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Chapter 12 Part B The Central Nervous System © Annie Leibovitz/Contact Press Images © 2016 Pearson Education, Inc. PowerPoint® Lecture Slides prepared by Karen Dunbar Kareiva Ivy Tech Community College 12.2 Cerebral Hemispheres (cont.) Cerebral White Matter • Second of the three basic regions of cerebral hemispheres • Responsible for communication between cerebral areas, and between cortex and lower CNS • Consists of myelinated fibers bundled into large tracts • Classified according to direction they run: – Association, commissural, and projection fibers © 2016 Pearson Education, Inc. Cerebral White Matter (cont.) – Association fibers: horizontal running fibers that connect different parts of same hemisphere – Commissural fibers: horizontal fibers that connect gray matter of two hemispheres – Projection fibers: vertical fibers that connect hemispheres with lower brain or spinal cord • Internal capsule: projection fibers on each side of brain stem form compact band – Passes between thalamus and some of basal nuclei • Corona radiata: projection fibers that radiate through cerebral white matter to cortex © 2016 Pearson Education, Inc. Figure 12.9a White fiber tracts of the cerebral hemispheres. Superior Longitudinal fissure Lateral ventricle Basal nuclei • Caudate • Putamen • Globus pallidus Thalamus Association fibers (within hemisphere) Commissural fibers (between hemispheres) • Corpus callosum Projection fibers (cerebral cortex to or from lower area) • Corona radiata • Internal capsule Gray matter Third ventricle Pons Medulla oblongata Frontal section © 2016 Pearson Education, Inc. White matter Decussation (cross-over) of pyramids Figure 12.9b White fiber tracts of the cerebral hemispheres. Association fibers Commissural fibers • Corpus callosum Projection fibers • Corona radiata • Internal capsule Parasagittal section and dissection © 2016 Pearson Education, Inc. Gray matter Basal Nuclei (Ganglia) • Third of the three basic regions of cerebrum • Each hemisphere’s basal nuclei include a: – Caudate nucleus – Putamen – Globus pallidus • Caudate nucleus + putamen = striatum • Closely associated with subthalamic nuclei (diencephalon) and substantia nigra (midbrain) © 2016 Pearson Education, Inc. Figure 12.10a Basal nuclei. Striatum Caudate nucleus Putamen © 2016 Pearson Education, Inc. Thalamus Tail of caudate nucleus Basal Nuclei (Ganglia) (cont.) • Functions of basal nuclei are thought to: – Influence muscle movements – Play role in cognition and emotion – Regulate intensity of slow or stereotyped movements – Filter out incorrect/inappropriate responses – Inhibit antagonistic/unnecessary movements • Parkinson’s disease and Huntington’s disease are disorders of the basal nuclei © 2016 Pearson Education, Inc. Figure 12.10b Basal nuclei. Anterior Cerebral cortex Cerebral white matter Corpus callosum Anterior horn of lateral ventricle Head of caudate nucleus Putamen Globus pallidus Thalamus Tail of caudate nucleus Third ventricle Inferior horn of lateral ventricle Posterior © 2016 Pearson Education, Inc. 12.3 The Diencephalon • Consists of three paired gray-matter structures: – Thalamus – Hypothalamus – Epithalamus • All three enclose third ventricle © 2016 Pearson Education, Inc. Figure 12.11a Midsagittal section of the brain. Cerebral hemisphere Septum pellucidum Corpus callosum Interthalamic adhesion (intermediate mass of thalamus) Fornix Choroid plexus Thalamus (encloses third ventricle) Interventricular foramen Posterior commissure Pineal gland Anterior commissure Corpora quadrigemina Midbrain Cerebral aqueduct Hypothalamus Optic chiasma Pituitary gland Mammillary body Pons Medulla oblongata Spinal cord © 2016 Pearson Education, Inc. Epithalamus Arbor vitae (of cerebellum) Fourth ventricle Choroid plexus Cerebellum Thalamus • Bilateral egg-shaped nuclei that form superolateral walls of third ventricle • Makes up 80% of diencephalon • Bilateral nuclei connected by interthalamic adhesion (intermediate mass) – Contains several nuclei, named for location – Nuclei project and receive fibers from cerebral cortex © 2016 Pearson Education, Inc. Figure 12.12a Selected