area is a region of the premotor area of one hemisphere
(usually the left). Damage to Broca’s area does not prevent a person
from vocalizing but makes it impossible to speak whole words other
than occasional simple words such as “yes” or “no.” The primary motor
cortex works with other areas of the brain to plan and execute
movements. The cerebellum plays a critical role in motor control; it does
not initiate movement but contributes to coordination, precision, and
accurate timing of movements.
TMP14 pp. 729–730
33. C) A positive Babinski sign (also called the Babinski reflex) occurs
normally in children up to 2 years of age. The reflex occurs after the sole
of the foot has been stroked with a blunt instrument; the big toe moves
upward, and the other toes fan out. A positive Babinski sign in adults
can indicate damage to the corticospinal tract.
TMP14 p. 695
34. C) The lateral cerebellar hemispheres function with the cerebral cortex
in the planning of complex movements.
TMP14 p. 719
35. A) The most potent stimulator of cerebral blood flow is a local increase
in carbon dioxide tension, followed in order by a decrease in oxygen
tension and an increase in local neuronal activity.
TMP14 pp. 777–778
36. E) Axons of motor neurons in the anterior horn exit the spinal cord
through the anterior root. The posterior root serves as the entry point for
sensory fibers coming into the posterior horn region of the spinal cord.
The posterior column and ventral white commissure are fiber tracts
located solely within the spinal cord.
TMP14 pp. 685–686
37. D) All preganglionic sympathetic neurons are located in the
intermediolateral cell column (lateral horn); this cell group extends from
T1 to L2.
TMP14 p. 763
38. D) A subdural hematoma can lead to increased intracranial pressure
because it takes up space in the cranium; papilledema (optic disc
swelling) suggests an increase in intracranial pressure. The increase in
intracranial pressure does not affect production of cerebrospinal fluid
(CSF), but it may cause decreased CSF volume because the high
pressure pushes CSF into venous blood through the arachnoidal villi
and compresses the volume of brain structures that contain CSF.
Cerebral blood flow should remain normal with small increases in
intracranial pressure, but larger increases can decrease cerebral blood
flow.
TMP14 pp. 782–783
39. E) The veins have lower pressures compared with arteries and
capillaries, making them easier to compress. When the veins are
compressed, the capillary pressure increases, which increases the
ultrafiltration of fluid from the capillaries into the interstitial spaces,
thereby increasing the intracranial pressure even more. The increase in
intracranial pressure can cause compression of lateral ventricles and the
subarachnoid space, but this mechanism is compensatory rather than a
cause for deterioration of blood flow and brain oxygenation.
TMP14 pp. 782–783
40. C) Preganglionic sympathetic axons pass through the white
communicating rami to enter the sympathetic trunk. Postganglionic
sympathetic axons course through gray rami and might be found in
dorsal and ventral primary rami.
TMP14 p. 763
41. D) The gigantocellular neurons of the reticular formation reside in the
pons and mesencephalon. These neurons release acetylcholine, which
functions as an excitatory neurotransmier in most brain areas.
TMP14 p. 743
42. E) Increased neuronal activity in the brain causes the neurotransmier
glutamate to diffuse from the site of release at the synapses into the
adjacent tissues. The glutamate triggers a calcium wave in astrocytes,
which leads to astrocytic release of vasodilatory prostaglandins that
cause arterioles to dilate. In this way, the local blood flow to the tissues
can be matched with the metabolic activity of the neurons.
TMP14 pp. 777–778
43. B) The endothelial cells lining all blood vessels in the brain constitute
the blood-brain barrier. The purpose of the blood-brain barrier is to
protect the chemical environment of the brain from rapid changes in
composition that occur normally in the rest of the body fluids. Brain
capillary endothelial cells have special structural and biochemical
aributes that impede diffusion of ions, nutrients, and fat-soluble
substances; these substances can diffuse through the endothelial barrier
and thereby enter all other tissues of the body.
TMP14 p. 783
44. C) Gamma motor neurons form direct synaptic contact with the
skeletal muscle fibers known as intrafusal fibers. Extrafusal muscle
fibers are innervated by alpha motor neurons, whereas Purkinje,
granule, and pyramidal neurons have no synaptic contact with muscles
in the periphery.
TMP14 p. 686
45. B) Cerebellothalamic projections are contained in the superior
cerebellar peduncle.
TMP14 p. 714
46. E) In this example, the flexor withdrawal reflex is activated by a painful
stimulus to the right foot. Flexor muscles in the right leg and extensor
muscles in the left leg are simultaneously stimulated to contract, causing
reflex removal of the foot from the painful stimulus while shifting body
weight to the other leg. The patellar tendon reflex (also called knee jerk),
which is activated by tapping the patellar tendon, is a type of stretch
reflex. The Golgi tendon reflex provides a negative feedback mechanism
that prevents the development of too much tension in a muscle.
TMP14 pp. 691–692
47. E) The flexor withdrawal reflex is a polysynaptic reflex arc activated by
stimulation of nociceptors in the skin. Multiple excitatory and inhibitory
interneurons in the spinal cord are involved. The stretch reflex is a
monosynaptic reflex arc involving two neurons. The Golgi tendon reflex
is a disynaptic reflex arc because the reflex involves two synapses—an
afferent and efferent neuron synapse with an inhibitory interneuron in
the spinal cord.
TMP14 pp. 691–692
48. A) The hypothalamus, despite its small size, is the most important
control center for the limbic system. It controls most of the vegetative
and endocrine functions of the body and many aspects of behavior.
TMP14 p. 745
49. C) The association cortex is defined by the fact that it receives multiple
inputs from a wide variety of sensory areas of cortex. It is the true
multimodal cortex.
TMP14 p. 729
50. C) The corpus callosum is the main fiber pathway for communication
between the two hemispheres of the brain.
TMP14 pp. 731–732
51. B) Corticospinal fibers pass through the medullary pyramid.
TMP14 pp. 699–700
52. D) Prosopagnosia is the inability to recognize faces. This inability
occurs in people who have extensive damage on the medial undersides
of both occipital lobes and along the medioventral surfaces of the
temporal lobes.
TMP14 p. 730
53. E) The somatic, visual, and auditory association areas all meet one
another at the junction of the parietal, temporal, and occipital lobes. This
area is known as Wernicke’s area. This area on the dominant side of the
brain plays the single greatest role for the highest comprehension levels
we call intelligence.
