Karius- Motor Control: Reflexes

Question 1

Reflex activity is mediated where?

Answer 1

all levels of CNS

Question 2

which kind of activity needs consciousness?

Answer 2

volitional activity

Question 3

what has more rapid onset: volitional or reflex activity?

Answer 3

reflexes

volitonal has a longer onset due to processing

Question 4

what kind of fibers are primary afferent to m. spindle?

Answer 4

large, Ia fibers, myelinated

Question 5

what do 1a fibers detect?

Answer 5

length and change in length

Question 6

what kind of fibers are secondary afferent to m. spindle?

Answer 6

group II, smaller diameter, less myelin

Question 7

what do 1a fibers innervate?

Answer 7

both nuclear bag and chain

Question 8

what do group II fibers innervate?

Answer 8

just nuclear chain

Question 9

what do group II fibers detect?

Answer 9

only length

Question 10

what do alpha motor neurons innervate?

Answer 10

NMJ- skeletal m.

Question 11

what do gamma motor neurons innervate?

Answer 11

contractile component of m. spindle via NMJ

Question 12

which motor neuron directly leads to motion?

Answer 12

alpha

Question 13

what is gamma motor neuron control?

Answer 13

sensitivity of m. spindle

Question 14

what initiates a myotactic reflex?

Answer 14

m. spindle, passive stretch of m.

Question 15

what kind of reflex is myotactic?

Answer 15

monosynaptic

Question 16

what initiates golgi tendon reflex?

Answer 16

golgi tendon, active contraction of m.

Question 17

what does golgi tendon reflex cause?

Answer 17

abrupt relaxation of contracted m. to prevent damage

Question 18

what kind of reflex is golgi tendon?

Answer 18

polysynaptic

Question 19

what causes spasticity?

Answer 19

damage to cortex that abolishes activation of brainstem to inhibitory region (brain arousal system), increased gamma motor neuron firing

Question 20

what causes rigidity?

Answer 20

loss of cortical influence that inhibits medullary input to alpha-motorneurons

Question 21

what does spasticity present as?

Answer 21

pt resists passive stretch of m., no contraction until stretch

Question 22

what does rigidity present as?

Answer 22

contraction of m. in absence of other stimuli

Question 23

what does spinal shock present as?

Answer 23

all reflexes abolished, even below transection

Question 24

what does decorticate posture present as?

Answer 24

internal rotation of legs in extended position, flexed arms

Question 25

which posture depends on head position?

Answer 25

decorticate

Question 26

what is the cause of decorticate posture?

Answer 26

loss of cortical input; usually lesion of internal capsule in humans

Question 27

what does decerebrate posture present as?

Answer 27

contraction of all anti-gravity m.

Question 28

what causes decerebrate posture?

Answer 28

loss of input to all things rostral to pons