Spinal Cord & Peripheral Nerves

Question 1

Describe the protective coverings of the spinal cord

Answer 1

meninges
dura mater (thick outer layer)
arachnoid mater (delicate fibrous layer)
pia mater (thin transparent layer, has denticulate ligaments & filum terminale)

Question 2

Describe location & contents of spinal cord spaces

Answer 2

epidural: between vertebra & dura mater, contains fat & internal vertebral venous plexus
subdural: potential space between dura & arachnoid mater
subarachnoid: space between arachnoid & pia mater, contains CSF & spinal vessels

Question 3

Describe organization & contents of white & gray matter in the spinal cord

Answer 3

white matter: outside edge, myelinated axons
gray matter: inside with horns, unmyelinated cell bodies

Question 4

Describe organization & function of gray matter in the spinal cord

Answer 4

anterior (ventral) horns: lower motor neuron cell bodies
posterior (dorsal) horns: sensory synapses with cell bodies in dorsal root ganglion

Question 5

Describe the organization of spinal nerves beginning with roots

Answer 5

ventral (anterior) roots: motor axons
dorsal (posterior) roots: sensory axons (has ganglion)
spinal nerve: combination of dorsal & ventral roots
dorsal & ventral rami: contain motor & sensory axons

Question 6

Distinguish vertebral and spinal levels

Answer 6

vertebral: related to vertebrae, C1-C7 emerge above associated vertebrae, C8 between C7-T1, T1-S5 emerge below associated vertebrae

spinal: spinal segment associated with cells of emerging nerve

Question 7

Where is the vertebral level of the C2 spinal level?

Answer 7

C1

Question 8

Where is the vertebral level of the L5 spinal level?

Answer 8

L1

Question 9

Where is the vertebral level of the S5 spinal level?

Answer 9

L2

Question 10

What spinal levels do a L4/L5 disc herniation affect? C4/C5?

Answer 10

L5
C5

Question 11

Describe & identify the regional characteristics of the spinal cord

Answer 11

cervical enlargement: cervical & brachial plexus
lumbar enlargement: lumbar & sacral plexus
conus medularis: around L1/L2 vertebral level

Question 12

Describe the blood supply to the spinal cord

Answer 12

single anterior spinal artery
paired posterior spinal arteries
- arise from vertebral, intercostal, lumbar, or sacral arteries
similarly named veins

Question 13

Explain & differentiate the types of reflexes

Answer 13

Deep tendon: sudden stretch; sensed by golgi tendon organ-> spinal cord & brain-> activate stretched muscle & inhibit antagonists
Flexor: withdrawal to painful stimulus; noxious signal-> spinal cord-> ipsilateral hip & knee flexor activation, extensor inhibition
(crossed) Extension: (same as flexor) spinal cord interneurons cross midline-> contralateral hip & knee extensor activation, flexor inhibition (weight bearing)

Question 14

Describe & give examples of the organization of peripheral innervation

Answer 14

peripheral nerve plexus: cervical, brachial, lumbar, sacral (brachial roots from C5-T1 ventral rami)
dermatomes: areas of skin associated with spinal level, C6 dermatome from C5-C8, medial cutaneous from C8-T2
myotomes: muscles innervated by a single spinal level

Question 15

Where do the C5, C6, C7, and C8 dermatomes represent?

Answer 15

C5 - middle arm
C6 - thumb
C7 - middle finger
C8 - pinky

Question 16

What do the C5-T1 myotomes represent?

Answer 16

C5 – Shoulder abduction
C6 – Elbow flexion
C7 – Elbow extension
C8 – Finger flexion
T1 – Finger abduction

Question 17

What do the L2-S1 myotomes represent?

Answer 17

L2 - Hip flexion
L3 – Knee extension
L4 – Ankle dorsiflexion
L5 – Hallux extension
S1 – Ankle plantarflexion

Question 18

What is the difference between epidural versus spinal anesthesia?

Answer 18

epidural - slower acting as medicine is spread through fatty tissues
spinal - fast acting within subarachnoid space