TMP14 pp. 731–732
54. D) A stroke involving the left middle cerebral artery is likely to cause
an aphasic syndrome that may involve the loss of speech
comprehension and/or the loss of the ability to produce speech sounds.
Any paralysis resulting from the lesion would affect the right side of the
body; similarly, any visual field deficits would affect the right visual
field of each eye.
TMP14 pp. 734, 780
55. C) For an event or sensory experience to be remembered, it must first
be consolidated. The consolidation of memory takes time. A disruption
of consciousness during the process of consolidation will prevent the
development of memory for the event or sensory experience.
TMP14 p. 738
56. A) Sympathetic stimulation of blood vessels typically causes
vasoconstriction; parasympathetic stimulation has lile or no direct
effect on blood vessels. The heart, lungs, gastrointestinal tract, and
urinary bladder are affected significantly by both divisions of the
autonomic nervous system.
TMP14 pp. 769–770
57. C) Posterior spinocerebellar fibers pass through the inferior cerebellar
peduncle.
TMP14 p. 713
58. D) The main pathway linking the cerebral cortex and the cerebellum
involves cortical projections to the ipsilateral basilar pontine nuclei, the
cells of which then project to the contralateral cerebellum.
TMP14 pp. 712–713
59. C) The cerebrospinal fluid outside the brain and spinal cord is located
within the subarachnoid space. Dilated regions of the subarachnoid
space are identified as cisterns. The cisterna magna is one of the largest
cisterns and is positioned at the caudal end of the fourth ventricle
between the cerebellum and posterior surface of the medulla.
TMP14 pp. 780–781
60. D) This woman has Huntington’s disease. This hereditary disorder
results from expansion of a CAG triplet repeat in the Huntingtin gene
on chromosome 4. Typical symptoms are listed in the question stem.
Huntington’s disease is a neurodegenerative disorder that at first causes
flicking movements in individual muscles and then progresses to
distortional movements of the entire body; severe dementia develops
along with the motor dysfunctions.
TMP14 p. 724
61. C) The abnormal movements of Huntington’s disease are thought to be
caused by loss of GABA-secreting neurons in the caudate nucleus and
putamen; acetylcholine-secreting neurons in many parts of the brain are
also thought to be affected. The axon terminals of GABA-secreting
neurons normally inhibit portions of the globus pallidus and substantia
nigra. This loss of inhibition is thought to allow spontaneous outbursts
of globus pallidus and substantia nigra activity that cause the
distortional movements.
TMP14 p. 724
62. A) Pontocerebellar axons are contained in the middle cerebellar
peduncle.
TMP14 p. 713
63. A) Pain signals traveling through the anterolateral system, but not any
of the discriminative sensations coursing through the medial lemniscal
system, provide input to the cells in the reticular formation that give rise
to ascending projections to the intralaminar nuclei of the thalamus.
TMP14 pp. 741–742
64. A) Preganglionic sympathetic axons synapse on cells in the adrenal
medulla that function as postganglionic sympathetic neurons.
TMP14 p. 764
65. D) Gamma motor neurons innervate the contractile ends of the muscle
spindle receptor. Stimulation of gamma motor neurons will cause the
ends of the spindle to contract, which in turn will stretch the center of
the spindle receptor in the muscle in which the spindle receptor is
embedded. The activity of the gamma motor neurons is influenced by
the fusimotor system. Enhanced activity of this system will lead to an
increase in gamma motor tone and increase the sensitivity of the muscle
spindle as a stretch receptor.
TMP14 pp. 688–689
66. A) Complex spike output from the Purkinje cells of the cerebellum is a
response to activation of climbing fibers in cerebellar neural circuitry.
All climbing fibers originate in the inferior olivary nucleus.
TMP14 pp. 715–716
67. A) Cortical projections to the red nucleus provide an alternative
pathway for the cerebral cortex to control flexor muscles through the
rubrospinal tract.
TMP14 pp. 700–701
68. D) The pontine reticular nuclei are tonically active. These nuclei have a
stimulatory effect on the antigravity muscles of the body. The pontine
nuclei are normally opposed by the medullary reticular nuclei. The
medullary nuclei are not tonically active and require stimulation from
higher brain centers to counterbalance the signal from the pontine
nuclei. Decerebrate rigidity results when the stimulatory signal from
higher brain areas to the medullary nuclei is absent. This absence allows
an unopposed and vigorous activation of the antigravity muscles,
resulting in extension of the arms and legs and contraction of the axial
muscles of the spinal column.
TMP14 p. 704
69. E) Corticospinal axons originate from cell bodies (pyramidal neurons)
in layer V of the motor areas of the cortex.
TMP14 pp. 727–728
70. E) This man has Parkinson disease. No laboratory biomarkers exist for
Parkinson disease, and imaging results are unremarkable. Diagnosis
requires two of three cardinal signs that include (1) resting tremor, (2)
rigidity, and (3) bradykinesia (or slow movement); this man has all three
signs. Parkinson disease affects about 1% of persons older than 60 years.
Progressive disability can be slowed but not halted by treatment.
TMP14 pp. 723–724
71. C) This man with Parkinson disease has a loss of pigmented
dopaminergic neurons of the substantia nigra pars compacta that send
dopamine-secreting nerve fibers to the caudate nucleus and putamen.
The causes of the abnormal motor movements are poorly understood;
however, dopamine is an inhibitory transmier in the caudate nucleus
and putamen. It is therefore possible that overactivity of the caudate
nucleus and putamen could result from decreased dopamine levels in
this patient with Parkinson disease; these brain structures are largely
responsible for voluntary movement.
TMP14 pp. 723–724
72. C) The palmar (volar) surfaces of the skin contain receptors that project
through the medial lemniscal system to the primary somatosensory
cortex. When these fingers are flexed and grasp an object, the cutaneous
receptors send signals to the primary somatosensory cortex. These
cortical neurons then project to the adjacent motor cortex and the
pyramidal neurons that sent the original message down the
corticospinal tract to cause contraction of the finger flexors. The motor
cortex neurons are then said to be “informed of the muscle contractions”
that they originally specified.
TMP14 pp. 701–702
73. B) Sweat glands and the piloerector smooth muscle of hairy skin are
innervated by the population of cholinergic postganglionic sympathetic
neurons.
