Source:http://linkedlifedata.com/resource/umls/id/C0027871
MSH: Skeletal muscle structures that function as the mechanoreceptors responsible for the stretch or myotactic reflex (REFLEX, STRETCH). They are composed of a bundle of encapsulated SKELETAL MUSCLE FIBERS, i.e., the intrafusal fibers (nuclear bag1 fibers, nuclear bag2 fibers, and nuclear chain fibers) innervated by sensory neurons.,NCI: The Muscle Spindle is composed of intrafusal fibers that are located within and run parallel to the extrafusal fibers of skeletal muscle. When the extrafusal fibers are stretched, the intrafusal fibers of the spindle stretch as well. When stretching occurs, the sensory neuron from the muscle spindle signals the motor neurons located within the ventral horn of the spinal cord. This signal causes the motor neurons to fire, resulting in contraction of the muscle. This reflex arc provides negative feedback. The muscular contraction induced by the stretching works against or negates further muscle stretch. This mechanism helps to maintain proper muscle tension or tone. Although th