Motor Units and Reflexes

Question 1

What type of motoneurons innervate muscle spindles?

Answer 1

delta motoneurons

Question 2

What is found in intrafusal muscle fibers?

Answer 2

muscle spindles

Question 3

These are activated in response to moderate stretch

Answer 3

muscle spindles

Question 4

Ia spindle fibers are responsible for:
detecting velocity
detecting amplitude of stretch

Answer 4

detecting velocity

Question 5

II spindle fibers are responsible for:
detecting velocity
detecting amplitude of stretch

Answer 5

detecting amplitude of stretch

Question 6

What are the 5 steps of muscle spindle activation?

Answer 6

1. muscle stretch
2. mechanoreceptor-mediated depolarization of spindle afferent
3. activation of alpha- and delta-motoneurons
4. contraction of intrafusal and extrafusal muscle fibers
5. intrafusal contraction maintains tension in spindle (allows continued response)

Question 7

This is a monosynaptic reflex

Answer 7

stretch reflex

Question 8

Where are Golgi tendon organs located?

Answer 8

muscle-tendon junction

Question 9

How do Golgi tendon organs work?

Answer 9

depolarization of Golgi tendon organs increases the activity of inhibitory interneurons
=>decrease in alpha-motoneuron activity

Question 10

What is a “timed delay”?

Answer 10

complicated reflex arc where different sets of neurons fire at different times in response to the same stimulus, often due to synaptic delay

Question 11

What is the function of the Golgi tendon organ?

Answer 11

relax muscle when too much force is applied

Question 12

Which type of motoneuron modulates the lengthening reaction?

Answer 12

delta

Question 13

A strong stretch activates this reflex

Answer 13

inverse stretch (modulated by Golgi)

Question 14

What is spinal shock?

Answer 14

syndrome occurring right after CNS lesion when reflexes are absent
=>eventually return