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CHAPTER # 12(b)
THE CENTRAL NERVOUS
SYSTEM
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Lateralization of Cortical Function
• Lateralization
• Division of labor between hemispheres
• Cerebral dominance
• Designates the hemisphere dominant for
language (left hemisphere in 90% of people)
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Lateralization of Cortical Function
• Left hemisphere
• Controls language, math, and logic
• Right hemisphere
• Insight, visual-spatial skills, intuition, and
artistic skills
• Left and right hemispheres communicate via
fiber tracts in the cerebral white matter
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Cerebral White Matter
• Myelinated fibers and their tracts
• Responsible for communication
• Commissures (in corpus callosum)—connect
gray matter of the two hemispheres
• Association fibers—connect different parts of
the same hemisphere
• Projection fibers—(corona radiata) connect the
hemispheres with lower brain or spinal cord
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Longitudinal fissure
Lateral
ventricle
Superior
Commissural
fibers (corpus
callosum)
Association
fibers
Basal nuclei
• Caudate
• Putamen
• Globus
pallidus
Corona radiata
Thalamus
Internal
capsule
Fornix
Gray matter
Third
ventricle
White matter
Pons
Projection
fibers
Medulla oblongata
(a)
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Decussation
of pyramids
Figure 12.10a
Basal Nuclei (Ganglia)
• Subcortical nuclei
• Consists of the corpus striatum
• Caudate nucleus
• Lentiform nucleus (putamen + globus pallidus)
• Functionally associated with the subthalamic
nuclei (diencephalon) and the substantia nigra
(midbrain)
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Fibers of
corona radiata
Caudate
nucleus
Lentiform
Corpus
nucleus
striatum • Putamen
• Globus pallidus
(deep to putamen)
Projection fibers
run deep to
lentiform nucleus
(a)
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Thalamus
Tail of
caudate
nucleus
Figure 12.11a
Anterior
(b)
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Posterior
Cerebral cortex
Cerebral white matter
Corpus callosum
Anterior horn
of lateral ventricle
Caudate nucleus
Putamen
Lentiform
Globus
nucleus
pallidus
Thalamus
Tail of caudate nucleus
Third ventricle
Inferior horn
of lateral ventricle
Figure 12.11b (1 of 2)
Cerebral cortex
Cerebral white matter
Corpus callosum
Anterior horn
of lateral ventricle
Caudate nucleus
Lentiform nucleus
Thalamus
Third ventricle
Inferior horn
of lateral ventricle
(b)
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Figure 12.11b (2 of 2)
Functions of Basal Nuclei
• Though somewhat elusive, the following are
thought to be functions of basal nuclei
• Influence muscular control
• Help regulate attention and cognition
• Regulate intensity of slow or stereotyped
movements
• Inhibit antagonistic and unnecessary
movements
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Diencephalon
• Three paired structures
• Thalamus
• Hypothalamus
• Epithalamus
• Encloses the third ventricle
PLAY
Animation: Rotatable brain (sectioned)
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Cerebral hemisphere
Septum pellucidum
Interthalamic
adhesion
(intermediate
mass of
thalamus)
Interventricular
foramen
Anterior
commissure
Hypothalamus
Optic chiasma
Pituitary gland
Mammillary body
Pons
Medulla oblongata
Corpus callosum
Fornix
Choroid plexus
Thalamus
(encloses third
ventricle)
Posterior commissure
Pineal gland
(part of epithalamus)
Corpora
quadrigemina MidCerebral
brain
aqueduct
Arbor vitae (of
cerebellum)
Fourth ventricle
Choroid plexus
Cerebellum
Spinal cord
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Figure 12.12
Thalamus
• 80% of diencephalon
• Superolateral walls of the third ventricle
• Connected by the interthalamic adhesion
(intermediate mass)
• Contains several nuclei, named for their
location
• Nuclei project and receive fibers from the
cerebral cortex
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Dorsal nuclei
Medial Lateral Lateral
dorsal posterior
Pulvinar
Anterior
nuclear
group
Reticular
nucleus
Ventral
Ventral Ventral posteroanterior lateral lateral
Medial
geniculate
body
Lateral
geniculate
body
Ventral nuclei
(a) The main thalamic nuclei. (The reticular nuclei that “cap” the
thalamus laterally are depicted as curving translucent structures.)
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Figure 12.13a
Thalamic Function
• Gateway to the cerebral cortex
• Sorts, edits, and relays information
• Afferent impulses from all senses and all parts of the
body
• Impulses from the hypothalamus for regulation of
emotion and visceral function
• Impulses from the cerebellum and basal nuclei to help
direct the motor cortices
• Mediates sensation, motor activities, cortical arousal,
learning, and memory
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Hypothalamus
• Forms the inferolateral walls of the third
ventricle
• Contains many nuclei
• Example: mammillary bodies
• Paired anterior nuclei
• Olfactory relay stations
• Infundibulum—stalk that connects to the
pituitary gland
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Paraventricular
nucleus
Anterior
commissure
Preoptic
nucleus
Anterior
hypothalamic
nucleus
Supraoptic
nucleus
Suprachiasmatic
nucleus
Fornix
Arcuate
nucleus
Pituitary
gland
Optic
chiasma
Infundibulum
(stalk of the
pituitary gland)
(b) The main hypothalamic nuclei.
