Overview of Nervous system

Question 1

What are afferent axons?

Answer 1

Axons of sensory neurons that conduct signals toward the CNS

Question 2

What are efferent axons?

Answer 2

Axons of neurons that conduct signals away from the CNS

Most are motor axons that cause contractions

Question 3

What are cranial nerves?

Answer 3

Nerves that arise from/project to the brain

There are 12

Question 4

What are spinal nerves?

Answer 4

Nerves that arise from/project to the spinal cord

There are 31

Question 5

How are the spinal nerves divided up?

Answer 5

8 cervical

12 thoracic

5 lumbar

5 sacral

1 coccygeal

Question 6

Which spinal nerves exit above the vertebrae?

Answer 6

C1-C7

All others exit below

Question 7

What are the major functional divisions of the nervous system?

Answer 7

Somatic - voluntary conscious part of movement

Autonomic - involuntary, unconscious

Question 8

What are dorsal and ventral rootlets?

Answer 8

Unite to form Dorsal roots and ventral roots respectively

The roots then unite to form a spinal nerve

Question 9

What are dermatomes?

Answer 9

Area of skin innervated by a single spinal nerve

Question 10

What are the dermatomes for the hand?

Answer 10

C6 - Thumb

C7 - index and middle

C8 - ring and little finger

Question 11

What are the important dermatomes for the lower extremity?

Answer 11

L1 - region of Inguinal ligament (anterior to hip

L4 - Big Toe

S1 - Little Toe

Question 12

What are dorsal and ventral rami?

Answer 12

Divisions of the spinal nerves directly after they leave the intervertebral foramen

Both carry sensory AND motor neurons

Dorsal to back, smaller

Ventral to front

Question 13

What is the Conus medullaris and where is it located in an adult? Newborn?

Answer 13

Inferior (caudal) end of the spinal cord

Adult - L1

Newborn - L3

Question 14

What is the Cauda equina?

Answer 14

Lower dorsal and ventral rootlets that extend inferior to the conus medullaris so they can pass through the correct intervertebral foramina

Question 15

How does epidural anesthesia work?

Answer 15

Blocks conduction in spinal nerves by anesthetic injection into epidural space; effect is by diffusion

Question 16

Where do you insert the needle to sample CSF?

Answer 16

Between vertebra into the subarachnoid space

Needle must be inferior to the conus medullaris

Question 17

What layers does the needle pass through during a lumbar puncture?

Answer 17

Skin –> Superficial Fascia –> Supraspinous ligament –> Interspinous ligament –> Ligamentum flavum (first pop) –> Epidural space –> Dura mater (second pop) –> arachnoid