Name:
Exercise 2: Skeletal Muscle Physiology: Activity 2: The Effect of Stimulus Voltage on Skeletal Muscle Contraction Lab
Report
Pre-lab Quiz Results
You scored 100% by answering 4 out of 4 questions correctly.
1. Skeletal muscle fibers are innervated (stimulated) by
You correctly answered: c. motor neurons.
2. A single action potential propagating down a motor axon results in
You correctly answered: d. a single action potential and a single contractile event in the muscle fibers it innervates.
3. In resting skeletal muscle, calcium is stored in
You correctly answered: c. the sarcoplasmic reticulum.
4. During the latent period for an isometric contraction
You correctly answered: c. the cellular events involved in excitation-contraction coupling occur.

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page 1

Experiment Results
Predict Question:
Predict Question: As the stimulus voltage is increased from 1.0 volt up to 10 volts, what will happen to the amount of active force generated with each stimulus?
Your answer : c. The active force will first increase and then plateau at some maximal value as the stimulus voltage increases. Stop & Think Questions:
What do you see in the active force display when the stimulus voltage is set to 0.0, and why does this observation make sense? You correctly answered: a. 0.00 g; there was no activation of skeletal muscle fibers by this stimulus.
What is the lowest stimulus voltage that induces active force in the skeletal muscle?
You correctly answered: b. threshold voltage
6. Enter the threshold voltage for this experiment in the field below and then click Submit Data to record your answer in the lab report
You answered: 0.8 volts
12. Enter the maximal voltage for this experiment in the field below and then click Submit Data to record your answer in the lab report.
You answered: 10 volts
Experiment Data:
Voltage
0.0
0.2
0.3
0.4
0.5
0.8
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
8.0
8.5

Length
75
75
75
75
75
75
75
75
75
75
75
75
75
75
75
75
75
75
75
75
75
75

Active Force
0.0
0.0
0.0
0.0
0.0
0.02
0.15
0.43
0.66
0.87
1.04
1.19
1.32
1.42
1.51
1.59
1.65
1.70
1.74
1.78
1.81
1.82

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Passive Force
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0

page 2

Total Force
0.0
0.0
0.0
0.0
0.0
0.02
0.15
0.43
0.66
0.87
1.04
1.19
1.32
1.42
1.51
1.59
1.65
1.70
1.74
1.78
1.81
1.82

Voltage
9.0
9.5
10.0

Length
75
75
75

Active Force
1.82
1.82
1.82

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Passive Force
0.0
0.0
0.0

page 3

Total Force
1.82
1.82
1.82

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page 12

Post-lab Quiz Results
You scored 100% by answering 6 out of 6 questions correctly.
1. Motor unit recruitment refers to
You correctly answered: a. an increase in the number of active muscle fibers to increase the force developed in a muscle.
2. Active tension (or force) in a skeletal muscle fiber results from
You correctly answered: a. activation of cross bridge cycling via increased intracellular calcium levels.
3. The ________ is the minimal stimulus needed to cause a depolarization of the muscle plasma membrane (sarcolemma).
You correctly answered: d. threshold voltage
4. By definition, the ________ is the amount of stimulus required