Skeletal muscle experiments

You have seen that if you have two stimuli close in time, the muscle contractions due to each one can sum and produce more force. Let's extend that now to a succession of stimuli, closer and closer in time. That's what we will do here, to produce a large and powerful muscle contraction known as a tetanus.

The purpose of this simulated experiment is to examine how muscle twitches can sum to produce a larger response when there is a train of electrical pulses applied to the nerve. You will do this by applying a train of successive electrical pulses to the nerve and systematically decreasing the interval between the two pulses. The above video covers some physiology related to tetanus and fatigue of muscle contractions, and the results you should expect.

Please note that although this video demonstrates an older version of the simulation, it should function the same.

Instructions:

1. This experiment is very similar to the last one, except that you will use a train of 60 pulses, rather than two pulses.
2. However, other than that, the rest of the procedure is nearly-identical. You will collect muscle twitch data for the following interpulse intervals: 400 ms, 200 ms, 100 ms, 80 ms, 60 ms, 40 ms and 20 ms.

After collecting your data, look at the second graph, which has peak muscle contraction plotted against interval between stimuli. What trends do you observe? At which inter-pulse interval does fused tetanus begin to occur?