12-3: Spinal Cord - innervation, injuries

Question 1

Individual axons are covered in ___, a type of loose ___.

Answer 1

endoneurium, loose connective tissue

Question 2

Groups of axons are arranged in bundles called ___, wrapped in a layer of connective tissue called ___.

Answer 2

fascicles; epineurium

Question 3

How many pairs of spinal nerves are there?

Answer 3

31 pairs; named according to the region of the cord from which they emerge

Question 4

cervical nerves

Answer 4

8 - C1 - C8 (one is above the atlas)

Question 5

thoracic nerves

Answer 5

12 - T1 - T12

Question 6

lumbar nerves

Answer 6

5 - L1 - L5

Question 7

sacral nerves

Answer 7

5 - S1 - S5

Question 8

C0

Answer 8

coccygeal nerve (just one)

Question 9

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 _____.

Answer 9

dorsal and ventral roots; laterally; dorsal root ganglia; intervertebral foramen

Question 10

Why is a spinal nerve short?

Answer 10

almost immediately after emerging from its foramen, it divides into a small dorsal ramus and a larger ventral ramus

Question 11

nerve plexuses

Answer 11

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

Question 12

cervical plexus

Answer 12

found deep in the neck under the sternocleidomastoid muscle, and formed by the ventral rami of C1 - C4

Question 13

What is the most important nerve in the cervical plexus?

Answer 13

phrenic nerve, which innervates the diaphram; irritation causes hiccups

Question 14

brachial prexus

Answer 14

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

Question 15

median nerve

Answer 15

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

Question 16

ulnar nerve

Answer 16

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

Question 17

radial nerve

Answer 17

largest branch of brachial plexus; produces supination, elbow extension and wrist and finger extension. Damage causes wrist drop

Question 18

sacral plexus

Answer 18

L4 - S4

Question 19

What is the largest branch of the sacral plexus?

Answer 19

sciatic nerve, which supplies most of the lower limb; injury to this nerve may result in sciatica (stabbing pain) and/or footdrop

Question 20

All spinal nerves excepting C1 supply branches to the ___.

Answer 20

skin

Question 21

dermatome

Answer 21

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)

Question 22

What are the major plexuses, and the major nerves within them?

Answer 22

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)

Question 23

What can cause injury to the spinal cord?

Answer 23

compression from a tumor, blood clot, fracture or dislocated vertebra, trauma, demyelinating disorder

Question 24

What may occur form a spinal cord injury?

Answer 24

depending on location and extent:

parastesis (loss of sensation) or paralysis (loss of motor function)

Question 25

transection

Answer 25

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

Question 26

A cervical cord transection will result in ___.

Answer 26

quadraplegia - paralysis of both arms and legs

Question 27

A thoracic or lumbar cord transection will result in ___.

Answer 27

paraplegia - paralysis of legs only

Question 28

Paralysis of 1 side of the body is known as ___.

Answer 28

hemiplegia, usually due to a brain injury