TMP14 p. 765
74. D) Bilateral ablation of the amygdala causes behavioral changes known
as Klüver-Bucy syndrome. These changes include lack of fear, extreme
curiosity, forgetfulness, oral fixation, and a strong sex drive. The sex
drive can be so strong that monkeys will aempt to copulate with
immature animals, animals of the wrong sex, and even animals of the
wrong species. Although similar brain legions in humans are rare,
afflicted people have similar symptoms. The amygdala is thought to
make the person’s behavioral response appropriate for each occasion.
TMP14 p. 751
75. C) Although the majority of corticospinal axons synapse with the pool
of spinal cord interneurons, some synapse directly with the motor
neurons that innervate muscles controlling the wrist and finger flexors.
TMP14 p. 697
76. A) The foramen of Magendie and the two lateral foramina of Luschka
form the communication channels between the ventricular system
within the brain and the subarachnoid space that lies outside the brain
and spinal cord.
TMP14 pp. 780–781
77. A) A generalized tonic-clonic epileptic seizure is associated with the
sudden onset of unconsciousness and an overall steady but
uncoordinated contracture of many muscles of the body followed by
alternating contractions of flexor and extensor muscles—that is, tonicclonic activity. This effect is the result of widespread and uncontrolled
activity in many parts of the brain. It takes the brain from a few minutes
to a few hours to recover from this vigorous activity.
TMP14 p. 759
78. D) Golgi tendon organs provide direct synaptic input to type Ib
inhibitory interneurons. Type Ia interneurons and alpha motor neurons
receive input from muscle spindle afferents, whereas dynamic gamma
motor neurons and excitatory interneurons receive their input from
supraspinal systems.
TMP14 p. 691
79. A) Neurons in the locus coeruleus utilize the neurotransmier
norepinephrine in their widespread projections throughout the brain.
TMP14 p. 743
80. D) Dysdiadochokinesia is the inability to perform rapid alternating
movements. Patients with hemineglect are unaware of items to one side
of space. Astereognosis is the inability to recognize objects by touch.
Agraphesthesia is a disorientation of the skin’s sensation across its space
(e.g., it is difficult to identify a number or leer traced on the hand).
Dysarthria is a failure of progression in talking.
TMP14 pp. 719–720
81. A) The cerebellum plays major roles in the timing of motor activities
and in rapid, smooth progression from one muscle movement to the
next. Lesions of the cerebellum can also cause dysmetria, ataxia, past
pointing, nystagmus, dysarthria, intention tremor, and hypotonia. The
premotor cortex and primary motor cortex plan and execute
movements. The limbic system is involved with behavior, motivation,
emotion, long-term memory, and olfaction.
TMP14 pp. 719–720
82. A) The excitatory or inhibitory effect of a postganglionic sympathetic
fiber is determined solely by the type of receptor to which it binds.
TMP14 p. 767
83. C) The most characteristic deficit after damage to corticospinal tract
neurons involves discrete voluntary movement of the contralateral hand
and fingers.
TMP14 p. 702
84. A) A large area of the primary motor cortex is dedicated to activating
the muscles that control the movements of the fingers. Stimulation of the
primary motor cortex usually results in very discrete contractions of
small groups of muscles. Stimulation of the premotor cortex results in
the contraction of large groups of muscles, and stimulation of the
supplemental motor area results in bilateral movements.
TMP14 pp. 697–698
85. B) Nicotinic cholinergic receptors are found at synapses between
preganglionic and postganglionic sympathetic neurons.
TMP14 p. 767
86. D) The premotor cortex generates nerve signals for complex paerns of
movement rather than discrete paerns generated in the primary motor
cortex. The most anterior part of the premotor area first develops a
motor image of the total muscle movement that is to be performed.
Next, the successive paern of muscle activity required to achieve the
image excites neurons in the posterior premotor cortex; from here,
signals are sent directly to the primary motor cortex to excite specific
muscles or by way of the basal ganglia and thalamus and then to the
primary motor cortex.
TMP14 p. 698
87. A) Active transport of sodium ions through the epithelial cells lining
the choroid plexus is followed by passive diffusion of chloride ions to
maintain electroneutrality. The osmotic gradient created by the sodium
and chloride ions causes the immediate osmosis of water into the CSF.
The osmolarity of CSF is identical to that of blood plasma.
TMP14 p. 781
88. A) This patient has Friedreich’s ataxia, which is an autosomal-recessive
ataxia resulting from a mutation on chromosome 9. It accounts for about
50% of all hereditary ataxias. Huntington’s disease is a
neurodegenerative disease that affects muscle coordination and causes a
decline in cognitive function and psychiatric problems. Multiple
sclerosis is an inflammatory disease in which the myelin covering of
nerve cells in the brain and spinal cord is damaged, resulting in a wide
range of symptoms that include physical, mental, and psychiatric
problems.
TMP14 pp. 719–720
89. E) The major pathological finding in Friedreich’s ataxia is degeneration
and loss of axons, especially in the spinal cord and spinal roots; this
effect increases with age and duration of disease. Most major nerve
tracts in the spinal cord show demyelination, and the spinal cord itself
becomes thin. There are no lesions in the premotor cortex or primary
motor cortex, and the frontal lobe remains normal. The disorder does
not affect cognitive functions, and unmyelinated sensory fibers are
spared.
TMP14 pp. 719–720
90. B) Cells in the pars compacta portion of the substantia nigra use the
neurotransmier dopamine in their projections to the caudate and
putamen.
TMP14 pp. 723–724
91. A) Lesions that damage primary motor cortex and other surrounding
motor cortical areas lead to spastic paralysis in the affected muscles.
TMP14 pp. 702–703
92. C) Epinephrine activates alpha- and beta-adrenergic receptors equally
well. Norepinephrine excites both types of receptors but has a markedly
greater effect on alpha receptors.
TMP14 p. 768
93. A) The posterior and lateral hypothalamus, in combination with the
preoptic hypothalamus, form an important group of cells controlling
cardiovascular functions such as heart rate and blood pressure.
TMP14 p. 746
94. A) Ia sensory fibers synapse directly with alpha motor neurons,
whereas Ib sensory fibers synapse with inhibitory interneurons.
