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PowerPoint® Lecture Slides prepared by Leslie Hendon University of Alabama, Birmingham

C H A P T E R

Copyright © 2011 Pearson Education, Inc.

Part 1

14 PART 1

The Peripheral Nervous System



•  The PNS •  Is the nervous system outside the brain and

spinal cord •  Provides vital links to the body and outside

world •  Nerves allow the CNS to receive information

and initiate action



•  The PNS is functionally divided into sensory and motor divisions •  Sensory inputs and motor outputs are

subdivided into • Somatic and visceral • General and special

•  Nerves allow the CNS to receive information and initiate action


Organization of the Peripheral Nervous System •  General visceral motor part of the PNS is

known as the Autonomic nervous system (ANS) •  ANS has two divisions •  Parasympathetic (non-stress “rest & digest”) •  Sympathetic (stress responder “fight, flight, or

fight”)


Functional Organization of the PNS

Figure 14.1

Central nervous system (CNS) Peripheral nervous system (PNS)

Motor (efferent) division Sensory (afferent) division

Sympathetic division

Parasympathetic division

Somatic sensory General: Touch, pain, pressure, vibration, temperature, and proprioception in skin, body wall, and limbs Special: Hearing, equilibrium, vision

Visceral sensory General: Stretch, pain, temperature, chemical changes, and irritation in viscera; nausea and hunger Special: Taste, smell

Somatic nervous system

Motor innervation of all skeletal muscles

Autonomic nervous system

(ANS)

Motor innervation of smooth muscle, cardiac muscle, and glands


Basic Structural Components of the PNS

•  Sensory receptors—pick up stimuli from inside or outside the body

•  Nerves and ganglia •  Nerves—bundles of peripheral axons •  Ganglia—clusters of peripheral neuronal cell

bodies •  Motor endings—axon terminals of motor

neurons •  Innervate effectors (muscle fibers and glands)

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Peripheral Sensory Receptors

•  Structures that pick up sensory stimuli •  Initiate signals in sensory axons

•  (This section on sensory reception to be covered with Chapter 16)


Cranial Nerves

•  Attach to the brain and pass through specific foramina of the skull

•  Numbered from I to XII •  Cranial nerves I and II attach to the forebrain •  All others attach to the brain stem

•  Primarily serve head and neck structures •  The vagus nerve (X) is the only cranial nerve

that extends into the abdomen


Figure 14.4a The cranial nerves.

Olfactory bulb

Olfactory tract

Filaments of olfactory nerve (I)

Optic nerve (II)

Oculomotor nerve (III)

Trochlear nerve (IV)

Trigeminal nerve (V)

Abducens nerve (VI)

Facial nerve (VII)

Vestibulocochlear nerve (VIII)

Glossopharyngeal nerve (IX)

Vagus nerve (X) Accessory nerve (XI)

Hypoglossal nerve (XII)

Optic chiasma

Optic tract

Cerebellum

Medulla oblongata

Infundibulum

Temporal lobe

Frontal lobe


Figure 14.4b The cranial nerves.

Olfactory bulb with filaments of olfactory nerve (I)

Optic nerve (II)

Oculomotor nerve (III)

Trochlear nerve (IV)

Trigeminal nerve (V)

Abducens nerve (VI)

Facial nerve (VII)

Vestibulocochlear nerve (VIII)

Glossopharyngeal nerve (IX)

Vagus nerve (X)

Accessory nerve (XI)


Olfactory tract

Optic chiasma

Optic tract

Cerebellum

Medulla oblongata

Frontal lobe

Temporal lobe


The Cranial Nerves

Figure 14.4b (1 of 2)

Cranial nerves

I

II

III

IV

V

VI

Olfactory

Optic

Oculomotor

Trochlear

Trigeminal

Abducens

Vision

General

Smell

Somatic sensory

(SS)

Visceral sensory

(VS)

Somatic motor (SM)

Visceral motor: parasympathetic

(VM)

SM

SM

SM

SM

VM

Sensory function Motor function

(b)


The Cranial Nerves

Figure 14.4b (2 of 2)

Cranial nerves Sensory function Motor function

VII

VIII

IX

X

XI

XII

Facial

Vestibulocochlear

Glossopharyngeal

Vagus

Accessory

Hypoglossal

General; taste

General; taste

General

General

General; taste

General

Hearing; equilibrium

SM

Some

SM

SM

SM

SM

VM

VM

VM

(b)