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Dorsomedial
nucleus
Posterior
hypothalamic
nucleus
Lateral
hypothalamic
area
Ventromedial
nucleus
Mammillary
body
Figure 12.13b
Hypothalamic Function
• Autonomic control center for many visceral
functions (e.g., blood pressure, rate and force
of heartbeat, digestive tract motility)
• Center for emotional response: Involved in
perception of pleasure, fear, and rage and in
biological rhythms and drives
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Hypothalamic Function
• Regulates body temperature, food intake,
water balance, and thirst
• Regulates sleep and the sleep cycle
• Controls release of hormones by the anterior
pituitary
• Produces posterior pituitary hormones
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Epithalamus
• Most dorsal portion of the diencephalon;
forms roof of the third ventricle
• Pineal gland—extends from the posterior
border and secretes melatonin
• Melatonin—helps regulate sleep-wake cycles
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Cerebral hemisphere
Septum pellucidum
Interthalamic
adhesion
(intermediate
mass of
thalamus)
Interventricular
foramen
Anterior
commissure
Hypothalamus
Optic chiasma
Pituitary gland
Mammillary body
Pons
Medulla oblongata
Corpus callosum
Fornix
Choroid plexus
Thalamus
(encloses third
ventricle)
Posterior commissure
Pineal gland
(part of epithalamus)
Corpora
quadrigemina MidCerebral
brain
aqueduct
Arbor vitae (of
cerebellum)
Fourth ventricle
Choroid plexus
Cerebellum
Spinal cord
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Figure 12.12
Brain Stem
• Three regions
• Midbrain
• Pons
• Medulla oblongata
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Brain Stem
• Similar structure to spinal cord but contains
embedded nuclei
• Controls automatic behaviors necessary for
survival
• Contains fiber tracts connecting higher and
lower neural centers
• Associated with 10 of the 12 pairs of cranial
nerves
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Frontal lobe
Olfactory bulb
(synapse point of
cranial nerve I)
Optic chiasma
Optic nerve (II)
Optic tract
Mammillary body
Midbrain
Pons
Temporal lobe
Medulla
oblongata
Cerebellum
Spinal cord
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Figure 12.14
View (a)
Optic chiasma
Optic nerve (II)
Crus cerebri of
cerebral peduncles
(midbrain)
Diencephalon
• Thalamus
• Hypothalamus
Mammillary body
Thalamus
Hypothalamus
Diencephalon
Midbrain
Oculomotor nerve (III)
Trochlear nerve (IV)
Pons
Brainstem
Medulla
oblongata
Trigeminal nerve (V)
Pons
Facial nerve (VII)
Middle cerebellar
peduncle
Abducens nerve (VI)
Vestibulocochlear
nerve (VIII)
Pyramid
Glossopharyngeal nerve (IX)
Hypoglossal nerve (XII)
Vagus nerve (X)
Ventral root of first
cervical nerve
Decussation of pyramids
Accessory nerve (XI)
Spinal cord
(a) Ventral view
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Figure 12.15a
Crus cerebri of
cerebral peduncles
(midbrain)
Thalamus
View (b)
Infundibulum
Pituitary gland
Superior colliculus
Inferior colliculus
Trochlear nerve (IV)
Trigeminal nerve (V)
Pons
Superior cerebellar peduncle
Middle cerebellar peduncle
Facial nerve (VII)
Abducens nerve (VI)
Glossopharyngeal nerve (IX)
Hypoglossal nerve (XII)
Inferior cerebellar peduncle
Vestibulocochlear nerve (VIII)
Olive
Thalamus
Vagus nerve (X)
Hypothalamus
Diencephalon
Midbrain
Accessory nerve (XI)
Pons
Brainstem
Medulla
oblongata
(b) Left lateral view
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Figure 12.15b
Thalamus
View (c)
Diencephalon
Pineal gland
Anterior wall of
fourth ventricle
Choroid plexus
(fourth ventricle)
Dorsal median sulcus
Dorsal root of
first cervical nerve
Midbrain
• Superior
Corpora
colliculus quadrigemina
• Inferior
of tectum
colliculus
• Trochlear nerve (IV)
• Superior cerebellar peduncle
Pons
• Middle cerebellar peduncle
Medulla oblongata
• Inferior cerebellar peduncle
• Facial nerve (VII)
• Vestibulocochlear nerve (VIII)
• Glossopharyngeal nerve (IX)
• Vagus nerve (X)
• Accessory nerve (XI)
Thalamus
Hypothalamus
Midbrain
Pons
(c) Dorsal view
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Diencephalon
Brainstem
Medulla
oblongata
Figure 12.15c
Midbrain
• Located between the diencephalon and the
pons
• Cerebral peduncles
• Contain pyramidal motor tracts
• Cerebral aqueduct
• Channel between third and fourth ventricles
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Midbrain Nuclei
• Nuclei that control cranial nerves III (oculomotor) and
IV (trochlear)
• Corpora quadrigemina—domelike dorsal protrusions
• Superior colliculi—visual reflex centers
• Inferior colliculi—auditory relay centers
• Substantia nigra—functionally linked to basal nuclei
• Red nucleus—relay nuclei for some descending
motor pathways and part of reticular formation
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Tectum
