powerpoint ® lecture slides prepared by janice meeking, mount royal college c h a p t e r copyright...

PowerPoint® Lecture Slides prepared by Janice Meeking, Mount Royal College

C H A P T E R

Copyright © 2010 Pearson Education, Inc.

13

The Peripheral Nervous System and Reflex Activity: Part C


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)

Copyright © 2010 Pearson Education, Inc. Figure 13.6

CervicalnervesC1 – C8

ThoracicnervesT1 – T12

LumbarnervesL1 – L5

Sacral nervesS1 – S5

Coccygeal nerve Co1

Cervical plexus

Intercostalnerves

Cervicalenlargement

Lumbarenlargement

Cauda equina

Brachial plexus

Lumbar plexus

Sacral plexus


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

Copyright © 2010 Pearson Education, Inc. Figure 13.7 (a)

Dorsal rootganglion

Gray matterWhite matterVentral rootDorsal root

Dorsal andventral rootlets of spinal nerve

Dorsal ramusof spinal nerveVentral ramusof spinal nerve

Sympathetic trunkganglion

Spinal nerve

Rami communicantes

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.


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 via several branches

• Ventral rami of T2–T12 as intercostal nerves supply muscles of the ribs, anterolateral thorax, and abdominal wall

Copyright © 2010 Pearson Education, Inc. Figure 13.7 (b)

Dorsal ramus

Ventral ramus

Intercostal nerve

Spinal nerve

Rami communicantes

Dorsal rootganglion Dorsal rootVentral root

Sympathetic trunkganglion

Sternum

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

Branches of intercostalnerve

• Lateral cutaneous• Anterior 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)


Hypoglossalnerve (XII)

C1

C2

C3

C4

C5

Segmentalbranches

Lesser occipitalnerveGreater auricularnerve

Ansa cervicalis

Phrenic nerve

Supraclavicularnerves

Accessory nerve (XI)

Transversecervical nerve

Ventralrami:

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:

• Roots—five ventral rami (C5–T1)

• Trunks—upper, middle, and lower

• Divisions—anterior and posterior

• Cords—lateral, medial, and posterior


Upper

Middle Trunks

Lower

Roots (ventral rami):

Upper subscapular

Lower subscapular

Thoracodorsal

Medial cutaneousnerves of the armand forearm

Long thoracic

Medial pectoral

Lateral pectoral

Nerve tosubclaviusSuprascapular

Dorsal scapular

Posteriordivisions

Anteriordivisions

Lateral

PosteriorCords

Medial

Axillary

Musculo-cutaneousRadial

Median

Ulnar

Posteriordivisions

Trunks Roots

C4

C5

C6

C7

C8

T1

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

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

Anteriordivisions

(d) Flowchart summarizing relationships within the brachial plexus

Major terminalbranches(peripheral nerves)

Cords Divisions TrunksRoots(ventralrami)

Musculocutaneous

Median

Ulnar

Radial

Axillary

Anterior

Posterior

Anterior

Posterior

Posterior

Anterior

Upper

Middle

Lower

Lateral

Medial

Posterior

Posteriordivisions

Trunks Roots

C5

C6

C7

C8

T1


Brachial Plexus: Nerves

• Axillary—innervates the deltoid, teres minor, and skin and joint capsule of the shoulder

• Musculocutaneous—innervates the biceps brachii and brachialis and skin of lateral forearm

• Median—innervates the skin, most flexors and pronators in the forearm, and some intrinsic muscles of the hand

• Ulnar—supplies the flexor carpi ulnaris, part of the flexor digitorum profundus, most intrinsic muscles of the hand, and skin of medial aspect of hand

• Radial—innervates 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 (superficial branch)

Superficial branch of ulnar nerveDorsal branch of ulnar nerve

Digital branch of ulnar nerveMuscular branchDigital branch

(c) The major nerves of the upper limb

Axillarynerve

Anteriordivisions

Posteriordivisions

Trunks Roots


Lumbar Plexus

• Arises from L1–L4

• Innervates the thigh, abdominal wall, and psoas muscle

• Femoral nerve—innervates quadriceps and skin of anterior thigh and medial surface of leg

• Obturator nerve—passes through obturator foramen to innervate adductor muscles


(a) Ventral rami and major branches of the lumbar plexus

Iliohypogastric

L1

L2

L3

L4

L5

Ilioinguinal

Genitofemoral

Lateral femoralcutaneous

Obturator

Femoral

Lumbosacraltrunk

Lateral femoralcutaneous

Anterior femoralcutaneousSaphenous

Obturator

IliohypogastricIlioinguinalFemoral

Ventral rami Ventralrami:

(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


SuperiorglutealLumbosacraltrunkInferiorgluteal

CommonfibularTibialPosteriorfemoralcutaneousPudendal

Sciatic

Ventral rami and major branches of the sacral plexus

L4

L5

S1

S2

S3

S4

S5

Co1

Ventral rami Ventral rami:

Copyright © 2010 Pearson Education, Inc. Figure 13.11 (b)

Superior gluteal

Inferior gluteal

Common fibular

Deep fibular

Superficial fibular

Plantar branches

Tibial

Sural (cut)

Posterior femoralcutaneous

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 in dermatomes

• Most dermatomes overlap, so destruction of a single spinal nerve will not cause complete numbness


C2C3

C4

C5T1

T2

T2T3T4T5

C6

C8C7 C7

C6

T6T7T8T9

T10

T11

T12L1

S2S3

L1

L2

L3

L4

L5

L2

L3

L4

L5

S1

C5

C6

C8

T2

C5

C6

S1

Anterior view

C2

C3

C4C5C6C7C8

C8 C8

C7 C7

T1T2T3T4T5T6T7T8T9

T10

T11T12

L1L2 L3

S1(b) Posterior view

L5S2

S1

S1

S3

S2 S1S2

S4S5

L5L5

L4L5L5

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

powerpoint ® lecture slides prepared by janice meeking, mount royal college c h a p t e r copyright...

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