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).

1. According to Figure 1, over which of the following time periods of the isometric twitch of the adductor pollicis does the force generated by the adductor pollicis both increase and decrease?

Answer and Explanation

Your Answer is

Correct Answer is B

Explanation

According to figure 1, from 2msec to about 90msec, the ordinate force increases; after about 90 msec, the force decreases;

The time period that conforms to the increase and decrease of force only needs to include 90 msec is enough. Therefore choose 50-100 msec