Chapter 11 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

11.1: Introduction The central nervous system (CNS) consists of the brain and spinal cord. The brainstem connects the brain to the spinal cord. Communication to the peripheral nervous system (PNS) is by way of the spinal cord.

11.2: Meninges The meninges Membranes of CNS Protect the CNS Three (3) layers: Dura mater “Tough mother” Venous sinuses Falx Arachnoid mater “Spiderweb-like” Space contains cerebrospinal fluid (CSF) Pia mater “Faithful mother” Encapsulates blood vessels Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Skin Scalp Subcutaneous tissue Cranium Bone of skull Dural sinus Cerebrum Arachnoid granulation Tentorium cerebelli Dura mater Cerebellum Arachnoid mater Meninges Vertebra Pia mater Spinal cord Subarachnoid space Meninges Falx cerebri Gray matter (a) (b) White matter Cerebrum

Meninges of the Spinal Cord Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Spinal cord Ventral root Subarachnoid space Pia mater Dorsal root Spinal nerve Arachnoid mater Epidural space Dorsal root ganglion Dura mater Dorsal root Dorsal branch (dorsal ramus) Spinal nerve Ventral branch (ventral ramus) Dorsal root ganglion Spinal cord Ventral root Epidural space Thoracic vertebra Body of vertebra (a) (b)

11.3: Ventricles and Cerebrospinal Fluid There are four (4) ventricles The ventricles are interconnected cavities within cerebral hemispheres and brain stem The ventricles are continuous with the central canal of the spinal cord They are filled with cerebrospinal fluid (CSF) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lateral ventricle Interventricular foramen Third ventricle Cerebral aqueduct Fourth ventricle To central canal of spinal cord The four (4) ventricles are: Lateral ventricles (2) Known as the first and second ventricles Third ventricle Fourth ventricle Interventricular foramen Cerebral aqueduct (a) Interventricular foramen Lateral ventricle Third ventricle Cerebral aqueduct Fourth ventricle To central canal of spinal cord (b)

Cerebrospinal Fluid Secreted by the choroid plexus Circulates in ventricles, central canal of spinal cord, and the subarachnoid space Completely surrounds the brain and spinal cord Excess or wasted CSF is absorbed by the arachnoid villi Clear fluid similar to blood plasma Volume is only about 120 ml. Nutritive and protective Helps maintain stable ion concentrations in the CNS Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Arachnoid granulations Blood-filled dural sinus Choroid plexuses of third ventricle Pia mater Third ventricle Subarachnoid space Cerebral aqueduct Arachnoid mater Fourth ventricle Dura mater Choroid plexus of fourth ventricle Central canal of spinal cord Pia mater Subarachnoid space Filum terminale Arachnoid mater Dura mater

11.4: Spinal Cord Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Slender column of nervous tissue continuous with brain and brainstem Extends downward through vertebral canal Begins at the foramen magnum and terminates at the first and second lumbar vertebrae (L1/L2) interspace Brainstem Foramen magnum Cervical enlargement Cervical enlargement Spinal cord Vertebral canal Lumbar enlargement Lumbar enlargement Conus medullaris Conus medullaris Cauda equina Filum terminale (a) (b)

Structure of the Spinal Cord Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Posterior horn Posterior funiculus White matter Posterior median sulcus Gray matter Gray commissure Lateral funiculus Dorsal root of spinal nerve Central canal Anterior funiculus Dorsal root ganglion Ventral root of spinal nerve Anterior horn Anterior median fissure Portion of spinal nerve (a)

Functions of Spinal Cord Conduit (pathway) for nerve impulses to and from the brain and brainstem Center for spinal reflexes

Reflex Arcs Reflexes are automatic, subconscious responses to stimuli within or outside the body Simple reflex arc (sensory – motor) Most common reflex arc (sensory – association – motor) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sensory or afferent neuron Motor or efferent neuron Central Nervous System Receptor Effector (muscle or gland) (a)

Reflex Arcs

General Components of a Spinal Reflex Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Spinal cord Interneuron Dorsal 1 Receptor 3 Cell body of sensory neuron White matter 2 Sensory neuron Gray matter I m p u l s e 4 Ventral Central canal Motor neuron 5 Effector (muscle or gland) (b)

Reflex Behavior Example is the knee-jerk reflex Simple monosynaptic reflex Helps maintain an upright posture Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Axon of sensory neuron Spinal cord Effector (quadriceps femoris muscle group) Cell body of motor neuron Cell body of sensory neuron Receptor associated with dendrites of sensory neuron Axon of motor neuron Patella Direction of impulse Patellar ligament

