Pnb 2274 lab Practical 2 Review
Questions with All Solved Solutions.
A motor unit includes: - Answer Multiple muscle fibers innervated by one motor neuron
The EMG is a recording of: - Answer The action potentials of the innervated muscle fibers
In this week's lab, we will be using a transducer - Answer False (transducer converts a
mechanical signal into an analog voltage
The PowerLab hardware is NOT designed to: - Answer Display a signal
reciprocal activation - Answer simultaneous activation of an agonist muscle and inhibition of
an antagonist muscle
co-contraction - Answer simultaneous contraction of both the agonist and the antagonist
muscles around a joint
The figure shown above is an example of: - Answer co-contraction
Which of the following is an acceptable scientific hypothesis? - Answer Genetically modified
tomatoes contain more fructose than conventional tomatoes.
When placing recording electrodes on the biceps and triceps: - Answer Ensure that the
electrodes are in good contact with the skin.
During your recording, you see a flat line being recorded. What should you do? - Answer
Adjust the scale immediately.
Calculate the sampling rate in the image. It shows a rate of: - Answer 10 samples per second
What happens to your EMG signal when you increase the contraction strength? Explain the
observation. - Answer The peaks are larger
During reciprocal activation, why is the antagonist muscle not completely silent? - Answer It
is an antagonist pairing and the both work to stabilize the arm and joint
, Frame your question in the form of an experimentally testable hypothesis. - Answer If an
overhead triceps extension is performed using a heavier weight, the RMS triceps will be higher
than the RMS triceps without the weight because the heavier weight provides a greater
resistance.
Design the experiment you will do to examine the hypothesis you formulated above. Make sure
you include all the equipment you will need, the number of volunteers required, and that you
list all the measurements you are going to make. - Answer In this experiment, 2 people are
required. The first person will be connected to the electrodes and will be performing the
exercise with a 5 pound weight while the other person will hit the start and stop button. First
we will perform a control by recording the muscle activity while the arm is performing 3
repetitions of the exercise without a weight. After a resting period of 2 minutes, we will record
three repetitions of the overhead triceps extension using a two pound weight. After resting
period of 2 minutes, perform three repetitions of the overhead triceps extension using a five
pound weight. Compare sets of data.
Unlike the discrete waveform from an electrocardiogram, the electromyogram waveform is
irregular. Why do you suppose this is? - Answer Electrocardiograms record cardiac muscle
which all contract at the same time but electromyograms record skeletal muscle which do not
contract at the same time. These asynchronously contracting muscle fibers cause an irregular
waveform.
Which of the following statements about electromyography (EMG) recording is NOT true? -
Answer EMG is a technique that measures the contractile force of the muscles. EMG signals
are recorded from multiple muscle fibers.
Based on your recorded EMG trace and the values you measured in Exercise 1, describe this
phenomenon qualitatively. - Answer The biceps and triceps muscles work by reciprocal
activation, meaning that while one is contracted the other is relaxed, because they are
antagonistic muscles. It is shows through the data from the table on the left. When the biceps
are contracting by flexing the arm, the biceps have a larger EMG amplitude than the triceps.
When the arm is extended, the triceps are contracting while the biceps are relaxing, which is
shown by the larger EMG amplitude in the triceps. The table on the right shows that as you
increase the weight or force that the muscles have to exert on, the EMG amplitude of the
muscles contracting together increases, as expected.
Feedback: The agonist muscle is mainly activated, while the antagonist is partially inhibited.
In your own words, explain how the EMG trace changed when you added weights to your arm?
Based on the data you collected what can you infer is happening to the muscles as weight is
added? - Answer As you increase the weight, more motor units need to be recruited in order
to contract the muscle. This was seen in the data as the electrical activity of the muscles
increased as weight was added to the arm.
Questions with All Solved Solutions.
A motor unit includes: - Answer Multiple muscle fibers innervated by one motor neuron
The EMG is a recording of: - Answer The action potentials of the innervated muscle fibers
In this week's lab, we will be using a transducer - Answer False (transducer converts a
mechanical signal into an analog voltage
The PowerLab hardware is NOT designed to: - Answer Display a signal
reciprocal activation - Answer simultaneous activation of an agonist muscle and inhibition of
an antagonist muscle
co-contraction - Answer simultaneous contraction of both the agonist and the antagonist
muscles around a joint
The figure shown above is an example of: - Answer co-contraction
Which of the following is an acceptable scientific hypothesis? - Answer Genetically modified
tomatoes contain more fructose than conventional tomatoes.
When placing recording electrodes on the biceps and triceps: - Answer Ensure that the
electrodes are in good contact with the skin.
During your recording, you see a flat line being recorded. What should you do? - Answer
Adjust the scale immediately.
Calculate the sampling rate in the image. It shows a rate of: - Answer 10 samples per second
What happens to your EMG signal when you increase the contraction strength? Explain the
observation. - Answer The peaks are larger
During reciprocal activation, why is the antagonist muscle not completely silent? - Answer It
is an antagonist pairing and the both work to stabilize the arm and joint
, Frame your question in the form of an experimentally testable hypothesis. - Answer If an
overhead triceps extension is performed using a heavier weight, the RMS triceps will be higher
than the RMS triceps without the weight because the heavier weight provides a greater
resistance.
Design the experiment you will do to examine the hypothesis you formulated above. Make sure
you include all the equipment you will need, the number of volunteers required, and that you
list all the measurements you are going to make. - Answer In this experiment, 2 people are
required. The first person will be connected to the electrodes and will be performing the
exercise with a 5 pound weight while the other person will hit the start and stop button. First
we will perform a control by recording the muscle activity while the arm is performing 3
repetitions of the exercise without a weight. After a resting period of 2 minutes, we will record
three repetitions of the overhead triceps extension using a two pound weight. After resting
period of 2 minutes, perform three repetitions of the overhead triceps extension using a five
pound weight. Compare sets of data.
Unlike the discrete waveform from an electrocardiogram, the electromyogram waveform is
irregular. Why do you suppose this is? - Answer Electrocardiograms record cardiac muscle
which all contract at the same time but electromyograms record skeletal muscle which do not
contract at the same time. These asynchronously contracting muscle fibers cause an irregular
waveform.
Which of the following statements about electromyography (EMG) recording is NOT true? -
Answer EMG is a technique that measures the contractile force of the muscles. EMG signals
are recorded from multiple muscle fibers.
Based on your recorded EMG trace and the values you measured in Exercise 1, describe this
phenomenon qualitatively. - Answer The biceps and triceps muscles work by reciprocal
activation, meaning that while one is contracted the other is relaxed, because they are
antagonistic muscles. It is shows through the data from the table on the left. When the biceps
are contracting by flexing the arm, the biceps have a larger EMG amplitude than the triceps.
When the arm is extended, the triceps are contracting while the biceps are relaxing, which is
shown by the larger EMG amplitude in the triceps. The table on the right shows that as you
increase the weight or force that the muscles have to exert on, the EMG amplitude of the
muscles contracting together increases, as expected.
Feedback: The agonist muscle is mainly activated, while the antagonist is partially inhibited.
In your own words, explain how the EMG trace changed when you added weights to your arm?
Based on the data you collected what can you infer is happening to the muscles as weight is
added? - Answer As you increase the weight, more motor units need to be recruited in order
to contract the muscle. This was seen in the data as the electrical activity of the muscles
increased as weight was added to the arm.
