Brain and Cranial Nerves Lecture Notes PDF

Chapter 14  Overview of the brain – Read (section 14.1)  Meninges and ventricles – Read (section 14.2)  Hindbrain and midbrain – Study (section 14.3)  The Forebrain – Study (section 14.4)  Integrative functions – Read (section 14.5)  Cranial nerves – Study (the list and section...

Chapter 14  Overview of the brain – Read (section 14.1)  Meninges and ventricles – Read (section 14.2)  Hindbrain and midbrain – Study (section 14.3)  The Forebrain – Study (section 14.4)  Integrative functions – Read (section 14.5)  Cranial nerves – Study (the list and section 14.6) Divisions of Brain Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer.  Major Landmarks Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Three major portions of the Rostral Caudal brain – Cerebrum is 83% of brain Central sulcus volume; cerebral hemispheres, gyri and sulci, longitudinal Gyri Cerebrum fissure, corpus callosum Lateral sulcus – Cerebellum contains 50% of the Temporal lobe Cerebellum neurons; second largest brain region, located in posterior cranial fossa Brainstem – Brainstem is the portion of the Spinal cord (b) Lateral view brain that remains if the cerebrum and cerebellum are removed; diencephalon, midbrain, pons, and medulla oblongata Three Major Portions of the Brain Cerebrum Brainstem Cerebellum  Major Landmarks Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Longitudinal fissure—deep Cerebral hemispheres groove that separates cerebral hemispheres Gyri—thick folds Frontal lobe Central sulcus Sulci—shallow grooves Parietal lobe Corpus callosum—thick nerve bundle at bottom of Occipital lobe longitudinal fissure that Longitudinal fissure connects hemispheres (a) Superior view Corpus Callosum Gyri & Sulci  Brainstem Diencephalon Midbrain Pons Medulla oblongata  Major Landmarks Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Central sulcus Parietal lobe Cingulate gyrus Corpus callosum Parieto–occipital sulcus Frontal lobe Occipital lobe Thalamus Anterior Habenula Epithalamus commissure Pineal gland Hypothalamus Optic chiasm Posterior commissure Mammillary body Cerebral aqueduct Pituitary gland Fourth ventricle Temporal lobe Midbrain Cerebellum Pons Medulla oblongata (a)  Major Landmarks Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cingulate gyrus Corpus callosum Lateral ventricle Parieto–occipital sulcus Choroid plexus Pineal gland Thalamus Hypothalamus Occipital lobe Midbrain Posterior commissure Pons Fourth ventricle Cerebellum Medulla oblongata (b) b: © The McGraw-Hill Companies, Inc./Dennis Strete, photographer  Medulla Oblongata  The Medulla Oblongata All nerve fibers connecting the brain to the spinal cord pass through the medulla Four pairs of cranial nerves begin or end in medulla—IX, X, XI, XII Cardiac center – Adjusts rate and force of heart Vasomotor center – Adjusts blood vessel diameter Respiratory centers – Control rate and depth of breathing Reflex centers – For coughing, sneezing, gagging, swallowing, vomiting, salivation, sweating, movements of tongue and head Pons  The Pons Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Central sulcus Parietal lobe Cingulate gyrus Corpus callosum Parieto–occipital sulcus Frontal lobe Occipital lobe Thalamus Anterior Habenula Epithalamus commissure Pineal gland Hypothalamus Optic chiasm Posterior commissure Mammillary body Cerebral aqueduct Pituitary gland Temporal lobe Fourth ventricle Midbrain Cerebellum Pons Medulla oblongata Figure 14.2a (a) Metencephalon—develops into the pons and cerebellum Pons—anterior bulge in brainstem, rostral to medulla Cerebral peduncles—connect cerebellum to pons and midbrain 14-16  The Pons Ascending sensory tracts Descending motor tracts Pathways in and out of cerebellum Cranial nerves V, VI, VII, and VIII – Sensory roles: hearing, equilibrium, taste, facial sensations – Motor roles: eye movement, facial expressions, chewing, swallowing, urination, and secretion of saliva and tears Reticular formation in pons contains additional nuclei concerned with sleep, respiration, posture Midbrain  The Midbrain Copyright © The McGraw-Hill Companies, Inc. 