Problem:
An axon, an action potential is travelling down it. Freeze frame right when the AP is in the center, the site where you injected current, and consider that the sodium ions rushing in are analogous to injecting current.
Required:
Question: Describe what happens next, in both directions, from the standpoint of channels, currents, and voltages.
Again in the same axon, fully insulate a segment just ahead of the action potential, and again describe the channels, currents and voltages.
I dont need long explanation. Just few sentences of expanation.