PEX-02-03
4 Pages

PEX-02-03

Course Number: BIOL 2304, Fall 2012

College/University: Austin Community College

Word Count: 478

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Exercise 2: Skeletal Muscle Physiology: Activity 3: The Effect of Stimulus Frequency on Skeletal Muscle Contraction Lab Report Pre-lab Quiz Results You have not completed the Pre-lab Quiz. 010/03/12 page 1 Experiment Results You have not completed the Experiment. Experiment Data: 010/03/12 page 2 Post-lab Quiz Results You have not completed the Post-lab Quiz. 010/03/12 page 3 Tina Hong Nguyen PhysioEx...

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2: Exercise Skeletal Muscle Physiology: Activity 3: The Effect of Stimulus Frequency on Skeletal Muscle Contraction Lab Report Pre-lab Quiz Results You have not completed the Pre-lab Quiz. 010/03/12 page 1 Experiment Results You have not completed the Experiment. Experiment Data: 010/03/12 page 2 Post-lab Quiz Results You have not completed the Post-lab Quiz. 010/03/12 page 3 Tina Hong Nguyen PhysioEx 2-3 Review Sheet Results 1. What is the difference between stimulus intensity and stimulus frequency? Your answer: Stimulus intensity: is the amount of force that is generated to cause the stimulus. the more force will increase the stimulus intensity. Stimulus frequency: is the measured frequency and the amount of stimulus to a muscle that has occurred in "x" amount of time. 2. In this experiment you observed the effect of stimulating the isolated skeletal muscle multiple times in a short period with complete relaxation between the stimuli. Describe the force of contraction with each subsequent stimulus. Are these results called treppe or wave summation? Your answer: When the isolated skeletal muscle is stimulated multple times in a short period of time, with relaxation in between each of the stimuli, the amount of force in between each of the stimulus increases slowly to create a maximum peak and flattens out at the top of the force; this is a Treppe. 3. How did the frequency of stimulation affect the amount of force generated by the isolated muscle skeletal when the frequency of stimulation was increased such that the muscle twitches did not fully relax between subsequent stimuli? Are these results called treppe or wave summation? How well did the results compare with your prediction? Your answer: My prediction was correct, when the frequency was increased, the muscle relaxation did not happen because of the force was increasing with each stimulus. When the twitches are overlapped, there is no muscle relaxation and the stimulu only occurs one after another in a short period of time. The muscle contraction is higher when there is a single contraction occurrance, this is wave summation. 4. To achieve an active force of 5.2 g, did you have to increase the stimulus voltage above 8.5 volts? If not, how did you achieve an active force of 5.2 g? How well did the results compare with your prediction? Your answer: No, I applied wave summation to get 5.2g of the active force. I also delivered the stimulus rapidly and I did not let the full muscle relaxation. 5. Compare and contrast frequency-dependent wave summation with motor unit recruitment (previously observed by increasing the stimulus voltage). How are they similar? How was each achieved in the experiment? Explain how each is achieved in vivo. Your answer: The frequency dependent wave summation depends on the stimulation by the nervous system and the motor recruitment depends on the number of motor fibers that are available. 010/03/12 page 4
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