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Brain

Anterior view

Brain

Superior view

Brain

Inferior view

Brain

Posterior view

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 1 Spinal cord

 2 Medulla oblongata

 3 Pons

 4 Cerebellum

 5 Fourth ventricle

 6 Midbrain

 7 Inferior colliculus

Sagittal section of the brain

Medial view

As the spinal cord ascends through the foramen magnum to enter the skull, the

cranial central nervous system gradually expands in size to form the large central

processing circuitry we call the brain. The increasing size of the brain results from

Brain Regions

 8 Superior colliculus

 9 Thalamus of diencephalon

10 Hypothalamus of diencephalon

 11 Interthalamic adhesion

12 Pineal gland

13 Mammillary body

14 Optic tract

the addition of more and more gray processing centers to the basic cord-like brain stem. The caudal part of the brain, called

the brain stem, consists of the medulla oblongata, pons, and midbrain. Though all of these structural regions exhibit their

own specializations, they have certain fi ber tracts in common and all have nuclei for the cranial nerves. Added to the brain

stem are the more rostral portions of the brain — the cerebellum, diencephalon, and cerebral hemispheres. These large processing centers greatly increase the size of the brain. The images on the facing page show the principal parts of the brain.

15 Frontal lobe of cerebrum

16 Parietal lobe of cerebrum

17 Occipital lobe of cerebrum

18 Temporal lobe of cerebrum

19 Corpus callosum

20 Lateral ventricle

21 Fornix

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Medulla oblongata Pons

Cerebellum

Cerebrum

Midbrain

Diencephalon – epithalamus, thalamus, hypothalamus

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 1 Central sulcus

 2 Precentral gyrus

 3 Postcentral gyrus

 4 Precentral sulcus

 5 Postcentral sulcus

 6 Parieto-occipital sulcus

 7 Transverse occipital sulcus

Brain dissection revealing insular lobe

Lateral view

The cerebrum, by far the largest part of the human brain, consists of the cerebral hemispheres

and the basal nuclei. The large, obvious cerebrum is divided into two halves, the right and left

cerebral hemispheres. Each cerebral hemisphere has an outer layer of gray matter, the cereCerebrum

 8 Calcarine sulcus

 9 Superior temporal gyrus

10 Middle temporal gyrus

 11 Inferior temporal gyrus

12 Inferior frontal gyrus

13 Middle frontal gyrus

14 Superior frontal gyrus

bral cortex, covering deeper networks of interconnecting white tracts that connect different areas of the cortex with one

another and with lower brain centers. The amount of cortex is greatly increased by a complex folding of the cerebral surface.

The folds produce hills, gyri (singular gyrus), and depressions, sulci (singular sulcus). This cortical surface forms the highest

level of processing circuitry in the brain. The two hemispheres are connected to each other by the corpus callosum, a thick

band consisting of an estimated 300 million neuronal axons traversing between the two hemispheres. Located deep within

the cerebrum is another region of gray matter, the basal nuclei, which form key integration centers between the cortex and

lower brain centers.

15 Short gyri

16 Long gyrus

17 Limen

18 Pons

19 Cerebellum

20 Medulla oblongata

21 Spinal cord

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Frontal lobe Parietal lobe

Occipital lobe Temporal lobe

Insular lobe

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 1 Folia of cerebellum

 2 Anterior lobe of cerebellum

 3 Posterior lobe of cerebellum

 4 Superior vermis

 5 Inferior vermis

 6 Postlunate fissure

 7 Posterior cerebellar notch

 8 Tonsil

 9 Quadrangular lobe of anterior

Immediately above the medulla oblongata the central nervous system expands dorsally

to form the cerebellum, which means little brain. The cerebellum, like the cerebrum, has

a highly folded surface that greatly increases the surface area of its outer gray matter

Cerebellum

10 Primary fissure

 11 Flocculus

12 Lingula

13 Central lobule

14 Culmen

15 Declive

16 Folium

17 Tuber

18 Pyramid

cortex. It is estimated that the cerebellum has in the neighborhood of 10 billion neurons, which have a variety of functional

roles. The cerebellum processes input received from the cerebral cortex, various brain stem nuclei, and peripheral sensory

receptors to smooth and coordinate complex, skilled movements. It plays an important role in posture and balance and

functions in cognition and language processing.

Cerebellum

Posterior view

Cerebellum

Lateral view

Sagittal section of cerebellum

Medial view

19 Uvula

20 Nodulus

21 Midbrain

22 Superior medullary velum

23 Fourth ventricle

24 Median aperture

25 Cerebral aqueduct

26 Pons

27 Medulla oblongata

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 1 Infundibulum

 2 Anterior perforated substance

 3 Tuber cinereum

 4 Mammillary body

 5 Posterior perforated substance

 6 Pulvinar of thalamus

 7 Pineal gland

 8 Superior colliculus

 9 Inferior colliculus

10 Medial geniculate ganglion

 11 Pons

12 Superior cerebellar peduncle

13 Middle cerebellar peduncle

14 Inferior cerebellar peduncle

The diencephalon, rostral to the midbrain

and almost completely surrounded by the

cerebral hemispheres, consists of four

Diencephalon and Brainstem

major parts — the thalamus, subthalamus, epithalamus, and hypothalamus. Projecting from the hypothalamus is the

hypophysis, or pituitary gland. The brainstem consists of the medulla oblongata, pons, and midbrain. The medulla resembles the

spinal cord in many ways. Like the cord it gives rise to many nerve roots; however, these are the roots of cranial nerves

rather than spinal nerves. The pons is the bridge between the two cerebellar hemispheres. The ventral portion of the pons

forms a large synaptic relay station consisting of scattered gray centers called the pontine nuclei. The dorsal portion of the

pons is more like the other regions of the brainstem, the medulla and midbrain. The midbrain sits just above the pons and

is obscured by the large, overlapping cerebral hemispheres. It contains nuclei for cranial nerves III and IV, as well as

ascending and descending fi ber tracts from the cerebrum.

Brainstem

Ventral view

Brainstem

Posterior view

15 Medial eminence

16 Facial colliculus

17 Locus ceruleus

18 Trigeminal tubercle

19 Hypoglossal tubercle

20 Vestibular area

21 Sulcus limitans

22 Lateral recess

23 Obex

24 Olive

25 Pyramid

26 Third ventricle

27 Fourth ventricle

28 Cerebral crus

29 Superior medullary vellum

30 Flocculus of cerebellum

31 Caudate nucleus

32 Optic tract

33 Optic chiasm

34 Optic nerve

35 Oculomotor nerve

36 Trochlear nerve

37 Abducens nerve

38 Trigeminal nerve

39 Facial nerve

40 Vestibulocochlear nerve

41 Glossopharyngeal nerve

42 Vagus nerve

43 Accessory nerve

44 Hypoglossal nerve

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