PhysioEx Lab Report
Exercise 3: Neurophysiology of Nerve Impulses Activity 3: The Action Potential: Threshold Name: 21-152 Cheryl Nathania Siahaan Date: 7 October 2021
Session ID: session-13f6d752-2129-e437-7837-1f0f2370c8a1
Pre-lab Quiz Results
You scored 100% by answering 4 out of 4 questions correctly.
Experiment Results
Predict Question
Stop & Think Questions Axons are
You correctly answered: long, thin structures that extend from a neuronal cell body.
1
Which of the following is easier?
You correctly answered: Extracellular recordings of the action potential.
2
An action potential is usually initiated in an axon at or near You correctly answered: all of the above.
3
The initiation of an action potential in a sensory neuron in the body normally You correctly answered: follows a sufficiently large depolarizing receptor potential.
4
Predict Question: How will the action potential at R1 (or R2) change as you continue to increase the stimulus voltage?
Your answer: The action potential will not change.
1
Why is the action potential recorded by the second recording electrode (R2) delayed relative to the action potential recorded by the first recording electrode (R1)?
You correctly answered: The action potential had to propagate from R1 to R2.
1
An increase in extracellular K would depolarize a neuron. This depolarization would occur if neurons were damaged. From what you have just learned about generating an action potential, what effect would this have on nearby axons? The nearby axonal membranes will _______.
You correctly answered: be depolarized to values near or above threshold voltages.
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10/7/21, 11:22 AM PhysioEx Exercise 3 Activity 3
Experiment Data Stimulus Voltage
(mv) Peak Value at R1
(μV) Peak Value at R2
(μV) Action Potential
10 0 0 No
20 100 100 Yes
30 100 100 Yes
40 100 100 Yes
50 100 100 Yes
Post-lab Quiz Results
You scored 100% by answering 3 out of 3 questions correctly.
The threshold voltage in an axon is usually 1
10/7/21, 11:22 AM PhysioEx Exercise 3 Activity 3
Review Sheet Results
If a graded receptor potential made the resting membrane potential of the axon more negative (for example, -70 mV changes to -75 mV), you would expect
You correctly answered: it to be more difficult for this axon to reach the threshold voltage.
2
Failure to reach the threshold voltage in the axon of a sensory neuron could be caused by You correctly answered: all of the above.
3
Define the term threshold as it applies to an action potential.
Your answer:
Threshold potential is the critical level to which a membrane potential must be depolarized to further initiate an action potential.
1
What change in membrane potential (depolarization or hyperpolarization) triggers an action potential?
Your answer:
Depolarization is the trigger of action potential.The membrane potential has to be less negative to initiate an action potential.
2
How did the action potential at R1 (or R2) change as you increased the stimulus voltage above the threshold voltage? How well did the results compare with your prediction?
Your answer:
Action potential didn't change even if the stimulus voltage increase.Action potential is a fixed value whenever it occurs because the event is not graded or in other words is known as "all-or-nothing" principle.Looking back at the experiment,the results were the same as my prediction.
3
An action potential is an "all-or-nothing" event. Explain what is meant by this phrase Your answer:
An action potential occurs when the membrane depolarises to a certain threshold, if this threshold is not reached the action potential will not be triggered.Action potential is not a graded value.Essentially, there will either be a full response or there will be no response at all.
4
What part of a neuron was investigated in this activity?
Your answer:
The part of neuron that was investigated in this activity is the trigger zone.This is where the axon hillock and the initial segment come together.
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