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Transcript
Chapter 13 The Brain and Cranial Nerves PowerPoint® Lecture Slides prepared by Jason LaPres Lone Star College - North Harris Copyright © 2010 Pearson Education, Inc. An Introduction to the Brain and Cranial Nerves • The Adult Human Brain • Ranges from 750 cc to 2100 cc • Contains almost 97% of the body’s neural tissue • Average weight about 1.4 kg (3 lb) Copyright © 2010 Pearson Education, Inc. The Brain • Six Regions of the Brain • Cerebrum • Cerebellum • Diencephalon • Mesencephalon • Pons • Medulla oblongata 3D Peel-Away of the Brain Copyright © 2010 Pearson Education, Inc. The Brain • Cerebrum • Largest part of brain • Controls higher mental functions • Divided into left and right cerebral hemispheres • Surface layer of gray matter (neural cortex) Copyright © 2010 Pearson Education, Inc. The Brain • Cerebrum • Neural cortex • Also called cerebral cortex • Folded surface increases surface area • Elevated ridges (gyri) • Shallow depressions (sulci) • Deep grooves (fissures) Copyright © 2010 Pearson Education, Inc. The Brain • Cerebellum • Second largest part of brain • Coordinates repetitive body movements • Two hemispheres • Covered with cerebellar cortex Copyright © 2010 Pearson Education, Inc. The Brain • Diencephalon • Located under cerebrum and cerebellum • Links cerebrum with brain stem • Three divisions • Left thalamus • Right thalamus • Hypothalamus Copyright © 2010 Pearson Education, Inc. The Brain • Diencephalon • Thalamus • Relays and processes sensory information • Hypothalamus • Hormone production • Emotion • Autonomic function • Pituitary gland • • • • Major endocrine gland Connected to hypothalamus Via infundibulum (stalk) Interfaces nervous and endocrine systems Copyright © 2010 Pearson Education, Inc. The Brain • The Brain Stem • Processes information between • Spinal cord and cerebrum or cerebellum • Includes • Mesencephalon • Pons • Medulla oblongata Copyright © 2010 Pearson Education, Inc. The Brain • The Brain Stem • Mesencephalon • Also called midbrain • Processes sight, sound, and associated reflexes • Maintains consciousness • Pons • Connects cerebellum to brain stem • Is involved in somatic and visceral motor control Copyright © 2010 Pearson Education, Inc. The Brain • The Brain Stem • Medulla oblongata • Connects brain to spinal cord • Relays information • Regulates autonomic functions: • heart rate, blood pressure, and digestion Copyright © 2010 Pearson Education, Inc. The Brain Figure 13–1 An Introduction to Brain Structures and Functions. Copyright © 2010 Pearson Education, Inc. The Brain • Embryological Development • Determines organization of brain structures • Neural tube • Origin of brain • Enlarges into three primary brain vesicles • prosencephalon • mesencephalon • rhombencephalon Copyright © 2010 Pearson Education, Inc. The Brain • Five Secondary Brain Vesicles • Telencephalon • Diencephalon • Mesencephalon • Metencephalon • Myelencephalon Copyright © 2010 Pearson Education, Inc. The Brain • Origins of Brain Structures • Diencephalon and mesencephalon persist • Telencephalon: • Becomes cerebrum • Metencephalon • Forms cerebellum and pons • Myelencephalon • Becomes medulla oblongata Copyright © 2010 Pearson Education, Inc. The Brain Copyright © 2010 Pearson Education, Inc. The Brain • Ventricles of the Brain • Origins of ventricles • Neural tube encloses neurocoel • Neurocoel expands to form chambers (ventricles) lined with ependymal cells • Each cerebral hemisphere contains one large lateral ventricle • Separated by a thin medial partition (septum pellucidum) Copyright © 2010 Pearson Education, Inc. The Brain • Ventricles of the Brain • Third ventricle • Ventricle of the