3.21 Spinal Region Lecture 2

Question 1

What do radicular arteries arise from?

Answer 1

thoracic and abdominal aortae

Question 2

Each radicular artery gives rise to

Answer 2

one spinal artery (anterior spinal artery)

Question 3

What happens to the 2 anterior spinal arteries?

Answer 3

• fuse and run in anterior median fissure

- run the entire length of SC

Question 4

What supplies the anterior 2/3 of the SC?

Answer 4

branches of anterior spinal arteries

Question 5

What supplies the posterior 1/3 of SC?

Answer 5

PICA

Question 6

What happens to the PICA to supply the SC?

Answer 6

PICA
» 2 posterior spinal arteries
» proceed along dorsal rootlet attachments

Question 7

Where are the dorsal rootlet attachments?

Answer 7

in posterolateral sulci

Question 8

Does fusion occur with posterior blood supply?

Answer 8

nope

Question 9

T12 significance with SC blood supply

Answer 9

• great radicular artery

- supplies lumbosacral in addition to everything else

Question 10

How does venous drainage occur?

Answer 10

• via radicular veins

- drains into epidural venous plexus

Question 11

functions of SC

Answer 11

• exchanging info from other segments via columns

- exchanging info from periphery

Question 12

What is the “key” to SC that helps with modulation?

Answer 12

interneurons

Question 13

3 things interneurons help with

Answer 13

• stepping pattern generators
• reflexes
• inhibitory circuits

Question 14

function of inhibitory circuits

Answer 14

modulation of fine motor activity

Question 15

What is a stepping pattern generator a subtype of?

Answer 15

central pattern generator

Question 16

What do stepping pattern generators do?

Answer 16

help keep normal cadence/rhythm when you walk

Question 17

stepping pattern generators in lower thoracic/lumbar regions

Answer 17

help with locomotion

Question 18

stepping pattern: external stimulation

Answer 18

electrically stimulating LMNs

- no cortical input necessary

Question 19

What produces stepping pattern generators?

Answer 19

SC

Question 20

initial decision to move comes from

Answer 20

motor cortex

motor planning regions

Question 21

adaptability of stepping pattern generators to different scenarios (ex.)

Answer 21

think feet on treadmills going different directions

Question 22

Are stepping pattern generators sufficient for walking? Why or why not?

Answer 22

• no

- higher neural control for purposeful movements

Question 23

What is necessary for activation of interneuron circuits for stepping pattern?

Answer 23

UMN activation

Question 24

overall action of UMN with step pattern

Answer 24

fires to both flexor and extensor motor neurons

• extensors contract
• flexors inhibited

reciprocal inhibition

Question 25

Interneuron activity in stepping pattern

Answer 25

• causes reciprocal inhibition
• get a refractory period
• cycle repetition

Question 26

refractory period of interneurons: implication

Answer 26

• flexors now free to contract because they aren’t getting inhibition
• inhibition of extensors happen now as well

Question 27

UMN contribution to walking

Answer 27

• doesn’t have to act much

- initial firing due to decision made

Question 28

How does sensory input come into play with stepping pattern gen?

Answer 28

GTO helps with proprioception and appropriate level of firing of LMN to muscles

Question 29

• inhibition of antagonist

- activation of agonist

Answer 29

reciprocal inhibition

Question 30

• inhibition of agonist

- activation of antagonist

Answer 30

recurrent inhibition

Question 31

When might reciprocal inhibition fail to occur?

Answer 31

when anxious (makes you really tired!)

Question 32

What cells allow recurrent inhibition?

Answer 32

Renshaw cells

Question 33

What are Renshaw cells?

Answer 33

• branches of alpha motor neurons

- feed back and inhibit themselves

Question 34

Renshaw cells and inhibition: example

Answer 34

• playing piano and fine motor control

- keeps from overshooting notes

Question 35

reciprocal and recurrent inhibition work _______

Answer 35

simultaneously