<P> Action potentials result from the presence in a cell's membrane of special types of voltage - gated ion channels . A voltage - gated ion channel is a cluster of proteins embedded in the membrane that has three key properties: </P> <Ol> <Li> It is capable of assuming more than one conformation . </Li> <Li> At least one of the conformations creates a channel through the membrane that is permeable to specific types of ions . </Li> <Li> The transition between conformations is influenced by the membrane potential . </Li> </Ol> <Li> It is capable of assuming more than one conformation . </Li> <Li> At least one of the conformations creates a channel through the membrane that is permeable to specific types of ions . </Li>

The action potential travels in the direction of