Somatic sensory

(SS)

Visceral sensory

(VS)

Somatic motor (SM)

Visceral motor: parasympathetic

(VM)

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I Olfactory Nerves

•  Special visceral sensory—sense of smell •  Olfactory receptor cells located in olfactory

epithelium of nasal cavity •  Pass through the cribriform foramina of the

ethmoid bone


Table 14.2 Cranial Nerves (1 of 18)


II The Optic Nerves

•  Special somatic sensory—vision •  Originate on the retina of the eye •  Pass through the optic canals of the

sphenoid bone




III The Oculomotor Nerves

•  Somatic motor function—innervates four of the extrinsic eye muscles •  Superior rectus, medial rectus, inferior rectus,

inferior oblique •  Visceral motor function •  Constricts pupil •  Controls shape of lens

•  Pass through the superior orbital fissure



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IV The Trochlear Nerves

•  Somatic motor function—innervate the superior oblique muscle (an extrinsic eye muscle)

•  Pass ventrally and laterally around midbrain •  Pass through superior orbital fissure




V The Trigeminal Nerves

•  Largest of the cranial nerves •  Has three divisions • Ophthalmic division (V1) • Maxillary division (V2) • Mandibular division (V3)

•  Cell bodies of sensory neurons located in the trigeminal ganglion

•  Mandibular division contains motor fibers that innervate the chewing muscles


V The Trigeminal Nerves

•  Pathways of divisions •  V1 – Superior orbital fissure •  V2 – Foramen rotundum •  V3 – Foramen ovale; mandibular foramen




VI The Abducens Nerves

•  Abducts the eyeball—innervates lateral rectus muscle

Table 14.2 (6 of 12)

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VI The Abducens Nerves

•  Somatic motor function •  Innervates lateral rectus muscle—abducts

the eye •  Pass through the superior orbital fissure




VII The Facial Nerves

•  Sensory function •  Special visceral sensory from taste buds on

anterior two-thirds of tongue •  Somatic motor function •  Five branches—innervate facial muscles

•  Visceral motor function •  Innervation of lacrimal glands, submandibular

and sublingual salivary glands


VII The Facial Nerves

•  Visceral motor function •  Innervation of lacrimal glands, submandibular

and sublingual salivary glands •  Pathway •  Enter temporal bone through the internal

acoustic meatus





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VIII The Vestibulocochlear Nerves

•  Sensory nerve of hearing and equilibrium •  Vestibular branch—special somatic sensory:

equilibrium •  Cochlear branch—special somatic sensory:

hearing •  Pathway •  From inner ear cavity, fibers pass through the

internal acoustic meatus




IX The Glossopharyngeal Nerves

•  Sensory function •  Special visceral sensory from taste buds on

posterior one-third of tongue •  General visceral sensory • Posterior one-third of tongue • Pharyngeal mucosa • Chemoreceptors in carotid body • Baroreceptors of carotid sinus


IX The Glossopharyngeal Nerves

•  Somatic motor function •  Elevate pharynx during swallowing

•  Visceral motor function •  Innervate the parotid salivary gland

•  Pathway •  Fibers pass through the jugular foramen


IX The Glossopharyngeal Nerves •  Innervates structures of the tongue (taste)

and pharynx

Table 14.2 (9 of 12) Copyright © 2011 Pearson Education, Inc.


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X The Vagus Nerves

•  Sensory functions •  General visceral sensory from thoracic and

abdominal viscera •  Special visceral sensory—taste buds on

epiglottis •  Somatic motor functions •  Skeletal muscles of the pharynx and larynx


X The Vagus Nerves

•  Visceral motor functions •  Parasympathetic innervation to • Heart • Lungs • Abdominal viscera

•  Pathway •  Fibers exit through the jugular foramen


X The Vagus Nerves

•  A mixed sensory and motor nerve

•  “Wanders” into

thorax and abdomen

•  Parasympathetic innervation of organs




XI The Accessory Nerves

•  Somatic motor function •  Innervates trapezius and sternocleidomastoid

•  Formed from ventral rootlets of C1–C5 •  Do not arise from the brain stem

•  Spinal rootlets merge to form this nerve •  Pass into skull through foramen magnum •  Exit skull through the jugular foramen



