Problem:
Question 1: When the membrane of an axon depolarizes to threshold, voltage-gated sodium channels open. Explain how this creates a positive feedback loop. Now, explain why this feedback loop doesn't continue forever.
Question 2: Inject some current at a center point along the length of an axon. If the voltage crosses threshold, describe what happens next, in both directions, from the standpoint of channels, currents, and voltages.
Question 3: Using the same axon, but 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. Describe what happens next, in both directions, from the standpoint of channels, currents, and voltages.
Question 4: Again in the same axon, fully insulate a segment just ahead of the action potential, and again describe the channels, currents and voltages.
Please can anyone help me to answer these question in detail.