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Synopsis of Experiment

These experiments begin with the preparation of a mouse soleus muscle and sciatic nerve, which are exposed and maintained in an oxygenated solution at a constant temperature. The individual axons of the sciatic nerve that innervate separate motor units are isolated. When stimulated, the motor unit develops force that is measured in weight units (gram force or gf) by the myograph (use the scrollbar to see more).

Experiment 1: The Effect of Muscle Fiber Length on Contraction

Threshold voltage (lowest voltage that results in an action potential) will be applied to an axon innervating a motor unit at different muscle fiber, and therefore, sarcomere lengths. The contraction force the muscle produces will be measured. The optimal muscle length (length that produces maximal contraction force) will be used for all subsequent experiments.

Experiment 2: The Effect of Stimulation Frequency on Contraction

A motor unit will be stimulated by a single action potential (pulse) and then continuously at different frequencies to determine the frequency needed for tetanus.

Predictions

Based on what you know, predict the outcome of the experiment. Complete the numbered statements below by choosing one response for each number.

When you are done, click the Submit button to save your responses to the laboratory report.

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Your Predictions have been submitted to the Lab Report.

Scroll down to select Variables.

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You have correctly defined all of the variables.

Click or tap the Submit to Lab Report button to continue.

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Correct.

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You have not defined all of the variables correctly. Try again.

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Variables

Now determine the dependent, independent, and controlled variables for each experiment in this laboratory activity by clicking on the appropriate answers.

Check your answers until you have chosen all variables correctly. There will be one choice for Dependent and Independent Variables and multiple choices for Controlled Variables. When you are done, click the Submit button to save your responses to the laboratory report.

Submit to Lab Report

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