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Posterior Superior colliculus Tectum Cerebral aqueduct Medial geniculate nucleus Reticular formation Central gray matter Cerebral peduncle: Oculomotor nucleus Tegmentum Medial lemniscus Red nucleus Substantia nigra (a) Midbrain Cerebral crus (b) Pons Oculomotor nerve (III) Anterior (c) Medulla (a) Midbrain  The Midbrain Mesencephalon becomes one mature brain structure, the midbrain – Short segment of brainstem that connects the hindbrain to the forebrain – Contains cerebral aqueduct – Contains continuations of the medial lemniscus and reticular formation – Contains the motor nuclei of two cranial nerves that control eye movements: CN III (oculomotor) and CN IV (trochlear)  The Midbrain Mesencephalon (cont.) – Tectum: rooflike part of the midbrain posterior to cerebral aqueduct Exhibits four bulges, the corpora quadrigemina Upper pair, the superior colliculi, function in visual attention, tracking moving objects, and some reflexes Lower pair, the inferior colliculi, receives signals from the inner ear – Relays them to other parts of the brain, especially the thalamus  The Midbrain – Substantia nigra Dark gray to black nucleus pigmented with melanin Motor center that relays inhibitory signals to thalamus and basal nuclei preventing unwanted body movement Degeneration of neurons leads to tremors of Parkinson disease – Cerebral crus Bundle of nerve fibers that connect the cerebrum to the pons Carries corticospinal tracts  The Reticular Formation Copyright © The McGraw-Hill Companies, Inc. 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Radiations to cerebral cortex Thalamus Loosely organized web of gray matter that runs vertically through all levels of the brainstem Clusters of gray matter scattered throughout pons, midbrain, and medulla Occupies space between white fiber tracts and Auditory input brainstem nuclei Visual input Has connections with many Reticular formation Ascending general areas of cerebrum sensory fibers Descending motor – More than 100 small neural fibers to spinal cord networks without distinct boundaries  The Reticular Formation Networks – Somatic motor control Adjust muscle tension to maintain tone, balance, and posture Especially during body movements Relays signals from eyes and ears to the cerebellum Integrates visual, auditory, and balance and motion stimuli into motor coordination Gaze center—allows eyes to track and fixate on objects Central pattern generators—neural pools that produce rhythmic signals to the muscles of breathing and swallowing  The Reticular Formation Cont. – Cardiovascular control Includes cardiac and vasomotor centers of medulla oblongata – Pain modulation One route by which pain signals from the lower body reach the cerebral cortex Origin of descending analgesic pathways—fibers act in the spinal cord to block transmission of pain signals to the brain  The Reticular Formation – Sleep and consciousness Plays central role in states of consciousness, such as alertness and sleep Injury to reticular formation can result in irreversible coma – Habituation Process in which the brain learns to ignore repetitive, inconsequential stimuli while remaining sensitive to others Cerebellum  The Cerebellum Anterior Vermis Anterior lobe Posterior lobe Folia Cerebellar Posterior hemisphere (b) Superior view The largest part of the hindbrain and the second largest part of the brain as a whole Consists of right and left cerebellar hemispheres connected by vermis Cortex of gray matter with folds (folia) and four deep nuclei in each hemisphere Contains more than half of all brain neurons—about 100 billion – Granule cells and Purkinje cells synapse on deep nuclei White matter branching pattern is called arbor vitae  The Cerebellum Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Superior colliculus Inferior colliculus Pineal gland Posterior commissure Cerebral aqueduct Mammillary body Midbrain White matter (arbor vitae) Oculomotor nerve Gray matter Fourth ventricle Pons Medulla oblongata (a) Median section Monitors muscle contractions and aids in motor coordination Evaluation of sensory input – Comparing textures without looking at them – Spatial perception and comprehension of different views of three- dimensional objects belonging to the same object Timekeeping center – Predicting movement of objects – Helps predict how much the eyes must move in order to compensate for head movements and remain fixed on an object  The Cerebellum Cont. Hearing – Distinguish pitch and similar-sounding words Planning and scheduling tasks Lesions may result