Peripheral Nervous System Flashcards
What are the roots of the cervical plexus?
C1-C5
What nerve roots innervate the brachial plexus?
C5-T1
What is the mnemonic for remembering the brachial plexus?
Really tired drink coffee black
roots trunks divisions cords branches
What muscles does the musculocutaneous nerve innervate?
the anterior arm muscles (biceps brachii, coracobrachialis, and brachialis)
Which age group tend to have the most brachial plexus injuries?
Newborns because of the upper extremity being awkwardly stretched in the birth canal.
Damage is caused to Suprascapular nerve, musculocutaneous and axillary nerves.
What are the nerve roots of the lumbar plexus?
L1-L4
What is the function of the obturator nerve?
sensation to the medial thigh, and motor control of the hip adductor muscles
What is the function of the femoral nerve?
Innervates the muscles of the anterior thigh and hip. Also, sensation to the anterior thigh, hip and knee joints.
Does compression of a nerve affect touch perception or pain first?
Touch perception
Herpes Zoster
Viral infection of sensory ganglia of spinal and cranial nerves
caused by varicella virus
Which Lumbar plexus nerves are sensory only?
Genitofemoral (scrotum and labia)
Lateral Femoral Cutaneous(lateral part of thigh)
Saphenous (medial leg and foot; part of knee joint)
Which lumbar plexus nerves are motor and sensory?
Iliohypogastric (anterior abdominal wall sensory and motor)
Ilioinguinal (anterior abdominal muscles; groin sensation)
Obturator (L2-L4) (sensation medial thigh; motor to hip adductors)
Femoral
What forms the Sacral Plexus?
L4-L5; S1-S4
Largest branch in sacral plexus?
Sciatic nerve
also largest nerve in body
Sacral plexus divides into what nerves?
tibial nerve (L4-S3)
Common fibular nerve (L4-S2)
Superior Gluteal nerve (L4-S1) innervates
hip muscles: gluteus medius, gluteus minimus, tensor fascia lata
Inferior gluteal nerve (L5-S2) innervate
gluteus maximus
Is posterior cutaneous nerve sensory or motor?
purely sensory to buttocks, posterior thigh and anus
Superficial fibular nerve innervates
lateral compartment muscles (fibularis longus and brevis)
Deep fibular nerve innervates
anterior compartment (dorsiflexors)
Pudendal nerve (inferior branch of sacral plexus) (S2-S4) innervates
perineum and pelvic floor, bladder, sensation to genitals, etc
Epineurium is
outermost covering of peripheral nerves.
continuous with dura mater around spinal cord
Perineurium is
groups individual nerve fibers into bundles
protects nerves from blood
Endoneurium is
innermost connective tissue sheath
Axoplasm
fluid inside axons
Alpha motor neurons
innervate muscles to create muscle tension and produce movement
Fast conducting with a thick myelin sheath
Gamma Motor Neurons
innervate muscle spindles to maintain and alter muscle tension
Does not cause movement. Slow conducting.
Lower motor neurons
neurons that innervate muscles
B fibers
small and myelinated
C fibers
unmyelinated
Diabetic neuropathy sympoms
paresthesias paresis hypotension tachycardia digestive problems bowel and bladder incontinence sexual dysfunction thickening of blood vessels leading to ischemia
Musculocutaneous nerve roots
C5-C7
Musculocutaneous motor function
muscles in the anterior compartment of the arm (coracobrachialis, biceps brachii and the brachialis).
Musculocutaneous sensory function
gives rise to the lateral cutaneous nerve of forearm, which innervates the lateral aspect of the forearm.
Axillary nerve roots
C5 and C6
Axillary sensory function
Gives rise to the upper lateral cutaneous nerve of arm, which innervates the skin over the lower deltoid
Axillary motor function
Innervates the teres minor and deltoid muscles.
Radial nerve roots
C5-T1
Radial sensory function
Innervates most of the skin of the posterior forearm, the lateral aspect of the dorsum of the hand, and the dorsal surface of the lateral three and a half digits.
