Extrafusal muscle fiber

Extrafusal muscle fibers are a class of muscle fiber innervated by alpha motor neurons.

They generate tension, do mechanical work and allow for movement by contracting.

Compare with intrafusal muscle fiber - is of sensory type and innervated by gamma motor neurons.

Extrafusal muscle fibers and associated alpha motor neurons are called a motor unit. The connection between alpha motor neuron and extrafusal muscle fiber is a neuromuscular junction, and the neurotransmitter responsible for contraction is acetylcholine.

External links

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* [http://www.blackwellpublishing.com/11thhour/matt/about/u4c12a.html Cartoon of intrafusal vs. extrafusal fibers]