Excitatory interneurons play an important role in the withdrawal reflex.
Gamma motor neurons receive input primarily from supraspinal
systems.
TMP14 pp. 687–688
95. E) Noncommunicating hydrocephalus results when a blockage of CSF
flow occurs within the ventricular system or at the sites of
communication between the ventricular system and the subarachnoid
space. Communicating hydrocephalus occurs when a blockage occurs
either within the subarachnoid space or at the arachnoid villi, thus
preventing communication between the subarachnoid space and the
superior sagial sinus.
TMP14 p. 783
96. E) Behavioral deficits, changes in personality, and diminished problemsolving ability are all signs of damage to the prefrontal association
cortex.
TMP14 p. 730
97. B) The posterior temporal lobe is larger at birth in the dominant
hemisphere of the brain, which is the left hemisphere in 95% of people.
Because of the tendency to direct one’s aention to the beer developed
region, the rate of learning in the cerebral hemisphere that gains the first
start increases rapidly, whereas learning remains slight in the opposite,
less-used side. Hence, the left hemisphere normally becomes dominant
over the right.
TMP14 pp. 731–732
98. A) The neurons located in the locus coeruleus release norepinephrine at
their nerve terminals.
TMP14 p. 743
99. D) The cerebrocerebellum and the dentate nucleus are involved with
the thalamus and cortex in the planning of complex movements.
TMP14 p. 718
100. D) The stretch reflex is mediated by muscle spindles. Autogenic
inhibition involves Golgi tendon organs. Reciprocal inhibition is also
related to muscle spindles.
TMP14 pp. 688–689
101. C) The junction of the parietal, temporal, and occipital lobe is
commonly referred to as Wernicke’s area. This area of the brain is
responsible for the ability to comprehend both the wrien and spoken
word.
TMP14 pp. 729–730
102. D) The corpus callosum connects the left and right cerebral
hemispheres and hence facilitates communication between them.
Agenesis of the corpus callosum is a rare defect in which there is a
complete or partial absence of the corpus callosum.
TMP14 pp. 699, 732
103. D) Damage to the subthalamic nucleus of the basal ganglia often leads
to flailing movements of an entire limb; this condition is called
hemiballismus. Stroke is the most common cause of hemiballismus in
adults, but this condition is rare. The globus pallidus is part of the basal
ganglia and is involved with movement; however, damage to the globus
pallidus does not cause hemiballismus. The lateral hypothalamus is
mostly concerned with hunger. The red nucleus serves as an alternative
pathway for transmiing cortical signals to the spinal cord; it controls
the crawling of babies and may be responsible for swinging the arms
while walking. The ventrobasal complex of thalamus is a sensory relay
area of the brain.
TMP14 pp. 721–723
104. B) The amygdala seems to function in behavioral awareness at a
semiconscious level. The amygdala also is thought to project into the
limbic system the individual’s current status with respect to his or her
surroundings. Therefore, the amygdala is believed to help paern
behavior appropriate for each occasion.
TMP14 pp. 750–751
105. E) Schizophrenia is thought to be caused in part by excessive release
of dopamine. Occasionally, patients with Parkinson’s disease exhibit
schizophrenic symptoms because of uncontrolled L-dopa therapy and
the subsequent production of dopamine.
TMP14 pp. 760–761
106. C) The magnocellular portion of the red nucleus has a somatographic
representation of all the muscles of the body, similar to the motor cortex.
Stimulation of this area in the red nucleus results in contraction of a
single muscle or small groups of muscles.
TMP14 p. 700
107. C) Lesions involving the ventromedial hypothalamus lead to excessive
eating (hyperphagia), excessive drinking, rage and aggression, and
hyperactivity.
TMP14 pp. 746–747
108. D) The vermis and the intermediate zone of the cerebellar hemisphere
have a distinct topographic representation of the body. These areas are
responsible for coordinating the contraction of the muscles of the body
for intended motion.
TMP14 p. 712
109. E) The medial forebrain bundle extends from the septal and
orbitofrontal regions of the cerebral cortex downward through the
center of the hypothalamus to the brain stem reticular area. This
structure serves as a communication system between the limbic system
and the brain stem.
TMP14 p. 745
110. C) This man has Alzheimer’s disease. Increased amounts of betaamyloid peptide are found in the brains of patients with Alzheimer’s
disease. The peptide accumulates in amyloid plaques with diameters up
to several hundred millimeters in widespread areas of the brain,
including the cerebral cortex, hippocampus, basal ganglia, thalamus,
and cerebellum. A key role for excess accumulation of beta-amyloid
peptide in the pathogenesis of Alzheimer’s disease is suggested by
multiple observations.
TMP14 p. 761
111. E) Dysdiadochokinesia is a cerebellar deficit that involves a failure of
progression from one part of a movement to the next. Consequently,
movements that include rapid alternation between flexion and extension
are most severely affected.
TMP14 pp. 719–720
112. C) Linear acceleration is in a straight line; angular acceleration is that
which occurs by
turning about a point. The semicircular canals respond to the turning
motions of the head and body.
TMP14 pp. 706–707
113. D) This man has schizophrenia, which is characterized by a
breakdown of cognitive and emotional responses. Dissociative identity
disorder was formerly called multiple personality disorder. Bipolar
disorder is characterized by episodes of elevated mood (mania)
alternating with episodes of depression.
TMP14 pp. 760–761
114. B) A consistent finding in most individuals with schizophrenia is that
the hippocampus is reduced in size. The hippocampus is part of the
limbic system. Incoming sensory information activates various parts of
the hippocampus that, in turn, initiate behavioral reactions for different
purposes. Removal of the hippocampus makes it impossible to learn
new information based on verbal symbolism; however, past memories
are preserved.
TMP14 pp. 760–761
115. B) Hair cells in the macula of the saccule are maximally sensitive to
linear head movement in the vertical plane.
TMP14 p. 706
116. D) Lesions involving the thalamus lead to retrograde amnesia because
they are believed to interfere with the process of retrieving long-term
memory stored in other portions of the brain.
TMP14 p. 739
117. C) The caudate nucleus is involved in the basal ganglia circuits that
control memory-guided motor activity.
