Ch 13 Lecture Outline Thursday

8/8/2019 Ch 13 Lecture Outline Thursday

http://slidepdf.com/reader/full/ch-13-lecture-outline-thursday 1/47

Copyright © 2010 Pearson Education, Inc.

Structure of a Nerve

Cordlike organ of the PNS

Bundle of myelinated and unmyelinated

peripheral axons enclosed by connective

tissue




Structure of a Nerve

Connective tissue coverings include:

Endoneurium²loose connective tissue that

encloses axons and their myelin sheaths

Perineurium²coarse connective tissue that

bundles fibers into fascicles

Epineurium²tough fibrous sheath around a

nerve



Copyright © 2010 Pearson Education, Inc. Figure 13.3b

Blood

vessels

Fascicle

Epineur ium

Per ineur iumEndoneur ium

Axon

Myelin sheath

(b)




Classif ication of Nerves

Most nerves are mixtures of afferent and efferent

fibers and somatic and autonomic (visceral) fibers

Pure sensory (afferent) or motor (efferent) nerves are

rare Types of fibers in mixed nerves:

Somatic afferent and somatic efferent

Visceral afferent and visceral efferent

Peripheral nerves classified as cranial or spinal

nerves




Cranial Nerves

Twelve pairs of nerves associated with the

brain

Most are mixed in function; two pairs are

purely sensory

Each nerve is identified by a number

(I through XII) and a name

³On occasion, our trusty truck acts f unny²very

good vehicle anyhow´



Copyright © 2010 Pearson Education, Inc. Figure 13.5 (a)

Frontal lobe

Temporal lobe

Infundibulum

Facialnerve (VII)

Vestibulo-

cochlear

nerve (VIII)Glossopharyngeal

nerve (IX)Vagus nerve (X)

Accessory nerve (XI)

Hypoglossal nerve (XII)

(a)

Filaments of

olfactory

nerve (I)

Olfactor y bulb

Olfactor y tract

Optic chiasma

Optic nerve

(II)

Optic tractOculomotor nerve (III)Trochlear

nerve (IV) Trigeminal

nerve (V)

Abducensnerve (VI)

Cerebellum

Medulla

oblongata



Copyright © 2010 Pearson Education, Inc. Figure 13.5 (b)

*PS = parasympathetic(b)

Cranial nerves

I ² VI

I

II

III

IV

V

VI

Olfactor y

Optic

Oculomotor

Trochlear

Tr igeminal

Abducens

Yes (smell)

Yes (vision)

No

No

Yes (general

sensation)

No

No

No

Yes

Yes

Yes

Yes

No

No

Yes

No

No

No

Cranial nerves

VII ² XII

Sensory

f unction

Motor

f unction

PS*

fibers

Sensory

f unction

Motor

f unction

PS*

fibers

VII

VIII

IX

X

XI

XII

Facial

Vestibulocochlear

Glossophar yngeal

Vagus

Accessor y

Hypoglossal

Yes (taste)

Yes (hear ing

and balance)

Yes (taste)

Yes (taste)

No

No

Yes

Some

Yes

Yes

Yes

Yes

Yes

No

Yes

Yes

No

No




I: The Olfactor y Nerves

Arise from the olfactory

receptor cells of nasalcavity

Pass through the

cribriform plate of theethmoid bone

Fibers synapse in the

olfactory bulbs

Pathway terminates in the

primary olfactory cortex

Purely sensory (olfactory)function




II: The Optic Nerves Arise from the retinas

Pass through the opticcanals, converge and

partially cross over at the

optic chiasma

Optic tracts continue to the

thalamus, where they

synapse

Optic radiation fibers run

to the occipital (visual)

cortex

Purely sensory (visual) function




III: The Oculomotor Nerves Fibers extend from the

ventral midbrainthrough the superior

orbital fissures to the

extrinsic eye muscles

Functions in raising the

eyelid, directing the

eyeball, constricting the

iris (parasympathetic),and controlling lens

shape




IV: The Trochlear Nerves Fibers from the

dorsal midbrainenter the orbits via

the superior orbital

fissures to innervate

the superior oblique

muscle

Primarily a motor

nerve that directsthe eyeball




V: The Tr igeminal Nerves Largest cranial nerves; fibers

extend from pons to face Three divisions

Ophthalmic (V1) passesthrough the superior orbital

fissure

Maxillary (V2) passes throughthe foramen rotundum

Mandibular (V3) passes

through the foramen ovale

Convey sensory impulses frovarious areas of the face (V1)and (V2), and supplies motor