Radial motor function
Innervates the triceps brachii and the extensor muscles in the forearm.
Median Nerve root
C6-T1
Median motor functions
Innervates the flexor and pronator muscles in theanterior compartment of the forearm(except the flexor carpi ulnaris and part of the flexor digitorum profundus, innervated by theulnar nerve). Also supplies innervation to the thenar muscles and lateral two lumbricals in the hand.
Median sensory function
Gives rise to the palmar cutaneous branch, which innervates the lateral aspect of the palm, and the digital cutaneous branch, which innervates the lateral three and a half fingers on the anterior (palmar) surface of the hand.
Ulnar nerve roots
C8-T1
Ulnar motor function
Two muscles of the anterior forearm – flexor carpi ulnaris and medial half of flexor digitorum profundus
Intrinsic muscles of thehand(apart from the thenar muscles and two lateral lumbricals)
Ulnar sensory function
Medial one and half fingers and the associated palm area.
What is the most severe form of Brachial plexus?
Avulsion
shows flaccid paralysis of upper extremity
Femoral nerve root
L2-L4
Femoral Motor function
Innervates the anterior thigh muscles that flex the hip joint (pectineus, iliacus, sartorius) and extend the knee (quadriceps femoris: rectus femoris, vastus lateralis, vastus medialis and vastus intermedius),
Femoral Sensory function
Supplies cutaneous branches to the anteromedial thigh (anterior cutaneous branches of the femoral nerve) and the medial side of the leg and foot(saphenous nerve).
Sciatic nerve root
L4-S3
Sciatic motor functin
Innervates the muscles of the posterior thigh (biceps femoris, semimembranosus and semitendinosus) and the hamstring portion of the adductor magnus (remaining portion of which is supplied by the obturator nerve).
Indirectly innervates(via its terminal branches) all the muscles of the leg and foot.
Sciatic sensory function
No direct sensory functions. Indirectly innervates (via its terminal branches) the skin of the lateral leg, heel, and both the dorsal and plantar surfaces of the foot.
Injury to musculocutaneous nerve functions
Flexion at the shoulder and elbow are weakened but can still be performed by the pectoralis major and brachioradialis respectively.
Supination of the forearm is weak, but can still be performed by the brachioradialis.
Injury to musculocutaneous nerve sensory
loss of sensation over the lateral side of the forearm.
Injury to axillary nerve functions
the deltoid and teres minor muscles will be affected, rendering the patient unable to abduct the affected limb.
Injury to axillary sensory functions
the upper lateral cutaneous nerve of arm will be affected, resulting in loss of sensation over the inferior deltoid
Erbs palsy
a condition resulting from damage to C5-C6 roots of the brachial plexus. The axillary nerve is affected, and the individual is usually unable to abduct or externally rotate the shoulder joint.
Injury to radial nerve motor functions
the triceps brachii and muscles in posterior compartment are affected. The patient is unable to extend at the forearm, wrist and fingers. Unopposed flexion of wrist occurs, known as wrist-drop.
Injury to radial nerve sensory functions
all four cutaneous branches of the radial nerve are affected. There will be a loss of sensation over the lateral and posterior arm, posterior forearm, and dorsal surface of the lateral three and a half digits.
Injury to median nerve motor functions
Thenar muscles paralysed, as are the lateral two lumbricals. This affects opposition of the thumb and flexion of the index and middle fingers.
Injury to median nerve sensory function
Lack of sensation over the areas that the median nerve innervates.
Injury to Ulnar nerve motor function
Only the intrinsic muscles of the hand are affected.
Abduction and adduction of the fingers cannot occur (due to paralysis of the interossei).
Movement of the 4th and 5th digits is impaired (due to paralysis of the medial two lumbricals and hypothenar muscles).
Adduction of the thumb is impaired, and the patient will have a positive Froment’s sign (due to paralysis of adductor pollicis).
Injury to Ulnar nerve sensory function
All sensory branches are affected, so there will be a loss of sensation over the areas that the ulnar nerve innervates.
