Kantak: Neural Control & Muscle Contraction

Question 1

What does the lateral system direct? What does the medial system direct?

Answer 1

Goal directed movement.

Antigravity muscles, posture.

Question 2

Where is a motor neuron located?

Answer 2

In the spinal cord in anterior (ventral) horn cells in motor neuron columns.

Question 3

Which fires first and why? Small motor units or large?

Answer 3

Small first, then large.

For the small the time to peak force is slower, sustained longer, but have a low inner action ratio. These have high R-input which means voltage is high.

For the large, the time to peak is faster, sustained less, and they have a high innervation ratio. These have low R-input which means voltage is low.

Question 4

Intrafusal fibers: What do static fibers sense? What do dynamic fibers sense?

Answer 4

Static fibers stay on and sense the length of the muscle. Dynamic fibers sense the rate of change.

Question 5

What are the two types of motor neurons and what do they affect?

Answer 5

Alpha motor neurons (go to extrafusal muscle fibers).
Gamma motor neurons (go to intrafusal muscle fibers). - these you can affect by stretching or by affecting the gamma motor neurons.