What happens during the depolarization phase of nerve cells? a. the cell membrane decreases its permeability to sodium. b. a rapid change in polarity to one that is positive on the inside, and the membrane becomes open to sodium ions. c. it is an undisturbed period of the action potential during which the nerve is not transmitting impulses. d. the neurons are stimulated to fire.

The correct option is b. A rapid change in polarity to one that is positive on the inside, and the membrane becomes open to sodium ions.

Explanation:

Depolarization refers to the increase in electrical charge along the cell membrane (the stimulation of a neuron, causes an electrical change of sufficient excitatory intensity in the neuron membrane), allowing the opening of the sodium channels that are in the membrane, letting the flow of positive ions to enter to the interior of the cell when its channels open. In this way, the potential changes, since the inside of the neuron becomes positive and the outside is negative, due to the positively charged sodium ions inside the neuron membrane.