The Peripheral Nervous System

© 2014 Pearson Education, Inc.

PowerPoint® Lecture Presentations prepared byLeslie HendonUniversity of Alabama, Birmingham

14The PeripheralNervous System


I. The Peripheral Nervous System (PNS)

A. Nerves allow the CNS to receive information and initiate action

B. The PNS is functionally divided into sensory and motor divisions

C. Sensory (afferent) division

1. somatic sensory

2. visceral sensory

3. special sensory (e.g. eye, ear)

D. Motor (efferent) division

1. somatic motor

2. visceral motor (Autonomic Nervous System)

a. sympathetic division

b. parasympathetic division


Peripheral nervous system (PNS)

Sensory (afferent) division Motor (efferent) division

Central nervous system (CNS)

Somatic sensory Visceral sensory Somatic nervoussystem

Autonomic nervoussystem (ANS)

Sympatheticdivision

Parasympatheticdivision

General: Touch, pain,pressure, vibration,temperature, andproprioception in skin,body wall, and limbs

Special: Hearing,equilibrium, vision

General: Stretch, pain,temperature, chemicalchanges, and irritationin viscera; nausea andhunger

Special: Taste, smell

Motor innervation of allskeletal muscles

Motor innervation of smooth muscle, cardiacmuscle, and glands


II. General TermsA. sensation - awareness of external/internal conditions

B. perception - conscious registration of conditions

C. stimulus - change that can initiate nerve impulse

E. transduction - changing stimulus signal into nerve signal

F. adaptation - decreased sensitivity with repeat stimuli

a. rapidly adapting - pressure, touch, smell

b. slowly adapting - pain, position, blood chemicals

G. afterimage - sensation even after stimulus is gone

H. modality - distinct property of each sensation


I. receptor (sense organ) - converts stimulus to impulse

J. nerve – bundle of axons carrying sensory or motor information

a. can be motor only

b. can be sensory only

c. can be both sensory and motor (most)

K. ganglion – collection of nerve cell bodies located outside the CNS

a. mostly the autonomic nervous system


III. General Classification of ReceptorsA. Two main categories of sensory receptors

1. Free nerve endings of sensory neurons

a. monitor general sensory information

2. Complete receptor cells

a. specialized epithelial cells or small neurons

b. monitor most types of special sensory information

c. special senses = vision, hearing, smell, taste, balance


B. Receptors Named by Location

1. exteroreceptors – (“outside”) respond to external environment

a. located at or near body surfaces

b. include receptors for touch, pressure, pain, and temperature

2. enteroreceptors – (“inside”) respond to internal environment

a. located in digestive tube, bladder, and lungs

b. monitor a variety of stimuli

i. chemical concentration, taste, tissue stretching, temperature

3. proprioreceptors - respond to body position/motion

a. located in skeletal muscles, tendons, joints, and ligaments

b. monitor degree of stretch

c. send inputs on body movement to the CNS


C. Receptors Named by Type of Stimulus Detected

1. mechanoreceptors - any mechanical deviation

a. touch, pressure, vibration, proprioception etc.

b. baroreceptors – monitor blood pressure

2. thermoreceptors - changes in temperature

3. nocireceptors - pain; physical or chemical damage

4. photoreceptors - light; rods & cones of the eye

5. chemoreceptors - shapes of different molecules

a. taste, smell, chemicals of blood


IV. General Sensory Receptors

A. General sensory receptors (not special – vision, hearing, etc.)1. widely distributed2. nerve endings of sensory neurons monitor:

a. touch, pressure, stretch, pain, temperature, proprioception

B. Divided into two different groups1. free nerve endings2. encapsulated nerve endings


C. Free nerve endings1. abundant in epithelia and underlying connective tissue2. respond to pain and temperature3. monitor affective senses (emotional response – e.g. pain!)4. epithelial tactile complexes (Merkel discs)

a. tactile epithelial cell innervated by sensory nerve ending

b. slowly adapting receptors for light touch5. hair follicle receptors—wrap around hair follicles

