The Action Potential:  Images

These following images should help you to see how the action potential moves along the axon's membrane.  Take a look at the animated figure (16 k) which includes these imagese in motion (it may not work on all web browsers) .

	At rest, the inside of the neuron is slightly negative due to a higher concentration of positively charged sodium ions outside the neuron.
	When stimulated past threshold, sodium channels open and sodium rushes into the axon, causing a region of positive charge within the axon.
	The region of positive charge causes nearby sodium channels to open. Just after the sodium channels close, the potassium channels open wide, and potassium exits the axon.
	This process continues as a chain-reaction along the axon.  The influx of sodium depolarizes the axon, and the ourflow of potassium repolarizes the axon.
	The sodium/potassium pump restores the resting concentrations of sodium and potassium ions