Holes Human Anatomy and Physiology Eleventh Edition Shier

Hole’s Human Anatomy and Physiology Eleventh Edition Shier w Butler w Lewis Chapter 11 1

Chapter 11: Nervous System II SECTION 1 2

Chapter 11: Nervous System II Meninges • membranes surrounding CNS • protect CNS • three layers 1. dura mater 2. arachnoid mater 3. pia mater 3

Meninges dura mater • Outer most • Tough, white connective tissue • Contains blood vessels and nerves arachnoid mater • Middle layer • Thin, weblike • Sub-arachnoid space below which is filled with cerebrospinal fluid pia mater • Innermost • Thin delicate connective tissues • Many nerves and blood vessels for nourishment • Dips into grooves and contours of brain 4

Meninges of the Spinal Cord Space between vertebrae and dura mater is called epidural space and is filled with loose connective tissue and fat. 5

Epidural used for pain during childbirth 6

Meningitis • infection within the meninges • 2 types – viral and bacterial 7

Meningitis • May be diagnosed by drawing CSF from sub-arachnoid space at the lumbar region in a procedure called a lumbar puncture. This procedure is also called a spinal tap. 8

Major Divisions of the Brain Also classified as: 9

Ventricles • interconnected cavities • lateral ventricles • third ventricle • fourth ventricle • cerebral aqueduct • within cerebral hemispheres and brain stem • continuous with central canal of spinal cord • filled with cerebrospinal fluid (CSF) 10

Cerebrospinal Fluid • secreted by choroid plexus • circulates in: • Ventricles • central canal of spinal cord • subarachnoid space • completely surrounds brain and spinal cord • clear liquid • nutritive and protective • helps maintain stable ion concentrations in CNS 11

Ommaya Reservior

Chapter 11: Nervous System II SECTION 2 13

Spinal Cord • slender column of nervous tissue continuous with brain • extends downward through vertebral canal • begins at level of foramen magnum and terminates near first and second lumbar 14

Cross Section of Spinal Cord 15

Functions of Spinal Cord • center for spinal reflexes • conduit for nerve impulses to and from the brain 16

Reflex Arcs Reflexes – automatic, subconscious responses to stimuli within or outside the body 17

General Components of a Spinal Reflex 18

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 19

Chapter 11: Nervous System II SECTION 3 20

Brain Major Parts • cerebrum • two hemispheres • basal nuclei • • diencephalon • brainstem • cerebellum Functions • interprets sensations • determines perception • stores memory • reasoning • makes decisions • coordinates muscular movements • regulates visceral activities • determines personality 21

Brain 22

Brain Development Three Major Vesicles 1. Forebrain 2. Midbrain 3. Hindbrain 23

Brain Development 24

Structure of Cerebrum • corpus callosum • connects cerebral hemispheres • convolutions • bumps or gyri • sulci • grooves • longitudinal fissure • separates hemispheres • transverse fissure • separates cerebrum from cerebellum 25

Lobes of Cerebral Hemispheres • Frontal • Parietal • Temporal • Occipital • Insula 26

Functions of the Cerebrum • interpreting impulses • initiating voluntary movements • storing information as memory • retrieving stored information • reasoning • seat of intelligence and personality 27

Functional Regions of Cerebral Cortex – thin layer of gray matter that constitutes the outermost portion of cerebrum; contains 75% of all neurons in nervous system 28

Sensory Areas • Cutaneous Sensory Area • parietal lobe • interprets sensations on skin • Visual Area • occipital lobe • interprets vision • Sensory Area for Taste • near bases of the central sulci • Sensory Area for Smell • arise from centers deep within the cerebrum • Auditory Area • temporal lobe • interprets hearing 29

Sensory Areas 30

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 31

Association Areas Frontal Lobe Association Areas • concentrating • planning • complex problem solving Parietal Lobe Association Areas • understanding speech • choosing words to express thought Temporal Lobe Association Areas • interpret complex sensory experiences • store memories of visual scenes, music, and complex patterns Occipital Lobe Association Areas • analyze and combine visual images with other sensory experiences 32

Hemisphere Dominance • The left hemisphere is dominant is 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 33

Memory Short Term • 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 • changes structure or function of neurons • enhances synaptic transmission 34

Motor Areas • 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 35

Motor Areas 36

Functions of the Cerebral Lobes 37

Basal Nuclei • masses of gray matter • deep within cerebral hemispheres • caudate nucleus, putamen, globus pallidus • produce dopamine • control certain muscular activities • primarily by inhibiting motor functions 38

