Physio Ex Exercise 2 Activity 5 PDF

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10/26/2020

PhysioEx Exercise 2 Activity 5

PhysioEx Lab Report Exercise 2: Skeletal Muscle Physiology Activity 5: Fatigue in Isolated Skeletal Muscle Name: A'Mond Jade O'Steen Date: 26 October 2020 Session ID: session-0356272b-489f-9035-fa8a-46b6eb9eaec2

Pre-lab Quiz Results You scored 100% by answering 4 out of 4 questions correctly. 1 When skeletal muscle twitches fuse so that the peaks and valleys of each twitch become indistinguishable from each other, the muscle is in a state known as You correctly answered: complete (fused) tetanus. 2 When the stimulus frequency reaches a value beyond which no further increase of skeletal muscle force can occur, the muscle has reached its You correctly answered: maximal tetanic tension. 3 A decline in a muscle's ability to maintain a constant level of force, or tension, after prolonged, repetitive stimulation is called You correctly answered: fatigue. 4 Which of the following is not thought to be a contributing factor to the development of fatigue? You correctly answered: buildup of Ca 2+ in the muscle fibers.

Experiment Results Predict Question 1 Predict Question: If the stimulator is briefly turned off for defined periods of time, what will happen to the length of time that the muscle is able to sustain maximal developed tension when the stimulator is turned on again? Your answer: The length of the rest period will proportionately increase the length of time for sustained muscle tension. Stop & Think Questions i https://media.pearsoncmg.com/bc/bc 0media ap/physioex/10/ex2/act5/

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PhysioEx Exercise 2 Activity 5

1 Why does the stimulated muscle force begin to decrease over time despite the maintained stimuli? (Note that a decrease in maximal force indicates muscle fatigue is developing.) You correctly answered: More than one of these answers could be correct. 2 Why did the length of the intervening rest period affect the length of time the skeletal muscle can maintain maximum tension once the stimulator is turned on again? You correctly answered: Intracellular concentrations of ADP and P i declined during the rest period. Experiment Data Voltage (v)

Stimuli/sec

Rest Period (sec)

Active Force

Sustained Maximal Force (sec)

8.5

120

0

5.86

0.08

8.5

120

0

5.86

0.08

8.5

120

12

5.86

0.02

8.5

120

22

5.86

0.06

120 Stimuli/sec at 8.5 V

120 Stimuli/sec at 8.5 V

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PhysioEx Exercise 2 Activity 5

Post-lab Quiz Results You scored 100% by answering 5 out of 5 questions correctly. 1 During cross bridge cycling in skeletal muscle, force is created by the You correctly answered: power stroke of the myosin heads. 2 The term tetanus refers to You correctly answered: sustained muscle tension due to repetitive stimuli. 3 A decline in a muscle's ability to maintain a constant level of force, or tension, after prolonged, repetitive stimulation is called You correctly answered: fatigue. 4 During fatigue You correctly answered: the number of active cross bridges begins to decline although the rate of stimulus delivery (frequency) remains constant. 5 If an intervening rest period is imposed on active skeletal muscle You correctly answered: the development of fatigue will be delayed.

Review Sheet Results 1 When a skeletal muscle fatigues, what happens to the contractile force over time? Your answer: Contractile force decrease over time because no additional force is generated after reaching maximal tetanic tension by previous contractile activity. 2 What are some proposed causes of skeletal muscle fatigue? Your answer: The build-up of lactic acid, ADP, and Pi, as well as low blood calcium level. 3 Turning the stimulator off allows a small measure of muscle recovery. Thus, the muscle will produce more force for a longer time period if the stimulator is briefly turned off than if the stimuli were allowed to continue without interruption. Explain why this might occur. How well did the results compare with your prediction? Your answer: i https://media.pearsoncmg.com/bc/bc 0media ap/physioex/10/ex2/act5/

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PhysioEx Exercise 2 Activity 5

Turning off the stimulator, a period of rest is introduced which can delay the onset of fatigue because that allows the increase in the intracellular ADP, lactic acid, Pi. Lower concentrations of these things let the muscle sustain muscle tension longer. So the length of the rest period is proportional to the length of time for sustained muscle tension. 4 List a few ways that humans could delay the onset of fatigue when they are vigorously using their skeletal muscles. Your answer: Doing multiple sets of low repetition exercises. Allow for multiple rest periods, exercising frequently can build endurance for the muscles to withstand higher tension.

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