structures of the diencephalon. Medial Lateral Lateral dorsal dorsal posterior nucleus nucleus nucleus Pulvinar Anterior nuclei Medial geniculate body Reticular nucleus Lateral geniculate body Ventral Ventral Ventral posteroanterior lateral lateral Ventral nuclei The main thalamic nuclei. (The reticular nuclei that “cap” the thalamus laterally are depicted as curving translucent structures.) © 2016 Pearson Education, Inc. Thalamus (cont.) • Main thalamic function is to act as relay station for information coming into cortex – Sorts, edits, and relays ascending input such as: • Impulses from hypothalamus for regulating emotion and visceral function • Impulses from cerebellum and basal nuclei to help direct motor cortices • Impulses for memory or sensory integration • Overall, it acts to mediate sensation, motor activities, cortical arousal, learning, and memory © 2016 Pearson Education, Inc. Hypothalamus • Located below thalamus • Forms cap over brain stem and forms inferolateral walls of third ventricle • Contains many important nuclei such as: – Mammillary bodies: paired anterior nuclei that act as olfactory relay stations • Infundibulum: stalk that connects to pituitary gland © 2016 Pearson Education, Inc. Figure 12.12b Selected structures of the diencephalon. Paraventricular nucleus Anterior commissure Preoptic nucleus Anterior hypothalamic nucleus Supraoptic nucleus Suprachiasmatic nucleus Optic chiasma Infundibulum (stalk of the pituitary gland) The main hypothalamic nuclei. © 2016 Pearson Education, Inc. Fornix Dorsomedial nucleus Posterior hypothalamic nucleus Lateral hypothalamic area Ventromedial nucleus Arcuate nucleus Pituitary gland Mammillary body Hypothalamus (cont.) • The hypothalamus is the main visceral control and regulating center that is vital to homeostasis • Chief homeostasis controls: – Controls autonomic nervous system • Examples: blood pressure, rate and force of heartbeat, digestive tract motility, pupil size – Initiates physical responses to emotions • Part of limbic system: perceives pleasure, fear, rage, biological rhythms, and drives (sex drive) © 2016 Pearson Education, Inc. Hypothalamus (cont.) • The hypothalamus also: – Regulates body temperature: sweating or shivering – Regulates hunger and satiety in response to nutrient blood levels or hormones – Regulates water balance and thirst – Regulates sleep-wake cycles • Suprachiasmatic nucleus of thalamus sets our biological clock © 2016 Pearson Education, Inc. Hypothalamus (cont.) – Controls endocrine system functions such as: • Secretions of anterior pituitary gland • Production of posterior pituitary hormones © 2016 Pearson Education, Inc. Clinical – Homeostatic Imbalance 12.4 • Hypothalamic disturbances cause a number of disorders such as: – Severe body wasting – Obesity – Sleep disturbances – Dehydration – Emotional imbalances • Implicated in failure to thrive: delay in growth or development – Occurs when child is deprived of a warm, nurturing relationship © 2016 Pearson Education, Inc. Epithalamus • Most dorsal portion of diencephalon • Forms roof of third ventricle • Contains pineal gland (body) – Extends from posterior border – Secretes melatonin that helps regulate sleepwake cycle © 2016 Pearson Education, Inc. Figure 12.11a Midsagittal section of the brain. Cerebral hemisphere Septum pellucidum Corpus callosum Interthalamic adhesion (intermediate mass of thalamus) Fornix Choroid plexus Thalamus (encloses third ventricle) Interventricular foramen Posterior commissure Pineal gland Anterior commissure Corpora quadrigemina Midbrain Cerebral aqueduct Hypothalamus Optic chiasma Pituitary gland Mammillary body Pons Medulla oblongata Spinal cord © 2016 Pearson Education, Inc. Epithalamus Arbor vitae (of cerebellum) Fourth ventricle Choroid plexus Cerebellum Figure 12.11b Midsagittal section of the brain (continued). Corpus callosum Fornix Lateral ventricle Thalamus Third ventricle Posterior commissure Pineal gland Epithalamus Corpora quadrigemina Cerebral aqueduct Anterior commissure Hypothalamus Arbor vitae Optic chiasma Fourth ventricle Mammillary body Pons Medulla oblongata © 2016 Pearson Education, Inc. Cerebellum Midbrain Figure 