When a skeletal muscle fiber is given a single stimulus, a single twitch with numerous electrical phases is observed. Of the following, which is the CORRECT order for the phases or periods seen in a skeletal muscle fiber after stimulation?
A. Contraction, latent, relaxation, refractory.
B. Refractory, contraction, latent, relaxation.
C. Latent, contraction, relaxation, refractory.
D. Latent, refractory, contraction, relaxation.
A single muscle twitch is caused by an initiating action potential; however, there is a latent period after the generation of the action potential and initiation of the muscle twitch. After the latent period, the muscle contracts and then relaxes, followed by a refractory period in which the muscle will not respond to another action potential.