tonic muscle


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tonic muscle

Skeletal muscle fibers that contract slowly and that cannot propagate an action potential along their cell membranes. Tonic muscles are uncommon in humans and are found only in the extraocular muscles, stapedius muscle, and intrafusal fibers of the muscle spindles. The remainder of human skeletal muscle contains only twitch fibers.
See also: muscle
References in periodicals archive ?
When the percentage of tonic adductor muscle in the overall adductor muscle was calculated from the impression on the right valve, Amusium balloti was shown to have very little tonic muscle compared with the other species (Fig.
The impressions of the tonic adductor muscle did not differ between the two valves in any species except Equichlamys bifrons in which the area of the tonic muscle was larger on the right than the left valve (Fig.
In most species, the tonic muscle was oblique in the opposite direction than the phasic muscle, with the insertion on the left valve being closer to the hinge.
The sustained contraction of tonic muscle facilitates the determination of its force production.
Tonic muscle force production maintains valve closure and resists predators trying to open the valves.