September 24, 2021
Intrafusal Muscle Fibers Muscle Fiber Spindle
The intrafusal muscle fibers also serve which of the following purposes?
A. Force generation
B. Maintain spindle tension
C. Protein storage
D. Protect nerves
Answer: Maintain spindle tension
The intrafusal muscle fibers are innervated by gamma and beta motor neurons and contract or relax to maintain the sensitivity of the spindle. For example when the quadriceps muscle contracts and becomes shorter, the intrafusal muscle fibers take up slack in the spindle to maintain its sensitivity to stretch.
The intrafusal muscle fibers do not contribute significantly to the force of the muscle contraction, store significant protein, or protect nerves.
Kröger S, Watkins B. Muscle spindle function in healthy and diseased muscle. Skelet Muscle. 2021 Jan 7;11(1):3. doi: 10.1186/s13395-020-00258-x. PMID: 33407830; PMCID: PMC7788844.