Exercise 2: Skeletal Muscle Physiology: Activity 4: Tetanus in Isolated Skeletal Muscle Lab Report Pre-lab Quiz Results You scored 66% by answering 2 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 tetanus from a state of complete complete (fused) tetanus? tetanus? Your answer : a. The rate of stimulus delivery (frequency) is greater during a state of unfused tetanus. Correct answer: 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.
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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? Your answer : d. maximal tetanic tension is reached Correct answer: 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? Your answer : b. Fused tetanus ceases with these very high stimulation frequencies. Correct answer: d. Maximal tetanic tension develops with these very high stimulation frequencies. Experiment Data: Voltage 8.5 8.5 8.5 8.5 8.5 8.5 8.5 8.5
Length 75 75 75 75 75 75 75 75
Stimuli/sec 50 130 140 142 144 146 148 150
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Active Force 5.12 5.88 5.91 5.94 5.94 5.95 5.95 5.95
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Passive Force 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Total Force 5.12 5.88 5.91 5.94 5.94 5.95 5.95 5.95
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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.
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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: When the stimulus frequency was at the lowest (50s/s) the force was at its lowest level out of all of the experiments. As the stimulus frequency was increased to 130 s/s the force increased slightly but fused tetanus developed at the higher frequency. When the stimulus frequency was increased to the amounts of 146-150 s/s, the force reached a plateau and maximal tetanic tension occurred, where no further increases in force occur from additional stimulus frequency. 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: 50- Unfused Tetanus 140-Fused Tetanus 146+ Maximal Tetanic Tension
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: Maximal Tetanic Tension
