Refer to the following graph of an action potential to answer the question.

Which Roman numeral in the graph indicates when the neuronal membrane is at its resting potential?

Question

Refer to the following graph of an action potential to answer the question.

Which Roman numeral in the graph indicates when the neuronal membrane is at its resting potential?

BlackTom AI · Accepted Answer

Begin by identifying what resting potential means in an action potential graph: it is the stable, baseline membrane potential when the neuron is not actively transmitting signals, typically around -70 mV. 
Option I: This label appears near the initial segment of the curve, corresponding to the small initial depolarization before the rapid rise. It does not represent the stable resting state, so this choice is incorrect. 
Option II: This mark aligns with the peak of the action potential, where the membrane is most depolarized (about +30 to +35 mV). Since resting potential is the baseline, not the peak, II is not correct. 
Option III: This label sits along the plateau or after the peak, not at the baseline. It does not indicate the resting state, so III is incorrect. 
Option IV: This label corresponds to the trough after repolarization, when the membrane briefly becomes more negative than the resting potential (hyperpolarization) before settling back to baseline. Although it is close to the resting potential, the standard resting potential is represented by the baseline level, which is indicated by V in this graph. Therefore, IV is not the resting potential. 
Option V: This mark aligns with the baseline membrane potential, the stable state when no action potential is occurring. It matches the typical resting potential around -70 mV and is consistent with the graph’s horizontal resting level. Consequently, V correctly denotes resting potential. 
In summary, the resting potential is the steady, baseline level of membrane potential, which the graph marks as V, while the other Roman numerals correspond to depolarization (I, II) or hyperpolarization/return to baseline (III, IV).

Bio 93 Section CDE 2025 Final Exam Practice, Part 1

Refer to the following graph of an action potential to answer the question. Which Roman numeral in the graph indicates when the neuronal membrane is at its resting potential?

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