Nuclear bag fiber

Nuclear bag fiber
Details
Identifiers
Latin	myofibra sacculiformis
TH	H3.03.00.0.00013
Anatomical terms of microanatomy [edit on Wikidata]

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.

1. BAG2 fibers are the largest. They have no striations in middle region and swell to enclose nuclei, hence their name.
2. 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.

See also

• Nuclear chain fiber
• List of distinct cell types in the adult human body

References

1. 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.
2. 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.

External links

• http://www.unmc.edu/Physiology/Mann/mann11.html Archived 2007-07-03 at the Wayback Machine