in emotional overreactions and trouble with impulse control  The Forebrain Forebrain consists of two parts – Diencephalon Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Encloses the third ventricle Telencephalon Forebrain Most rostral part of the Diencephalon Mesencephalon Midbrain brainstem Pons Metencephalon Cerebellum Hindbrain Has three major Myelencephalon (medulla oblongata) embryonic derivatives Spinal cord – Thalamus (c) Fully developed – Hypothalamus – Epithalamus Figure 14.4c – Telencephalon Develops chiefly into the cerebrum 14-31  Thalamus Hypothalamus  The Diencephalon: Thalamus Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Thalamic Nuclei Anterior group Part of limbic system; memory and emotion Medial group Emotional output to prefrontal cortex; awareness of emotions Ventral group Somesthetic output to postcentral gyrus; signals from cerebellum and basal nuclei to motor areas of cortex Figure 14.12a Lateral group Somesthetic output to association areas of cortex; contributes to emotional function Lateral geniculate nucleus of limbic system Medial geniculate nucleus Posterior group Relay of visual signals to occipital lobe (via lateral (a) Thalamus geniculate nucleus) and auditory signals to temporal lobe (via medial geniculate nucleus) Thalamus—ovoid mass on each side of the brain perched at the superior end of the brainstem beneath the cerebral hemispheres – Constitutes about four-fifths of the diencephalon – Two thalami are joined medially by a narrow intermediate mass – Composed of at least 23 nuclei; to consider five major functional groups 14-33  The Diencephalon: Thalamus Cont. – “Gateway to the cerebral cortex”: nearly all input to the cerebrum passes by way of synapses in the thalamic nuclei, filters information on its way to cerebral cortex – Plays key role in motor control by relaying signals from cerebellum to cerebrum and providing feedback loops between the cerebral cortex and the basal nuclei – Involved in the memory and emotional functions of the limbic system: a complex of structures that include some cerebral cortex of the temporal and frontal lobes and some of the anterior thalamic nuclei Hypothalamus  The Diencephalon: Hypothalamus Copyright © The McGraw-Hill Companies, Inc. 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Hypothalamus—forms part Cingulate gyrus Central sulcus Parietal lobe of the walls and floor of the Corpus callosum Parieto–occipital sulcus Frontal lobe third ventricle Thalamus Anterior Occipital lobe Habenula Epithalamus Pineal gland commissure Hypothalamus Optic chiasm Posterior commissure Mammillary body Extends anteriorly to optic Cerebral aqueduct Pituitary gland Temporal lobe Fourth ventricle Cerebellum chiasm and posteriorly to Midbrain Pons the paired mammillary (a) Medulla oblongata bodies Figure 14.2a Each mammillary body contains three or four mammillary nuclei – Relay signals from the limbic system to the thalamus 14-36  The Diencephalon: Hypothalamus Infundibulum—a stalk that attaches the pituitary gland to the hypothalamus Major control center of autonomic nervous system and endocrine system – Plays essential role in homeostatic regulation of all body systems Functions of hypothalamic nuclei – Hormone secretion Controls anterior pituitary Regulates growth, metabolism, reproduction, and stress responses Hypothalamus, Infundibulum, & Pituitary  The Diencephalon: Hypothalamus Cont. – Hormone secretion Controls anterior pituitary Regulates growth, metabolism, reproduction, and stress responses – Autonomic effects Major integrating center for autonomic nervous system Influences heart rate, blood pressure, gastrointestinal secretions, motility, etc. – Thermoregulation Hypothalamic thermostat monitors body temperature Activates heat-loss center when temp is too high Activates heat-promoting center when temp is too low 14-39  The Diencephalon: Hypothalamus Cont. – Food and water intake Hunger and satiety centers monitor blood glucose and amino acid levels – Produce sensations of hunger and satiety Thirst center monitors osmolarity of the blood – Rhythm of sleep and waking Controls 24-hour (circadian) rhythm of activity – Memory Mammillary nuclei receive signals from hippocampus – Emotional behavior Anger, aggression, fear, pleasure, and contentment 14-40  The Diencephalon: Epithalamus Copyright © The McGraw-Hill Companies, Inc. 