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Intrafusal muscle fibre

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Title: Intrafusal muscle fibre  
Author: World Heritage Encyclopedia
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Subject: Muscle spindle, Gamma motor neuron, Alpha motor neuron
Publisher: World Heritage Encyclopedia

Intrafusal muscle fibre

Intrafusal muscle fiber
A muscle spindle, with γ motor and Ia sensory fibers
Latin myofibra intrafusalis
Code Template:TerminologiaHistologica

Intrafusal muscle fibers are skeletal muscle fibers that comprise the muscle spindle and are innervated by gamma motor neurons. These fibers are proprioceptors that detect the amount and rate of change in length of a muscle.[1] Intrafusal muscle 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."

There are two types of intrafusal muscle fibers: nuclear bag and nuclear chain fibers. They bear two types of sensory ending, known as annulospiral and flower-spray endings.

Intrafusal muscle fibers are not to be confused with extrafusal muscle fibers, which are innervated by alpha motor neurons and contract, generating skeletal movement.

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.

See also


External links

  • Histology at
  • Histology at

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