Based on the neurophysiological properties of the contractile components of muscle, a high-intensity, quick stretch of a muscle-tendon unit is believed to create phasic elevation of tension in the stretched muscle by:
A)Facilitating the muscle spindle via the Ib fibers.
B)Facilitating the GTO.
C)Facilitating the primary (Ia) afferents, which in turn stimulate the extrafusal fibers of the muscle.
D)Inhibiting the secondary (II) afferents, which in turn stimulate the extrafusal fibers of the muscle.

Question

Quizplus · Accepted Answer

A quick stretch of a muscle-tendon unit stimulates the primary (Ia) afferents, which in turn stimulate the extrafusal fibers of the muscle. This leads to a phasic elevation of tension in the muscle. The activation of the muscle spindle via the Ib fibers and facilitation of GTO can also contribute to the tensile response, but the primary mechanism is the activation of the Ia afferents. Inhibiting the secondary (II) afferents would not lead to muscle activation, as these afferents do not directly stimulate the extrafusal fibers of the muscle.

Based on the Neurophysiological Properties of the Contractile Components of Muscle