Question

At label ________, the cell is not hyperpolarized; however, repolarization is in progress, as the sodium channels are inactivated or becoming inactivated, and many potassium channels have opened.

Answer 1

Answer: C

Explanation:

When a neuron receives a stimulus, the sodium channels present in the membrane are opened, and therefore Na+ enters the cell in favour of the concentration gradient, so that the membrane potential changes to positive by means of ion exchange, producing depolarization. If this depolarization reaches a certain threshold value, an action potential is generated. The next step is the opening of the potassium channels and the inactivation of the sodium channels, so that the repolarization of the membrane takes place. The sodium channels, will return to the closed state in the hyperpolarization to continue in this state during all the rest potential achieving the action potential to return to -70 mV (repolarization).; until the arrival of a new action potential which produces the activation and opening of the sodium channels, repeating the cycle again and generating a new depolarizing action. This process is part of the synaptic transmission.

So, hyperpolarization is any change in the cell's membrane potential, which makes it more polarized. This means, hyperpolarization is an increase in the absolute value of the cell's membrane potential. Thus, changes in membrane voltage where the membrane potential is more distinctly positive or negative are hyperpolarizations.

During the repolarization period after an action potential, the membrane potential is more negative than when the cell is in "rest period". In the picture, this repolarization period is about 1-2 milliseconds. So, repolarization is the time in which the membrane potential is hyperpolarized with respect to the resting potential.

In the attached figure, part C indicates this repolarization period.