Now, these neurons differ from one another not only in their size and shape, but they also differ in the speed at which they move the action potential along the axon of that neuron. Now, some of these neurons in our body are capable of moving action potential potentials at speeds over 100 meters/second, while other neurons are capable of moving action potentials at speeds of only 1 meter/second. The question is, what exactly determines the speed at which that action potential moves along the axon of the neuron within our body? Now, let's begin by recalling some physics. Now, if we study the movement of the action potential along the axon from a physics perspective, we see that the action potential is nothing more than a moving electric current and the axon is nothing more than a biological wire. So recall that what determines the velocity with which the current moves inside the wire is the resistance of that wire to the flow of that current.