Copyright © 2010 Pearson Education, Inc. Chapter 12 The Central Nervous System Part B Shilla Chakrabarty, Ph.D.

Copyright © 2010 Pearson Education, Inc. Lateralization of Cortical Function  Lateralization is the division of labor between hemispheres  Cerebral dominance designates the hemisphere dominant for language (left hemisphere in 90% of people)  Left hemisphere: Controls language, math, and logic  Right hemisphere: Responsible for insight, visual- spatial skills, intuition, and artistic skills  Other basic regions of the hemispheres include the cerebral white matter and basal nuclei  Left and right hemispheres communicate via fiber tracts in the cerebral white matter

Copyright © 2010 Pearson Education, Inc. Cerebral White Matter And Fiber Tracts Comprised of myelinated fibers and their tracts that facilitate communication Types of fiber tracts:  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 Corona radiata Projection fibers Longitudinal fissure Gray matter White matter Association fibers Lateral ventricle Fornix Third ventricle Thalamus Pons Medulla oblongata Decussation of pyramids Commissural fibers (corpus callosum) Internal capsule Superior Basal nuclei Caudate Putamen Globus pallidus (a)

Copyright © 2010 Pearson Education, Inc. Basal Nuclei (Ganglia) Subcortical nuclei Main nuclei are the caudate nucleus and lentiform nucleus, which are collectively called the corpus striatum. Functionally associated with the subthalamic nuclei (in diencephalon) and the substantia nigra (in midbrain) Receive input from entire cerebral cortex and other subcortical nuclei Fibers of corona radiata Corpus striatum (a) Projection fibers run deep to lentiform nucleus Caudate nucleus Thalamus Tail of caudate nucleus Lentiform nucleus Putamen Globus pallidus (deep to putamen)

Copyright © 2010 Pearson Education, Inc. Figure 12.11b (1 of 2) Corpus callosum Anterior horn of lateral ventricle Caudate nucleus Putamen Lentiform nucleus (b) Globus pallidus Thalamus Tail of caudate nucleus Third ventricle Cerebral cortex Cerebral white matter Anterior Posterior Inferior horn of lateral ventricle

Copyright © 2010 Pearson Education, Inc. Functions of Basal Nuclei Have no direct access to motor pathways Communicate with premotor and prefrontal cortices via relays through thalamus, and influence muscle movements directed by primary motor cortex 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. Corpus callosum Choroid plexus Thalamus (encloses third ventricle) Pineal gland (part of epithalamus) Posterior commissure Corpora quadrigemina Cerebral aqueduct Arbor vitae (of cerebellum) Fourth ventricle Choroid plexus Cerebellum Septum pellucidum Interthalamic adhesion (intermediate mass of thalamus) Interven- tricular foramen Anterior commissure Hypothalamus Optic chiasma Pituitary gland Cerebral hemisphere Mammillary body Pons Medulla oblongata Spinal cord Mid- brain Fornix Diencephalon Three paired structures Thalamus Hypothalamus Epithalamus Encloses the third ventricle

Copyright © 2010 Pearson Education, Inc. Thalamus Occupies 80% of diencephalon Forms 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 Dorsal nuclei Medial Anterior nuclear group Reticular nucleus Ventral anterior Ventral lateral Ventral postero- lateral Lateral geniculate body Medial geniculate body Pulvinar Lateral dorsal Lateral posterior (a) The main thalamic nuclei. (The reticular nuclei that “cap” the thalamus laterally are depicted as curving translucent structures.) Ventral nuclei

Copyright © 2010 Pearson Education, Inc. 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 inferolateral walls of the third ventricle Contains many nuclei Infundibulum—stalk that connects to the pituitary gland Preoptic nucleus Supraoptic nucleus Supra- chiasmatic nucleus Anterior hypothalamic nucleus Dorsomedial nucleus Paraventricular nucleus Fornix Anterior commissure Posterior hypothalamic nucleus Lateral hypothalamic area Ventromedial nucleus Optic chiasma Infundibulum (stalk of the pituitary gland) Pituitary gland Mammillary body (b) The main hypothalamic nuclei. Arcuate nucleus

Copyright © 2010 Pearson Education, Inc. 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 Regulator of body temperature, food intake, water balance, and thirst Regulates sleep-wake cycles by working with other brain regions Control of endocrine system functioning:  Regulates 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 Corpus callosum Choroid plexus Thalamus (encloses third ventricle) Pineal gland (part of epithalamus) Posterior commissure Corpora quadrigemina Cerebral aqueduct Arbor vitae (of cerebellum) Fourth ventricle Choroid plexus Cerebellum Septum pellucidum Interthalamic adhesion (intermediate mass of thalamus) Interven- tricular foramen Anterior commissure Hypothalamus Optic chiasma Pituitary gland Cerebral hemisphere Mammillary body Pons Medulla oblongata Spinal cord Mid- brain Fornix

Copyright © 2010 Pearson Education, Inc. Brain Stem Three regions  Midbrain  Pons  Medulla oblongata 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 Frontal lobe Olfactory bulb (synapse point of cranial nerve I) Optic chiasma Optic nerve (II) Optic tract Mammillary body Pons Medulla oblongata Cerebellum Temporal lobe Spinal cord Midbrain

