Chapter 13: The Peripheral Nervous System and Reflex Activity

Flashcards reviewing the peripheral nervous system and reflex activity, focusing on the innervation of specific body regions, nerve plexuses, and major nerves.

Dorsal rami

Supply the posterior body trunk.

Ventral rami

Supply the rest of the trunk and the limbs.

Roots

Lie medial to and form the spinal nerves; strictly sensory or motor.

Rami

Lie distal to and are lateral branches of the spinal nerves; carry both sensory and motor fibers.

Nerve plexuses

Interlacing nerve networks formed by ventral rami lateral to the vertebral column, occurring in the cervical, brachial, lumbar, and sacral regions.

Cervical Plexus

Formed from the ventral rami of the first four cervical nerves (C1-C4, with minor contribution from C5); supplies the skin of the neck, ear area, back of the head, and shoulder.

Phrenic Nerve

Receives fibers from C3, C4, and C5; supplies motor and sensory fibers to the diaphragm.

Brachial Plexus

Situated partly in the neck and partly in the axilla; gives rise to virtually all the nerves that innervate the upper limb; formed by ventral rami of C5-T1.

Roots

Ventral rami of the brachial plexus.

Trunks

Formed by the union of roots at the lateral border of the sternocleidomastoid muscle.

Divisions

Result from the division of trunks.

Cords

Large fiber bundles arising from the anterior and posterior divisions in the axilla; named for their relationship to the axillary artery.

Axillary Nerve

Branches off the posterior cord; innervates the deltoid and teres minor muscles and the skin and joint capsule of the shoulder.

Musculocutaneous Nerve

Major end branch of the lateral cord; supplies motor fibers to the biceps brachii, brachialis, and coracobrachialis muscles; provides cutaneous sensation in the lateral forearm.

Median Nerve

Descends through the arm to the anterior forearm, innervating the skin and most flexor muscles; activates muscles that pronate the forearm, flex the hand and fingers, and oppose the thumb.

Ulnar Nerve

Branches off the medial cord of the plexus; supplies the flexor carpi ulnaris and the medial part of the flexor digitorum profundus; innervates most intrinsic hand muscles and the skin of the medial aspect of the hand.

Radial Nerve

Largest branch of the brachial plexus; supplies the posterior skin of the limb and motor branches to essentially all extensor muscles of the upper limb.

Lumbar Plexus

Arises from spinal nerves L1-L4; innervates parts of the abdominal wall muscles and the psoas muscle; major branches descend to innervate the anterior and medial thigh.

Femoral Nerve

Largest terminal nerve of the lumbar plexus; innervates anterior thigh muscles (quadriceps) and the skin of the anterior thigh and the medial surface of the leg.

Obturator Nerve

Enters the medial thigh via the obturator foramen; innervates the adductor muscles.

Lumbosacral Plexus

Arises from spinal nerves L4-S4; serves mainly the lower limb but also sends some branches to the abdomen, pelvis, and buttock.

Sacral Plexus

Arises from spinal nerves L4-S4; supplies the entire lower limb, except the anteromedial thigh.

Sciatic Nerve

Largest branch of the sacral plexus; composed of the tibial and common fibular nerves in a common sheath.

Tibial Nerve

Continues through the popliteal fossa; supplies the posterior compartment muscles of the leg and the skin of the posterior calf and sole of the foot.

Common Fibular Nerve

Descends from its point of origin, wraps around the neck of the fibula, and then divides into superficial and deep branches; innervates the knee joint, skin of the anterior and lateral leg and dorsum of the foot, and muscles of the anterolateral leg.

Superior and inferior gluteal nerves

Innervate the buttock (gluteal) and tensor fascia lata muscles.

Pudendal Nerve

Innervates the muscles and skin of the perineum; helps stimulate erection and control urination.

Ventral rami of T1-T12

Course anteriorly, deep to each rib, as the intercostal nerves; supply the intercostal muscles, the muscle and skin of the anterolateral thorax, and most of the abdominal wall.