Diencephalon • between cerebral hemispheres and above the brainstem • surrounds third ventricle • • thalamus hypothalamus optic tracts optic chiasma infundibulum posterior pituitary mammillary bodies pineal gland 39

Diencephalon Thalamus • gateway for sensory impulses heading to cerebral cortex • receives all sensory impulses (except smell) • channels impulses to appropriate part of cerebral cortex for interpretation Hypothalamus • maintains homeostasis by regulating visceral activities • links nervous and endocrine systems 40

Diencephalon Limbic System Consists of • portions of frontal lobe Functions • portions of temporal lobe • controls emotions • produces feelings • hypothalamus • interprets sensory impulse • thalamus • basal nuclei • other deep nuclei 41

Brain Stem Three Parts 1. Midbrain 2. Pons 3. Medulla Oblongata 42

Midbrain • between diencephalon and pons • contains bundles of fibers that join lower parts of brainstem and spinal cord with higher part of brain • cerebral aqueduct • cerebral peduncles – bundles of nerve fibers • corpora quadrigemina – centers for visual and auditory reflexes 43

Pons • rounded bulge on underside of brainstem • between medulla oblongata and midbrain • helps regulate rate and depth of breathing • relays nerve impulses to and from medulla oblongata and cerebellum 44

Medulla Oblongata • enlarged continuation of spinal cord • conducts ascending and descending impulses between brain and spinal cord • contains cardiac, vasomotor, and respiratory control centers • contains various nonvital reflex control centers (coughing, sneezing, swallowing, vomiting) 45

Reticular Formation • complex network of nerve fibers scattered throughout the brain stem • extends into the diencephalon • connects to centers of hypothalamus, basal nuclei, cerebellum, and cerebrum • filters incoming sensory information • arouses cerebral cortex into state of wakefulness 46

Types of Sleep Slow Wave Rapid Eye Movement (REM) • non-REM sleep • paradoxical sleep • person is tired • some areas of brain • decreasing activity of active reticular system • heart and respiratory • restful rates irregular • dreamless • dreaming occurs • reduced blood pressure and respiratory rate • ranges from light to heavy • alternates with REM 47

Cerebellum • inferior to occipital lobes • posterior to pons and medulla oblongata • two hemispheres • vermis connects hemispheres • cerebellar cortex – gray matter • arbor vitae – white matter • cerebellar peduncles – nerve fiber tracts • dentate nucleus – largest nucleus in cerebellum • integrates sensory information concerning position of body parts • coordinates skeletal muscle activity • maintains posture 48

Major Parts of the Brain 49

Chapter 11: Nervous System II SECTION 4 50

Peripheral Nervous System Subdivided into 2 branches: 1. Sensory Divison 2. Motor Divison 51

PNS: Motor Division Subdivided into 2 branches: 1. Somatic NS – from CNS to skin and skeletal muscles 2. Autonomic NS – from CNS to smooth muscle, cardiac muscle and endocrine glands 52

Peripheral Nervous System Includes: 1. Cranial nerves arising from the brain 2. Spinal nerves arising from the spinal cord Both have • Somatic fibers connecting to the skin and skeletal muscles • Autonomic fibers connecting to viscera 53

Nerve Fiber Classification A nerve is a cord-like bundle of axons wrapped in connective tissue. There are 3 types of nerve fibers. • Sensory Nerves – conduct impulses into brain or spinal cord • Motor Nerves – conduct impulses to muscles or glands • Mixed Nerves – contain both sensory nerve fibers and motor nerve fibers; most nerves 54

Nerve Fiber Classification Two Subdivisions of spinal and cranial nerves: These are the 2 subdivisions of Sensory division of PNS 1. General – fibers associated with general structures such as the skin, skeletal muscles, glands, and viscera. 2. Special – fibers associated with more specialized structures such as eyes and ears 55

Nerve Fiber Classification General somatic efferent fibers • carry motor impulses from CNS to skeletal muscles General visceral efferent fibers • carry motor impulses away from CNS to smooth muscles and glands General somatic afferent fibers • carry sensory impulses to CNS from skin and skeletal muscles General visceral afferent fibers • carry sensory impulses to CNS from blood vessels and internal organs 56

