12-3: Spinal Cord - innervation, injuries Flashcards
Individual axons are covered in ___, a type of loose ___.
endoneurium, loose connective tissue
Groups of axons are arranged in bundles called ___, wrapped in a layer of connective tissue called ___.
fascicles; epineurium
How many pairs of spinal nerves are there?
31 pairs; named according to the region of the cord from which they emerge
cervical nerves
8 - C1 - C8 (one is above the atlas)
thoracic nerves
12 - T1 - T12
lumbar nerves
5 - L1 - L5
sacral nerves
5 - S1 - S5
C0
coccygeal nerve (just one)
Spinal nerves attach to the cord at the __ and ___, which pass ___ from the cord and unite just distal to the ___ to form a spinal nerve. The spinal nerve emerges from the vertebral column via a _____.
dorsal and ventral roots; laterally; dorsal root ganglia; intervertebral foramen
Why is a spinal nerve short?
almost immediately after emerging from its foramen, it divides into a small dorsal ramus and a larger ventral ramus
nerve plexuses
formed by ventral rami branching and joining one another laterally to the vertebral column; occur in the cervical, brachial, lumbar and sacral regions and primarily serve the limbs
cervical plexus
found deep in the neck under the sternocleidomastoid muscle, and formed by the ventral rami of C1 - C4
What is the most important nerve in the cervical plexus?
phrenic nerve, which innervates the diaphram; irritation causes hiccups
brachial prexus
Can be palpated just superior to the clavicle at the lateral border of the sternocleidomastoid muscle; formed by ventral rami of C4 - T1. Injuries common; when severe, can cause weakness or paralysis of the entire upper limb
median nerve
part of brachial plexus; descends through the arm to the hand and innervates muscles that flex the wrist, pronate the forearm and oppose the thumb
ulnar nerve
part of brachial plexus; innervates muscles producing wrist and finger flexion and adduction and abduction of the fingers. Striking the “funny bone” (ulnar nerve resting against the medial epicondyle) causes tingling of the little finger
radial nerve
largest branch of brachial plexus; produces supination, elbow extension and wrist and finger extension. Damage causes wrist drop
sacral plexus
L4 - S4
What is the largest branch of the sacral plexus?
sciatic nerve, which supplies most of the lower limb; injury to this nerve may result in sciatica (stabbing pain) and/or footdrop
All spinal nerves excepting C1 supply branches to the ___.
skin
dermatome
region of skin supplied by the dorsal root of a spianl nerve; if stimulated and not felt, the spinal nerves supplying that region are malfunctioning (used diagnostically)
What are the major plexuses, and the major nerves within them?
cervical (C1 - C4)
>phrenic nerve (innervates diaphragm)
brachial (C4 - T1)
>median nerve (wrist flexion, forearm pronation and oppose the thumb)
>ulnar nerve (wrist and finger flexion, adduction and abduction of the fingers)
>radial nerve (largest - supination, elbow extenion, and wrist and finger extension)
sacral (L4 - S4)
>sciatic nerve (supplies most of lower limb)
What can cause injury to the spinal cord?
compression from a tumor, blood clot, fracture or dislocated vertebra, trauma, demyelinating disorder
What may occur form a spinal cord injury?
depending on location and extent:
parastesis (loss of sensation) or paralysis (loss of motor function)
transection
spinal cord is cut in half, severing all ascending (sensory) and descending (motor) tracts. Results in loss of sensation and voluntary movement below the level of the cut
A cervical cord transection will result in ___.
quadraplegia - paralysis of both arms and legs
A thoracic or lumbar cord transection will result in ___.
paraplegia - paralysis of legs only
Paralysis of 1 side of the body is known as ___.
hemiplegia, usually due to a brain injury