a. rapidly adapting receptors



D. Encapsulated nerve endings1. consist of one or more end fibers of sensory neurons2. enclosed in connective tissue

3. mechanoreceptors

a. tactile (Meissner’s) corpuscles

b. lamellar (Pacinian) corpuscles

c. bulbous corpuscles (Ruffini endings)

d. proprioceptors


4. Tactile (Meissner’s) corpuscles

a. spiraling nerve ending surrounded by Schwann cells

b. occur in the dermal papillae

c. rapidly adapting receptors for discriminative touch

d. occur in sensitive, hairless areas of the skin

5. Lamellar corpuscles

a. nerve ending surrounded by layers of flat Schwann cells

b. occur in the hypodermis

c. sensitive to deep pressure—rapidly adapting receptors


6. Bulbous corpuscles

a. located in the dermis and respond to pressure

b. monitor continuous pressure on the skin - adapt slowly


7. Proprioceptors

a. monitor stretch in locomotory organs

Three different types:

i. muscle spindles ► measure the changing length of a muscle ► embedded in the perimysium between muscle fasciclesii. intrafusal muscle fibers

► modified skeletal muscle fibers located within muscle spindles

iii. anulospiral endings ► located around middle of intrafusal fibers ► stimulated by rate and degree of stretch


c. tendon organs ► are located near the muscle-tendon junction ► monitor tension within tendons

d. joint kinesthetic receptors ► sensory nerve endings within the joint capsulesi. lamellar corpusclesii. bulbous corpusclesiii. free nerve endingsiv. receptors resembling tendon organs




Extrafusalmuscle fibers(contact)

Intrafusalmuscle fibers

Sensoryfiber

Tendon

Anulo-spiralendings (primarysensory endings)

Capsule

Musclespindle

Tendon organ(tension)


V. Cranial Nerves – An Overview

A. Attach to the brain and pass through specific foramina of the skull

B. Numbered from I to XII (roman numerals)

1. Cranial nerves I and II attach to the forebrain

2. All others attach to the brain stem

C. Primarily serve head and neck structures

D. vagus nerve (X) is the only cranial nerve that extends into the abdomen


Filaments ofolfactory nerve (I)

Optic nerve (II)

Oculomotornerve (III)Trochlearnerve (IV)

Trigeminalnerve (V)

Abducensnerve (VI)

Facial nerve (VII)

Vestibulocochlearnerve (VIII)

Glossopharyngealnerve (IX)

Vagus nerve (X)Accessory nerve (XI)Hypoglossal nerve (XII)


Olfactory nerve (I)

Optic nerve (II)

Oculomotornerve (III)

Trochlearnerve (IV)

Trigeminalnerve (V)

Abducensnerve (VI)

Facial nerve (VII)

Vestibulocochlearnerve (VIII)

Glossopharyngealnerve (IX)

Vagus nerve (X)Accessory nerve (XI)Hypoglossal nerve (XII)


I Olfactory

II Optic

III Oculomotor

IV Trochlear

V Trigeminal

VI Abducens

Somaticsensory

(SS)

Visceralsensory

(VS)

Somaticmotor(SM)

Visceral motor:parasympathetic

(VM)

Cranial nerves Sensory function Motor functionSomaticsensory

(SS)

Visceralsensory

(VS)

Somaticmotor(SM)

Visceral motor:parasympathetic

(VM)

Cranial nerves Sensory function Motor function

VII Facial

VIII Vestibulocochlear

IX Glossopharyngeal

X Vagus

XI Accessory

XII Hypoglossal

Smell

Vision

General

SM

SM

SM

SM

VM

VM

VM

VM

SM

SM

SM

SM

SM

Some

General General;taste

General;taste

General;taste

General

General

Hearing;equilibrium

The Cranial Nerves


Create your own memory device:

O__________________ F_________________

O__________________ V_________________

O__________________ G_________________

T___________________ V_________________

T___________________ A_________________

A___________________H_________________


Mike’s memory device (not for a mixed audience)

Oh! Feel

Oh! Very

Oh! Good

To V_________________

Touch A_________________

And H_________________


The Cranial Nerves


Olfactory Nerves (I)

