Sodium and Potassium ions tend to move inside of the axin when the membrane is depolarized.
A change in polarity occurs in the axon membrane when a nerve impulse travels across it. At the beginning of an action potential or nerve impulse , the ions of sodium tend to move inside of axon causing depolarization. As a result potassium ions tend to move outside of the axon causing re polarization. Hence, this effect causes the nerve impulse to travel in one direction only inside the axon.