diencephalon • Lateral ventricles communicate with third ventricle: • via interventricular foramen (foramen of Monro) Copyright © 2010 Pearson Education, Inc. The Brain • Ventricles of the Brain • Fourth ventricle • Extends into medulla oblongata • Becomes continuous with central canal of the spinal cord • Connects with third ventricle: • via narrow canal in mesencephalon • aqueduct of midbrain Copyright © 2010 Pearson Education, Inc. The Brain Figure 13–2 Ventricles of the Brain. Copyright © 2010 Pearson Education, Inc. The Brain • The brain is a large, delicate mass of neural tissue containing internal passageways and chambers filled with cerebrospinal fluid • Each of the six major brain regions has specific functions • Ascending from the medulla oblongata to the cerebrum, brain functions become more complex and variable • Conscious thought and intelligence are produced in the neural cortex of the cerebral hemispheres Copyright © 2010 Pearson Education, Inc. Brain Protection and Support • Physical protection • Bones of the cranium • Cranial meninges • Cerebrospinal fluid • Biochemical isolation • Blood–brain barrier Copyright © 2010 Pearson Education, Inc. Brain Protection and Support • The Cranial Meninges • Have three layers: • Dura mater • Arachnoid mater • Pia mater • Are continuous with spinal meninges • Protect the brain from cranial trauma Copyright © 2010 Pearson Education, Inc. Brain Protection and Support • The Cranial Meninges • Dura mater • Inner fibrous layer (meningeal layer) • Outer fibrous layer (endosteal layer) fused to periosteum • Venous sinuses between two layers • Arachnoid mater • Covers brain • Contacts epithelial layer of dura mater • Subarachnoid space: between arachnoid mater and pia mater • Pia mater • Attached to brain surface by astrocytes Copyright © 2010 Pearson Education, Inc. Brain Protection and Support • Dural Folds • Folded inner layer of dura mater • Extend into cranial cavity • Stabilize and support brain • Contain collecting veins (dural sinuses) • Falx cerebri, tentorium cerebelli, and falx cerebelli Copyright © 2010 Pearson Education, Inc. Brain Protection and Support • Dural Folds • Falx cerebri • Projects between the cerebral hemispheres • Contains superior sagittal sinus and inferior sagittal sinus • Tentorium cerebelli • Separates cerebellum and cerebrum • Contains transverse sinus • Falx cerebelli • Divides cerebellar hemispheres below the tentorium cerebelli Copyright © 2010 Pearson Education, Inc. Brain Protection and Support Figure 13–3a The Relationship among the Brain, Cranium, and Meninges. Copyright © 2010 Pearson Education, Inc. Brain Protection and Support Figure 13–3b The Relationship among the Brain, Cranium, and Meninges. Copyright © 2010 Pearson Education, Inc. Brain Protection and Support • Cerebrospinal Fluid (CSF) • Surrounds all exposed surfaces of CNS • Interchanges with interstitial fluid of brain • Functions of CSF • Cushions delicate neural structures • Supports brain • Transports nutrients, chemical messengers, and waste products Copyright © 2010 Pearson Education, Inc. Brain Protection and Support • Cerebrospinal Fluid (CSF) • Choroid plexus • Specialized ependymal cells and capillaries: • secrete CSF into ventricles • remove waste products from CSF • adjust composition of CSF • Produces about 500 mL of CSF/day Copyright © 2010 Pearson Education, Inc. Brain Protection and Support • Cerebrospinal Fluid (CSF) • CSF circulates • From choroid plexus • Through ventricles • To central canal of spinal cord • Into subarachnoid space around the brain, spinal cord, and cauda equina Copyright © 2010 Pearson Education, Inc. Brain Protection and Support • Cerebrospinal Fluid (CSF) • CSF in subarachnoid space • Arachnoid