2.1 neuro - spinal nerves

Question 1

Describe the organization of the cervical spinal nerves and the rest of the spinal nerves

Answer 1

C1 emerges between the first vertebrae and the base of the skull, C8 emerges between C7 and T1, 1 more nerve than vertebrae
Other spinal nerves observe from below the intervertebral foramen below the vertebrae of the same number

Question 2

What is the functional unit of the spinal cord called

Answer 2

Spinal segment

Question 3

What does a spinal segment consist of

Answer 3

All the gray and white matter that send and receive information from one set (right and left) of spinal nerves

Question 4

The dorsal roots of spinal nerves send or receive information

Answer 4

Receive sensory / afferent information

Question 5

The ventral roots of spinal nerves send or receive information

Answer 5

Send motor / efferent information

Question 6

What is a dermatome

Answer 6

The area of the body’s surface innervated (sensory) by one pair of spinal nerves; they overlap

Question 7

What is a receptive field

Answer 7

Area of skin innervated by one dorsal root ganglia neuron; subset of a dermatome

Question 8

What is a motor unit

Answer 8

Total number of skeletal muscle fibers innervated by one Alpha Motor Neuron

Question 9

Describe how the number of fibers innervated by a motor unit affects fine vs. gross control

Answer 9

More motor neurons innervating one muscle = finer control. One motor neuron innervating many fibers = gross control

Question 10

Describe the organization of general sensory / motor afferent / efferent information in gray matter

Answer 10

Proximal dorsal horn = general sensory afferent
Distal dorsal horn = general visceral afferent
Proximal ventral horn = general sensory efferent
Distal ventral horn = general visceral efferent

Question 11

How many total pairs of spinal nerves do we have, and how many are in each spinal region

Answer 11

31 pairs
* 8 cervical
* 12 thoracic
* 5 lumbar
* 5 sacral
* 1 coccygeal

Question 12

What level of the vertebral column is the cervical plexus on?

Answer 12

C1-5

Question 13

What level of the vertebral column is the brachial plexus on?

Answer 13

C5-T1

Question 14

What level of the vertebral column is the lumbar plexus on?

Answer 14

L1-5

Question 15

What level of the vertebral column is the sacral plexus on?

Answer 15

L4-S5

Question 16

What are the terminal branches of the cervical plexus, and what regions do they innervate?

Answer 16

Motor:
- phrenic n., diaphragm
Sensory:
- lesser occipical n., skin behind ear
- great auricular n., skin in front of ear
- transverse cervical n., skin of anterior neck
- supraclavicular n., skin above clavicles

Question 17

What are the terminal branches of the brachial plexus, and what regions do they innervate?

Answer 17

• axillary n., deltoid
• musculocutaneous n., elbow flexors
• median n., wrist / finger flexors
• radial n., elbow / wrist / finger extensors
• ulnar n., wrist / finger flexors

Question 18

What are the terminal branches of the lumbar plexus, and what regions do they innervate?

Answer 18

• illiohypogastric n., skin / muscle of anterior body wall
• illioinguinal n., skin / muscle of anterior body wall
• genitofemoral n., skin of scrotum / labia majora, cremaster muscle
• lateral cutaneous n., skin of lateral thigh
• femoral n., skin of anterior thigh / knee extensors
• obturator n., skin of medial thigh / adductors

Question 19

What are the terminal branches of the sacral plexus, and what regions do they innervate?

Answer 19

• superior gluteal n., gluteus medius / minimus
• interior gluteal n., gluteus maximus
• pudendal n., perineum
• sciatic n., muscles of posterior thigh
• tibial n. (split from sciatic at knee), posterior leg / calf
• common fibular n. (split from sciatic at knee), anterior and lateral leg

Question 20

What types of tissues / cells do you find in peripheral nerves

Answer 20

Blood vessels, connective tissue, fibroblasts, schwann cells, macrophages

Question 21

What sheath surrounds every nerve

Answer 21

Epineurium

Question 22

What sheath surrounds bundles of axons within a nerve

Answer 22

Perineurium

Question 23

What sheath surrounds each nerve fiber

Answer 23

Endoneurium

Question 24

What is a node of ranvier

Answer 24

Portion of axons not wrapped in schwann cells, where the electrophysiology happens; space between schwann cells

Question 25

What is an axon internode

Answer 25

Portion on axon surrounded by schwann cells