Passage I

A muscle twitch (a stimulus-contraction-relaxation cycle) is divided into 3 phases (the latent period, the contraction phase, and the relaxation phase) based on the timing of the stimulus and changes in the force generated by the muscle. Table 1 shows when each phase starts and ends.

Figure 1 shows the force generated by an adductor pollicis (a thumb muscle) undergoing an isometric twitch (a twitch that does not change the muscle’s length). In Figure 1, force is given in newtons (N) and time is given in milliseconds (msec).

2. Based on Table 1 and Figure 1, what is the correct order of the 3 phases of the isometric twitch of the adductor pollicis, from the phase with the shortest duration to the phase with the longest duration?

Answer and Explanation

Your Answer is

Correct Answer is F

Explanation

Time spans are sorted from smallest to largest. According to the concept given in table 1, the Latent period should be the stage before the increase in force, corresponding to 0-2msec in table 2;

Contraction phase corresponds to the increase in force, that is, 2-90msec;

relaxation phase corresponds to the stage of force decline, that is, 90-250msec;

so latent