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XI The Accessory Nerves


XII The Hypoglossal Nerves

•  Somatic motor function •  Innervate the tongue muscles

•  Exit the skull through hypoglossal canal




XII The Hypoglossal Nerves

•  Runs inferior to the tongue •  Innervates the tongue muscles

Table 14.2 (12 of 12)


Spinal Nerves

•  31 pairs—contain thousands of nerve fibers •  Connect to the spinal cord •  Named for point of issue from the spinal

cord •  8 pairs of cervical nerves (C1–C8) •  12 pairs of thoracic nerves (T1–T12) •  5 pairs of lumbar nerves (L1–L5) •  5 pairs of sacral nerves (S1–S5) •  1 pair of coccygeal nerves (Co1)


Spinal Nerves Posterior View

Figure 14.5

Cervical nerves C1 – C8

Thoracic nerves T1 – T12

Lumbar nerves L1 – L5

Sacral nerves S1 – S5 Coccygeal

nerve Co1

Cervical plexus

Intercostal nerves

Cervical enlargement

Lumbar enlargement

Cauda equina

Brachial plexus

Lumbar plexus

Sacral plexus

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Spinal Nerves

•  Connect to the spinal cord by the dorsal root and ventral root

•  Dorsal root—contains sensory fibers •  Cell bodies—located in the dorsal root ganglion

•  Ventral root—contains motor fibers arising from anterior gray column


Spinal Nerves

•  Branch into dorsal ramus and ventral ramus •  Dorsal and ventral rami contain sensory and

motor fibers

•  Rami communicantes connect to the base of the ventral ramus •  Lead to the sympathetic chain ganglia


Spinal Nerves

Figure 14.6

Spinal nerve

Axon of motor neuron

Ventral ramus

Ventral root

Neuromuscular junction

Sensory receptors in skin (e.g., free nerve endings of sensory neuron)

Dorsal root Dorsal root ganglion

Dorsal ramus

Sensory axon and cell body

Nerves


Spinal Nerves

Figure 14.7a

Dorsal root ganglion

Gray matter White matter Ventral root Dorsal root

Dorsal and ventral rootlets of spinal nerve

Dorsal ramus of spinal nerve

Ventral ramus of spinal nerve

Sympathetic trunk ganglion

Spinal nerve

Rami communicantes

(a) Anterior view showing spinal cord, associated nerves, and vertebrae. The dorsal and ventral roots arise medially as rootlets and join laterally to form the spinal nerve.


Innervation of the Back

•  Dorsal rami •  Innervate back muscles •  Follow a neat, segmented pattern •  Innervate a horizontal strip of muscle and

skin •  In line with emergence point from the

vertebral column


Innervation of the Back

Figure 14.7b

Dorsal ramus

Ventral ramus

Intercostal nerve

Spinal nerve

Rami communicantes

Dorsal root ganglion Dorsal root Ventral root

Sympathetic trunk ganglion

Sternum

(b) Cross section of thorax showing the main roots and branches of a spinal nerve.

Branches of intercostal nerve Lateral cutaneous Anterior cutaneous

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Innervation of the Anterior Thoracic and Abdominal Wall •  Thoracic region •  Ventral rami arranged in simple, segmented

pattern •  Intercostal nerves—supply intercostal

muscles, skin, and abdominal wall • Each gives off lateral and anterior

cutaneous branches


Introduction to Nerve Plexuses •  Nerve plexus—a network of nerves •  Ventral rami of all spinal nerves (except T2–

T12) branch and join with one another to form nerve plexuses

•  These plexuses occur in cervical, brachial, lumbar, and sacral regions

•  Primarily serve the limbs •  Fibers from ventral rami crisscross -- so each muscle

in limb receives its nerve supply from more than one spinal nerve


The Cervical Plexus

•  Buried deep in the neck •  Under the sternocleidomastoid muscle

•  Formed by ventral rami of first four cervical nerves (cn 1–4)

•  Most are cutaneous nerves •  Some innervate muscles of the anterior neck •  Phrenic nerve — the most important nerve

of the cervical plexus


The Cervical Plexus

•  Phrenic nerve •  The most important nerve of the cervical

plexus •  Formed from fibers from C3, C4, and C5

•  Innervates the diaphragm


The Cervical Plexus

Figure 14.8


C1

C2

C3

C4

C5

Segmental branches

Lesser occipital nerve Greater auricular nerve

Ansa cervicalis

Phrenic nerve

Supraclavicular nerves

Accessory nerve (XI)

Transverse cervical nerve

Ventral rami:

Ventral rami


The Brachial Plexus and Innervation of the Upper Limb

•  Brachial plexus lies in the neck and axilla •  Formed by ventral rami of C5–C8 •  Cords give rise to main nerves of the upper limb

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Figure 14.9c The brachial plexus, anterior view.

