Without input from the gamma motor neurons,
A) extrafusal muscle fibers would be unable to contract.
B) intrafusal muscle fibers would not be able to relax.
C) extrafusal fibers would go limp whenever intrafusal fibers contracted.
D) intrafusal fibers would go limp whenever extrafusal fibers contracted.

Question

Quizplus · Accepted Answer

Gamma motor neurons innervate intrafusal fibers within muscle spindles. Without input from gamma motor neurons, intrafusal fibers would not maintain their sensitivity to stretch when the extrafusal muscle fibers (responsible for the actual muscle contraction) contract. This is because the contraction of extrafusal fibers without corresponding adjustment in intrafusal fibers (which gamma motor neurons would provide) would slacken the intrafusal fibers, making them "go limp" and unable to properly sense or respond to changes in muscle length.

Without Input from the Gamma Motor Neurons