During the relative refractory period, an initial threshold-level depolarization is usually not sufficient to trigger an action potential. Why?

A) Some Na+ channels have returned to their resting position and K+ channels are still open, so Na+ entry is offset by K+ loss.
B) Only some Na+ channels have returned to their resting position.
C) Only K+ channels are still open, so Na+ entry is offset by K+ loss.
D) The statement is incorrect; a threshold-level depolarization always triggers an action potential.
E) Only a few K+ channels have returned to their resting position.


A) Some Na+ channels have returned to their resting position and K+ channels are still open, so Na+ entry is offset by K+ loss.

Anatomy & Physiology

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Anatomy & Physiology

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Anatomy & Physiology

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Anatomy & Physiology

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Fill in the blank(s) with the appropriate word(s).

Anatomy & Physiology