C8

C7

C6

C5

T1

Major terminal branches (peripheral nerves)

Cords Divisions Trunks Roots (ventral rami)

Musculocutaneous

Median

Ulnar

Radial

Axillary

Lateral

Medial

Posterior

Anterior

Anterior

Anterior

Posterior

Posterior

Posterior

Upper

Middle

Lower

Flowchart summarizing relationships within the brachial plexus


Nerves from the Lateral and Medial Cords

•  Musculocutaneous—main branch of the lateral cord •  Innervates the biceps brachii and brachialis

•  Median—originates from both lateral and medial cords •  Innervates anterior forearm muscles and

lateral palm


Nerves from the Lateral and Medial Cords

•  Ulnar—branches from the medial cord •  Innervates intrinsic hand muscles and skin of

the medial hand


Figure 14.9a The brachial plexus, anterior view.

Humerus

Axillary nerve

Radial nerve

Musculo- cutaneous nerve

Ulnar nerve Median nerve

Ulna Radius

Radial nerve (superficial branch)

Dorsal branch of ulnar nerve

Superficial branch of ulnar nerve

Digital branch of ulnar nerve

Muscular branch

Digital branch

Median nerve

The major nerves of the upper limb


Figure 14.9b The brachial plexus, anterior view.

Cords

Roots (ventral rami)

Trunks

Roots (rami C5–T1), trunks, divisions, and cords

Dorsal scapular

Nerve to subclavius

Suprascapular

Posterior divisions

Lateral

Posterior

Medial

Axillary

Musculo- cutaneous

Radial

Median

Ulnar

Upper

Middle

Lower

C4

C5

C6 C7 C8

T1

Long thoracic Medial pectoral Lateral pectoral Upper subscapular Lower subscapular

Thoracodorsal Medial cutaneous nerves of the arm and forearm

Anterior divisions

Posterior divisions

Trunks Roots


Figure 14.9c The brachial plexus, anterior view.

C8

C7

C6

C5

T1

Major terminal branches (peripheral nerves)

Cords Divisions Trunks Roots (ventral rami)

Musculocutaneous

Median

Ulnar

Radial

Axillary

Lateral

Medial

Posterior

Anterior

Anterior

Anterior

Posterior

Posterior

Posterior

Upper

Middle

Lower

Flowchart summarizing relationships within the brachial plexus

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Nerves from the Posterior Cord

•  Radial—continuation of the posterior cord •  Largest branch of the brachial plexus •  Innervates muscles of the posterior upper limb

•  Axillary •  Innervates the deltoid and teres minor


Figure 14.11 Course of the axillary and radial nerves. Musculocutaneous nerve

Axillary nerve

Branches of axillary nerve

Radial nerve

Ulnar nerve (cut)

Median nerve (cut)

Posterior cutaneous nerve

Deep radial nerve

Superficial branch of radial nerve

Anterior divisions

Posterior divisions


Figure 14.10 Innervation of the Upper Limb (1 of 2)


Figure 14.10 Innervation of the Upper Limb (2 of 2)


The Lumbar Plexus and Innervation of the Lower Limb •  Lumbar plexus •  Arises from L1 to L4 •  Smaller branches innervate the posterior

abdominal wall and psoas muscle •  Main branches innervate the anterior thigh • Femoral nerve—innervates anterior thigh

muscles • Obturator nerve—innervates adductor

muscles


Figure 14.12 The lumbar plexus. Kidney

L3 vertebra

Ureter

Lateral femoral cutaneous nerve

Psoas major

External iliac artery

Urinary bladder

Femoral artery

Nerves of the lumbar plexus, anterior view

Ventral rami:

