Describe the events that occur in a nerve cell during an action potential.

Action potentials are the way in which information is conveyed along the length of a nerve cell and between nerve cells. At rest, the nerve cells membrane potential is around -70mV. During an action potential, sodium channels are stimulated and become open this allow sodium to flow down its concentration gradient into the cell. As sodium is a positively charged ion this causes the membrane potential inside the cell to become more positive. This process of increasing membrane potential is known as membrane depolarization. Once the membrane potential reaches around +30mV this causes the sodium channels to close and potassium channels to open allowing potassium to flow down its concentration gradient out of the nerve cell. This outward flow of positive charge potassium ions causes the cell's membrane potential to decrease in a process known as membrane repolarisation. This repolarisation occurs until the membrane potential reaches around -80mV at which point the potassium channels close. At this point, the nerve cell is in a state of hyperpolarization. Ion exchangers in the cell membrane then allow for compensatory exchange of ions across the cell membrane until the resting membrane potential is regained.