Reflex Behavior Example is a withdrawal reflex (flexor reflex) Prevents or limits tissue damage Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cell body of sensory neuron Axon of sensory neuron Direction of impulse Interneuron Spinal cord Effector (flexor muscle contracts and withdraws part being stimulated) Axon of motor neuron Cell body of motor neuron Dendrite of sensory neuron Pain receptor in skin Tack

Reflex Arc Example crossed extensor reflex Crossing of sensory impulses within the reflex center to produce an opposite effect Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Interneuron + = Stimulation – = Inhibition + – – + Sensory neuron Extensor relaxes Extensor contracts Flexor relaxes Motor neurons Motor neurons Flexor contracts

Tracts of the Spinal Cord Ascending tracts conduct sensory impulses to the brain Descending tracts conduct motor impulses from the brain to motor neurons reaching muscles and glands Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fasciculus gracilis Dorsal column Fasciculus cuneatus Posterior spinocerebellar tract Lateral corticospinal tract Lateral reticulospinal tract Rubrospinal tract Anterior spinocerebellar tract Lateral spinothalamic tract Anterolateral system Anterior spinothalamic tract Anterior reticulospinal tract Medial reticulospinal tract Anterior corticospinal tract

Ascending Tracts Major ascending (sensory) spinal cord tracts: Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Major ascending (sensory) spinal cord tracts: Fasciculus gracilis and fasciculus cuneatus Spinothalamic tracts Lateral and anterior Spinocerebellar tracts Posterior and anterior Sensory cortex of cerebrum Cerebrum (frontal section) Thalamus Midbrain Spinothalamic tract Brainstem (transverse sections) Pons Fasciculus Cuneatus tract Medulla Sensory impulse from skin temperature or pain receptors Spinal cord (transverse section) Sensory fibers cross over

Descending Tracts Major descending (motor) spinal cord tracts: Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Major descending (motor) spinal cord tracts: Corticospinal tracts Lateral and anterior Reticulospinal tracts Lateral, anterior and medial Rubrospinal tract Motor cortex of cerebrum Cerebrum (frontal section) Corticospinal tract Midbrain Brainstem (transverse sections) Pons Motor fibers cross over Medulla oblongata Spinal cord (transverse section) Motor impulse to Skeletal muscle

Nerve Tracts of the Spinal Cord

11.5: Brain Major parts of the brain: Functions of the brain: Cerebrum Frontal lobes Parietal lobes Occipital lobes Temporal lobes Insula Diencephalon Cerebellum Brainstem Midbrain Pons Medulla oblongata Functions of the brain: Interprets sensations Determines perception Stores memory Reasoning Makes decisions Coordinates muscular movements Regulates visceral activities Determines personality

© Martin M. Rotker/Photo Researchers, Inc. The Brain Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Gyrus Skull Sulcus Meninges Cerebrum Corpus callosum Diencephalon Midbrain Fornix Brainstem Pons Medulla oblongata Cerebellum Spinal cord (a) Fornix Cerebrum Midbrain Corpus callosum Pons Transverse fissure Diencephalon Cerebellum Medulla oblongata Spinal cord © Martin M. Rotker/Photo Researchers, Inc. (b)

Brain Development Neural tube Three primary vesicles: Forebrain (Prosencephalon) Midbrain (Mesencephalon) Hindbrain (Rhombencephalon) Five secondary vesicles: Telencephalon Diencephalon Mesencephalon Metencephalon Myelencephalon Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Prosencephalon (forebrain) Mesencephalon (midbrain) Rhombencephalon (hindbrain) Neural tube (a) Telencephalon Cerebral hemispheres Diencephalon Diencephalon Mesencephalon Midbrain Metencephalon Pons and Cerebellum Myelencephalon Medulla oblongata Neural tube Spinal cord (b) (c)

Brain Development

Structure of the Cerebrum Corpus callosum Connects cerebral hemispheres (a commissure) Gyri Bumps or convolutions Sulci Grooves in gray matter Central sulcus Fissures Longitudinal: separates the cerebral hemispheres Transverse: separates cerebrum from cerebellum Lateral fissure of Sylvius Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Central sulcus Parietal lobe Gyrus Sulcus Frontal lobe Lateral sulcus Occipital lobe Transverse fissure Temporal lobe Cerebellar hemisphere (a) Central sulcus Parietal lobe Central sulcus Longitudinal fissure Frontal lobe Occipital lobe Parietal lobe Insula Occipital lobe Retracted temporal lobe (b) (c)

Lobes of the Cerebrum Five (5) lobes bilaterally: Frontal lobe Parietal lobe Temporal lobe Occipital lobe Insula aka ‘Island of Reil’ Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Central sulcus Parietal lobe Occipital lobe Frontal lobe Insula Retracted temporal lobe (c)

Functions of the Cerebrum Interpreting impulses Initiating voluntary movements Storing information as memory Retrieving stored information Reasoning Seat of intelligence and personality

