Intrafusal muscle fiber
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2008-04-29T20:27:26Z
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[[Image:MuscleSpindle.svg|right|264px|thumbnail|A muscle spindle, with γ motor and Ia sensory fibers]]
'''Intrafusal fibers''' are [[muscle fibers]] that comprise the [[muscle spindle]]. These [[fibers]] are walled off from the rest of the [[muscle]] by a [[collagen]] sheath. This sheath has a spindle or "fusiform" shape, hence the name "intrafusal." While the intrafusal fibers are wrapped with [[sensory receptors]], their counterpart, [[extrafusal muscle fiber]]s are the ones responsible for the power-generating component of muscle and are innervated by [[motor neurons]].
It is by the sensory information from these two intrafusal fiber types that one is able to judge the position of their muscle, and the rate at which it is changing.
* [[Type Ia sensory fiber]]
* [[Type II sensory fiber]]
==External links==
* [http://meded.ucsd.edu/hist-img-bank/chapter_3/Slide_60_artery_vein/pages/b.2.60.2.5.htm Histology at ucsd.edu]
* [http://www3.umdnj.edu/histsweb/lab6/skeletalmuscle/skmotorend.html Histology at umdnj.edu]
* [http://www.blackwellpublishing.com/11thhour/matt/about/u4c12a.html Cartoon of intrafusal vs. extrafusal fibers]
{{somatosensory system}}
{{Muscle tissue}}
{{muscle-stub}}
[[pt:Fibra muscular intrafusal]]