Nerve Fiber Classification Special somatic efferent fibers • carry motor impulses from brain to muscles used in chewing, swallowing, speaking, and forming facial expressions Special visceral afferent fibers • carry sensory impulses to brain from olfactory and taste receptors Special somatic afferent fibers • carry sensory impulses to brain from receptors of sight, hearing, and equilibrium 57

Cranial Nerves 58

Cranial Nerves 12 pairs of cranial nerves 2 pair to/from forebrain 10 pairs to/from brain stem 59

Cranial Nerves I. Olfactory – sense of smell - sensory only II. Optic – sense of vision - sensory only III. Oculomotor – innervates eye muscles - motor only IV. Trochlear – innervates eye muscles - motor only V. Trigeminal – largest sensory from face motor to chewing muscles mixed VI. Abducens – innervates eye muscles - motor only 60

Cranial Nerves VII. Facial – innervates muscles of facial expression sensory taste - mixed VIII. Vestibulocochlear – sense of hearing and equilibrium - sensory only IX. Glossopharyngeal – moves tongue and pharynx muscles - mixed X. Vagus – innervates visceral smooth muscle - mixed XI. Accessory – innervates neck muscles - motor only XII. Hypoglossal – moves tongue - motor only 61

Spinal Nerves • ALL mixed nerves • 31 pairs • 8 cervical • 12 thoracic • 5 lumbar • 5 sacral • 1 coccygeal 62

Spinal Nerves Dorsal root (posterior or sensory root) • axons of sensory neurons in the dorsal root ganglion Dorsal root ganglion • cell bodies of sensory neurons whose axons conduct impulses inward from peripheral body parts 63

Spinal Nerves Ventral root (anterior or motor root) • axons of motor neurons whose cell bodies are in spinal cord Spinal nerve • union of ventral root and dorsal root 64

Nerve Plexus Nerve plexus – complex networks formed by anterior branches of spinal nerves; fibers of various spinal nerves are sorted and recombined Cervical Plexus - contribute to neck & phrenic (diaphragm) nerves Brachial Plexus – upper limbs Lumbar Plexus – anterior and medial thigh Sacral Plexus – posterior lower limb 65

Somatic NS vs. Autonomic NS Somatic NS One motor neuron No ganglia Uses acetylcholine Effector = skeletal muscle Autonomic NS Two motor neurons Synapse between neurons occur within a ganglion Effectors = smooth muscle, cardiac muscle, & glands 2 divisions: ○ Sympathetic ○ Parasympathetic 66

Autonomic Nervous System • functions without conscious effort • controls visceral activities • regulates smooth muscle, cardiac muscle, and glands • efferent fibers typically lead to ganglia outside CNS Two Divisions • sympathetic – prepares body for fight or flight situations • parasympathetic – prepares body for resting and digesting activities 67

Sympathetic Division Preganglionic neuron = short Postganglionic neuron = long Norepinephrine is the neurotransmitter used. 68

Life-Span Changes • Brain cells begin to die before birth • Over average lifetime, brain shrinks 10% • Most cell death occurs in temporal lobes • By age 90, frontal cortex has lost half its neurons • Number of dendritic branches decreases • Decreased levels of neurotransmitters • Fading memory • Slowed responses and reflexes • Increased risk of falling • Changes in sleep patterns that result in fewer sleeping hours 69

Clinical Application Cerebral Injuries and Abnormalities Concussion • brain jarred against cranium • loss of consciousness • temporary loss of memory • mental cloudiness • headache • recovery usually complete Cerebrovascular Accident • stroke • sudden interruption in blood flow • brain tissues die Cerebral Palsy • motor impairment at birth • caused by blocked cerebral blood vessels during development • seizures • learning disabilities 70

End here – rest are extras 71

Parasympathetic Division Preganglionic neuron = long Postganglionic neuron = short Acetylcholine is the neurotransmitter used. 72

Autonomic Nerve Fibers • all are neurons are motor (efferent) • preganglionic fibers • axons of preganglionic neurons • neuron cell bodies in CNS • postganglionic fibers • axons of postganglionic neurons • neuron cell bodies in ganglia 73

Sympathetic Division • thoracolumbar divison – location of preganglionic neurons • preganglionic fibers leave spinal nerves through white rami and enter paravertebral ganglia • paraverterbral ganglia and fibers that connect them make up the sympathetic trunk 74

Sympathetic Division • postganglionic fibers extend from sympathetic ganglia to visceral organs • postganglionic fibers usually pass through gray rami and return to a spinal nerve before proceeding to an effector • Exception: preganglionic fibers to adrenal medulla do not synapse with postganglionic neurons 75

