Unit 4 - Spinal Cord

Question 1

What are the 3 functions of the spinal cord?

Answer 1

1. process reflexes
2. integrate EPSP and IPSPs
3. conducts sensory impulses to the brain and motor impulses to the effectors

Question 2

Where does the spinal cord begin and terminate? What is its shape and length?

Answer 2

begins as an extension of the medulla oblongata at level of foramen magnum
terminates at the level of L2 (conus medullaris)

oval, 42-45 cm`

Question 3

What are the two enlargements of the spinal cord? What do they indicate? What is the filum terminale?

Answer 3

cervical enlargement - C4-T1: indicates nerves for upper limb

lumbar enlargement - T9-T12 indicates nerves for lower limbs

filum terminale - extension of the pia matter that extends inferiorly and uses with other meninges to angle the spinal cord to coccyx
- caudia equina: roots of lower spinal nerves angle inferiorly to the filum terminale like whips of hair

Question 4

Compare the dorsal root and ventral root of the spinal cord

Answer 4

dorsal root - sensory axons
- has DORSAL ROOT GANGLIA - swelling on dorsal root that contains the soma of sensory neurons

ventral root - motor neuron axons

Question 5

Describe what each part of the spinal cord contains: posterior gray horns, anterior gray horns, lateral gray horn

Answer 5

posterior gray: cell bodies and axons of interneurons and sensory neurons

anterior gray - contain somatic motor nuclei for skeletal muscle contraction

lateral gray - contain autonomic motor nuclei that regulate cardiac and smooth muscle and glands

Question 6

How many spinal nerves are there? How are they organized?

Answer 6

31 pairs of spinal nerves

8 cervical - 1st pair emerges between occipital bone and atlas

• C1-7 emerge above corresponding vertebrate
• C8 exits btw vertebrate C7 and T1

12 thoracic 
- T1-L5 exit vertebral canal below corresponding vertebrae
5 pairs lumbar 
5 pairs sacral 
1 pair coccygeal

Question 7

What are the names of the CT surrounding spinal nerves?

Answer 7

endoneurium: wraps individual axons
perineurium: wraps bundles of axons called fasciles
epineurium: outermost covering of the entire nerve

Question 8

What are rami? describe the functions of the posterior and anterior ramus, meningeal branch, and the rami communicantes

Answer 8

Rami - branches of spinal nerves

posterior: serves deep muscles of skin of posterior surface of the trunk

anterior - serves muscles and structures of the upper and lower limbs, and the skin of the lateral and anterior surfaces of the trunk

meningeal branch - supplies the vertebrae, vertebral ligaments, and blood vessels of the spinal cord and the meninges

rami communicates - component of autonomic nervous system

Question 9

What is the purpose of the cervical plexus? What is the phrenic nerve?

Answer 9

supplies the skin and muscles of hear, neck, superior portion of the shoulder and chest and diaphragm

phrenic = supplies diaphragm

Question 10

Describe the cdntipons of the 5 important nerves from the brachial plexus

Answer 10

roots (anterior rami) of C5-C8, T1

1. axillary nerve - supplies deltoid and teres minor
2. Musculocutaneous nerve - supplies anterior muscles of the arm
3. Radial nerve - supplies muscles of post aspect of arm and forearm
4. Median nerve - supplies most of the muscles of anterior forearm and some of the muscles of the hand
5. Ulnar nerve - supplies the anteromedial muscles of the forearm and most of the muscles of the hand

Question 11

What are some brachial plexus injuries?

Answer 11

wrist drop - injury to radial and axillary nerve

winged scapula - injury to long thoracic nerve - medial border of scapula procures

Question 12

Describe the functions of the lumbar plexus. Describe the function specifically of the femoral and obturator nerve

Answer 12

roots (anterior rami) of spinal nerves L1-L4 supplies:

• anterolateral abdominal wall
• external genitals
• part of the lower limbs

femoral: largest nerve from lumbar plexus, distributed to flexor muscles of hip joint and extensor muscles of knee joint, skin over anterior and medial aspect of thigh and medial side of leg and foot
obturator: adductor muscles of hip joint, sin over medial aspect of thigh

Question 13

Describe the sacral and coccygeal plexuses

Answer 13

sacral - anterior rami of spinal nerves L4-5
- supplies buttocks, perineum and lower limbs

coccygeal - anterior rami of spinal nerves S4-5
- supplies area of skin in coccygeal region

Question 14

What part of the spinal cord receives and integrates information?

Answer 14

gray matter

Question 15

Describe the spinothalamic and posterior column tract for nerve impulses in the spinal cord

Answer 15

spinothalamic tract: conveys nerve impulses for sensing pain, temp, itching, tickling, deep pressure and crude touch

posterior column: consists of the gracile fasciculus and the cuneate fasciculus
- conveys nerve impulses for discriminative touch, light pressure, vibration and conscious proprioception

Question 16

Describe the following reflexes: spinal, cranial, somatic, autonomic

Answer 16

spinal - integration takes place in the spinal cord gray matter

cranial - integration occurs in the brain stem

somatic - involves contraction of skeletal muscles

autonomic - involved response o]f smooth muscle, cardiac muscle and gland - typically not perceived

Question 17

Describe the stretch reflex. What is reciprocal innervation>

Answer 17

causes contraction of a skeletal muscle in response to stretching of the muscle

• MONOSYNAPTIC, IPSILATERAL - sensory nerve enters spinal cord on same side nerve impulse leaves
• elicited by tapping on tendons
• prevents overstretching of muscles

RECIPROCAL INNERVATION - when the stretch muscle contacts, antagonistic muscles that oppose the contraction relax

• polysynaptic, antagonistic reflex arc occurs at same time
• 3 neurons, 2 synapses
• helps maintain posture

Question 18

What is the tendon reflex?

Answer 18

operates as feedback mechanism to ctrl muscle tension by causing muscle relaxation before muscle force to prevent a torn tendon
- MONOSYNAPTIC, IPSILATERAL

tendon organs - sensory receptors that lie within a tendon near its junction with a muscle

Question 19

Describe the flexor and crossed extensor reflexes

Answer 19

flexor:
intersegmental reflex arc: single sensory neuron activates several motor neurons (effectors)
- moves entire lower or upper limb away from painful stimulus

crossed extensor: maintains balance after pulling leg away from painful stimulus

• AcH released by motor neurons causes extensor muscles in thigh of unstimulated leg to contract
• contralateral reflex arc: sensory stimulus on one side of the spinal cord and motor impulses exit on opposite side
• synchronized with the extension of the contralateral its with the flexion of the stimulated limb

Question 20

Describe the degenerative disorders of the spinal cord: Amyotrophic lateral sclerosis, shingles, and polio

Answer 20

ALS - muscle weakness and atrophy

shingles - herpres voster remains in post rood ganglion

polio - virus can produce paralysis by destroying cell bodies of motor neurons

Question 21

Describe the traumatic injuries of the spinal cord: complete transection, hemi section and spinal shock. What causes spinal cord compression>?

Answer 21

complete transection: loss of all sensation and voluntary movement below the level of transection

hemi section - partial transection of the cord

spinal shock - immediate response to spinal cord injury characterized temporary areflexia, loss of reflex function

spinal cord compression: fractured vertebrae, herniated discs, tumors, osteoporosis and infections