Intrafusal muscle fiber 2774134 209075598 2008-04-29T20:27:26Z Wdustbuster 5957892 [[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]]