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Spinal Nerves

-come directly off spinal cord
-peripheral nervous system
-31 pairs of spinal nerves
-on each side 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal


Spinal Nerves Composition

-anterior (ventral root): axons from motor neurons
-posterior (dorsal) root: axons from sensory neurons
-when they unite make the spinal nerve


2 Main Branches of Spinal Nerves

-posterior (dorsal) ramus
-anterior (ventral) ramus


Posterior (Dorsal) Ramus

-innervates skin of back, deep back muscles
-motor and sensory


Anterior (Ventral) Ramus

-innervates everything else from neck inferiorly
-also forms nerve plexuses
-motor and sensory


Nerve Plexus

-network of converging and/or diverging axons
-formed from anterior rami of spinal nerves
-named nerves come off of plexus
-allows for multiple nerves to innervate multiple structures
-most thoracic spinal nerves do not form plexuses (remain as individual spinal nerves)


Cervical Plexus

-anterior rami of C1-C4
-innervates sensory-SKIN of neck, ear, and shoulders. motor-anterior neck muscles


Phrenic nerve

-receives SOME axons from cervical plexus
-supplies diaphragm (3, 4, and 5 keep the diaphragm alive)


Brachial Plexus

-anterior rami of C5-T1
-primarily innervates upper limb
-each nerve has both motor and sensory components


Axillary Nerve

-part of brachial plexus
-innervates deltoid and teres minor
-can be injured with use of a crutch
-test for nerve damage: have patient abduct arm


Musculocutaneous Nerve

-part of brachial plexus
-innervates most muscles on anterior surface of ARM (coracobrachialis, biceps brachii, brachialis)
-elbow/forearm flexion is impaired when this nerve is damaged
-test for nerve damage: have patient flex elbow


Radial Nerve

-part of brachial plexus
-innervates posterior ARM muscles (triceps brachii-extend elbow/forearm) and posterior FOREARM muscles (extend wrist/fingers)
-nerve may be damaged if humerus is broken or with use of a crutch
-test for nerve damage: extend wrist, elbow, and fingers
-symptom of radial nerve damage is wrist drop


Median Nerve

-part of brachial plexus
-innervates almost all anterior FOREARM muscles (flex wrist/fingers) THENAR muscles (move thumb) and lumbricals going to fingers 2 and 3.
-may be damaged if someone tries to slit their wrists or by carpal tunnel syndrome
-test for nerve damage: flex wrist, move thumb


Ulnar Nerve

-part of brachial plexus
-innervates 1.5 anterior FOREARM muscles (medial 1/2 of flexor digitorum profundus and flexor carpi ulnaris) and most intrinsic hand muscles (hypothenar, lumbricals to 4 and 5, palmar and dorsal interossei)
-test for nerve damage: abduct and adduct fingers


Lumbar Plexus

-anterior rami of L1-L4
-innervates inferior abdominal wall, part of lower limb
-each nerve has motor and sensory components


Femoral Nerve

-part of lumbar plexus
-innervates anterior thigh muscle (illiacus, quadriceps, psoas-extend knee, flex hip)
-test for nerve damage: test knee reflex, have patient extend knee


Obturator Nerve

-part of lumbar plexus
-innervates medial thigh muscles (adductors, gracilis, pectinius-adduct and flex thigh)
-test for nerve damage: can patient adduct thigh when resistance is present?


Sacral Plexus

-anterior rami of L4-S4
-innervats the buttocks, pelvic structures, and majority of lower limb
-each nerve has motor and sensory components


Sciatic Nerve

-major nerve of sacral plexus
-splits into tibial nerve and common fibular nerve


Tibial nerve

-branch of sicatic nerve
-innervates mos posterior thigh muscles (hamstrings-flex knee, extend thigh) posterior leg muscles (plantar flex, flex toes) and muscles on sole of foot
--test for nerve damage:difficulty extending hip against resistance? flex knee with resistance? flexing (curling) toes?


Common Fibular Nerve

-branch of sciatic nerve
-innervates anterior leg muscles (dorsiflex, extend toes), lateral leg muscles (evert foot), muscles on dorsum of foot (extend toes)
-injury: may fall asleep when you cross your legs, may be injured by leg cast/tight ski boots
-test for nerve damage: dorsiflex, evert foot, extend toes, have foot drop?