The GTO is located near the musculotendinous junction, wraps around the ends of the extrafusal fibers of a muscle, and transmits afferent stimuli via II B fibers. It is sensitive to the tension in a muscle caused by either passive stretch or an active muscle contraction. The GTO is a protective mechanism that inhibits tension in the muscle in which it lies. This effect is called aatogenic inhibition. The GTO has a very low threshold for firing (fires easily) after an active muscle contraction and has a high threshold for firing with passive stretch. When excessive tension develops in a muscle the GTO fires, inhibits alpha motoneuron activity, and decreases tension in the muscle. During stretching procedures the tension within the tendon determines if the individual muscle fibers are inhibited and, thus, relaxed and able to be lengthened.