Sharing of sensory terminals between the dynamic bag1 and static bag2 fibers in the rat muscle spindle.

Title

Sharing of sensory terminals between the dynamic bag1 and static bag2 fibers in the rat muscle spindle.

Creator

Walro J M; Kucera J

Publisher

Brain research

Date

1987
1987-11

Description

The nuclear bag1 intrafusal fiber mediates the dynamic (velocity) sensitivity, whereas the nuclear bag2 and nuclear chain fibers mediate the static (length) sensitivity of muscle spindles to stretch. The pattern of branching of primary and secondary afferents, the distribution of their terminals to the 3 types of intrafusal fibers, and the incidence of sensory cross-terminals were determined by reconstruction of 4 spindles from serial 1-micron and ultrathin transverse sections of rat extensor digitorum longus muscles. A single primary afferent supplied each spindle, and secondary afferents innervated intrafusal fibers in 3 spindles. Only static intrafusal fibers shared cross-terminals of the secondary afferents. In contrast, the dynamic bag1 and static bag2 fibers of each spindle shared at least one terminal of the primary afferent. Cross-terminals shared by the dynamic bag1 and static bag2 fiber parallel the presence of fusimotor (gamma) axons which coinnervate these types of intrafusal fibers in muscle spindles of rats. Consequently, the greater degree of overlap of elements comprising the dynamic and static systems of spindles of the rat relative to that of the cat reduces the probability of generating a purely dynamic or purely static response to an applied stretch.

Subject

Female; Animals; Rats; Axons/ultrastructure; Muscle Spindles/*ultrastructure; Nerve Fibers/*ultrastructure; Neurons; Inbred Strains; Afferent/*ultrastructure

Rights

Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).

Pages

311–318

Issue

2

Volume

425

Citation

Walro J M; Kucera J, “Sharing of sensory terminals between the dynamic bag1 and static bag2 fibers in the rat muscle spindle.,” NEOMED Bibliography Database, accessed May 9, 2021, https://neomed.omeka.net/items/show/5686.

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