Extrafusal muscle fiber
 | This article includes a list of references, related reading, or external links, but its sources remain unclear because it lacks inline citations. (November 2013) |
| Extrafusal muscle fiber | |
|---|---|
| Details | |
| Identifiers | |
| Latin | myofibra extrafusalis |
| TH | H3.03.00.0.00007 |
| Anatomical terminology | |
Extrafusal muscle fiber is a term given to standard muscle fibers as to distinguish them from intrafusal muscle fibers. Extrafusal muscle fibers are innervated by alpha motor neurons and generate tension by contracting, thereby allowing for skeletal movement.
The alpha motor neuron and the extrafusal muscle fibers it innervates make up the motor unit. The connection between the alpha motor neuron and the extrafusal muscle fiber is a neuromuscular junction, where the neuron's signal, the action potential, is transduced to the muscle fiber by the neurotransmitter acetylcholine.
These fibres are attached to bone by fibrous tissue extensions (tendons) and are responsible for contractibility of a muscle.
Extrafusal muscle fibers are not to be confused with intrafusal muscle fibers, which are innervated by sensory nerve endings in central noncontractile parts and by gamma motor neurons in contractile ends and thus serve as a sensory proprioceptor.
See also
- Intrafusal muscle fiber
- Type Ia sensory fiber
- Type II sensory fiber
- Alpha motor neuron
- Gamma motor neuron
- Beta motor neuron
References
- "Chapter 1: The Muscle Spindle and the Central Nervous System". Neuromuscular Reeducation with Electromyometric Feedback (PDF). Advanced Therapy Institute. Retrieved 30 November 2013.
- Smith, RS; Ovalle, Jr, WK (October 1973). "Varieties of fast and slow extrafusal muscle fibres in amphibian hind limb muscles". J Anat. 116 ((Pt 1)): 1–24. PMC 1271546. PMID 4273105.
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