PhysioEx Lab Report
Exercise 2: Skeletal Muscle Physiology
Activity 3: The Effect of Stimulus Frequency on Skeletal Muscle Contraction Name: ACH RIFANDI
Date: 5 February 2025
Session ID: session-d98f5af1-04d9-6fae-5538-e21a562a623e
Pre-lab Quiz Results
You scored 100% by answering 4 out of 4 questions correctly.
Experiment Results
Predict Questions
Stop & Think Questions
During a single twitch of a skeletal muscle
You correctly answered: maximal force is never achieved.
1
When a skeletal muscle is repetitively stimulated, twitches can overlap each other and result in a stronger muscle contraction than a stand-alone twitch. This phenomenon is known as
You correctly answered: wave summation.
2
Wave summation is achieved by
You correctly answered: increasing the stimulus frequency (the rate of stimulus delivery to the muscle).
3
Wave summation increases the force produced in the muscle. Another way to increase the force produced by a muscle is to
You correctly answered: increase the number of activated motor units.
4
Predict Question 1: As the stimulus frequency increases, what will happen to the muscle force generated with each successive stimulus? Will there be a limit to this response?
Your answer: As the stimulus frequency increases, the muscle force generated by each successive stimulus will increase. There will be a limit to this increase.
1
Predict Question 2: In order to produce sustained muscle contractions with an active force value of 5.2, do you think you will need to increase the stimulus voltage?
Your answer: No.
2
Experiment Data
Voltage (v) Length (mm) Stimulus Active Force Passive Force Total Force
8.5 75 Single 1.83 0.0 1.83
8.5 75 Multiple 2.95 0.0 2.95
8.5 75 Multiple 2.96 0.0 2.96
8.5 75 Multiple 3.96 0.0 3.96
10 75 Multiple 4.11 0.0 4.11
8.5 75 Multiple 5.54 0.0 5.54
Voltage = 8.5 V Single Stimulus Active Force = 1.83 Was there any change in the force generated by the muscle during the second stimulated twitch?
You correctly answered: Yes, the second twitch generated more muscle force.
1
Is the total muscle force generated by the higher frequency stimulation greater than the force generated in previous stimulations?
You correctly answered: Yes, it is greater than the previous stimulations.
2
Does the force generated by the muscle change with each additional stimulus?
You correctly answered: As the stimulus frequency increased, the muscle tension
generated by each successive stimulus also increased, and a limiting maximum value was observed.
3
Voltage = 8.5 V Multiple Stimulus Active Force = 2.95
Voltage = 8.5 V Multiple Stimulus Active Force = 2.96
Voltage = 8.5 V Multiple Stimulus Active Force = 3.96
Voltage = 10 V Multiple Stimulus Active Force = 4.11
Voltage = 8.5 V Multiple Stimulus Active Force = 5.54
Post-lab Quiz Results
You scored 100% by answering 4 out of 4 questions correctly.
Which of the following is not one of the ways that the body can increase the force produced by a skeletal muscle?
You correctly answered: application of higher voltages to the whole muscle.
1
When a muscle receives a stimulus frequency that causes non-overlapping twitches to follow each other closely in time such that the peak tension of each twitch rises in a stepwise fashion up to a plateau value, the result is known as
You correctly answered: treppe.
2
In this experiment the isolated skeletal muscle was repetitively stimulated such that individual twitches overlapped with each other and resulted in a stronger muscle contraction than a standalone twitch. This phenomenon is known as
3
Review Sheet Results
Wave summation is achieved by
You correctly answered: increasing the rate of stimulus delivery (frequency) to the muscle.
4
What is the difference between stimulus intensity and stimulus frequency?
Your answer:
The intensity of stimulus refers to the large voltage of electricity applied to Stimulating the muscle, whereas the stimulus frequency is how often the stimulus is administered Within a certain period of time.
1
In this experiment you observed the effect of stimulating the isolated skeletal muscle multiple times in a short period with complete relaxation between the stimuli. Describe the force of contraction with each subsequent stimulus. Are these results called treppe or wave summation?
Your answer:
The contraction style increases gradually with each subsequent stimulus because Increased efficiency of enzymes and the availability of calcium, this phenomenon is known as plasticia (ladder phenomenon).
2
How did the frequency of stimulation affect the amount of force generated by the isolated skeletal muscle when the frequency of stimulation was increased such that the muscle twitches did not fully relax between subsequent stimuli? Are these results called treppe or wave summation? How well did the results compare with your prediction?
Your answer:
The contraction rate increases because of the overlap of previous contractions, The phenomenon is called wave summation. The outcome is in line with the prediction that the force will be Increasing to maximum.
3
To achieve an active force of 5.2, did you have to increase the stimulus voltage above 8.5 volts? If not, how did you achieve an active force of 5.2? How well did the results compare with your prediction?
Your answer:
There's no need to increase voltage above 8.5 volts. Active style 5.2 achieved with Increasing stimulus frequency. The result is consistent with the predictions that the increase Frequency enough to boost the force.
4
Compare and contrast frequency-dependent wave summation with motor unit recruitment (previously observed by increasing the stimulus voltage). How are they similar? How was each achieved in the experiment? Explain how each is achieved in vivo. Your answer:
Wave summation increases the contraction style by increasing the stimulus frequency So contraction overlapped. Motor units boost force with Recruiting more motorcycle units through increased voltage. Both elevates Muscle style, but wave summation is achieved at high frequency, whereas chaff Achieved with increased intensity. In vivo, wave
summation occurred because Increased frequency of nerve impulses, while seizures occur with more activation Many motor neurons.
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