Electrical Stimulation
1. Name each phase of a typical muscle twitch, and, on the following line, describe what is happening in each phase.
a.
b.
c.
2. In Activity 2, how long was the latent period? _______________ msec
Describe the chemical changes that are occurring during this period. _____________________________
_______________
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?
4. How does this change occur in vivo?
Skeletal Muscle Physiology
E X E R C I S E
NAME _____________________________
_______
LAB TIME/DATE ________________________
28 Review Sheet 2
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. _____________________________
__________________
6. Describe the chemical changes that are thought to correlate to this change in vivo.
7. In Activity 5, what was the effect of increasing the frequency of stimulation?
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 at a given force level. ______________________
11. In Activity 7, explain why the force of the muscle decreased over time during uninterrupted stimulation. Describe the
multiple causes of this phenomenon, which occurs in vivo with prolonged use of a muscle. __________________________
Isometric Contraction
12. In Activity 8, at what length of the muscle does the passive force start to increase?
13. Explain what happens to the active force with an increase in the muscle length.
14. Explain what happens to the active force with a decrease in the muscle length.
15. Explain what is happening in the sarcomere that results in the changes in total force when the muscle length changes. ________
Isotonic Contraction
16. In Activity 9, which weight resulted in the highest initial velocity of shortening?
17. Explain the relationship between the amount of resistance and the initial velocity of shortening.
18. Explain why it will take you longer to perform 10 repetitions lifting a 20-pound weight than it would to perform the same
number of repetitions with a 5-pound weight. _____________________________
_____________________________
____
Review Sheet 21 29