Neuro: Organization of Spinal Cord

Question 1

how many articulating vertebrae compose the vertebral column?

Answer 1

24 (7 cervical, 12 thoracic, 5 lumbar)

Question 2

structures of the spinal cord that provide stability, connecting the pia mater to the arachnoid and dura maters

Answer 2

denticulate ligaments

Question 3

a delicate strand of fibrous tissue proceeding downward from the apex of the conus medullaris that gives longitudinal support to the spinal cord

Answer 3

filum terminale

Question 4

preganglionic sympathetic neurons are present at what spinal levels?

Answer 4

IML of T1 - L2

Question 5

where are preganglionic parasympathetic cell bodies located?

Answer 5

brainstem (CN III, VII, IX and X) or sacral levels S2-S4 (pelvic splanchnics)

Question 6

Ventral root (motor) fibers of each spinal nerve innervate a group of skeletal muscles called a ________.

Answer 6

myotome

Question 7

Why is it that multiple spinal segments innervate individual muscles?

Answer 7

because lower motor neurons are in columns that span

several segments

Question 8

The skin area innervated by the dorsal root (sensory) fibers of each spinal nerve is referred to as a ________.

Answer 8

dermatome

Question 9

the knee-jerk reflex test is testing which spinal cord segment(s)?

Answer 9

L3/L4

Question 10

the ankle-jerk reflex test is testing which spinal cord segment(s)?

Answer 10

S1/S2

Question 11

In a transverse section through the spinal cord, the amount of gray matter is greatest in what segments?

Answer 11

those that are innervating the upper and lower limbs

Question 12

in regards to landmarks of spinal cord sections, cervical segments contain the most ____ ____ and sacral and
coccygeal segments the least

Answer 12

white matter

Question 13

at what spinal levels is the lateral horn present?

Answer 13

T1 - L2

Question 14

why is the lateral part of the ventral horn absent at thoracic levels?

Answer 14

the lateral ventral horn houses motor cell bodies to control limbs, which are absent at thoracic levels

Question 15

Lower motor neurons in the ventral horn are divided into two groups: medial groups innervate ____ muscles while lateral groups innervate ____ muscles.

Answer 15

trunk; limb

Question 16

name the 3 important “independent” motor nuclei in the ventral horn, and their spinal levels.

Answer 16

spinal accessory nucleus (C1-C3)
phrenic nucleus (C3-C5)
onuf’s nucleus (S1-S4)

Question 17

this nucleus is the origin of the pudendal nerve and is important for somatomotor control of external urethral/anal spincters.

Answer 17

onuf’s nucleus (S1-S4)

Question 18

this nucleus is the origin of the spinal accessory nerve and is important for somatomotor control of trapezius and SCM muscles.

Answer 18

spinal accessory nucleus (C1-C3)

Question 19

this nucleus is the origin of the phrenic nerve and is important for somatomotor control of the diaphragm

Answer 19

phrenic nucleus (C3-C5)

Question 20

Spinal lesions above vertebral level T12 (= spinal cord levels L1/L2) result in _____ bladder.

Answer 20

reflex (spastic)

Question 21

Spinal lesions below vertebral level T12 result in _____ bladder.

Answer 21

flaccid (atonic)

Question 22

The urinary bladder receives inputs from the sympathetic nervous system located in what IML levels of the spinal cord?

Answer 22

L1-L2

Question 23

____ nucleus is a major relay center for unconcious proprioception, and is located in lamina ___ at spinal cord levels C8-L3.

Answer 23

Clarke’s; VII