At the peak of the action potential, the electrical gradient of potassium ____.
A) is the same as during the resting potential
B) pulls sodium into the cell
C) pushes potassium out of the cell
D) pulls potassium into the cell

Question

Quizplus · Accepted Answer

During the peak of the action potential, the electrical gradient of potassium changes and becomes more positive outside the cell. As a result, potassium ions are pushed out of the cell due to electrostatic repulsion, leading to the repolarization phase of the action potential. This is in contrast to the resting potential, where the electrical gradient of potassium is balanced by the concentration gradient, leading to a steady state where potassium ions diffuse out of the cell at the same rate they are pumped in through the sodium-potassium pump. Option A is incorrect because the electrical gradient of potassium changes during the action potential. Option B is incorrect because the electrical gradient of sodium is more positive outside the cell than inside, so it would not be pulled into the cell during the peak of the action potential where the potential is already positive inside the cell. Option D is incorrect because the electrical gradient of potassium during the peak of the action potential pushes potassium ions out, not in.

At the Peak of the Action Potential, the Electrical Gradient