Biology:Extrafusal muscle fiber
| Extrafusal muscle fiber | |
|---|---|
| Details | |
| Part of | Skeletal muscle |
| Identifiers | |
| Latin | myofibra extrafusalis |
| Anatomical terminology | |
Extrafusal muscle fibers are the standard skeletal muscle fibers that are innervated by alpha motor neurons and generate tension by contracting, thereby allowing for skeletal movement. They make up the large mass of skeletal striated muscle tissue and are attached to bone by fibrous tissue extensions (tendons).
Each alpha motor neuron and the extrafusal muscle fibers innervated by it make up a motor unit.[1] 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.
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.
Extrafusal muscle fibers can be generated in vitro (in a dish) from pluripotent stem cells through directed differentiation.[2] This allows study of their formation and physiology.
See also
- Intrafusal muscle fiber
- Type Ia sensory fiber
- Type II sensory fiber
- Alpha motor neuron
- Gamma motor neuron
- Beta motor neuron
References
- ↑ Purves, Dale (2011). Neuroscience (5th ed.). Sunderland, Mass.: Sinauer. pp. 355–358. ISBN 978-0-87893-695-3.
- ↑ "Differentiation of pluripotent stem cells to muscle fiber to model Duchenne muscular dystrophy". Nature Biotechnology 33 (9): 962–9. September 2015. doi:10.1038/nbt.3297. PMID 26237517. http://www.hal.inserm.fr/inserm-01484878.
Further reading
- "Chapter 1: The Muscle Spindle and the Central Nervous System". Neuromuscular Reeducation with Electromyometric Feedback. Advanced Therapy Institute. http://www.advtherapy.net/html/book_01.pdf. Retrieved 30 November 2013.
- "Varieties of fast and slow extrafusal muscle fibres in amphibian hind limb muscles". Journal of Anatomy 116 (Pt 1): 1–24. October 1973. PMID 4273105.
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