PhysioEx Exercise 2 Activity 7

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California State University, Northridge *

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PHYSICAL C

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Mechanical Engineering

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Dec 6, 2023

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3/16/23, 6:51 PM PhysioEx Exercise 2 Activity 7 https://media.pearsoncmg.com/bc/bc_0media_ap/physioex/10/ex2/act7/ 1/5 PhysioEx Lab Report Exercise 2: Skeletal Muscle Physiology Activity 7: Isotonic Contractions and the Load-Velocity Relationship Name: Gabriel Sanchez Date: 16 March 2023 Session ID: session-12a9499c-8a35-ffff-3c0e-f9f45040832a Pre-lab Quiz Results You scored 100% by answering 5 out of 5 questions correctly. Experiment Results Predict Question Stop & Think Question During an isotonic concentric contraction, the You correctly answered: force generated by the muscle is greater than the weight of the attached load. 1 During an isotonic concentric contraction You correctly answered: the latent period increases with heavier loads. 2 During the latent period for an isotonic concentric contraction You correctly answered: cross bridges cycle and, when muscle tension exceeds the load, muscle shortening occurs. 3 Muscle shortening velocity You correctly answered: decreases with heavier loads. 4 An isotonic contraction of a muscle is one in which You correctly answered: the length of the muscle changes. 5 Predict Question: As the load on the muscle increases , what will happen to the latent period, the shortening velocity, the distance that the weight moves, and the contraction duration? Your answer: The latent period will increase, the shortening velocity will decrease, the distance will decrease, and the contraction duration will decrease. 1
3/16/23, 6:51 PM PhysioEx Exercise 2 Activity 7 https://media.pearsoncmg.com/bc/bc_0media_ap/physioex/10/ex2/act7/ 2/5 Experiment Data Voltage (v) Length (mm) Weight (g) Velocity* (mm/ms) Distance Lifted (mm) Time (contracting) Time (relaxing) Twitch Duration (total) 8.5 75 0.5 0.100 4.0 40.00 38.00 78.00 8.5 75 1.0 0.057 2.0 35.00 14.00 49.00 8.5 75 1.5 0.022 0.5 23.00 7.00 30.00 8.5 75 2.0 0.000 0.0 0.00 0.00 0.00 *Distance divided by time (contracting). weight = 0.5 g duration of twitch = 78.00 msec velocity = 0.100 mm/msec distance lifted = 4.0 mm weight = 1.0 g duration of twitch = 49.00 msec velocity = 0.057 mm/msec distance lifted = 2.0 mm What kind of contraction did you observe when you attached the 2.0 gram weight to the skeletal muscle and stimulated a contraction? You correctly answered: isometric. 1
3/16/23, 6:51 PM PhysioEx Exercise 2 Activity 7 https://media.pearsoncmg.com/bc/bc_0media_ap/physioex/10/ex2/act7/ 3/5 weight = 1.5 g duration of twitch = 30.00 msec velocity = 0.022 mm/msec distance lifted = 0.5 mm weight = 2.0 g duration of twitch = 0.00 msec velocity = 0.000 mm/msec distance lifted = 0.0 mm Post-lab Quiz Results You scored 100% by answering 6 out of 6 questions correctly. Which of the weights allowed the fastest muscle shortening velocity? You correctly answered: 0.5-g weight. 1 Which of the weights induced the longest latent period of the muscle contraction? 2
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3/16/23, 6:51 PM PhysioEx Exercise 2 Activity 7 https://media.pearsoncmg.com/bc/bc_0media_ap/physioex/10/ex2/act7/ 4/5 Review Sheet Results You correctly answered: 1.5-g weight. Which weight did the muscle contraction move the greatest distance? You correctly answered: 0.5-g weight. 3 Which of the weights allowed the longest duration of muscle contraction? You correctly answered: 0.5-g weight. 4 An isotonic contraction of a muscle is one in which You correctly answered: the length of the muscle changes. 5 When lifting a heavy load You correctly answered: the muscle shortening velocity is decreased in comparison with lighter loads. 6 If you were using your bicep muscles to curl a 7-kg dumbbell, when would your muscles be contracting isotonically? Your answer: Before and after you return your arm to the downward position. 1 Explain why the delay between muscle stimulation and load movement became longer as the load became heavier in the experiment. How well did the results compare with your prediction? Your answer: My prediction was true. 2 Explain why the shortening velocity became slower as the load became heavier in this experiment. How well did the results compare with your prediction? Your answer: The distance increases which increases the shortening velocity and therefore the contraction duration is longer. 3 Describe how the shortening distance changed as the load became heavier in this experiment. How well did the results compare with your prediction? Your answer: 4
3/16/23, 6:51 PM PhysioEx Exercise 2 Activity 7 https://media.pearsoncmg.com/bc/bc_0media_ap/physioex/10/ex2/act7/ 5/5 My prediction was correct. Explain why it would take you longer to perform 10 repetitions lifting a 10-kg weight than it would to perform the same number of repetitions with a 5-kg weight. Your answer: Shortening velocity decreases increasing the time of the latent period. 5 Describe what would happen in the following experiment: A 2.5-g weight is attached to the end of the isolated whole skeletal muscle used in these experiments. Simultaneously, the muscle is maximally stimulated by 8.5 volts and the platform supporting the weight is removed. Will the muscle generate force? Will the muscle change length? What is the name for this type of contraction? Your answer: Isometric contraction. The muscle generates force as it stretches. The change in length is from the weight. 6