villi: • extensions of subarachnoid space • extend through dura mater to superior sagittal sinus • Arachnoid granulations: • large clusters of villi • absorb CSF into venous circulation Copyright © 2010 Pearson Education, Inc. Brain Protection and Support Figure 13–4 The Formation and Circulation of Cerebrospinal Fluid. Copyright © 2010 Pearson Education, Inc. Brain Protection and Support Figure 13–4a The Formation and Circulation of Cerebrospinal Fluid. Copyright © 2010 Pearson Education, Inc. Brain Protection and Support Figure 13–4b The Formation and Circulation of Cerebrospinal Fluid. Copyright © 2010 Pearson Education, Inc. Brain Protection and Support • Blood Supply to the Brain • Supplies nutrients and oxygen to brain • Delivered by internal carotid arteries and vertebral arteries • Removed from dural sinuses by internal jugular veins Copyright © 2010 Pearson Education, Inc. Brain Protection and Support Figure 19–22 Arteries of the Neck and Head. Copyright © 2010 Pearson Education, Inc. Brain Protection and Support Figure 19–23 Arteries of the Brain. Copyright © 2010 Pearson Education, Inc. Brain Protection and Support Figure 19–28 Major Veins of the Head, Neck, and Brain. Copyright © 2010 Pearson Education, Inc. Brain Protection and Support Figure 19–28 Major Veins of the Head, Neck, and Brain. Copyright © 2010 Pearson Education, Inc. Brain Protection and Support • Cerebrovascular Disease • Disorders interfere with blood circulation to brain • Stroke or cerebrovascular accident (CVA) • Shuts off blood to portion of brain • Neurons die Copyright © 2010 Pearson Education, Inc. Brain Protection and Support • Blood–Brain Barrier • Isolates CNS neural tissue from general circulation • Formed by network of tight junctions • Between endothelial cells of CNS capillaries • Lipid-soluble compounds (O2, CO2), steroids, and prostaglandins diffuse into interstitial fluid of brain and spinal cord • Astrocytes control blood–brain barrier by releasing chemicals that control permeability of endothelium Copyright © 2010 Pearson Education, Inc. Brain Protection and Support • Blood–CSF Barrier • Formed by special ependymal cells • Surround capillaries of choroid plexus • Limits movement of compounds transferred • Allows chemical composition of blood and CSF to differ Copyright © 2010 Pearson Education, Inc. Brain Protection and Support • Four Breaks in the BBB • Portions of hypothalamus • Secrete hypothalamic hormones • Posterior lobe of pituitary gland • Secretes hormones ADH and oxytocin • Pineal glands • Pineal secretions • Choroid plexus • Where special ependymal cells maintain blood–CSF barrier Copyright © 2010 Pearson Education, Inc. Brain Protection and Support • Meninges stabilize brain in cranial cavity • Cerebrospinal fluid protects against sudden movement • CSF provides nutrients and removes wastes • Blood–brain barrier and blood–CSF barrier • Selectively isolate brain from chemicals in blood that might disrupt neural function Copyright © 2010 Pearson Education, Inc. The Medulla Oblongata • The Medulla Oblongata • Allows brain and spinal cord to communicate • Coordinates complex autonomic reflexes • Controls visceral functions • Nuclei in the Medulla • Autonomic nuclei: control visceral activities • Sensory and motor nuclei: of cranial nerves • Relay stations: along sensory and motor pathways Copyright © 2010 Pearson Education, Inc. The Medulla Oblongata Figure 13–5a The Diencephalon and Brain Stem. Copyright © 2010 Pearson Education, Inc. The Medulla Oblongata Figure 13–5b The Diencephalon and Brain Stem. Copyright © 2010 Pearson Education, Inc. The Medulla Oblongata Figure 13–5c The Diencephalon and Brain Stem. Copyright © 2010 Pearson Education, Inc. The Medulla Oblongata • The Medulla Oblongata • Includes three groups of nuclei • Autonomic nuclei • Sensory and motor nuclei of cranial nerves • Relay stations along sensory and motor pathways Copyright © 2010 Pearson Education, Inc. The Medulla Oblongata • Autonomic Nuclei of the Medulla Oblongata • Reticular formation • Gray matter with embedded nuclei • Regulates autonomic functions • Reflex centers • Control peripheral systems: • cardiovascular centers: • cardiac center • control blood flow through peripheral tissues • respiratory rhythmicity centers sets pace for respiratory movements Copyright © 2010 Pearson Education, Inc. The Medulla Oblongata • Sensory and Motor Nuclei of the Medulla Oblongata • Associated with 5 of 12 cranial nerves (VIII, IX, X, XI, XII) Copyright © 2010 Pearson Education, Inc. The Medulla Oblongata • Relay Stations of the Medulla Oblongata • Nucleus gracilis and nucleus cuneatus • Pass somatic sensory information to thalamus • Solitary nucleus • Receives visceral sensory information • Olivary nuclei (olives) • Relay information about somatic motor commands Copyright © 2010 Pearson Education, Inc. The Medulla Oblongata Figure 13–6a The Medulla Oblongata and Pons. Copyright © 2010 Pearson Education, Inc. The Medulla Oblongata Figure 13–6b The Medulla Oblongata and Pons. Copyright © 2010 Pearson Education, Inc. The Pons • The Pons • Links cerebellum with mesencephalon, diencephalon, cerebrum, and spinal cord • Sensory and motor nuclei of cranial nerves V, VI, VII, VIII Copyright © 2010 Pearson Education, Inc. The Pons • The Pons • Nuclei involved with respiration • Apneustic center and pneumotaxic center: • modify respiratory rhythmicity center activity • Nuclei and tracts • Process and relay information to and from cerebellum • Ascending, descending, and transverse tracts: • transverse fibers (axons): • link nuclei of pons with opposite cerebellar hemisphere Copyright © 2010 Pearson Education, Inc. The Pons Figure 13–6a The Medulla Oblongata and Pons. Copyright © 2010 Pearson Education, Inc. The Pons Figure 13–6b The Medulla Oblongata and Pons. Copyright © 2010 Pearson Education, Inc. The Pons Figure 13–6c The Medulla Oblongata and Pons. Copyright © 2010 Pearson Education, Inc. The Pons Copyright © 2010 Pearson Education, Inc. The Pons Copyright © 2010 Pearson Education, Inc. The Cerebellum • Functions of the Cerebellum • Adjusts postural muscles • Fine-tunes conscious and subconscious movements Copyright © 2010 Pearson Education, Inc. The Cerebellum • Structures of the Cerebellum • Folia • Surface of cerebellum • Highly folded neural cortex • Anterior and posterior lobes • Separated by primary fissure • Cerebellar hemispheres: • Separated at midline by vermis • Vermis • Narrow band of cortex • Flocculonodular lobe • Below fourth ventricle Copyright © 2010 Pearson Education, Inc. The Cerebellum • Structures of the Cerebellum • Purkinje cells • Large, branched cells • Found in cerebellar cortex • Receive input from up to 200,000 synapses • Arbor vitae • Highly branched, internal white matter of cerebellum • Cerebellar nuclei: embedded in arbor vitae: • relay information to Purkinje cells Copyright © 2010 Pearson Education, Inc. The Cerebellum • Structures of the Cerebellum • The peduncles • Tracts link cerebellum with brain stem, cerebrum, and spinal cord: • superior cerebellar peduncles • middle cerebellar peduncles • inferior cerebellar peduncles Copyright © 2010 Pearson Education, Inc. The Cerebellum • Disorders of the Cerebellum • Ataxia • Damage from trauma or stroke • Intoxication (temporary impairment) • Disturbs muscle coordination Copyright © 2010 Pearson Education, Inc. The Cerebellum Figure 13–7a The Cerebellum. Copyright © 2010 Pearson Education, Inc.
