De fibra estriada: Son robustos y potentes, ya que forman parte del aparato locomotor. Son músculos voluntarios, es decir, que puedes contraer mediante una orden del cerebro, excepto el corazón, un músculo involuntario formado por un tipo de fibra estriada especial.

Otra explicación:
Tension on the stretch receptors is maintained during muscle contraction by gamma efferent activation to the "spindle muscle" fibers.

muscle spindle or neuromuscular spindle. Muscle spindle maintains the muscle tone by monitoring the length of the muscle fibers. It also monitors the number of times the length of the muscle fiber needs to be adjusted

Smooth muscle features long, narrow "spindle" shaped cells with a single central, somewhat elongated, nucleus


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