EK bio, action potential (p86)

[anbuitachi]

on Page 86, they drew a action potential with 5 sets of protein channels labelled 1-5 and they said 5 already received action potential and 1 is about to have it. they described it as

1) membrane at rest, Na and K channels are closed
2) sodium channel opens and cell depolarizes
3) potassium channels open as Na channels inactivate
4) Na channels are inactivated. pen potassium channels repolarize membrane
5) potassium channels close and membrane equilibrate to its resting potential.

I don't understand why the action potential is going from right to left (as in 5 already received it and 1 is about to have it)

Can someone explain please. thanks

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[fizzgig]

1-5 is the order of stuff that happens when an AP passes. so each channel set goes through all 5 steps. 1 hasn't begun and 5 is on the final step. since 5 is on the final step, it must have started the process earlier. it's like doing the wave. if the dude on the right is currently bringing his arms down and the guy on the left is raising his arms, the wave has passed dude on right and is heading toward guy on left.

 

[anbuitachi]

oh ... thanks

 

[Phantastic]

The depolarization travels down the axon, and in the case of saltatory conduction, moves between myelinated sheaths at sites called Nodes of Ranvier.

The depolarization spontaneously causes the next sodium channel to open in the chain etc. because the ions are shared inside the neuron.