The action potential is caused by permeability changes in the plasma membrane.

True

Explanation:

During resting potential, the inside of the membrane is more negative compared to the outside. The activation gates of Na + channels are closed and the membrane is impermeable for sodium ions. When a stimulus is strong enough to fire an action potential, change in the shape of the channel proteins opens the activation gates.

Now, the gated Na + channels are opened making the membrane more permeable for sodium ions. The membrane is permeable for sodium ions for a brief period only when both activation and inactivation gates are open. This allows the entry of sodium ions inside the axon and makes is more positive.