fibers (V3) for mastication




VII: The Facial Nerves Fibers from the pons travel

through the internal acousticmeatuses, and emerge through

the stylomastoid foramina to the

lateral aspect of the face

Chief motor nerves of the facewith 5 major branches

Motor functions include facial

expression, parasympathetic

impulses to lacrimal andsalivary glands

Sensory function (taste) from

the anterior two-thirds of the

tongue




VIII: The Vestibulocochlear Nerves

Afferent fibers from the hearing

receptors (cochlear division)and equilibrium receptors

(vestibular division) pass from

the inner ear through the

internal acoustic meatuses,

and enter the brain stem at the

pons-medulla border

Mostly sensory function; smallmotor component for

adjustment of sensitivity of

receptors




IX: The Glossophar yngeal Nerves Fibers from the medulla

leave the skull via the jugular foramen and run to thethroat

Motor functions: innervate

part of the tongue andpharynx for swallowing, andprovide parasympatheticfibers to the parotid salivaryglands

Sensory functions: fibers conducttaste and general sensoryimpulses from the pharynx andposterior tongue, and impulses

from carotid chemoreceptors and




X: The Vagus Nerves The only cranial nerves that

extend beyond the head and

neck region

Fibers from the medulla exit the

skull via the jugular foramen

Most motor fibers are

parasympathetic fibers that helpregulate the activities of the

heart, lungs, and abdominal

viscera

Sensory fibers carry impulses from

thoracic and abdominal viscera,

baroreceptors, chemoreceptors,

and taste buds of posterior tongue

and pharynx




XII: The Hypoglossal Nerves Fibers from the

medulla exit theskull via the

hypoglossal canal

Innervate extrinsicand intrinsic

muscles of the

tongue that

contribute toswallowing and

speech




Spinal Nerves

31 pairs of mixed nerves named according to

their point of issue from the spinal cord

8 cervical (C1 ±C8)

12 thoracic (T1 ±T12)

5 Lumbar (L1 ±L5)

5 Sacral (S1 ±S5) 1 Coccygeal (C0)




Spinal Nerves: Roots

Each spinal nerve connects to the spinal cord

via two roots

Ventral roots

Contain motor (efferent) fibers from the ventral

horn motor neurons

Fibers innervate skeletal muscles)




Spinal Nerves: Roots

Dorsal roots

Contain sensory (afferent) fibers from sensory

neurons in the dorsal root ganglia

Conduct impulses from peripheral receptors

Dorsal and ventral roots unite to form spinal

nerves, which then emerge from the vertebral

column via the intervertebral foramina




Dorsal rootganglion

Gray matter

White matter

Ventral root

Dorsal root

Dorsal and

ventral rootletsof spinal nerve

Dorsal ramusof spinal nerve

Ventral ramus

of spinal nerve

Sympathetic trunkganglion

Spinal nerve

Rami communicantes

Anterior view showing spinal cor d, associated nerves, and vertebrae.

The dorsal and ventral roots arise medially as rootlets and join

laterally to form the spinal nerve.




Spinal Nerves: Rami

Each spinal nerve branches into mixed rami

Dorsal ramus

Larger ventral ramus

Meningeal branch

Rami communicantes (autonomic pathways)

join to the ventral rami in the thoracic region




Spinal Nerves: Rami

All ventral rami except T2 ±T12 form interlacing

nerve networks called plexuses (cervical,

brachial, lumbar, and sacral)

The back is innervated by dorsal rami viaseveral branches

Ventral rami of T2 ±T12 as intercostal nerves

supply muscles of the ribs, anterolateralthorax, and abdominal wall




Dorsal ramus

Ventral ramus

Intercostal nerve

Spinal nerve

Rami communicantes

Dorsal root

ganglion Dorsal rootVentral root

Sympathetic trunk

ganglion

Ster num

(b) Cross section of thorax showing the main roots and

branches of a spinal nerve.

Branches of intercostal

nerve Lateral cutaneous Anter ior cutaneous




Cervical Plexus

Formed by ventral rami of C1 ±C4

Innervates skin and muscles of the neck, ear,

back of head, and shoulders

Phrenic nerve

Major motor and sensory nerve of the

diaphragm (receives fibers from C3

±C5

)



Copyright © 2010 Pearson Education, Inc. Figure 13.8

Hypoglossal

nerve (XII)

C1

C2

C3

C4

C5

Segmental

branches

Lesser occipitalnerveGreater aur icular

nerve

Ansa cervicalis

Phrenic nerve

Supraclavicular

nerves

Accessor y nerve (XI)

Transverse

cervical nerve

Ventral

rami:

Ventral rami




Brachial Plexus

Formed by ventral rami of C5 ±C8 and T1 (and often

C4 and T2)

It gives rise to the nerves that innervate the upper

limb Major branches of this plexus:

Roots²five ventral rami (C5 ±T1)