TMP14 p. 722
118. C) This infant has shaken baby syndrome. The subdural hematoma
has increased intracranial pressure, which in turn has caused cerebral
edema. The venous vasculature in the brain is compressed due to the
high intracranial pressure. Continued compression of brain structures
can lead to worsening cerebral edema with decreased oxygenation of
the brain.
TMP14 p. 783
119. B) The punishment center is primarily localized to the periventricular
hypothalamus and the midbrain central gray area.
TMP14 p. 749
120. A) An example of a relatively restricted or local sympathetic action is
the vasodilation or vasoconstriction of blood vessels that occurs upon
warming or cooling of a patch of skin. When a bright light is introduced
to one eye, the pupils of both eyes constrict. The pupillary light reflex is
a multiple-neuron event that involves the Edinger-Westphal nucleus of
the brainstem; it is not a local event.
TMP14 p. 773
121. E) The most conspicuous stimulation area for causing sleep is the
raphe nuclei in the lower half of the pons and in the medulla. Many
nerve endings of fibers from raphe neurons secrete serotonin. When the
formation of serotonin is blocked by drugs, sleep is often disrupted for
hours to days. Therefore, it has been assumed that serotonin is a
transmier associated with the production of sleep.
TMP14 p. 754
122. B) The Golgi tendon organ senses tension in the tendons. When
tension becomes exceedingly high, an inhibitory reflex is activated that
causes relaxation of the entire muscle, which serves to protect the
muscle from tearing. However, the Golgi tendon organ is also thought
to play a key role in maintaining equal tension in the muscle fibers of a
skeletal muscle so that imbalances in tension among the different muscle
fibers can be equalized.
TMP14 pp. 690–691
123. B) Degeneration of the dopaminergic cells in the pars compacta of the
substantia nigra is thought to be the primary defect in Parkinson’s
disease.
TMP14 pp. 723–724
124. A) Athetosis is a symptom characterized by spontaneous and often
continuous writhing movements of a hand, an arm, the neck, or the face;
it is caused by lesions in the globus pallidus. A lesion in the
subthalamus often leads to sudden flailing movements of an entire limb,
a condition called hemiballismus. Lesions of the substantia nigra lead to
the common and extremely severe disease of rigidity, akinesia, and
tremors known as Parkinson’s disease. Multiple small lesions of the
putamen lead to flicking movements in the hands, face, and other parts
of the body, called chorea.
TMP14 p. 721
Unit XII: Gastrointestinal Physiology
1. A 25-year-old man is severely injured in a motor vehicle collision. After
6 weeks of total parenteral nutrition (intravenous feeding), the stomach
and small intestines have atrophied substantially. A lack of which of the
following gastrointestinal hormones is most likely to account for the
atrophy in this man?
A) Cholecystokinin
B) Gastrin
C) Glucose-dependent insulinotropic peptide
D) Motilin
E) Secretin
2. A 43-year-old woman eats a meal consisting of 70% carbohydrate, 20%
protein, and 10% fat. Six hours after consuming the meal, intense
peristaltic contractions travel from the stomach to the colon over a
period of about 90 minutes. Which of the following hormones is most
likely to mediate the intense peristaltic contractions in this woman?
A) Cholecystokinin
B) Gastrin
C) Glucose-dependent insulinotropic peptide
D) Motilin
E) Secretin
3. Dietary fat can cause the release of all gastrointestinal hormones
EXCEPT one. Which one is the EXCEPTION?
A) Cholecystokinin
B) Gastrin
C) Glucose-dependent insulinotropic peptide
D) Motilin
E) Secretin
4. A 90-year-old man with congestive heart failure explains to his
physician that he has dull, aching chest pains when he consumes a large
meal. Which of the following mechanisms can best explain the cause of
ischemic chest pain following a large meal in this patient?
A) Vasoconstriction of skeletal muscle arterioles
B) Vasoconstriction of intestinal arterioles
C) Vasodilation of skeletal muscle arterioles
D) Vasodilation of intestinal arterioles
5. A clinical study is performed to test a newly developed pilocarpine
analogue. Test subjects receiving the analogue experience very high
increases in salivary flow. Which of the following changes are most
likely to occur in salivary electrolytes following treatment with the
pilocarpine analogue?
A) Decreased sodium concentration; increased chloride concentration
B) Decreased sodium concentration; increased potassium
concentration
C) Increased sodium concentration; decreased chloride concentration
D) Increased sodium concentration; decreased potassium
concentration
6. A 24-year-old student with an acute intestinal viral syndrome develops
a new onset of intolerance to dairy products. The student had never
experienced an intolerance to milk products prior to the infection.
Which of the following recommendations would you include for this
student?
A) No recommendation to avoid any foods
B) Permanent avoidance of dairy products
C) Permanent avoidance of fruit
D) Temporary avoidance of dairy products
E) Temporary avoidance of fruit
7. A 46-year-old woman consumes a meal consisting of 60% carbohydrate,
30% protein, and 10% fat. Gastric acid secretion increases by 35-fold
within 3 minutes of consuming the meal, reaches a peak value within 25
minutes, and then gradually decreases over the next 4 hours. Which of
the following substances is most likely to mediate the decrease in
gastric acid secretion in this woman?
A) Gastrin only
B) Secretin only
C) Cholecystokinin only
D) Somatostatin only
E) Secretin and cholecystokinin
F) Secretin and somatostatin
G) Secretin, gastrin, and somatostatin
8. A 35-year-old woman is admied to the emergency department because
of severe upper right quadrant pain and fever. The woman has claycolored stools. Her body mass index is 51 kg/m2
(normal range, 18.5 - 25
kg/m2). Physical examination shows a positive Murphy sign. Heart rate
is 105 beats/min; blood pressure is 102/65 mm Hg. CT scan shows a
mass at the sphincter of Oddi. This woman is at risk for developing
which of the following acute problems?
A) Ascites
B) Crohn’s disease
C) Esophageal cancer
D) Gastritis
E) Pancreatitis
F) Peptic ulcer disease
9. Which of the following best describes the mechanism for fructose
movement across the luminal cell membrane of an enterocyte in a
normal adult human?
A) Endocytosis
B) Exocytosis
C) Facilitated diffusion
D) Passive diffusion
E) Primary active transport
F) Secondary active transport
10. A 65-year-old man with a 30-year history of alcoholism and liver
disease visits his physician because of swelling in his abdomen. Which
of the following sets of changes are most likely in the splanchnic
circulation of this man?
