Skeletal Muscle Physiology

Determining the Latent Period 1. Click Clear Tracings to erase the oscilloscope display. The voltage should be set to 5.0 volts. 2. Drag the 200 msec button to the right edge of the oscilloscope. 3. Click the Stimulate button once, and allow the tracing to complete. 4. When you measure the length of the latent period from a printed graph, you measure the time between the application of the stimulus and the beginning of the first observable response(increase in force). The computer can’t “look ahead,” anticipating the change in active force. To measure the length of the latent period using the computer, click the Measure button. Then click the right arrow button next to the Time window repeatedly until you notice the first increase in the Active Force window. This takes you beyond the actual length of the latent period. Now click the left arrow button next to the Time window until the Active Force window again reads zero. At this point the computer is measuring the time between the application of the stimulus and the last point where the active force is zero (just prior to contraction). How long is the latent period? _2.78_ msec What occurs in the muscle during this apparent lack of activity? The muscle is reacting internally and getting the signals to contract. Investigating Graded Muscle Response to Increased Stimulus Intensity 1. Click Clear Tracings if there are tracings on your screen. 2. Set the voltage to 0.0, and click Stimulate. 3. Click Record Data. If you decide to redo a single stimulus, choose the data line in the grid and click Delete Line to erase that single line of data. If you want to repeat the entire experiment, click the Clear Table button to erase all data recorded to that point. 4. Repeat steps 2 and 3, increasing the voltage by 0.5 each time until you reach the maximum voltage of 10.0. Be sure to select Record Data each time. 5. Observe the twitch tracings. Click on the Tools menu and then choose Plot Data. 6. Use the slider bars to display