Question

17) Students in a physiology lab generated the graph below. The top trace (myogram) shows contraction force, the bottom (EMG) shows the electrical stimulus. On the graph, label a muscle twitch. What property of muscle is being tested here? What caused the increase in force (and subsequent decrease)?

MAAN MYOGRAM EMG

Answer 1

A muscle twitch is a nerve stimulation that occurs in the muscle. This stimulation occurs due to the presence of a threshold stimulus, which is the minimum amount of stimulation required for the contraction to take place. The entire process of muscle lasts for only a few milliseconds. However, the process can be subdivided into three stages which are-the latent phase, the contraction phase, and the relaxation phase. Post the twitch, the muscle undergoes the phase of wave stimulation, which leads to the stage of tetanus.

The increase in force is caused by the initial stimulation which begins an action potential. This action potential is followed by a period called refractory period where the muscle does not get excited, irrespective of any stimulus. In this way, the graph rises and then falls.