Reflexes

Question 1

What is the crossed extension reflex?

Answer 1

noxious stimuli causes an extension reaction through limbs on the contralateral side of the stimulation, to provide support when the flexion response occurs on the other side
- from the withdrawal reflex (flexor reflex)

Question 2

What is reciprocal inhibition?

Answer 2

antagonist muscles are inhibited to allow for a contraction

- stretch stimulus inhibits antagonists via inhibitory interneurons

Question 3

What three actions occur with the stretch reflex? (think about what muscles are activated, not, etc)

Answer 3

Stretch reflex sets off:

1) agonist reaction (homonomous muscle getting stretched is facilitated)
2) antagonist reaction (antagonists are inhibited)
3) synergistic muscles to the homonomous muscle are facilitated to help contraction

Question 4

Describe the reflex arc for the stretch reflex.

Answer 4

1) muscle spindle detects stretch through afferent 1a fibers (flowerspray/annulospiral)
2) these 1a fibers send message to alpha motor neuron in spinal cord, which synapses back onto muscle
3) muscle then contracts to offset stretch

This is an intact reflex arc

Question 5

What happens if muscle spindle is too sensitive?

Answer 5

meaning that the muscle spindle tells alpha motor neuron to contract muscle for even the slightest bit of stretch
- muscle becomes hypertonic; too much contraction compared to very little stretch stimulus (think overactive low back muscles)

opposite occurs if muscle spindle is less sensitive - too stretched out and doesn’t sense stretched muscle, so little contraction occurs
- this is with low tone issues

Question 6

What is the inverse stretch reflex?

Answer 6

involves golgi tendon organ

• afferent 1b fiber from GTO senses the stretch and synapses via inhibitory interneuron to muscle of origin
• functions to provide stretch protection

Question 7

Cuntaneous receptors are involved in what reflex arcs?

Answer 7

crossed extension and flexor reflex (withdrawal)