3.19 Spinal Region 2

Question 1

spinal reflexes involve

Answer 1

interneurons

Question 2

withdrawal reflex allows

Answer 2

capacity of interneuronal circuits to generate complex movements

Question 3

What can elicit withdrawal movements?

Answer 3

afferent info from

• skin
• muscles
• joints

Question 4

reflexes: local sign

Answer 4

• determines specificity of the movement pattern

- response depends on the site of stimulation

Question 5

In withdrawal reflexes, why do the interneurons and collaterals of primary afferents relay information to other cord segments?

Answer 5

because muscles removing the part from the stimulation aren’t usually innervated by the same segment that received the afferent input

Question 6

Inhibitory interneurons provide

Answer 6

• reciprocal inhibition

- recurrent inhibition

Question 7

Interneurons in inhibitory circuits contribute to

Answer 7

spinal cord motor function

Question 8

reciprocal inhibition separates muscles into

Answer 8

agonists and antagonists

Question 9

What prevents unwanted activity in antagonists when agonists are voluntarily recruited?

Answer 9

reciprocal inhibition interneurons

Question 10

recurrent inhibition

Answer 10

opposite to reciprocal inhibition

• inhibits agonists and synergists
• disinhibition of antagonists

Question 11

Renshaw cells

Answer 11

interneurons that produce recurrent inhibition

Question 12

Renshaw cells are stimulated by

Answer 12

a recurrent collateral branch from the alpha motor neuron

Question 13

What do Renshaw cells inhibit?

Answer 13

inhibit alpha motor neurons of synergists (and alpha motor neurons that give rise to collateral branches)

Question 14

Renshaw cells do what to motor activity?

Answer 14

focus motor activity

Question 15

loss of descending influence on Renshaw cell activity

Answer 15

may cause difficulty with fine motor control

Question 16

What factors allow for bladder filling?

Answer 16

• frontal cortex inhibits pontine urination center
• sacral SC urination center (sympathetic and somatic signals)
• may need corticospinal input with a powerful urge to urinate

Question 17

bladder filling and sympathetic signals

Answer 17

• relax bladder wall

- constrict internal sphincter

Question 18

bladder filling and somatic signals

Answer 18

constrict external sphincter

Question 19

corticospinal input with bladder filling

Answer 19

to LMN: cause contraction of pelvic floor muscles and external sphincter

Question 20

bladder emptying: factors

Answer 20

• frontal cortex allows pontine urination center to activate

- parasympathetic signals from sacral spinal cord urination

Question 21

parasympathetic signals from sacral spinal cord urination center

Answer 21

• contraction of bladder wall

- relaxation of internal sphincter

Question 22

What is the signal to empty the bowels?

Answer 22

stimulation of stretch receptors in the wall of the rectum

Question 23

What part of the SC vital for sexual function?

Answer 23

lower spinal cord

Question 24

erection of penis or clitoris controlled by

Answer 24

parasympathetic fibers from S2-S4

Question 25

ejaculation elicited by

Answer 25

• sympathetic nerves from L1-L2

- pudendal nerve

Question 26

pudendal nerve cell bodies in

Answer 26

S2-S4

Question 27

lesions in spinal region may interfere with these:

Answer 27

• segmental function
• vertical tract function
• both

Question 28

segmental function: lesions

Answer 28

lesions interfere with neural function only at the level of the lesion

Question 29

vertical tract function: lesions

Answer 29

loss of function below the level of the lesion

Question 30

segmental signs

Answer 30

include

• abn or lost sensation in a dermatomal distribution and/or
• LMN neuron signs in a myotomal distribution

Question 31

ascending tract signs

Answer 31

problems with regulation of

• BP
• sweating
• bowel/bladder control

Question 32

descending tract signs include

Answer 32

• paralysis
• spasticity
• muscle hypertonia

Question 33

What happens if the lateral CST is interrupted?

Answer 33

Babinski’s sign

Question 34

All signs of damage to vertical tracts occur here

Answer 34

below level of the lesion

Question 35

peripheral region lesions produce

Answer 35

deficits in peripheral nerve distribution

Question 36

peripheral nerve lesions cause

Answer 36

• altered or lost sensation in peripheral nerve distribution

- decrease or loss of muscle power in peripheral nerve distribution

Question 37

Are there vertical tract signs in peripheral region lesions?

Answer 37

NO

Question 38

spinal region segmental signs occur when

Answer 38

nerve roots and/or spinal nerves are compromised

Question 39

spinal region segmental signs include

Answer 39

• altered or lost sensation in a dermatome
• decreased/lost muscle power in a myotome
• decreased/lost phasic stretch reflex

Question 40

spinal region vertical tract signs include:

Answer 40

• altered/lost sensation below lesion level

- altered/lost descending control of BP, pelvic viscera, and thermoregulation

Question 41

UMN signs include

Answer 41

• decrease/loss in muscle power
• spasticity
• hypertonia
• positive babinski/clonus (if lateral CST is involved)