Electrical Stimulation
1. Name each phase of a typical muscle twitch, and, on the following line, describe what is happening in each phase.
a. Latent- from the stimulus activity til the muscle begins to shorten.

b. Contraction- when muscle fibers shorten.

c. Relaxation- when muscles go back to their original state of relaxation.

2. In Activity 2, how long was the latent period? ____2.2______ msec
Describe the chemical changes that are occurring during this period.
Calcium levels are low since muscles contraction is not at its peak

The Graded Muscle Response to Increased Stimulus Intensity
3. From Activity 3, describe the effect of increasing the voltage. What happened to the force generated and why did this change occur?
Higher voltage results in higher force and a higher contractile force. 4. How does this change occur in vivo?
The more stimulus of muscle require more work on the cells which requires more Ca+2 to facilitate this stimulus increase.

5. In Activity 4, you looked at the effect of stimulating the muscle multiple times in a short period with complete relaxation between the stimuli.
Describe the force of contraction with each subsequent stimulus.
The force of contraction is higher with each subsequent stimulus.

6. Describe the chemical changes that are thought to correlate to this change in vivo.
This requires more Ca+2 in the sarcoplasm and more activity on the thin filament for cross-bridge attachments.

7. In Activity 5, what was the effect of increasing the frequency of stimulation?
Increase frequency of stimuli result in increased muscle tension.

8. Compare and contrast wave summation with recruitment (multiple motor unit summation). How are they similar? How was each achieved in the simulation?

9. Explain how wave summation and recruitment are achieved in vivo.

10. For Activity 6, explain how you were able to achieve smooth contraction