Final answer:
Gamma dynamic efferent neurons cause contraction of the ends of intrafusal muscle fibers, allowing the central regions to maintain sensitivity to stretch during muscle length changes, which is essential for the central nervous system to regulate muscle tone and movement coordination.
Step-by-step explanation:
The action of intrafusal muscle fibers produced by gamma dynamic efferent neurons is to adjust the sensitivity of the muscle spindle sensory apparatus. Specifically, these neurons cause the contraction of the ends of the intrafusal muscle fibers, which are part of the sensory organs in muscles known as muscle spindles. The contraction of these ends allows the central region of the intrafusal fibers, where the sensory nerve endings are located, to maintain sensitivity to stretch even when the muscle length changes. This sensitivity is crucial for the central nervous system to regulate muscle tone and to make fine adjustments to muscle movements.
Gamma efferent neurons ensure that there is constant tension on the sensory receptors within the muscle spindle, allowing for precise detection of muscle length changes by the sensory afferent neurons. As muscle spindles detect changes in muscle length, they send action potentials back to the central nervous system to adjust the strength and speed of muscle contractions accordingly. This feedback loop involving gamma efferent neurons is a key component of muscle coordination and control.