To identify the type of membrane potential (graded receptor potential or action potential) that occurred at R1, R2, R3, and R4, you would typically assess the following:
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Graded Receptor Potential:
- These are local changes in membrane potential that are proportional to the strength of the stimulus. They can vary in amplitude and can summate.
- They occur in response to stimuli but do not necessarily result in an action potential unless they reach a certain threshold.
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Action Potential:
- This is a rapid, all-or-nothing depolarization of the membrane that occurs if the graded potential reaches a specific threshold.
- Action potentials are characteristic of neurons and muscle cells and involve a rapid influx of sodium ions, followed by potassium ion efflux.
With this understanding, you need to evaluate the response at R1, R2, R3, and R4 under a moderate stimulus:
- R1: If you observe a small change in membrane potential that varies with stimulus strength but does not reach a threshold, it would be a graded receptor potential.
- R2: If this response shows a stronger depolarization that also does not reach action potential threshold, this would again represent a graded receptor potential.
- R3: If a clear threshold is met and there is a rapid depolarization followed by repolarization, this would be classified as an action potential.
- R4: If the stimulus causes a similar larger change as R3 but does not reach a threshold, it would be another graded receptor potential. If there is a distinct action potential, then it would be classified as an action potential.
In summary, you will determine whether each response corresponds to a graded receptor potential or action potential based on whether the change in membrane potential reaches a threshold for firing an action potential or remains a graded response.
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