12.13a Three views of the brain stem (green) and the diencephalon (purple). Thalamus Hypothalamus Midbrain Pons Medulla oblongata Diencephalon View (a) View (c) Brain stem View (b) Optic chiasma Optic nerve (II) Optic tract Diencephalon • Thalamus • Hypothalamus Mammillary body Crus cerebri of cerebral peduncles (midbrain) Oculomotor nerve (III) Trochlear nerve (IV) Abducens nerve (VI) Trigeminal nerve (V) Pons Facial nerve (VII) Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Pyramid Ventral root of first cervical nerve Decussation of pyramids Hypoglossal nerve (XII) Middle cerebellar peduncle Ventral view © 2016 Pearson Education, Inc. Spinal cord Vagus nerve (X) Accessory nerve (XI) Figure 12.13b Three views of the brain stem (green) and the diencephalon (purple). Thalamus Hypothalamus Midbrain Pons Medulla oblongata Diencephalon View (a) View (c) Brain stem View (b) Optic tract Infundibulum Pituitary gland Crus cerebri of cerebral peduncles (midbrain) Trigeminal nerve (V) Pons Facial nerve (VII) Abducens nerve (VI) Glossopharyngeal nerve (IX) Hypoglossal nerve (XII) Vagus nerve (X) Accessory nerve (XI) Left lateral view © 2016 Pearson Education, Inc. Thalamus Superior colliculus Inferior colliculus Trochlear nerve (IV) Superior cerebellar peduncle Middle cerebellar peduncle Inferior cerebellar peduncle Vestibulocochlear nerve (VIII) Olive Figure 12.13c Three views of the brain stem (green) and the diencephalon (purple). Thalamus Hypothalamus Midbrain Pons Medulla oblongata Diencephalon View (a) View (c) Brain stem View (b) Thalamus Pineal gland Midbrain Corpora • Superior colliculus quadrigemina • Inferior colliculus of tectum • Trochlear nerve (IV) • Superior cerebellar peduncle Floor of fourth ventricle Pons • Middle cerebellar peduncle Diencephalon Facial nerve (VII) Choroid plexus (fourth ventricle) Dorsal median sulcus Dorsal root of first cervical nerve Dorsal view © 2016 Pearson Education, Inc. Medulla oblongata • Inferior cerebellar peduncle • Vestibulocochlear nerve (VIII) • Glossopharyngeal nerve (IX) • Vagus nerve (X) • Accessory nerve (XI) 12.4 Brain Stem • Consists of three regions: midbrain, pons, medulla oblongata • Similar in structure to spinal cord but contains nuclei embedded in white matter • Controls automatic behaviors necessary for survival • Contains fiber tracts connecting higher and lower neural centers • Nuclei are associated with 10 of the 12 pairs of cranial nerves © 2016 Pearson Education, Inc. Figure 12.14 Inferior view of the brain, showing the three parts of the brain stem: midbrain, pons, and medulla oblongata. 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 © 2016 Pearson Education, Inc. Midbrain • Located between diencephalon and pons • Cerebral peduncles: two ventral bulges that contain pyramidal motor tracts – Form pillars that hold up cerebrum • Cerebral aqueduct: channel running through midbrain that connects third and fourth ventricles © 2016 Pearson Education, Inc. Midbrain (cont.) • Periaqueductal gray matter: nuclei that play a role in pain suppression and fight-or-flight response – Also include nuclei that control cranial nerve III (oculomotor) and IV (trochlear) © 2016 Pearson Education, Inc. Figure 12.13c Three views of the brain stem (green) and the diencephalon (purple). Thalamus Hypothalamus Midbrain Pons Medulla oblongata Diencephalon View (a) View (c) Brain stem View (b) Thalamus Pineal gland Midbrain Corpora • Superior colliculus quadrigemina • Inferior colliculus of tectum • Trochlear nerve (IV) • Superior cerebellar peduncle Floor of fourth ventricle Pons • Middle cerebellar peduncle Diencephalon Facial nerve (VII) Choroid plexus (fourth ventricle) Dorsal median sulcus Dorsal root of first cervical nerve Dorsal view © 2016 Pearson Education, Inc. Medulla oblongata • Inferior cerebellar peduncle • Vestibulocochlear nerve (VIII) • Glossopharyngeal nerve (IX) • Vagus nerve (X) • Accessory nerve (XI) Midbrain (cont.) • Midbrain nuclei scattered throughout white matter include: – Corpora quadrigemina: paired dorsal protrusions • Superior colliculi: visual reflex centers • Inferior colliculi: auditory relay centers – Substantia nigra: functionally linked