A nuclear bag fiber is a type of
intrafusal muscle fiber
Intrafusal muscle fibers are skeletal muscle fibers that serve as specialized sensory organs ( proprioceptors). They detect the amount and rate of change in length of a muscle.Casagrand, Janet (2008) ''Action and Movement: Spinal Control of ...
that lies in the center of a
muscle spindle
Muscle spindles are stretch receptors within the body of a skeletal muscle that primarily detect changes in the length of the muscle. They convey length information to the central nervous system via afferent nerve fibers. This information can be ...
. Each has many
nuclei concentrated in bags and they cause excitation of the
primary sensory fibers.
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.
See also
*
Nuclear chain fiber
A nuclear chain fiber is a specialized sensory organ contained within a muscle. Nuclear chain fibers are intrafusal fibers that, along with nuclear bag fibers, make up the muscle spindle responsible for the detection of changes in muscle leng ...
*
List of distinct cell types in the adult human body
The list of human cell types provides an enumeration and description of the various specialized cells found within the human body, highlighting their distinct functions, characteristics, and contributions to overall physiological processes. Cell ...
References
External links
* http://www.unmc.edu/Physiology/Mann/mann11.html
Nervous system
Muscular system
{{neuroscience-stub