Periaqueductal gray
matter
Oculomotor
nucleus (III)
Medial
lemniscus
Red
nucleus
Substantia
nigra
Fibers of
pyramidal tract
(a) Midbrain
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Dorsal
Superior
colliculus
Cerebral aqueduct
Reticular formation
Ventral
Crus cerebri of
cerebral peduncle
Figure 12.16a
Pons
• Forms part of the anterior wall of the fourth ventricle
• Fibers of the pons
• Connect higher brain centers and the spinal cord
• Relay impulses between the motor cortex and the
cerebellum
• Origin of cranial nerves V (trigeminal), VI (abducens),
and VII (facial)
• Some nuclei of the reticular formation
• Nuclei that help maintain normal rhythm of breathing
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Fourth
ventricle
Superior cerebellar
peduncle
Trigeminal main
sensory nucleus
Trigeminal
motor nucleus
Middle
cerebellar
peduncle
Trigeminal
nerve (V)
Medial lemniscus
(b) Pons
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Reticular
formation
Pontine
nuclei
Fibers of
pyramidal
tract
Figure 12.16b
Medulla Oblongata
• Joins spinal cord at foramen magnum
• Forms part of the ventral wall of the fourth
ventricle
• Contains a choroid plexus of the fourth
ventricle
• Pyramids—two ventral longitudinal ridges
formed by pyramidal tracts
• Decussation of the pyramids—crossover of
the corticospinal tracts
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Medulla Oblongata
• Inferior olivary nuclei—relay sensory
information from muscles and joints to
cerebellum
• Cranial nerves VIII, X, and XII are associated
with the medulla
• Vestibular nuclear complex—mediates
responses that maintain equilibrium
• Several nuclei (e.g., nucleus cuneatus and
nucleus gracilis) relay sensory information
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Medulla Oblongata
• Autonomic reflex centers
• Cardiovascular center
• Cardiac center adjusts force and rate of heart
contraction
• Vasomotor center adjusts blood vessel
diameter for blood pressure regulation
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Medulla Oblongata
• Respiratory centers
• Generate respiratory rhythm
• Control rate and depth of breathing, with
pontine centers
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Medulla Oblongata
• Additional centers regulate
• Vomiting
• Hiccuping
• Swallowing
• Coughing
• Sneezing
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Reticular formation
Fourth ventricle
Choroid
Hypoglossal nucleus (XII)
plexus
Dorsal motor nucleus
of vagus (X)
Inferior cerebellar
peduncle
Lateral
nuclear
group
Medial
nuclear
group
Raphe
nucleus
Medial lemniscus
(c) Medulla oblongata
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Solitary
nucleus
Vestibular nuclear
complex (VIII)
Cochlear
nuclei (VIII)
Nucleus
ambiguus
Inferior olivary
nucleus
Pyramid
Figure 12.16c
The Cerebellum
• 11% of brain mass
• Dorsal to the pons and medulla
• Subconsciously provides precise timing and
appropriate patterns of skeletal muscle
contraction
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Anatomy of the Cerebellum
• Two hemispheres connected by vermis
• Each hemisphere has three lobes
• Anterior, posterior, and flocculonodular
• Folia—transversely oriented gyri
• Arbor vitae—distinctive treelike pattern of the
cerebellar white matter
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Anterior lobe
Cerebellar cortex
Arbor
vitae
Cerebellar
peduncles
• Superior
• Middle
• Inferior
Medulla
oblongata
(b)
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Flocculonodular
lobe
Posterior
lobe
Choroid
plexus of
fourth
ventricle
Figure 12.17b
Anterior
lobe
Posterior
lobe
(d)
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Vermis
Figure 12.17d
Cerebellar Peduncles
• All fibers in the cerebellum are ipsilateral
• Three paired fiber tracts connect the
cerebellum to the brain stem
• Superior peduncles connect the cerebellum to
the midbrain
• Middle peduncles connect the pons to the
cerebellum
• Inferior peduncles connect the medulla to the
cerebellum
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Cerebellar Processing for Motor Activity
• Cerebellum receives impulses from the cerebral
cortex of the intent to initiate voluntary muscle
contraction
• Signals from proprioceptors and visual and
equilibrium pathways continuously “inform” the
cerebellum of the body’s position and momentum
• Cerebellar cortex calculates the best way to smoothly
coordinate a muscle contraction
• A “blueprint” of coordinated movement is sent to the
cerebral motor cortex and to brain stem nuclei
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Cognitive Function of the Cerebellum
• Recognizes and predicts sequences of events
during complex movements
• Plays a role in nonmotor functions such as
word association and puzzle solving
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