Diagram the elements that comprise skeletal muscle. Indicate the location and function of (a) extrafusal muscle fibers, (b) alpha motor neurons, (c) the muscle spindle, (d) intrafusal muscle fibers, and (e) the gamma motor neuron
What will be an ideal response?
Answer: This diagram is based on that of Figure 8.2 (page 234). The extrafusal fibers should be labeled as being in parallel with the intrafusals and showing that their contraction performs the work of the muscle. The gamma motor neurons should be shown as innervating the intrafusal fibers; their firing contracts the intrafusal fiber and takes up the slack of that fiber. GTOs are in series with the extrafusal fibers—their activation inhibits the alpha motor neuron, thus preventing overcontraction of the muscle on a joint.
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