Iliohypogastric

Ilioinguinal nerve

Femoral nerve

Lateral femoral cutaneous

Obturator

Anterior femoral cutaneous

Saphenous

Ventral rami Anterior division Posterior division

Iliohypogastric

Ilioinguinal

Genitofemoral

Lateral femoral cutaneous

Obturator

Femoral

Lumbosacral trunk

L1

L2

L3

L4

L5

Ventral rami and major branches of the lumbar plexus

Distribution of the major nerves from the lumbar plexus to the lower limb

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The Sacral Plexus

•  Arises from spinal nerves L4–S4 •  Caudal to the lumbar plexus •  Often considered with the lumbar plexus •  Lumbosacral plexus


Innervation of the Lower Limb

•  Sciatic nerve—the largest nerve of the sacral plexus •  Actually two nerves in one sheath • Tibial nerve—innervates most of the

posterior lower limb • Common fibular (peroneal) nerve—

innervates muscles of the anterolateral leg


Innervation of the Lower Limb

•  Superior and inferior gluteal nerves •  Innervate the gluteal muscles

•  Pudendal nerve •  Innervates muscles of the perineum


Figure 14.14 The sacral plexus.

Ventral rami Anterior division Posterior division

Gluteus maximus

Piriformis

Common fibular nerve

Tibial nerve

Sciatic nerve

Dissection of the gluteal region, posterior view

Ventral rami:

Ventral rami and major branches of the sacral plexus, anterior view

Distribution of the major nerves from the sacral plexus to the lower limb, posterior view

Superior gluteal

Lumbosacral trunk

Inferior gluteal

Common fibular

Tibial

Posterior femoral cutaneous

Pudendal

Sciatic

L4

L5

S1

S2

S3

S4

S5 Co1

Superior gluteal

Inferior gluteal nerve

Pudendal nerve

Sciatic

Posterior femoral cutaneous nerve

Common fibular

Tibial

Sural (cut)

Deep fibular

Superficial fibular

Plantar branches


Figure 14.13 Innervation of the Lower Limb (1 of 2)


Figure 14.13 Innervation of the Lower Limb (2 of 2)

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Innervation of the Skin: Dermatomes

•  Dermatome—an area of skin •  Innervated by cutaneous branches/dorsal root

of a single spinal nerve •  Upper limb •  Skin is supplied by nerves of the brachial

plexus •  Lower limb •  Lumbar nerves—anterior surface •  Sacral nerves—posterior surface


Figure 14.15a Map of dermatomes.

T2

C6

C5

C6 C7

C8

Anterior view

S1

L5 L5

S1

L4 L4

L3 L3

L2 L2

L1 L1

S3 S2

C8 C7

C6

C5

C6

T2

T12 T11 T10 T9 T8 T7 T6 T5 T4 T3 T2 T1 C5

C4

C3 C2


Figure 14.15b Map of dermatomes.

Posterior view

C2

C3 C4 C5 C6 C7 C8 T1 T2 T3 T4 T5 T6 T7 T8 T9

T10

T11 T12

L1 L3 L5

L2 L4

C6

C7

C8 C8

C7

C6

S1 S2

S3 S4

S2

S4

S2 S1 S1

L5 L5

L1

L2

L3

L4

L4 L4 L5 L5 S1


Disorders of the PNS

•  Shingles (herpes zoster) •  Viral infection •  Stems from childhood chicken pox •  Often brought on by stress •  Mostly experienced by people over 50



•  Migraine headache •  Relates to sensory innervation of cerebral

arteries • Arteries dilate and compress and irritate

sensory nerve endings



•  Peripheral neuropathy •  Pathological condition of peripheral nerves •  Symptoms of sensory nerve involvement • Paresthesia, pain, burning, loss of sensation

•  Symptoms of motor nerve involvement • Muscle weakness and paralysis

•  Causes: • Trauma, repetitive use • Systemic disorders—HIV, diabetes, vitamin

B deficiency

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The PNS Throughout Life

•  Spinal nerves form late in week 4 •  Each of the 31 pairs of spinal nerves: •  Sends motor fibers to an individual myotome •  Sends sensory fibers to the overlying band of

skin •  During week 5, nerves reach the organs they

innervate


The PNS Throughout Life

•  Embryonic muscles migrate to new locations •  Some skin dermatomes become displaced •  Muscles and skin always retain their original

nerve supply

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