Trunks²upper, middle, and lower Divisions²anterior and posterior

Cords²lateral, medial, and posterior



Copyright © 2010 Pearson Education, Inc. Figure 13.9 (d)

Anter ior

divisions

(d) Flowchart summarizing relationships within the

brachial plexus

Major terminal

branches

(peripheral nerves)

Cor ds Divisions Tr unksRoots

(ventral

rami)

MusculocutaneousMedian

Ulnar

Radial

Axillar y

Anter ior

Poster ior

Anter ior

Poster ior

Poster ior

Anter ior

Upper

Middle

Lower

Lateral

Medial

Poster ior

Poster ior

divisions

Trunks Roots

C5

C6

C7

C8

T1




Brachial Plexus: Nerves

Axillary²innervates the deltoid, teres minor, and skinand joint capsule of the shoulder

Musculocutaneous²innervates the biceps brachiiand brachialis and skin of lateral forearm

Median²innervates the skin, most flexors andpronators in the forearm, and some intrinsic musclesof the hand

Ulnar²supplies the flexor carpi ulnaris, part of theflexor digitorum profundus, most intrinsic muscles of the hand, and skin of medial aspect of hand

Radial²innervates essentially all extensor muscles,supinators, and posterior skin of limb



Copyright © 2010 Pearson Education, Inc. Figure 13.9 (c)

Median nerve

Musculocutaneous nerve

Radial nerveHumerus

Ulna

Ulnar nerveMedian nerve

Radius

Radial nerve (superf icial branch)

Superf icial branch of ulnar nerveDorsal branch of ulnar nerve

Digital branch of ulnar nerve

Muscular branch

Digital branch

(c) The major nerves of the upper limb

Axillary

nerveAnter ior

divisions

Poster ior

divisions

Trunks Roots




Lumbar Plexus

Arises from L1 ±L4

Innervates the thigh, abdominal wall, and

psoas muscle

Femoral nerve²innervates quadriceps and

skin of anterior thigh and medial surface of leg

Obturator nerve²passes through obturator

foramen to innervate adductor muscles




(a) Ventral rami and major branches

of the lumbar plexus

Iliohypogastr ic

L1

L2

L3

L4

L5

Ilioinguinal

Genitofemoral

Lateral femoral

cutaneous

Obturator

Femoral

Lumbosacral

trunk

Lateral femoral

cutaneous

Anter ior femoralcutaneous

Saphenous

Obturator

Iliohypogastr icIlioinguinal

Femoral

Ventral ramiVentral

rami:

(b) Distribution of the major nerves from

the lumbar plexus to the lower limb




Sacral Plexus

Arises from L4 ±S4

Serves the buttock, lower limb, pelvic structures, and

perineum

Sciatic nerve

Longest and thickest nerve of the body

Innervates the hamstring muscles, adductor magnus,

and most muscles in the leg and foot Composed of two nerves: tibial and common fibular




Super ior gluteal

LumbosacraltrunkInfer ior

gluteal

Commonf ibular Tibial

Poster ior femoral

cutaneousPudendal

Sciatic

Ventral rami and major branches

of the sacral plexus

L4

L5

S1

S2

S3

S4

S5

Co1

Ventral rami Ventral rami:




Super ior glutealInfer ior gluteal

Common f ibular

Deep f ibular

Superf icial f ibular

Plantar branches

Tibial

Sural (cut)

Poster ior femoral

cutaneous

Pudendal

Sciatic

(b) Distribution of the major nerves from

the sacral plexus to the lower limb




Innervation of Skin

Dermatome: the area of skin innervated by

the cutaneous branches of a single spinal

nerve

All spinal nerves except C1 participate indermatomes

Most dermatomes overlap, so destruction of a

single spinal nerve will not cause completenumbness




C2

C3

C4

C5T1

T2

T2T3T4T5

C6

C8C7 C7

C6

T6

T7

T8

T9

T10

T11T12

L1

S2S3

L1

L2

L3

L4

L5

L2

L3

L4

L5

S1

C5

C6

C8

T2

C5

C6

S1

Anterior

view

C2

C3

C4

C5

C6C7C8

C8 C8

C7 C7

T1

T2

T3T4T5T6T7T8T9

T10

T11

T12

L1L2

L3

S1

(b) Posterior

view

L5S2

S1

S1

S3

S2 S1S2

S4

S5

L5L5

L4

L5L5

L4

C6 C6

C5

L4

L3

L2

L1

L4



Innervation of Joints

Hilton¶s law: Any nerve serving a muscle that

produces movement at a joint also innervates

the joint and the skin over the joint

Ch 13 Lecture Outline Thursday

Documents

Transcript of Ch 13 Lecture Outline Thursday