A. Special visceral sensory - sense of smell

B. Olfactory receptor cells located in olfactory epithelium of nasal cavity

C. Olfactory bulbs project fibers into the nasal cavity

C. Pass through the cribriform foramina of the ethmoid bone


Olfactory Nerves (I)


The Optic Nerves (II)

A. Special somatic sensory - vision

B. Originate on the retina of the eye

C. Pass through the optic canals of the sphenoid bone

D. Criss-cross at the optic chiasma


Optic Nerves (II)


The Oculomotor Nerves (III)

A. Somatic motor - innervate four extrinsic eye muscles

1. Superior rectus

2. medial rectus

3. inferior rectus

4. inferior oblique

B. Visceral motor

► Constricts pupil

► Controls shape of lens

C. Pass through the superior orbital fissure


Oculomotor Nerves (III)


The Trochlear Nerves (IV)

A. Somatic motor - the superior oblique muscle

B. Pass ventrally and laterally around midbrain

C. Pass through superior orbital fissure


Trochlear Nerves (IV)


The Trigeminal Nerves (V)

A. Largest of the cranial nerves

1. Ophthalmic division (V1) superior oribital fissure

2. Maxillary division (V2) foramen rotundum

3. Mandibular division (V3) foramen ovale

B. Cell bodies of sensory neurons located in the trigeminal ganglion

C. Mandibular division = motor fibers that innervate chewing muscles


Trigeminal Nerves (V)


The Abducens Nerves (VI)

A. Somatic motor - innervates lateral rectus muscle

B. Pass through the superior orbital fissure

NOTE: III (oculomotor); IV (trochlear) and VI (abducens) =

innervation of the muscles of the eye


Abducens Nerves (VI)


The Facial Nerves (VII)

A. Special visceral sensory - taste buds on anterior two-thirds of tongue

B. Somatic motor - innervate facial muscles

C. Visceral motor - innervation of lacrimal glands, submandibular and sublingual salivary glands

D. Enter temporal bone through the internal acoustic meatus


Facial Nerves (VII)



The Vestibulocochlear Nerves (VIII)

A. Sensory nerve of hearing and equilibrium

B. From inner ear - pass through the internal acoustic meatus

C. Carries information from vestibular apparatus and cochlea


Vestibulocochlear Nerves (VIII)


The Glossopharyngeal Nerves (IX)

A. General visceral sensory

1. posterior one-third of tongue

2. pharyngeal mucosa

3. chemoreceptors in carotid body

4. baroreceptors of carotid sinus

B. Somatic motor - elevate pharynx during swallowing

C. Visceral motor - innervate the parotid salivary gland

D. Fibers pass through the jugular foramen


Glossopharyngeal Nerves (IX)


The Vagus Nerves (X)

A. General visceral sensory - from thoracic and abdominal viscera

B. Special visceral sensory - taste buds on epiglottis

C. Somatic motor - skeletal muscles of the pharynx and larynx

D. Visceral motor - parasympathetic innervation to

1. Heart, lungs, abdominal organs

E. Fibers exit through the jugular foramen


Vagus Nerves (X)


The Accessory Nerves (XI)

A. Somatic motor - innervates trapezius and sternocleidomastoid

B. Pass into skull through foramen magnum

C. Exit skull through the jugular foramen


Accessory Nerves (XI)


The Hypoglossal Nerves (XII)

A. Somatic motor - innervate the tongue muscles

B. Exit the skull through hypoglossal canal


Hypoglossal Nerves (XII)


The Spinal Nerves


VI. Spinal Nerves

A. 31 pairs - contain thousands of nerve fibers

B. Connect to the spinal cord

C. Named for point of issue from the spinal cord

8 pairs of cervical nerves (C1–C8) (note: 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)


Cervical plexus

Brachial plexus

Ventral rami Spinal nerves

Cervicalenlargement

Intercostalnerves

Lumbarenlargement

Lumbar plexus

Sacral plexus

Cauda equina(spinal nerves)