Functional Regions of the Cerebral Cortex Thin layer of gray matter that constitutes the outermost portion of cerebrum Contains 75% of all neurons in the nervous system Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Central sulcus Motor areas involved with the control of voluntary muscles Sensory areas involved with cutaneous and other senses Concentration, planning, problem solving Frontal eye field Parietal lobe Auditory area Sensory speech area ( Wernicke’s area) Front lobe Occipital lobe Motor speech area (Broca’s area) Combining visual images, visual recognition of objects Lateral sulcus Interpretation of auditory patterns Visual area Cerebellum Temporal lobe Brainstem

Functions of the Cerebral Lobes

Sensory Areas (post-central sulcus) Cutaneous sensory area Parietal lobe Interprets sensations on skin Sensory area for taste Near base of the central sulcus Sensory area for smell Arises from centers deep within the cerebrum Visual area Occipital lobe Interprets vision Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Central sulcus Motor areas involved with the control of voluntary muscles Sensory areas involved with cutaneous and other senses Concentration, planning, problem solving Frontal eye field Parietal lobe Auditory area Temporal lobe Interprets hearing Auditory area Sensory speech area ( Wernicke’s area) Front lobe Occipital lobe Motor speech area (Broca’s area) Combining visual images, visual recognition of objects Lateral sulcus Interpretation of auditory patterns Visual area Cerebellum Temporal lobe Brainstem

Sensory Areas Trunk Pelvis Trunk Arm Neck Pelvis Forearm Thigh Forearm Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Trunk Pelvis Trunk Arm Neck Pelvis Forearm Thigh Forearm Arm Thigh Thumb, fingers, and hand Leg Hand, fingers, and thumb Leg Upper face Foot and toes Facial expression Foot and toes Genitals Lips Salivation Vocalization Mastication Teeth and gums Tongue and pharynx Swallowing Longitudinal fissure Longitudinal fissure (a) Motor area (b) Sensory area Frontal lobe Motor area Sensory area Central sulcus Parietal lobe

Association Areas Regions that are not primary motor or primary sensory areas Widespread throughout the cerebral cortex Analyze and interpret sensory experiences Provide memory, reasoning, verbalization, judgment, emotions Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Motor areas involved with the control of voluntary muscles Central sulcus Sensory areas involved with cutaneous and other senses Concentration, planning, problem solving Frontal eye field Parietal lobe Auditory area Sensory speech area ( Wernicke’s area) Front lobe Occipital lobe Motor speech area (Broca’s area) Combining visual images, visual recognition of objects Lateral sulcus Visual area Interpretation of auditory patterns Cerebellum Temporal lobe Brainstem

Association Areas Frontal lobe association areas Concentrating Planning Complex problem solving Temporal lobe association areas Interpret complex sensory experiences Store memories of visual scenes, music, and complex patterns Parietal lobe association areas Understanding speech Choosing words to express thought Occipital lobe association areas Analyze and combine visual images with other sensory experiences

Motor Areas (pre-central sulcus) Primary motor areas Frontal lobes Control voluntary muscles Broca’s area Anterior to primary motor cortex Usually in left hemisphere Controls muscles needed for speech Frontal eye field Above Broca’s area Controls voluntary movements of eyes and eyelids Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Motor areas involved with the control of voluntary muscles Central sulcus Sensory areas involved with cutaneous and other senses Concentration, planning, problem solving Frontal eye field Parietal lobe Auditory area Sensory speech area ( Wernicke’s area) Front lobe Occipital lobe Motor speech area (Broca’s area) Combining visual images, visual recognition of objects Lateral sulcus Visual area Interpretation of auditory patterns Cerebellum Temporal lobe Brainstem

Motor Areas Longitudinal fissure Longitudinal fissure (a) Motor area Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Trunk Pelvis Trunk Arm Neck Pelvis Thigh Forearm Forearm Arm Thigh Thumb, fingers, and hand Leg Hand, fingers, and thumb Leg Upper face Foot and toes Facial expression Foot and toes Genitals Lips Salivation Vocalization Mastication Teeth and gums Tongue and pharynx Swallowing Longitudinal fissure Longitudinal fissure (a) Motor area (b) Sensory area Frontal lobe Motor area Sensory area Central sulcus Parietal lobe

Hemisphere Dominance The left hemisphere is dominant in most individuals Dominant hemisphere controls: Speech Writing Reading Verbal skills Analytical skills Computational skills Nondominant hemisphere controls: Nonverbal tasks Motor tasks Understanding and interpreting musical and visual patterns Provides emotional and intuitive thought processes

Memory Short term memory Working memory Closed neuronal circuit Circuit is stimulated over and over When impulse flow ceases, memory does also unless it enters long-term memory via memory consolidation Long term memory Changes structure or function of neurons Enhances synaptic transmission