[PhysioEX Chapter 2 exercise 4] PEX-02-04

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Exercise 2: Skeletal Muscle Physiology: Activity 4: Tetanus in Isolated Skeletal Muscle Lab Report
Pre-lab Quiz Results
You scored 100% by answering 3 out of 3 questions correctly.

1. Stimulus frequency refers to
   You correctly answered: b. the rate that stimulating voltage pulses are applied to an isolated whole skeletal muscle.
2. Which of the following distinguishes a state of unfused tetanus from a state of complete (fused) tetanus?
   You correctly answered: d. Muscle tension increases and decreases during a state of unfused tetanus.
3. When the stimulus frequency reaches a value beyond which no further increases in force are generated by the muscle,
   the muscle has reached its
   You correctly answered: a. maximal tetanic tension.

Experiment Results
Predict Question:
Predict Question: As the stimulus frequency increases further, what will happen to the muscle tension and twitch
appearance with each successive stimulus? Will there be a limit to this response?
Your answer : b. As the stimulus frequency increases, the muscle tension generated by each successive stimulus will
increase. There will be a limit to this increase.
Stop & Think Questions:
What begins to happen at around 80 msec?
You correctly answered: c. unfused tetanus develops
How does the trace at 130 stimuli/sec compare with the trace at 50 stimuli/sec?
You correctly answered: b. Fused tetanus develops at this greater stimulus frequency.
How do the traces with 146–150 stimuli per second compare with the trace at 130 stimuli per second?
You correctly answered: d. Maximal tetanic tension develops with these very high stimulation frequencies.
Experiment Data:
Voltage Length Stimuli/sec Active Force Passive Force Total Force
8.5 75 50 5.12 0.00 5.12
8.5 75 130 5.88 0.00 5.88
8.5 75 140 5.91 0.00 5.91
8.5 75 142 5.94 0.00 5.94
8.5 75 144 5.94 0.00 5.94
8.5 75 146 5.95 0.00 5.95
8.5 75 148 5.95 0.00 5.95
8.5 75 150 5.95 0.00 5.95

Post-lab Quiz Results
You scored 100% by answering 3 out of 3 questions correctly.

1. The term tetanus refers to
   You correctly answered: b. sustained muscle tension due to very frequent stimuli.
2. Which of the following distinguishes a state of unfused tetanus from a state of complete (fused) tetanus?
   You correctly answered: d. Muscle tension increases and decreases between different values for an unfused tetanus.
3. When the stimulus frequency reaches a value beyond which no further increases in force are generated by the muscle,
   the muscle has reached its
   You correctly answered: a. maximal tetanic tension.

Review Sheet Results

1. Describe how increasing the stimulus frequency affected the force developed by the isolated whole skeletal muscle in
   this activity. How well did the results compare with your prediction?
   Your answer:
   Increasing stimulus frequency increases muscle tension generated by each successive force and it had limit, as predicted.
2. Indicate what type of force was developed by the isolated skeletal muscle in this activity at the following stimulus
   frequencies: at 50 stimuli/sec, at 140 stimuli/sec, and above 146 stimuli/sec.
   Your answer:
   At 50 stimuli/sec, the force generated is in a state called unfused tetanus, the muscle tension increase and decrease at
   different values
   At 140 stimuli/sec, the force generated is in a state called complete (fused) tetanus, the muscle tension are not wavering
   anymore.
   At above 146 stimuli/sec, the force generated is in a state called maximal tetanic tension which means it is highest value.
3. Beyond what stimulus frequency is there no further increase in the peak force? What is the muscle tension called at this
   frequency?
   Your answer:
   This muscle tension is called maximal tetanic tension.