to basal nuclei • Parkinson’s disease is degeneration of this area © 2016 Pearson Education, Inc. Midbrain (cont.) – Red nucleus: relay nuclei for some descending limb flexion motor pathways • Part of reticular formation © 2016 Pearson Education, Inc. Figure 12.13c Three views of the brain stem (green) and the diencephalon (purple). Thalamus Hypothalamus Midbrain Pons Medulla oblongata Diencephalon View (a) View (c) Brain stem View (b) Thalamus Pineal gland Midbrain Corpora • Superior colliculus quadrigemina • Inferior colliculus of tectum • Trochlear nerve (IV) • Superior cerebellar peduncle Floor of fourth ventricle Pons • Middle cerebellar peduncle Diencephalon Facial nerve (VII) Choroid plexus (fourth ventricle) Dorsal median sulcus Dorsal root of first cervical nerve Dorsal view © 2016 Pearson Education, Inc. Medulla oblongata • Inferior cerebellar peduncle • Vestibulocochlear nerve (VIII) • Glossopharyngeal nerve (IX) • Vagus nerve (X) • Accessory nerve (XI) Figure 12.15a Cross sections through different regions of the brain stem. Tectum Superior colliculus Periaqueductal gray matter Oculomotor nucleus (III) Medial lemniscus Cerebral aqueduct Reticular formation Dorsal Red nucleus Substantia nigra Fibers of pyramidal tract Ventral Midbrain © 2016 Pearson Education, Inc. Crus cerebri of cerebral peduncle Pons • Located between midbrain and medulla oblongata • Fourth ventricle separates pons from cerebellum • Composed of conduction tracts: – Longitudinal fibers connect higher brain centers and spinal cord – Transversal/dorsal fibers relay impulses between motor cortex and cerebellum © 2016 Pearson Education, Inc. Pons (cont.) • Origin of cranial nerves V (trigeminal), VI (abducens), and VII (facial) • Some nuclei play role in reticular formation, and some help maintain normal rhythm of breathing © 2016 Pearson Education, Inc. Figure 12.15b Cross sections through different regions of the brain stem. Superior cerebellar peduncle Trigeminal main sensory nucleus Fourth ventricle Reticular formation Trigeminal motor nucleus Middle cerebellar peduncle Trigeminal nerve (V) Medial lemniscus Pons © 2016 Pearson Education, Inc. Pontine nuclei Fibers of pyramidal tract Medulla Oblongata • Also known as medulla • Blends into spinal cord at foramen magnum • Contains fourth ventricle – Continuation of central canal of spinal cord – Medulla and pons form ventral wall – Contains choroid plexus: capillary-rich membrane that forms cerebral spinal fluid © 2016 Pearson Education, Inc. Medulla Oblongata (cont.) • Structures of the medulla oblongata – Pyramids: two ventral longitudinal ridges formed by pyramidal tracts from motor cortex – Decussation of the pyramids: point where pyramidal tracts cross over to opposite side of body – Olives: swellings caused by underlying inferior olivary nuclei that relay stretch information from muscles and joints to cerebellum © 2016 Pearson Education, Inc. Medulla Oblongata (cont.) – Cranial nerves VIII, IX, X, and XII – Vestibular and cochlear nuclei: mediate responses that maintain equilibrium – Nucleus cuneatus and nucleus gracilis: relay ascending sensory information from spinal cord © 2016 Pearson Education, Inc. Figure 12.11a Midsagittal section of the brain. Cerebral hemisphere Septum pellucidum Corpus callosum Interthalamic adhesion (intermediate mass of thalamus) Fornix Choroid plexus Thalamus (encloses third ventricle) Interventricular foramen Posterior commissure Pineal gland Anterior commissure Corpora quadrigemina Midbrain Cerebral aqueduct Hypothalamus Optic chiasma Pituitary gland Mammillary body Pons Medulla oblongata Spinal cord © 2016 Pearson Education, Inc. Epithalamus Arbor vitae (of cerebellum) Fourth ventricle Choroid plexus Cerebellum Figure 12.13c Three views of the brain stem (green) and the diencephalon (purple). Thalamus Hypothalamus Midbrain Pons Medulla oblongata Diencephalon View (a) View (c) Brain stem View (b) Thalamus Pineal gland Midbrain Corpora • Superior colliculus quadrigemina • Inferior colliculus of tectum • Trochlear nerve (IV) • Superior cerebellar peduncle Floor of fourth ventricle Pons • Middle cerebellar peduncle Diencephalon Facial nerve (VII) Choroid