13 The Brain and Cranial Nerves C h a p t e r PowerPoint® Lecture Slides prepared by Jason LaPres Lone Star College - North Harris

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 Hypothalamus Pituitary gland 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 Includes Spinal cord and cerebrum or cerebellum Includes Mesencephalon Pons Medulla oblongata Copyright © 2010 Pearson Education, Inc.

The Brain The Brain Stem Mesencephalon Pons 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 Nuclei and tracts 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.