3.19 Spinal Region

Question 1

rootlets

Answer 1

small groups of axons sending information to the periphery

Question 2

ventral root

Answer 2

combo of ventral rootlets

Question 3

dorsal root

Answer 3

• contains sensory axons bring info to the spinal cord

- enters posterolateral SC via rootlets

Question 4

How is the SC organized?

Answer 4

segmentally

Question 5

How is each segment of SC connected to a specific region of the body?

Answer 5

by axons traveling through a pair of spinal nerves

Question 6

What indicates segments?

Answer 6

connections of nerve rootlets to exterior of the cord

Question 7

What do spinal nerves carry?

Answer 7

all motor and sensory axons of a single spinal segment

Question 8

Where are the spinal nerves in the c-spine?

Answer 8

above corresponding vertebrae (except 8th)

Question 9

Where do the spinal nerves run in thoracic and lumbar spine?

Answer 9

below corresponding vertebrae

Question 10

dorsal horn processes:

Answer 10

sensory info

Question 11

lateral horn processes:

Answer 11

autonomic info

Question 12

ventral horn processes:

Answer 12

motor info

Question 13

most gray matter in SC composed of

Answer 13

interneurons

Question 14

interneuron locations

Answer 14

• cells entirely in gray matter AND

- cells with axons that travel to different levels of the cord

Question 15

meninges

Answer 15

• layers of connective tissue that surround the cord

- continuous with meninges that surround the brain

Question 16

arachnoid mater separated from pia by

Answer 16

CSF in the subarachnoid space

Question 17

What causes stretching of the lumbosacral roots?

Answer 17

hip flexion: produces anterior mvt of cauda equina

Question 18

effect of extension/lateral flexion on c-spine

Answer 18

increased intervertebral foramen pressure at all cervical levels

Question 19

effect of physiologic motions on vertebral canal

Answer 19

don’t significantly change size in people with normal vertebral canals

Question 20

What neck movement increases cervical nerve root s/s?

Answer 20

extension

Question 21

afferent and descending info converge on

Answer 21

the same spinal interneurons

Question 22

What acts together to produce goal-oriented movements?

Answer 22

• reflexes

- voluntary control

Question 23

What do reflexes depend on?

Answer 23

• environmental context
• task

not hardwired

Question 24

What does spinal circuitry provide by integrating volleys of peripheral, ascending, and descending inputs?

Answer 24

• modulation of sensory information
• coordination of movement patterns
• autonomic regulation

Question 25

These circuits integrate activity from all sources and adjust output of LMN

Answer 25

interneuronal circuits

Question 26

What do interneurons coordinate when a limb moves?

Answer 26

activity in all the muscles

Question 27

What determines whether a single alpha motor neuron will fire?

Answer 27

Summation of activity at 20,000 to 50,000 synapses determines whether an alpha motor neuron will fire.

Question 28

What is a stepping pattern generator?

Answer 28

adaptable neural networks that produce rhythmic output

Question 29

How does a stepping pattern generator contribute to stepping?

Answer 29

activating LMNs, causing alternating flexion and extension at the hips and knees

Question 30

Normal activation of stepping pattern generators occurs when

Answer 30

the person voluntarily sends signals from the brain to the stepping pattern generators (SPGs) in the spinal cord to initiate walking.

Question 31

When walking, __________ produces different responses, depending on the phase of the gait cycle

Answer 31

electrical stimulation to a single point on the foot

Question 32

stepping pattern generation

If stimulus occurs at the onset of swing phase, this activity increases

Answer 32

tibialis anterior activity

Question 33

stepping pattern generation

If stimulus occurs at the end of the swing phase, this happens

Answer 33

• tibialis anterior activity decreases

- antagonist muscle activity increases