current in an axon

[C. Wigren]

Can anyone out there provide me (a high school teacher) with a simple 
analogy or explanation on the propagation of current in an axon bringing 
into play concepts such as resistance, voltage, current, and the way the 
membrane (channels), intracellular and extracellular fluid come into 
play.  The only one I can come up with is a line of dominoes in which the 
effect is felt at the beginning and subsequently at the end but in which 
other than the dominoes falling over, no other displacement has occurred

Carl Wigren