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reviewsheet_ap02 - REVIEW SHEET EXERCISE 2 Skeletal Muscle...

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REVIEW SHEET EXERCISE 2 Skeletal Muscle Physiology NAME: Courtney Boyd LAB TIME/DATE: July 14, 2010 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 Period: Calcium ions are released by the sarcoplasmic reticulum as the action potential sweeps across the sarcolemma. During this period, there is no tension produced since the contraction has not begun. b. Contraction Phase: the calcium ions that were released now bind to troponin as the tension rises to a peak. Also, active sites on thin filaments are exposed, cross-bridge interactions occur, and this phase ends15msec after stimulation. c. Relaxation Phase: for about another 25msec, the calcium levels decline, tropomyosin covers the active sites that were once exposed and there is a decline in the number of cross-bridges. 2. In Activity 2, how long was the latent period? _3.33_ msec Describe the chemical changes that are occurring during this period. The chemical changes that occur during the latent period are that the sarcoplasmic reticulum releases calcium ions in the muscle. 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? As the voltage was increased, the active force produced by the muscle increases gradually. The force that was generated increases and activates the muscle fibers which generate a large amount of total force. This occurs because the active force increases as the voltage
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increases. 4. How does this change occur in vivo?
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