Lab 10 Activity 5: Fatigue in Isolated Skeletal Muscle

complete (fused) tetanus

if stimuli applied with greater frequency after prolonged frequent stimulus the twitches begin to fuse so there are no distinguishable peaks or valleys

When a skeletal muscle fatigues, what happens to the contractile force over time?

Contractile force decrease over time because no additional force is generated after reaching maximal tetanic tension by previous contractile activity.

What are some proposed causes of skeletal muscle fatigue?

Build-up of lactic acid, ADP, and Pi, as well as low blood calcium level.

List a few ways that humans could delay the onset of fatigue when they are vigorously using their skeletal muscles.

Doing multiple sets of low repetition exercise. Allow for multiple rest periods, exercising frequently can build endurance for the muscles to withstand higher tension.

What mechanisms are proposed to lead to fatigue?

Thought to be from build-up of lactic acid, ADP, and Pi.

What is the best way to delay onset of fatigue?

To take periodic rests in between rigorous activities that require the use of skeletal muscles

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?

Turning off the stimulator, a period of rest is introduced which can delay the onset of fatique 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 length of rest period is proportinoal to length of time for sustained muscle tension.

In general, how does muscle fatigue occur?

decline in skeletal muscles ability to maintain a constant level of force or tension after prolonged repetetive stimulation

What is activity 5 about?

observing developement of skeletal muscle fatigue and understanding that the length of intervening rest periods determines the onset of fatigue

Stimulus frequency

rate of stimulus delivery to the muscle

unfused tetanus

stimuli continue to be applied frequently over prolonged period of time, maximum force plateu

rest period

time with no muscle stimulation

muscle tetanic tension

when the stimulus frequency reaches a value beyond which no further increase in force is generated