PowerPoint to accompany• Sensory Nerves – conduct impulses into brain or spinal cord • Motor Nerves – conduct impulses to muscles or glands • Mixed Nerves – contain both

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Hole’s Human Anatomy and Physiology

Eleventh Edition

Shier w Butler w Lewis

Chapter

11

Chapter 11: Nervous System II

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Chapter 11: Nervous System II

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Meninges • membranes surrounding CNS

• protect CNS

• three layers

1. dura mater

2. arachnoid mater

3. pia mater

Meninges

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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

Meninges of the Spinal Cord

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Space between vertebrae and dura mater is called epidural space and is filled with loose connective tissue and fat.

Epidural used for pain

during childbirth

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Meningitis

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• infection within the meninges

• 2 types – viral and bacterial

Meningitis

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•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.

Major Divisions of the Brain

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Also classified as:

Ventricles

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• 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)

Cerebrospinal Fluid

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• 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

Ommaya Reservior

Chapter 11: Nervous System II

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Spinal Cord

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• 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

Cross Section of Spinal Cord

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Functions of Spinal Cord

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• center for spinal reflexes

• conduit for nerve impulses to and from the brain

Reflex Arcs

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

General Components of a Spinal Reflex

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Tracts of the Spinal Cord

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• Ascending tracts conduct sensory impulses to the brain

• Descending tracts conduct motor impulses from the brain to motor neurons reaching muscles and glands

Chapter 11: Nervous System II

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Brain

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Functions • interprets sensations • determines perception • stores memory • reasoning • makes decisions • coordinates muscular movements • regulates visceral activities • determines personality

Major Parts • cerebrum

• two hemispheres

• basal nuclei • • diencephalon

• brainstem

• cerebellum

Brain

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Brain Development

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Three Major Vesicles 1. Forebrain 2. Midbrain 3. Hindbrain

Brain Development

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Structure of Cerebrum

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• corpus callosum • connects cerebral hemispheres

• convolutions • bumps or gyri

• sulci • grooves

• longitudinal fissure • separates hemispheres

• transverse fissure • separates cerebrum from cerebellum

Lobes of Cerebral Hemispheres

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• Frontal

• Parietal

• Temporal

• Occipital

• Insula

Functions of the Cerebrum

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• interpreting impulses

• initiating voluntary movements

• storing information as memory

• retrieving stored information

• reasoning

• seat of intelligence and personality

Functional Regions of Cerebral Cortex

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

Sensory Areas

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• Cutaneous Sensory Area • parietal lobe • interprets sensations on skin

• Visual Area • occipital lobe • interprets vision

• Auditory Area • temporal lobe • interprets hearing

• Sensory Area for Taste • near bases of the central sulci

•Sensory Area for Smell •arise from centers deep within the cerebrum

Sensory Areas

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Association Areas

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• 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

Association Areas

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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

Hemisphere Dominance

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• 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

Memory

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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

Motor Areas

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• 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

Motor Areas

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Functions of the Cerebral Lobes

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Basal Nuclei

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• masses of gray matter • deep within cerebral hemispheres • caudate nucleus, putamen, globus pallidus • produce dopamine • control certain muscular activities

• primarily by inhibiting motor functions

Diencephalon

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• between cerebral hemispheres and above the brainstem • surrounds third ventricle

• thalamus • hypothalamus • optic tracts • optic chiasma • infundibulum • posterior pituitary • mammillary bodies • pineal gland

Diencephalon

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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

Diencephalon

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Consists of • portions of frontal lobe • portions of temporal lobe • hypothalamus • thalamus • basal nuclei • other deep nuclei

Functions • controls emotions • produces feelings • interprets sensory impulses

Limbic System

Brain Stem

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Three Parts 1. Midbrain 2. Pons 3. Medulla Oblongata

Midbrain

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• 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

Pons

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• 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

Medulla Oblongata

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• 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)

Reticular Formation

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• 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

Types of Sleep

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Slow Wave • non-REM sleep • person is tired • decreasing activity of reticular system • restful • dreamless • reduced blood pressure and respiratory rate • ranges from light to heavy • alternates with REM sleep

Rapid Eye Movement (REM) • paradoxical sleep • some areas of brain active• heart and respiratory rates irregular • dreaming occurs

Cerebellum

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• 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

Major Parts of the Brain

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Chapter 11: Nervous System II

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Peripheral Nervous System

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Subdivided into 2 branches:

1. Sensory Divison

2. Motor Divison

PNS: Motor Division

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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

Peripheral Nervous System

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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

Includes:

Nerve Fiber Classification

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• 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

A nerve is a cord-like bundle of axons wrapped in connective tissue. There are 3 types of nerve fibers.

Nerve Fiber Classification

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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

Nerve Fiber Classification

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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

Nerve Fiber Classification

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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

Cranial Nerves

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Cranial Nerves

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12 pairs of cranial nerves

2 pair to/from forebrain

10 pairs to/from brain stem

Cranial Nerves

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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

Cranial Nerves

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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

Spinal Nerves

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• ALL mixed nerves

• 31 pairs • 8 cervical • 12 thoracic • 5 lumbar • 5 sacral • 1 coccygeal

Spinal Nerves

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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

Spinal Nerves

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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

Nerve Plexus

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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

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

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Autonomic Nervous System

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• 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

Sympathetic Division

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

Life-Span Changes

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• 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

Clinical Application

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Cerebral Injuries and Abnormalities Concussion

• brain jarred against cranium • loss of consciousness • temporary loss of memory • mental cloudiness • headache • recovery usually complete

Cerebral Palsy • motor impairment at birth • caused by blocked cerebral blood vessels during development • seizures • learning disabilities

Cerebrovascular Accident • stroke • sudden interruption in blood flow • brain tissues die

End here – rest are

extras

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Parasympathetic Division

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

Autonomic Nerve Fibers

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• 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

Sympathetic Division

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• 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

Sympathetic Division

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• 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

Parasympathetic Division

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• 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

Autonomic

Neurotransmitters

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Cholinergic Fibers • release acetylcholine • preganglionic sympathetic and parasympathetic fibers • postganglionic parasympathetic fibers

Adrenergic Fibers

• release norepinephrine • most postganglionic sympathetic

Actions of Autonomic

Neurotransmitters

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• 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

Insert figure 11.39

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Actions of Autonomic Neurotransmitters

Control of Autonomic

Activity

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• 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

Cranial Nerves I and II

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Olfactory (I) • sensory • fibers transmit impulses associated with smell

Optic (II) • sensory • fibers transmit impulses associated with vision

Cranial Nerves III and IV

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Trochlear (IV) • some sensory

• proprioreceptors • primarily motor • motor impulses to muscles that move the eyes

Oculomotor (III) • some sensory

• proprioreceptors • primarily motor • motor impulses to muscles that

• raise eyelids • move the eyes • focus lens •adjust light entering eye

Cranial Nerve V

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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

Cranial Nerves VI and VII

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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

Cranial Nerves VIII and IX

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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

Cranial Nerve X

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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

Cranial Nerves XI and XII

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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

Cervical Plexuses

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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 C1-C4 • lies deep in the neck • supply muscles and skin of the neck • C3 – C5 contribute to phrenic nerves

Brachial Plexuses

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• C5-T1 • 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

Lumbosacral Plexuses

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• T12 – S5

• 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, and feet

Plexuses

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