 | This article relies largely or entirely on a single source. (October 2020) |
| Nuclear bag fiber | |
|---|---|
| Details | |
| Identifiers | |
| Latin | myofibra sacculiformis |
| TH | H3.03.00.0.00013 |
| Anatomical terms of microanatomy | |
A nuclear bag fiber is a type of intrafusal muscle fiber that lies in the center of a muscle spindle.[1] Each has many nuclei concentrated in bags and they cause excitation of the primary sensory fibers.[2]
There are two kinds of bag fibers based upon contraction speed and motor innervation.
- BAG2 fibers are the largest. They have no striations in middle region and swell to enclose nuclei, hence their name.
- BAG1 fibers, smaller than BAG2.
Both bag types extend beyond the spindle capsule.
These sense dynamic length of the muscle. They are sensitive to length and velocity.
- ^ Boyd, I A; Gladden, M H; McWilliam, P N; Ward, J (1 February 1977). "Control of dynamic and static nuclear bag fibres and nuclear chain fibres by gamma and beta axons in isolated cat muscle spindels". The Journal of Physiology. 265 (1): 133–162. doi:10.1113/jphysiol.1977.sp011709. PMC 1307812. PMID 139469.
- ^ Mihailoff, G.A.; Haines, D.E. (2018). "Motor System I". Fundamental Neuroscience for Basic and Clinical Applications. pp. 346–359.e1. doi:10.1016/B978-0-323-39632-5.00024-4. ISBN 978-0-323-39632-5.