Innervation
As intrafusal muscle fibers, nuclear chain fibers both send afferent innvervation and receive efferent innervation. The afferent innervation is via Group II and Ia neurons. These project to the nucleus proprius in the dorsal horn of the spinal cord. Efferent innervation is via static γ neurons. Stimulation of γ neurons causes the nuclear chain to shorten along with the extrafusal muscle fibers. This shortening allows the nuclear chain fiber to be sensitive to changes in length while its corresponding muscle is flexed.
Read more about this topic: Nuclear Chain Fiber