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Central sulcus Parietal lobe Cingulate gyrus Corpus callosum Parieto–occipital sulcus Frontal lobe Occipital lobe Thalamus Anterior Habenula Epithalamus commissure Pineal gland Hypothalamus Optic chiasm Posterior commissure Mammillary body Cerebral aqueduct Pituitary gland Temporal lobe Fourth ventricle Midbrain Cerebellum Pons Medulla (a) oblongata Figure 14.2a Epithalamus—very small mass of tissue composed of: – Pineal gland: endocrine gland – Habenula: relay from the limbic system to the midbrain – Thin roof over the third ventricle 14-41 Cerebrum  The Telencephalon: Cerebrum Central sulcus Parietal lobe Cingulate gyrus Corpus callosum Parieto–occipital sulcus Frontal lobe Occipital lobe Thalamus Anterior Habenula Epithalamus commissure Pineal gland Hypothalamus Optic chiasm Posterior commissure Mammillary body Cerebral aqueduct Pituitary gland Temporal lobe Fourth ventricle Midbrain Cerebellum Pons Medulla oblongata (a) Cerebrum—largest and most conspicuous part of the human brain – Seat of sensory perception, memory, thought, judgment, and voluntary motor actions  The Cerebrum Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cerebral hemispheres Rostral Caudal Central sulcus Frontal lobe Gyri Cerebrum Lateral sulcus Central sulcus Temporal lobe Cerebellum Parietal lobe Brainstem Occipital lobe Longitudinal fissure Spinal cord (b) Lateral view (a) Superior view Two cerebral hemispheres divided by longitudinal fissure – Connected by white fibrous tract, the corpus callosum – Gyri and sulci: increase amount of cortex in the cranial cavity – Gyri increases surface area for information-processing capability – Some sulci divide each hemisphere into five lobes named for the cranial bones overlying them Cerebral Hemispheres & Longitudinal Fissure  Frontal lobe The Cerebrum – Voluntary motor functions – Motivation, foresight, planning, memory, mood, emotion, social judgment, Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. and aggression Parietal lobe Rostral Caudal – Receives and integrates Frontal lobe Parietal lobe general sensory information, taste, and some visual Precentral processing gyrus Occipital lobe Postcentral gyrus – Primary visual center of Central sulcus brain Temporal lobe Insula Occipital lobe – Areas for hearing, smell, learning, memory, and Lateral sulcus some aspects of vision and emotion Insula (hidden by other Temporal lobe regions) – Understanding spoken language, taste and sensory information from visceral receptors Cerebrum-Frontal Lobe Cerebrum-Parietal Lobe Cerebrum-Occipital Lobe  The Basal Nuclei Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cerebrum Corpus callosum Lateral ventricle Thalamus Internal capsule Caudate nucleus Putamen Corpus Insula Lentiform striatum Third ventricle Globus pallidus nucleus Hypothalamus Subthalamic nucleus Optic tract Pituitary gland Basal nuclei—masses of cerebral gray matter buried deep in the white matter, lateral to the thalamus – Receives input from the substantia nigra of the midbrain and the motor areas of the cortex – Send signals back to both these locations – Involved in motor control  The Basal Nuclei At least three brain centers form basal nuclei – Caudate nucleus – Putamen – Globus pallidus Lentiform nucleus—putamen and globus pallidus collectively Corpus striatum—putamen and caudate nucleus collectively  The Limbic System Limbic system—important center of emotion and learning Medial Most anatomically prominent prefrontal cortex Corpus Fornix components are: callosum Cingulate – Cingulate gyrus: arches gyrus Thalamic nuclei Orbitofrontal Mammillary over the top of the corpus cortex Basal nuclei body Hippocampus callosum in the frontal and Amygdala parietal lobes Temporal lobe – Hippocampus: in the medial temporal lobe; memory – Amygdala: immediately rostral to the hippocampus; emotion  The Limbic System Limbic system components are connected through a complex loop of fiber tracts allowing for somewhat Medial prefrontal cortex circular patterns of Corpus callosum Fornix feedback Cingulate gyrus Thalamic nuclei Orbitofrontal Mammillary cortex body Basal nuclei Hippocampus Limbic system structures Amygdala have centers for both Temporal lobe gratification and aversion – Gratification: sensations of pleasure or reward – Aversion: sensations of fear or sorrow