A) High capillary hydrostatic pressure; low plasma colloid osmotic
pressure
B) Low capillary hydrostatic pressure; high plasma colloid osmotic
pressure
C) High capillary hydrostatic pressure; high plasma colloid osmotic
pressure
D) Low capillary hydrostatic pressure; low plasma colloid osmotic
pressure
E) Normal capillary hydrostatic pressure; high plasma colloid
osmotic pressure
F) High capillary hydrostatic pressure; normal plasma colloid
osmotic pressure
11. The gastrointestinal assimilation of proteins includes (1) absorption by
enterocytes, (2) proteolytic actions of pepsin, (3) release of
cholecystokinin, and (4) proteolytic actions of pancreatic enzymes.
Which of the following best describes the correct temporal order of
events for the assimilation of proteins?
A) 4, 3, 2, 1
B) 2, 3, 4, 1
C) 3, 4, 2, 1
D) 3, 4, 1, 2
E) 2, 1, 4, 3
F) 4, 2, 1, 3
G) 1, 2, 3, 4
H) 2, 3, 1, 4
I) 1, 3, 2, 4
12. All the following events are likely to occur during emesis EXCEPT one.
Which one is the EXCEPTION?
A) Antiperistalsis
B) Opening of lower esophageal sphincter
C) A deep breath
D) Contraction of diaphragm
E) Opening of glois
13. The single most quantitatively significant process for absorption of
nutrients in the small intestine is establishment of an electrochemical
gradient for which of the following ions?
A) Calcium
B) Chloride
C) Magnesium
D) Potassium
E) Sodium
14. Which portion of the villus shown is most likely to have the lowest
oxygen tension under normal physiological conditions?
A) A
B) C
C) C
D) D
E) E
15. A 24-year-old student consumes a meal consisting of 50%
carbohydrates, 30% proteins, and 20% fats. The student feels the urge to
defecate 20 minutes after consuming the meal. Which of the following
best describes a direct action that promotes the urge to defecate in this
student?
A) Relaxation of pylorus
B) Relaxation of duodenum
C) Distension of jejunum
D) Distension of rectal wall
E) Contraction of external anal sphincter
F) Contraction of internal anal sphincter
16. The regulation of gastric acid secretion in response to a meal involves
the following events: (1) a decrease in the pH of the gastric contents, (2)
an increase in the pH of the gastric contents, (3) an increase in the rate
of acid secretion, and (4) a decrease in the rate of acid secretion. Which
of the following best describes the correct temporal order of events over
a 4- or 5-hour period following a meal?
A) 4, 3, 2, 1
B) 3, 1, 4, 2
C) 3, 4, 1, 2
D) 2, 1, 4, 3
E) 4, 2, 1, 3
F) 1, 2, 3, 4
G) 2, 3, 1, 4
H) 1, 3, 2, 4
17. Biopsies are taken from the antral and duodenal mucosa of a 48-yearold woman. Which of the following hormones can be found in tissue
homogenates from both locations?
A) Secretin
B) Gastrin
C) Cholecystokinin (CCK)
D) Motilin
E) Glucose-dependent insulinotropic peptide (GIP)
18. Swallowing a bolus of food involves the following: (1) relaxation of
upper esophageal sphincter, (2) peristaltic contractions of pharynx, (3)
upward movement of the soft palate, and (4) medial placement of
palatopharyngeal folds. Which of the following best describes the
correct temporal order of events during the swallowing process?
A) 4, 1, 2, 3
B) 3, 4, 2, 1
C) 2, 1, 4, 3
D) 2, 3, 1, 4
E) 3, 4, 1, 2
19. Oral administration of a histamine H2 receptor antagonist is most
likely to cause which of the following changes in the ability of gastrin,
acetylcholine, and histamine to stimulate gastric acid secretion?
A) Gastrin increased; acetylcholine increased; histamine increased
B) Gastrin decreased; acetylcholine decreased; histamine decreased
C) Gastrin no change; acetylcholine decreased; histamine no change
D) Gastrin increased; acetylcholine decreased; histamine decreased
E) Gastrin decreased; acetylcholine no change; histamine decreased
20. A 34-year-old physician visits a gastroenterologist because of nausea,
abdominal pain, and diarrhea. The physician was exposed to raw
sewage and polluted water on a recent mission trip to an
underprivileged area. The gastroenterologist administers a proton
pump inhibitor and tetracycline. All the symptoms go away in 2 weeks.
Which of the following best describes the condition for which the
physician was treated?
A) Excessive alcohol consumption
B) Ulcerative colitis
C) Psychogenic diarrhea
D) Posraumatic stress syndrome
E) Helicobacter pylori infection
21. A 19-year-old woman visits her physician because of nausea, diarrhea,
light-headedness, and flatulence. After an overnight fast, the physician
administers 50g of oral lactose at time zero (indicated by the arrows in
the figures). Which combination is most likely in this patient during the
next 3 hours?
A) A
B) B
C) C
D) D
22. A 43-year-old man eats a meal consisting of 40% protein, 10% fat, and
50% carbohydrate. Thirty minutes later, the man feels the urge to
defecate. Which reflex results in the urge to defecate when the
duodenum is stretched?
A) Duodenocolic
B) Enterogastric
C) Intestinointestinal
D) Rectosphincteric
23. A 43-year-old man consumes a meal containing 30% protein, 15% fat,
and 55% carbohydrate. At which of the locations depicted in the figure
are bile salts most likely to be absorbed by an active transport process?
A) A
B) B
C) C
D) D
E) E
24. The ileum and distal jejunum of a 28-year-old man are ruptured in an
automobile accident. The entire ileum and a portion of the jejunum are
resected. What is most likely to occur in this man?
A) Atrophic gastritis
B) Constipation
C) Gastric ulcer
D) Gastroesophageal reflux disease (GERD)
E) Vitamin B12
deficiency
25. A 10-year-old boy consumes a cheeseburger, fries, and a chocolate
shake. The meal stimulates the release of several gastrointestinal
hormones. The presence of fat, carbohydrate, or protein in the
duodenum stimulates the release of which hormone from the duodenal
mucosa?