Copyright © 2010 Pearson Education, Inc. Figure 12.15a Optic chiasma View (a) Optic nerve (II) Mammillary body Oculomotor nerve (III) Crus cerebri of cerebral peduncles (midbrain) Trigeminal nerve (V) Abducens nerve (VI) Facial nerve (VII) Vagus nerve (X) Accessory nerve (XI) Hypoglossal nerve (XII) Ventral root of first cervical nerve Trochlear nerve (IV) Pons Middle cerebellar peduncle Pyramid Decussation of pyramids (a) Ventral view Spinal cord Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Diencephalon Thalamus Hypothalamus Diencephalon Brainstem Thalamus Hypothalamus Midbrain Pons Medulla oblongata

Copyright © 2010 Pearson Education, Inc. Figure 12.15c View (c) Diencephalon Brainstem Thalamus Hypothalamus Midbrain Pons Medulla oblongata Pineal gland Diencephalon Anterior wall of fourth ventricle (c) Dorsal view Thalamus Dorsal root of first cervical nerve Midbrain Superior colliculus Inferior colliculus Trochlear nerve (IV) Superior cerebellar peduncle Corpora quadrigemina of tectum Medulla oblongata Inferior cerebellar peduncle Facial nerve (VII) Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Vagus nerve (X) Accessory nerve (XI) Pons Middle cerebellar peduncle Dorsal median sulcus Choroid plexus (fourth ventricle)

Copyright © 2010 Pearson Education, Inc. Midbrain Located between the diencephalon and the pons Cerebral peduncles on ventral aspect form vertical pillars that hold up the cerebrum and contain pyramidal motor tracts Cerebral aqueduct connects third and fourth ventricles Periaqueductal gray matter surrounding cerebral aqueduct functions in pain suppression, and in fight- or-flight response

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 Dorsal Cerebral aqueduct Superior colliculus Reticular formation Crus cerebri of cerebral peduncle Ventral Fibers of pyramidal tract Substantia nigra (a) Midbrain Red nucleus Medial lemniscus Oculomotor nucleus (III) Periaqueductal gray matter Tectum

Copyright © 2010 Pearson Education, Inc. Reticular formation Trigeminal nerve (V) Pontine nuclei Fibers of pyramidal tract Middle cerebellar peduncle Trigeminal main sensory nucleus Trigeminal motor nucleus Superior cerebellar peduncle Medial lemniscus Fourth ventricle (b) Pons Pons Forms part of the anterior wall of the fourth ventricle Fibers of the pons  Connect higher brain centers and spinal cord  Relay impulses between the motor cortex and the cerebellum Origin of cranial nerves V (trigeminal), VI (abducens), and VII (facial) Nuclei help maintain normal rhythm of breathing

Copyright © 2010 Pearson Education, Inc. Medulla Oblongata Joins spinal cord at foramen magnum Forms part of ventral wall of fourth ventricle Contains a choroid plexus of fourth ventricle Pyramids—two ventral longitudinal ridges formed by pyramidal tracts Decussation of pyramids— crossover of corticospinal tracts Associated with cranial nerves VIII, X, and XII Vestibular nuclear complex— mediates responses that maintain equilibrium Inferior olivary nuclei—relay sensory information from muscles and joints to cerebellum

Copyright © 2010 Pearson Education, Inc. Figure 12.15a Optic chiasma View (a) Optic nerve (II) Mammillary body Oculomotor nerve (III) Crus cerebri of cerebral peduncles (midbrain) Trigeminal nerve (V) Abducens nerve (VI) Facial nerve (VII) Vagus nerve (X) Accessory nerve (XI) Hypoglossal nerve (XII) Ventral root of first cervical nerve Trochlear nerve (IV) Pons Middle cerebellar peduncle Pyramid Decussation of pyramids (a) Ventral view Spinal cord Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Diencephalon Thalamus Hypothalamus Diencephalon Brainstem Thalamus Hypothalamus Midbrain Pons Medulla oblongata

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 Respiratory centers  Generate respiratory rhythm  Control rate and depth of breathing, with pontine centers Additional centers regulate vomiting, hiccuping, swallowing, coughing and sneezing

Copyright © 2010 Pearson Education, Inc. Choroid plexus Fourth ventricle Pyramid Medial lemniscus Inferior olivary nucleus Nucleus ambiguus Inferior cerebellar peduncle Cochlear nuclei (VIII) Vestibular nuclear complex (VIII) Solitary nucleus Dorsal motor nucleus of vagus (X) Hypoglossal nucleus (XII) Lateral nuclear group Medial nuclear group Raphe nucleus Reticular formation

Copyright © 2010 Pearson Education, Inc. (b) Medulla oblongata Flocculonodular lobe Choroid plexus of fourth ventricle Posterior lobe Arbor vitae Cerebellar cortex Anterior lobe Cerebellar peduncles Superior Middle Inferior The Cerebellum 11% of brain mass Dorsal to the pons and medulla Subconsciously provides precise timing and appropriate patterns of skeletal muscle contraction Consists of two hemispheres connected by vermis Each hemisphere has three lobes: anterior, posterior, and flocculonodular Arbor vitae—distinctive treelike pattern of the cerebellar white matter (d) Anterior lobe Posterior lobe Vermis (d)

Copyright © 2010 Pearson Education, Inc. 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