I’ve been trying to understand salutatory conduction in myelinated axons and want a better understanding of how depolarization at one node of Ravier causes an action potential at the next. Is it caused by the actual mechanical movement of sodium ions through the axon? There is an animated diagram at http://www.edumedia-sciences.com/a503_l2-saltatory-conduction.html [Broken] that shows positive ions passing along the axon from one node to the other. I have also read at http://en.wikipedia.org/wiki/Saltatory_conduction in the “Speed” section that, “It can be compared with a line of marbles pushing on each other - when poking the marble in one end then each marble only moves slightly, but this small effect on the marble in the other end is almost instantaneous.” Is it sort of like the movement of electricity in alternating current, where it is a shoving back and forth? If the effect from one node to the other is supposed to be at the speed of light -- (The speed of the signal from one node to the other is the speed of the induced electromagnetic wave, that is, the speed of light in interaction with transparent materials like the cytoplasm. http://en.wikipedia.org/wiki/Saltatory_conduction) – how could it be the movement of atoms (ions)? Or is it the passing of electrons from one ion to the next? I have limited math experience, so try to explain conceptually if possible.