A) Cholecystokinin (CCK)
B) Glucose-dependent insulinotropic peptide (GIP)
C) Gastrin
D) Motilin
E) Secretin
26. A clinical experiment is conducted in which one group of subjects is
given 50 g of glucose intravenously, and another group is given 50 g of
glucose orally. Which factor can explain why the oral glucose load is
cleared from the blood at a faster rate compared with the intravenous
glucose load? (CCK, cholecystokinin; GIP, glucose-dependent
insulinotropic peptide; VIP, vasoactive intestinal peptide.)
A) CCK-induced insulin release
B) CCK-induced VIP release
C) GIP-induced glucagon release
D) GIP-induced insulin release
E) VIP-induced GIP release
27. Digestion of which of the following is impaired to the greatest extent in
patients with achlorhydria?
A) Carbohydrate
B) Fat
C) Protein
28. A 22-year-old man visits his physician because his chest hurts when he
eats, especially when he eats meat. He also belches excessively and has
heartburn. Physical exam shows halitosis. A radiograph shows a dilated
esophagus. Which pressure tracing shown in the figure was most likely
taken at the lower esophageal sphincter (LES) of this patient before and
after swallowing (indicated by the arrow in the figure above)? The
doed line represents a pressure of 0 mm Hg.
A) A
B) B
C) C
D) D
E) E
29. The proenzyme pepsinogen is secreted mainly from which of the
following structures?
A) Acinar cells of the pancreas
B) Ductal cells of the pancreas
C) Epithelial cells of the duodenum
D) Gastric glands of the stomach
30. Which hormone is released by the presence of fat and protein in the
small intestine and has a major effect in decreasing gastric emptying?
A) Cholecystokinin
B) Glucose-dependent insulinotropic peptide
C) Gastrin
D) Motilin
E) Secretin
31. Which of the following can inhibit gastric acid secretion?
Somatostatin Secretin GIP Enterogastrones Nervous Reflexes
A) No No Yes No Yes
B) No Yes No No No
C) No Yes No Yes No
D) Yes No No Yes Yes
E) Yes No Yes No No
F) Yes Yes Yes Yes Yes
32. The gastrointestinal hormones have physiological effects that can be
elicited at normal concentrations, as well as pharmacological effects that
require higher than normal concentrations. What is the direct
physiological effect of the various hormones on gastric acid secretion?
Gastrin Secretin Cholecystokinin GIP Motilin
A) No effect Stimulate Stimulate No effect No effect
B) Stimulate Inhibit No effect Inhibit No effect
C) Stimulate Inhibit No effect No effect No effect
D) Stimulate Inhibit Inhibit Stimulate Stimulate
E) Stimulate Stimulate Inhibit Inhibit No effect
33. The cephalic phase of gastric secretion accounts for about 30% of the
acid response to a meal. Which of the following can eliminate the
cephalic phase of gastric secretion?
A) Antacids
B) Antigastrin antibody
C) Atropine
D) Histamine H2
blocker
E) Vagotomy
F) Sympathectomy
34. Migrating motility complexes (MMCs) occur about every 90 minutes
between meals and are thought to be stimulated by the gastrointestinal
hormone, motilin. An absence of MMCs causes an increase in which of
the following?
A) Duodenal motility
B) Gastric emptying
C) Intestinal bacteria
D) Mass movements
E) Swallowing
35. Which manometric recording in the figure illustrates normal function
of the esophagus at midthoracic level before and after swallowing
(indicated by the arrow in the figure above)? The doed lines represent
a pressure of 0 mm Hg.
A) A
B) B
C) C
D) D
E) E
36. Gastric emptying is tightly regulated to ensure that chyme enters the
duodenum at an appropriate rate. Which event promotes gastric
emptying under normal physiological conditions in a healthy person?
Tone of Orad Stomach Segmentation Contractions in Small Intestine Tone of Pyloric Sphincter
A) Decrease Decrease Decrease
B) Decrease Increase Decrease
C)
Increase Decrease Decrease
D)
Increase Decrease Increase
E)
Increase Increase Increase
Questions 37–39
A tropical hurricane hits a Caribbean island, and the people living there are
forced to drink unclean water. Within the next several days, many people
experience severe diarrhea, and about half of these people die. Samples of
drinking water are positive for the bacterium Vibrio cholerae. Use this
information to answer the next three questions.
37. A toxin from V. cholerae is most likely to stimulate an increase in which
of the following in the epithelial cells of the crypts of Lieberkühn in the
infected people?
A) Cyclic adenosine monophosphate (cAMP)
B) Cyclic guanosine monophosphate (cGMP)
C) Chloride absorption
D) Sodium absorption
38. Which type of ion channel is most likely to be irreversibly opened in
the intestinal epithelial cells of the infected people?
A) Calcium
B) Chloride
C) Magnesium
D) Potassium
E) Sodium
39. Which range best describes the life span (in days) of an intestinal
enterocyte infected with V. cholerae in a person who survives?
A) 1 to 3
B) 3 to 6
C) 6 to 9
D) 9 to 12
E) 12 to 15
40. The gastrointestinal hormones have physiological effects that can be
elicited at normal concentrations as well as pharmacologic effects that
require higher than normal concentrations. What is the physiological
effect of the various hormones on gastric emptying?
Gastrin Secretin Cholecystokinin GIP Motilin
A) Decrease Decrease Decrease Decrease Increase
B)
Increase Decrease None Decrease Increase
C)
Increase None None Increase Increase
D) None None Decrease Increase Increase
E) None None Decrease None None
F) None None Increase None None
41. A healthy 12-year-old boy ingests a meal containing 20% fats, 50%
carbohydrates, and 30% proteins. The gastric juice is most likely to have
the lowest pH in this boy at which time after the meal (in hours)?
A) 0.5
B) 1.0
C) 2.0
D) 3.0
E) 4.0
42. CCK and gastrin share multiple effects at pharmacological
concentrations. Which effects do CCK and gastrin share (or not share) at
physiological concentrations?
Stimulation of Acid
Secretion
Inhibition of Gastric
Emptying
Stimulation of Gastric Mucosal Growth
Stimulation of Pancreatic
Growth
A) Not shared Not shared Not shared Not shared
B) Not shared Not shared Shared Not shared
C) Not shared Shared Not shared Not shared
D) Shared Shared Not shared Not shared
E) Shared Shared Shared Shared
43. A 48-year-old woman consumes a meal consisting of 50%
carbohydrates, 30% proteins, and 20% fats. At which location in the
figure above are smooth muscle contractions most likely to have the
highest frequency?