plexus (fourth ventricle) Dorsal median sulcus Dorsal root of first cervical nerve Dorsal view © 2016 Pearson Education, Inc. Medulla oblongata • Inferior cerebellar peduncle • Vestibulocochlear nerve (VIII) • Glossopharyngeal nerve (IX) • Vagus nerve (X) • Accessory nerve (XI) Figure 12.15c Cross sections through different regions of the brain stem. Hypoglossal nucleus (XII) Dorsal motor nucleus of vagus (X) Reticular formation Inferior cerebellar peduncle Lateral nuclear group Medial nuclear group Raphe nucleus Fourth ventricle Choroid plexus Solitary nucleus Vestibular nuclei (VIII) Cochlear nuclei (VIII) Nucleus ambiguus Inferior olivary nucleus Medial lemniscus Pyramid Medulla oblongata © 2016 Pearson Education, Inc. Medulla Oblongata (cont.) • Functions of the medulla oblongata – Medulla is an autonomic reflex center • Many functions overlap with hypothalamus – Hypothalamus relays instructions via medulla – Functional groups of medulla include: • Cardiovascular center – Cardiac center adjusts force and rate of heart contraction – Vasomotor center adjusts blood vessel diameter for blood pressure regulation © 2016 Pearson Education, Inc. Medulla Oblongata (cont.) • Respiratory centers – Generate respiratory rhythm – Control rate and depth of breathing (with pontine centers) • Various other centers regulate: – Vomiting – Hiccupping – Swallowing – Coughing – Sneezing © 2016 Pearson Education, Inc. 12.5 Cerebellum • 11% of brain mass • Located dorsal to pons and medulla • Processes input from cortex, brain stem, and sensory receptors to provide precise, coordinated movements of skeletal muscles • Also plays a major role in balance © 2016 Pearson Education, Inc. Cerebellar Anatomy • Cerebellar hemispheres connected by wormlike vermis • Folia: transversely oriented gyri • Each hemisphere has three lobes – Anterior, posterior, and flocculonodular • Contains thin cortex of gray matter with distinctive treelike pattern of white matter called arbor vitae © 2016 Pearson Education, Inc. Cerebellar Anatomy (cont.) • Purkinje fibers originate in cortex, synapse with cerebellum • Cerebellar homunculi show sensory maps of entire body © 2016 Pearson Education, Inc. Figure 12.16a Cerebellum. Anterior lobe Arbor vitae Cerebellar cortex Folia Pons Fourth ventricle Choroid plexus Medulla oblongata © 2016 Pearson Education, Inc. Posterior lobe Figure 12.16b Cerebellum. Anterior lobe Cerebellar cortex Arbor vitae Cerebellar peduncles • Superior • Middle • Inferior Medulla oblongata © 2016 Pearson Education, Inc. Posterior lobe Flocculonodular lobe Choroid plexus of fourth ventricle Figure 12.16c Cerebellum. Anterior lobe Primary fissure Posterior lobe Horizontal fissure Vermis © 2016 Pearson Education, Inc. Cerebellar Peduncles • All fibers in cerebellum are ipsilateral—from and to the same side of body • Three paired fiber tracts connect cerebellum to brain stem – Superior cerebellar peduncles connect cerebellum to midbrain – Middle cerebellar peduncles connect pons to cerebellum – Inferior cerebellar peduncles connect medulla to cerebellum © 2016 Pearson Education, Inc. Figure 12.16b Cerebellum. Anterior lobe Cerebellar cortex Arbor vitae Cerebellar peduncles • Superior • Middle • Inferior Medulla oblongata © 2016 Pearson Education, Inc. Posterior lobe Flocculonodular lobe Choroid plexus of fourth ventricle Cerebellar Processing • Cerebellum fine-tunes motor activity as follows: 1. Receives impulses from cerebral cortex of intent to initiate voluntary muscle contraction 2. Receives signals from proprioceptors throughout body, as well as visual and equilibrium pathways that: • Pathways continuously “inform” cerebellum of body’s position and momentum 3. Cerebellar cortex calculates the best way to smoothly coordinate muscle contraction 4. Sends “blueprint” of coordinated movement to cerebral motor cortex and brain stem nuclei © 2016 Pearson Education, Inc. Cognitive Functions of Cerebellum • Neuroimaging suggests that cerebellum plays role in thinking, language, and emotion • As it does for motor processes, it may compare actual output of higher functions with expected output and adjust accordingly © 2016 Pearson Education, Inc.