BIO 201: Chapter 4.3 Peripheral Nervous System

31, fusion

each of the ___ pairs of spinal nerves form 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

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

meningeal branches

reenter the vertebral canal to innervate spinal structures

anterior ramus

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 nerves that innervate the intercostal muscles, abdominal nerves, and the skin of the chest and abdomen

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 nerve

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 and mastoid area, 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

• serves the anterior arm muscles and skin

axillary nerve

short branch of the posterior cord

• serves structures near the axilla and skin around this region

radial nerve

distal continuation of the posterior cord and is located in the posterior upper limb

• 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 muscles of the forearm that flex 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

• supplies certain muscles in the forearm that flex 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

iliohypogastric and ilioinguinal nerves

both supply motor innervation to the transverse abdominis and internal oblique muscles and sensory to the pelvic area

• iliohypogastric nerve is superior to ilioinguinal nerve

genitofemoral nerve

curves around medially to supply the cremaster muscle in males and the skin around the anteromedial thigh and genitals in both sexes

• only nerve that pierces the psoas major muscle

obturator nerve

located in the medial thigh to supply the medial thigh muscles and skin

lateral femoral cutaneous nerve

provides sensory innervation to the skin of the anterolateral thigh

femoral nerve

largest nerve of the lumbar plexus, provides motor innervation to anterior thigh muscles and sensory innervation to skin of anterior and medial thigh

saphenous nerve

once the femoral nerve passes the medial side of the knee, it becomes the _____ which supplies the knee joint, medial leg, and foot

sacral plexus

forms from the anterior rami of L4-S4 spinal nerves

superior gluteal nerve

supplies the gluteus medius, gluteus minimus, and tensor fascia lata muscles

• located superficial to the gluteus minimus muscle and deep to the gluteus medius muscle

inferior gluteal nerve

supplies the gluteus maximus muscle

• located by the piriformis muscle

pudendal nerve

innervates the muscle of the pelvic floor, anogenital sphincters, and provides sensory innervation to the genitalia

• located traveling medially towards the anus and genitals

posterior femoral cutaneous nerve

located in the posterior thigh to provide sensory innervation to the skin

sciatic nerve

largest nerve of the sacral plexus and in the body

• travels in the posterior thigh where it splits into two branches: tibial and common fibular nerves

tibial nerve

provides motor innervation to posterior muscles of thigh, posterior leg, and foot

common fibular nerve

divided into superficial and deep fibular nerves

superficial fibular nerve

provides motor innervation to the lateral leg

deep fibular nerve

supplies the anterior muscles of the leg that dorsiflex the foot and intrinsic foot muscles

sural nerve

small superficial sensory branch that supplies the skin of the posterior leg and foot

• formed by both the tibial and common fibular nerves