A) A
B) B
C) C
D) D
E) E
44. The spinal cord of a 40-year-old woman is severed at T6 in an
automobile accident. She devises a method to distend the rectum to
initiate the rectosphincteric reflex. Rectal distention causes which of the
following responses in this woman?
Relaxation of the Internal Anal
Sphincter
Contraction of the External Anal
Sphincter
Contraction of the
Rectum
A) No No No
B) No No Yes
C) No Yes Yes
D) Yes No Yes
E) Yes Yes No
F) Yes Yes Yes
45. A 91-year-old woman with upper abdominal pain and blood in the
stool has been taking nonsteroidal anti-inflammatory drugs (NSAIDs)
for arthritis. Endoscopy reveals patchy gastritis throughout the
stomach. Biopsies are negative for Helicobacter pylori. Pentagastrin
administered intravenously would most likely lead to a less than
normal increase in which of the following?
A) Duodenal mucosal growth
B) Gastric acid secretion
C) Gastrin secretion
D) Pancreatic enzyme secretion
E) Pancreatic growth
46. Which substances have a physiological role in stimulating the release
of hormones or stimulating nervous reflexes, which in turn can inhibit
gastric acid secretion?
Acid Fay Acids Hyperosmotic Solutions Isotonic Solutions
A) No No Yes No
B) No No Yes Yes
C) Yes Yes No Yes
D) Yes Yes Yes Yes
E) Yes Yes Yes No
47. A clinical study is conducted to determine the time course of gastric
acid secretion and gastric pH in healthy volunteers after a meal
consisting of 10% fat, 30% protein, and 60% carbohydrate. The results
show an immediate increase in the pH of the gastric juice after the meal,
which is followed several minutes later by a secondary increase in the
rate of acid secretion. A decrease in which substance is most likely to
facilitate the secondary increase in the rate of acid secretion in these
volunteers?
A) Gastrin
B) Cholecystokinin
C) Somatostatin
D) Vasoactive intestinal peptide
48. Vomiting is a complex process that requires coordination of numerous
components by the vomiting center located in the medulla. Which of the
following occurs during the vomiting act?
Lower Esophageal Sphincter Upper Esophageal Sphincter Abdominal Muscles Diaphragm
A) Contract Contract Contract Contract
B) Contract Contract Relax Relax
C) Relax Contract Contract Relax
D) Relax Relax Contract Contract
E) Relax Relax Relax Relax
49. A 34-year-old woman has a recurrent history of duodenal ulcers
associated with diarrhea, steatorrhea, and hypokalemia. Her fasting
gastrin level is 550 pg/ml, and basal acid secretion is 18 mmol/hour.
Human secretin at a dose of 0.4 µg/kg of body weight is administered
intravenously over 1 minute. Postinjection blood samples are collected
after 1, 2, 5, 10, and 30 minutes for determination of serum gastrin
concentrations. Which serum gastrin concentration is considered
diagnostic for gastrinoma in this woman (in pg/ml)?
A) 450
B) 500
C) 550
D) 600
E) 700
50. Various proteolytic enzymes are secreted in an inactive form into the
lumen of the gastrointestinal tract. Which of the following substances
can activate one or more proteolytic enzymes, converting them to an
active form?
Trypsin Enterokinase Pepsin
A) No No No
B) No No Yes
C) No Yes No
D) Yes Yes No
E) Yes Yes Yes
51. A 71-year-old man with hematemesis and melena has a cresenteric
ulcer in the duodenum. Lavage dislodged the clot, revealing an
underlying raised blood vessel, which was successfully eradicated via
cautery with a bipolar gold probe. Which of the following factors are
diagnostic for duodenal ulcer?
Endoscopy Plasma Gastrin Levels Rate of Acid Secretion
A) No No No
B) Yes No No
C) Yes No Yes
D) Yes Yes No
E) Yes Yes Yes
52. A 23-year-old medical student consumes a cheeseburger, fries, and a
chocolate shake. Which of the following hormones produce
physiological effects at some point during the next several hours?
Gastrin Secretin Cholecystokinin GIP
A) No Yes Yes Yes
B) Yes No Yes Yes
C) Yes Yes No Yes
D) Yes Yes Yes Yes
E) Yes Yes Yes Yes
53. A 68-year-old woman with hematemesis has heartburn and stomach
pain. Endoscopy shows inflammation involving the gastric body and
antrum as well as a small gastric ulcer. Biopsies are positive for H.
pylori. H. pylori damages the gastric mucosa primarily by increasing
mucosal levels of which of the following?
A) Ammonium
B) Bile salts
C) Gastrin
D) NSAIDs
E) Pepsin
54. A physiology experiment is conducted in an isolated rat small
intestine. The intestine is bathed with all essential nutrients, ions, and
gases in a glass dish maintained at a temperature of 37°C. The proximal
jejunum is observed to contract at a frequency of 5 contractions per
minute. A glass micropipee is then inserted into an interstitial cell of
Cajal (pacemaker cell) at the same location in the jejunum, and a slowwave frequency of 10 occurrences per minute is recorded.
Norepinephrine is then added to the bathing solution. Which of the
following best describes the most likely slow-wave frequency and
contraction frequency after treatment with norepinephrine (in
occurrences per minute)?
Slow-Wave Frequency Contraction Frequency
A) 0 0
B) 10 0
C) 10 10
D) 10 5
E) 5 10
55. A healthy 21-year-old woman eats a big meal and then takes a 3-hour
ride on a bus that does not have a bathroom. Twenty minutes after
eating, the woman feels a strong urge to defecate but manages to hold
it. Which mechanisms have occurred in this woman?
Relaxation of the Internal Anal
Sphincter
Contraction of the External Anal
Sphincter
Contraction of the
Rectum
A) No No No
B) No Yes Yes
C) Yes No Yes
D) Yes No No
E) Yes Yes Yes
56. A physiology experiment is conducted in an anesthetized rat. The
distal duodenum is opened without disturbing its blood supply, and an
oxygen-recording micropipee is inserted into the tip of a villus that is
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introduction to physiology
human physiology
الفيزيولوجيا الطبية
محاضرات physiology
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F, Female; M, Male.
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