What is hypopolarization?

What is hypopolarization?

• A. A state where the resting membrane potential (RMP) is reset to a more positive number than normal, shortening the polar gap and making cells more sensitive.
• B. A state where the RMP drops to more negative values, increasing membrane stability.
• C. RMP becomes less positive than normal, reducing excitability.
• D. Cells become refractory to stimulation.

Answer: (A)

The main idea is how the resting membrane potential (RMP) determines how easily a cell fires. Hypopolarization means the membrane potential becomes less negative (more positive) than normal, moving closer to the threshold for an action potential. Because the inside is closer to the voltage needed to open voltage-gated channels, excitatory inputs are more likely to push the cell over the threshold, so the cell becomes more excitable. This is why describing hypopolarization as the RMP shifting to a more positive value and shortening the distance to threshold captures the essence: easier to reach firing. In contrast, if the RMP were more negative (hyperpolarization), the cell would be harder to excite, and becoming less positive than normal would reduce excitability. The idea of the cell becoming refractory is a separate state tied to the recovery period after firing, not a shift in the baseline membrane potential.

The main idea is how the resting membrane potential (RMP) determines how easily a cell fires. Hypopolarization means the membrane potential becomes less negative (more positive) than normal, moving closer to the threshold for an action potential. Because the inside is closer to the voltage needed to open voltage-gated channels, excitatory inputs are more likely to push the cell over the threshold, so the cell becomes more excitable. This is why describing hypopolarization as the RMP shifting to a more positive value and shortening the distance to threshold captures the essence: easier to reach firing. In contrast, if the RMP were more negative (hyperpolarization), the cell would be harder to excite, and becoming less positive than normal would reduce excitability. The idea of the cell becoming refractory is a separate state tied to the recovery period after firing, not a shift in the baseline membrane potential.