Parasympathetic Division • craniosacral division – location of preganglionic neurons • ganglia are near or within various organs • terminal ganglia • short postganglionic fibers • continue to specific muscles or glands • preganglionic fibers of the head are included in nerves III, VII, and IX • preganglionic fibers of thorax and abdomen are parts of nerve X 76

Autonomic Neurotransmitters Cholinergic Fibers • release acetylcholine • preganglionic sympathetic and parasympathetic fibers • postganglionic parasympathetic fibers Adrenergic Fibers • release norepinephrin e • most postganglionic 77

Actions of Autonomic Neurotransmitters • depend on receptors in the membrane Cholinergic receptors • bind to acetlycholine • muscarinic • excitatory • slow • nicotinic • excitatory • rapid Adrenergic Receptors • bind to epinephrine and norepinephrine • alpha and beta • both elicit different responses on various effectors 78

Actions of Autonomic Neurotransmitters Insert figure 11. 39 79

Control of Autonomic Activity • Controlled largely by CNS • Medulla oblongata regulates cardiac, vasomotor and respiratory activities • Hypothalamus regulates visceral functions, such as body temperature, hunger, thirst, and water and electrolyte balance • Limbic system and cerebral cortex control emotional responses 80

Cranial Nerves I and II Olfactory (I) • sensory • fibers transmit impulses associated with smell Optic (II) • sensory • fibers transmit impulses associated with vision 81

Cranial Nerves III and IV Oculomotor (III) • some sensory • proprioreceptors • primarily motor • motor impulses to muscles that • raise eyelids • move the eyes • focus lens • adjust light entering eye Trochlear (IV) • some sensory • proprioreceptors • primarily motor • motor impulses to muscles that move the eyes 82

Cranial Nerve V Trigeminal (V) • mixed • opthalmic division • sensory from surface of eyes, tear glands, scalp, forehead, and upper eyelids • maxillary division • sensory from upper teeth, upper gum, upper lip, palate, and skin of face • mandibular division • sensory from scalp, skin of jaw, lower teeth, lower gum, and lower lip • motor to muscles of mastication and muscles in floor of mouth 83

Cranial Nerves VI and VII Abducens (VI) • primarily motor • motor impulses to muscles that move the eyes • some sensory with proprioreceptors Facial (VII) • mixed • sensory from taste receptors • motor to muscles of facial expression, tear glands, and salivary glands 84

Cranial Nerves VIII and IX Vestibulocochlear (VIII) • sensory • vestibular branch • sensory from equilibrium receptors of ear • cochlear branch • sensory from hearing receptors Glossopharyngeal (IX) • mixed • sensory from pharynx, tonsils, tongue, and carotid arteries • motor to salivary glands and muscles of pharynx 85

Cranial Nerve X Vagus (X) • mixed • somatic motor to muscles of speech and swallowing • autonomic motor to viscera of thorax and abdomen • sensory from pharynx, larynx, esophagus, and viscera of thorax and abdomen 86

Cranial Nerves XI and XII Accessory (XI) • primarily motor • cranial branch • motor to muscles of soft palate, pharynx, and larynx • spinal branch • motor to muscles of neck, and back; some proprioreceptor Hypoglossal (XII) • primarily motor • motor to muscles of the tongue; some proprioreceptor 87

Cervical Plexuses Nerve plexus – complex networks formed by anterior branches of spinal nerves; fibers of various spinal nerves are sorted and recombined Cervical Plexus • formed by anterior branches of C 1 -C 4 • lies deep in the neck • supply muscles and skin of the neck • C 3 – C 5 contribute to phrenic nerves 88

Brachial Plexuses • C 5 -T 1 • lies deep within shoulders • musculocutaneous nerves • supply muscles of anterior arms and skin of forearms • ulnar and median nerves • supply muscles of forearms and hands • supply skin of hands • radial nerves • supply posterior muscles of arms and skin of forearms and hands • axillary nerves • supply muscles and skin of anterior, lateral, and posterior arms 89

Lumbosacral Plexuses • T 12 – S 5 • extend from lumbar region into pelvic cavity • obturator nerves • supply motor impulses to adductors of thighs • femoral nerves • supply motor impulses to muscles of anterior thigh and sensory impulses from skin of thighs and legs • sciatic nerves • supply muscles and skin of thighs, legs, 90

Plexuses 91