CervicalnervesC1 – C8

ThoracicnervesT1 – T12

LumbarnervesL1 – L5

SacralnervesS1 – S5

CoccygealnerveCo1


D. Connect to the spinal cord by the dorsal root and ventral root

1. Dorsal root—contains sensory fibers

► cell bodies—located in the dorsal root ganglion

2. Ventral root—contains motor fibers

► arising from anterior gray horn of spinal cord

E. Each branch into dorsal ramus and ventral ramus

► Dorsal and ventral rami contain sensory and motor fibers

F. Sympathetic chain ganglia – from T1 – L2


Sensory axon and cell body

Nerves

Spinalnerve

Axon ofmotorneuron

Sensory receptors inskin (e.g., free nerveendings of sensoryneuron)

Ventralramus

Dorsalramus

Dorsal rootganglion

Dorsal root

Ventral root


Gray matter

White matterDorsal and ventralrootlets of spinal nerve

Sympathetic chainganglion

Ventral rootDorsal root

Dorsal rootganglion

Dorsal ramusof spinal nerve

Ventral ramusof spinal nerve

Spinal nerve

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


VII. Innervation of the Back

A. Dorsal rami - innervate back muscles

1. follow a neat, segmented pattern

2. innervate a horizontal strip of muscle and skin

B. Ventral rami - arranged in simple, segmented pattern

1. intercostal nerves - supply intercostal muscles, skin, and abdominal wall

2. each gives off lateral and anterior cutaneous branches


Dorsal ramus

Ventral ramus

Spinal nerve

Sympathetic chainganglion

Intercostal nerve

Sternum

Branches of intercostal nerve

Cross section of thorax showing the main roots and branches of a spinal nerve


VIII. Introduction to Nerve Plexuses

A. Nerve plexus - a network of spinal nerves that criss-cross with each other – give rise to the nerves of the body

1. branch and join with one another

2. fibers from ventral rami crisscross (except T2–T12)

3. form the four nerve plexuses

a. cervical plexus

b. brachial plexus

c. lumbar plexus

d. sacral plexus

4. primarily serve the limbs


B. Cervical plexus

1. formed by ventral rami of first four cervical nerves (C1–C4)

a. most are cutaneous nerves

b. some innervate muscles of the anterior neck

2. phrenic nerve C3–C5

a. the most important nerve of the cervical plexus

b. innervates the diaphragm

3. accessory nerve (XI) C5

Note: a nerve can have nerve fibers from different spinal nerves


Ventral rami

Hypoglossalnerve (XII)

Accessory nerve (XI) (C3,4,5)

C1

C2

C3

C4

C5

Ventralrami:

Phrenic nerve (C3,4,5)


C. Brachial plexus

1. lies in the neck and axilla

2. formed by ventral rami of C5–T1

3. cords give rise to 5 main nerves of the upper limba. musculotaneous nerve - biceps brachii and brachialis C5–C7

b. axillary nerve - deltoid and teres minor C5–C6

c. ulnar nerve - hand muscles and skin of the medial hand C8–T1

d. median nerve - anterior forearm muscles and lateral palm C5–T1

e. radial nerve - muscles of the posterior upper limb C5–T1

4. Roots >>> Trunks >>> Divisions >>> Cords >>> Nerves

Note: a nerve can be composed of fibers from different spinal nerves


C8

C7

C6

C5

T1

Major terminalbranches(peripheral nerves)

Cords Divisions TrunksRoots(ventralrami)

Musculocutaneous

Median

Ulnar

Radial

Axillary

Lateral

Medial

Posterior

Anterior

Anterior

Anterior

Posterior

Posterior

Posterior

Upper

Middle

Lower

Flowchart summarizing relationships within the brachial plexus

The Brachial Plexus


Roots (C5–T1)

Trunks

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

Lateral

PosteriorMedial

AxillaryMusculo-cutaneous

Radial

MedianUlnar

Upper

Middle

Lower

C5

C6

C7C8

T1

Anteriordivisions

Posteriordivisions

Trunks Roots

Divisions

Cords

The Brachial Plexus


Axillary nerve

Radial nerve

Musculo-cutaneous nerve

Ulnar nerve

Median nerve

Digitalbranches

The major nerves of the upper limb

The Brachial Plexus


Digitalbranches

The major nerves of the upper limb

The Brachial Plexus




D. Lumbar plexus

1. Arises from L1 to L4

2. innervate the posterior abdominal wall and psoas muscle

3. Main branches innervate the anterior thigh

a. femoral nerve - anterior thigh muscles L2–L4

b. obturator nerve - innervates adductor muscles L2–L4



Nerves of the lumbar plexus,anterior view

Ventralrami:

Ilioinguinalnerve

Femoral nerve

Lateralfemoralcutaneous

Obturator

Anteriorfemoralcutaneous

Saphenous

Ventral ramiAnterior divisionPosterior division

Iliohypogastric

Ilioinguinal

Genitofemoral

Lateral femoralcutaneous

Obturator

Femoral

L1

L2

L3

L4

L5

Ventral rami and major branches of thelumbar plexus

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


Nerves of the lumbar plexus,anterior view

Ventralrami:Ventral rami

Anterior divisionPosterior division

L1

L2

L3

L4

L5

Ventral rami and major branches of thelumbar plexus

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


E. Sacral plexus

1. Arises from spinal nerves L4–S4

2. sciatic nerve - the largest nerve of the sacral plexus L4–S3

a. actually two nerves in one sheath

b. tibial nerve - most of the posterior lower limb L4–S3

c. common fibular nerve - muscles of anterolateral leg L4–S2

3. superior and inferior gluteal nerves - the gluteal muscles L4–S2

4. pudendal nerve - muscles of the perineum S2–S4





Common fibularnerve

Tibial nerve

Sciatic nerve

Dissection of the gluteal region,posterior view

Ventralrami:

Ventral rami and major branches of thesacral plexus, anterior view

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

Superiorgluteal

Lumbosacraltrunk

Inferior gluteal

Commonfibular

Tibial

Posteriorfemoralcutaneous

Pudendal

Sciatic

L4

L5

S1

S2

S3

S4

S5

Co1

Superiorgluteal

Inferiorglutealnerve

Pudendalnerve

Sciatic

Posteriorfemoralcutaneousnerve

Commonfibular

Tibial

Deep fibular

Superficialfibular



Dissection of the gluteal region,posterior view

Ventral rami and major branches of thesacral plexus, anterior view

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

L4

L5

S1

S2

S3

S4

S5

Co1




IV. Innervation of the Skin: Dermatomes

A. Dermatome - an area of skin innervated by cutaneous branches of a single spinal nerve

B. Upper limb - supplied by nerves of the brachial plexus

C. Lower limb

1. lumbar nerves - anterior surface

2. sacral nerves - posterior surface


T2

C6

C5

C6C7

C8

Anterior view

S1

L5 L5

S1

L4 L4

L3 L3

L2 L2

L1 L1

S3S2

C8C7

C6

C5

C6

T2

T12T11T10T9T8T7T6T5T4T3T2T1C5

C4

C3C2

Dermatomes of theAnterior

© 2014 Pearson Education, Inc.Posterior view

C2

C3C4C5C6C7C8T1T2T3T4T5T6T7T8T9

T10T11T12

L1L3L5

L2L4

C6C7

C8 C8C7

C6

S1S2S3

S4

S2

S4

S2S1 S1

L5 L5

L1

L2

L3

L4

L4L4L5 L5 S1

Dermatomes of thePosterior


IX. Disorders of the PNS

A. Shingles (herpes zoster)

1. viral infection - stems from childhood chicken pox

2. often brought on by stress

3. mostly experienced by people over 50

4. extremely painful

B. Migraine headache

1. relates to sensory innervation of cerebral arteries

2. arteries dilate and compress and irritate sensory nerve endings


C. Peripheral neuropathy1. pathological condition of peripheral nerves2. symptoms of sensory nerve involvement:

a. paresthesia, pain, burning, loss of sensation3. symptoms of motor nerve involvement:

a. muscle weakness and paralysis4. causes:

a. trauma, repetitive use (e.g. carpal tunnel syndrome)b. systemic disorders: HIV, diabetes, vitamin B deficiency

The Peripheral Nervous System

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