BIO 201: Chapter 4.3 Peripheral Nervous System

31, fusion

each of the ___ pairs of spinal nerves forms from the ____ of the anterior and posterior roots of the spinal cord

8

how many pairs of cervical spinal nerves?

12

how many pairs of thoracic spinal nerves?

5

how many pairs of lumbar spinal nerves?

5

how many pairs of sacral spinal nerves?

1

how many pairs of coccygeal spinal nerves?

motor, away

anterior roots carry ___ axons ___ from the spinal cord

sensory, to

posterior roots carry ___ axons ___ the spinal cord

posterior ramus, anterior ramus, and meningeal branch

after the anterior and posterior roots fuse to form the spinal nerve, it splits into three branches called …

posterior rami

serve the skin, joints, and musculature of the posterior trunk

meningeal branches

reenter the vertebral canal to innervate spinal structures

anterior rami

travel anteriorly to supply the muscles of the upper and lower limbs, anterior thorax and abdomen, and part of the back

intercostal nerves

anterior rami of the thoracic spinal nerves that travel between the ribs as 11 separate pairs of intercostal nerves that innervate the intercostal muscles, abdominal nerves, and the skin of the chest and abdomen

4 large plexuses

the anterior rami of the cervical, lumbar, and sacral nerves combine to form ____ or networks of nerves

cervical plexus

consists of the anterior rami of C1-C4 spinal nerves with small contributions from C5 to serve the skin of the head and neck and some neck muscles

lesser occipital nerve

C2-C3, associated with cutaneous and sensory innervation of the external ear and nape (back of the neck), heads to the direction of the occipital bone

ansa cervicalis

C1-C3, loop of nerves that innervate some neck muscles like the omohyoid, sternohyoid, and sternothyroid muscles

supraclavicular nerve

C3-C4, associated with the cutaneous and sensory innervation of the lower anterior and lateral neck, shoulder, and anterior chest, goes to the direction of the clavicle

transverse cervical nerve

C3, associated with the cutaneous and sensory innervation of the anterior and lateral neck and under the chin, travels laterally in a horizontal line

great auricular nerve

C3, associated with the cutaneous and sensory innervation of the external ear, mastoid area, and parotid salivary gland, travels toward the ear’s direction

phrenic nerve

C3-C5, travels superficially to the scalene muscles and internal jugular vein, goes inferiorly to the direction of the diaphragm

brachial plexus

consists of the anterior rami of C5-T1 spinal nerves

• spinal nerve → 3 large trunks → 2 divisions → 3 cords → 5 nerve branches

superior trunk of brachial plexus

formed by the C5 and C6 spinal nerves

• splits into anterior and posterior divisions

middle trunk of the brachial plexus

formed by the C7 spinal nerve

• splits into anterior and posterior divisions

inferior trunk of the brachial plexus

formed by the C8 and T1 spinal nerves

• splits into anterior and posterior divisions

medial cord

formed by contribution of the anterior division of the inferior trunk and descends in the medial arm

lateral cord

formed by the anterior divisions of the superior and middle trunks and descends in the lateral arm

posterior cord

formed by the contribution of all posterior divisions of all 3 trunks and is located in the posterior arm

musculocutaneous nerve

distal continuation of the lateral cord, located in the lateral arm, and serves the anterior arm muscles and skin

• located deep to biceps brachii muscle but superficial to the brachialis muscle

axillary nerve

short branch of the posterior cord and serves structures near the axilla and skin around this region

• travels by the subscapularis muscle and pierces posteriorly between the teres minor and major muscles

radial nerve

distal continuation of the posterior cord, located in the posterior upper limb, and serves the muscles that extend the forearm and skin in the lateral hand

• travels on the radial groove on the posterior side of the humerus

median nerve

formed by the fusion of both the medial and lateral cords, travels down the middle arm and forearm, supplies most of the muscle of the forearm that flex, intrinsic hand muscle, and skin over the anterior and lateral hand

• travels under the flexor retinaculum as it enters the wrist

carpal tunnel syndrome

results from the median nerve becoming trapped and inflamed under the flexor retinaculum

ulnar nerve

distal continuation of the medial cord, beings posteriorly but then crosses over to anterior side of forearm, supplies certain muscles in the forearm that flex, most intrinsic hand muscle, and skin over the medial hand

• “funny bone nerve”

lumbar plexus

consists of the anterior rami of L1-L4 with a small contribution from T12 spinal nerves

• found by the iliopsoas muscle group and quadratus lumborum muscle