CHAPTER 12b THE CENTRAL NERVOUS SYSTEM Copyright 2010

Lateralization of Cortical Function • Lateralization • Division of labor between hemispheres • Cerebral dominance • Designates the hemisphere dominant for language (left hemisphere in 90% of people) Copyright © 2010 Pearson Education, Inc.

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 Copyright © 2010 Pearson Education, Inc.

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 Copyright © 2010 Pearson Education, Inc.

Longitudinal fissure Lateral ventricle Basal nuclei • Caudate • Putamen • Globus pallidus Thalamus Superior Commissural fibers (corpus callosum) Association fibers Corona radiata Fornix Internal capsule Gray matter Third ventricle White matter Pons Projection fibers Medulla oblongata (a) Copyright © 2010 Pearson Education, Inc. Decussation of pyramids Figure 12. 10 a

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) Copyright © 2010 Pearson Education, Inc.

Fibers of corona radiata Caudate nucleus Lentiform Corpus nucleus striatum • Putamen • Globus pallidus (deep to putamen) Projection fibers run deep to lentiform nucleus (a) Copyright © 2010 Pearson Education, Inc. Thalamus Tail of caudate nucleus Figure 12. 11 a

Anterior (b) Copyright © 2010 Pearson Education, Inc. 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. 11 b (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) Copyright © 2010 Pearson Education, Inc. Figure 12. 11 b (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 Copyright © 2010 Pearson Education, Inc.

Diencephalon • Three paired structures • Thalamus • Hypothalamus • Epithalamus • Encloses the

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 Mid. Cerebral brain aqueduct Arbor vitae (of cerebellum) Fourth ventricle Choroid plexus Cerebellum Spinal cord Copyright © 2010 Pearson Education, Inc. 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 Copyright © 2010 Pearson Education, Inc.

Dorsal nuclei Medial Lateral dorsal posterior Pulvinar Anterior nuclear group Reticular nucleus Ventral posteroanterior 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. ) Copyright © 2010 Pearson Education, Inc. Figure 12. 13 a

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 Copyright © 2010 Pearson Education, Inc.

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 Copyright © 2010 Pearson Education, Inc.

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. Copyright © 2010 Pearson Education, Inc. Dorsomedial nucleus Posterior hypothalamic nucleus Lateral hypothalamic area Ventromedial nucleus Mammillary body Figure 12. 13 b

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 Copyright © 2010 Pearson Education, Inc.

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 Copyright © 2010 Pearson Education, Inc.

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 Copyright © 2010 Pearson Education, Inc.

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 Mid. Cerebral brain aqueduct Arbor vitae (of cerebellum) Fourth ventricle Choroid plexus Cerebellum Spinal cord Copyright © 2010 Pearson Education, Inc. Figure 12. 12

Brain Stem • Three regions • Midbrain • Pons • Medulla oblongata Copyright ©

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 Copyright © 2010 Pearson Education, Inc.

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 Copyright © 2010 Pearson Education, Inc. Figure 12. 14

Optic chiasma Optic nerve (II) Crus cerebri of cerebral peduncles (midbrain) Diencephalon • Thalamus • Hypothalamus Mammillary body View (a) Thalamus Hypothalamus Diencephalon Midbrain Oculomotor nerve (III) Trochlear nerve (IV) Pons Brainstem Medulla oblongata Trigeminal nerve (V) Pons Middle cerebellar peduncle Abducens nerve (VI) Facial nerve (VII) 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 Copyright © 2010 Pearson Education, Inc. Figure 12. 15 a

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 Copyright © 2010 Pearson Education, Inc. Figure 12. 15 b

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 Copyright © 2010 Pearson Education, Inc. Diencephalon Brainstem Medulla oblongata Figure 12. 15 c

Midbrain • Located between the diencephalon and the pons • Cerebral peduncles • Contain pyramidal motor tracts • Cerebral aqueduct • Channel between third and fourth ventricles Copyright © 2010 Pearson Education, Inc.

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 Copyright © 2010 Pearson Education, Inc.

Tectum Periaqueductal gray matter Oculomotor nucleus (III) Medial lemniscus Red nucleus Substantia nigra Fibers of pyramidal tract (a) Midbrain Copyright © 2010 Pearson Education, Inc. Dorsal Superior colliculus Cerebral aqueduct Reticular formation Ventral Crus cerebri of cerebral peduncle Figure 12. 16 a

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 Copyright © 2010 Pearson Education, Inc.

Fourth ventricle Superior cerebellar peduncle Trigeminal main sensory nucleus Trigeminal motor nucleus Middle cerebellar peduncle Trigeminal nerve (V) Medial lemniscus (b) Pons Copyright © 2010 Pearson Education, Inc. Reticular formation Pontine nuclei Fibers of pyramidal tract Figure 12. 16 b

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 Copyright © 2010 Pearson Education, Inc.

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 Copyright © 2010 Pearson Education, Inc.

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 Copyright © 2010 Pearson Education, Inc.

Medulla Oblongata • Respiratory centers • Generate respiratory rhythm • Control rate and depth

Medulla Oblongata • Additional centers regulate • Vomiting • Hiccuping • Swallowing • Coughing

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 Copyright © 2010 Pearson Education, Inc. Solitary nucleus Vestibular nuclear complex (VIII) Cochlear nuclei (VIII) Nucleus ambiguus Inferior olivary nucleus Pyramid Figure 12. 16 c

The Cerebellum • 11% of brain mass • Dorsal to the pons and medulla • Subconsciously provides precise timing and appropriate patterns of skeletal muscle contraction Copyright © 2010 Pearson Education, Inc.

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 Copyright © 2010 Pearson Education, Inc.

Anterior lobe Cerebellar cortex Arbor vitae Cerebellar peduncles • Superior • Middle • Inferior Medulla oblongata (b) Copyright © 2010 Pearson Education, Inc. Flocculonodular lobe Posterior lobe Choroid plexus of fourth ventricle Figure 12. 17 b

Anterior lobe Posterior lobe (d) Copyright © 2010 Pearson Education, Inc. Vermis Figure 12.

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 Copyright © 2010 Pearson Education, Inc.

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 Copyright © 2010 Pearson Education, Inc.

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 Copyright © 2010 Pearson Education, Inc.