BIO365Rdiscussion - is an efferent--i.e. it is entirely...

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I'm a little confused about the function of 1a afferent and gamma motor neurons. I know they're different, but their functions seem so similar, especially since they both innervate the intrafusal fibers. It is my understanding that 1a track changes in stretch and gamma motor neurons modify spindle sensitivity. Is there any way you could explain in more detail the differences and how they work together in the function of intrafusal fibers? Thompson: I hope you understand that the Ia afferent is an afferent--a sensory axon conveying information to the CNS. It does not itself directly influence the contraction of the intrafusal fibers on which it is located--here it is entirely sensory. The gamma motor neuron
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Unformatted text preview: is an efferent--i.e. it is entirely motor in function and produces the contraction of the intrafusal fibers. I would argue that the functions are quite different. One (the afferent) senses stretch, while the other contracts the fibers in the spindle ensuring that the spindle continues to respond to muscle stretch if the extrafusal fibers are contracted to shorten the muscle. Conversely, a decrease in the activity of the gamma motor neuron will decrease the contraction of the intrafusal fibers and allow the spindle to lengthen if the extrafusal fibers are also less active....
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This note was uploaded on 05/12/2010 for the course BIO 365R taught by Professor Draper during the Spring '08 term at University of Texas at Austin.

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