Na+/K+ channels

[chiddler]

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3 sodiums out, and 2 potassiums in for 1 ATP. Cells with the resting membrane potential also have potassium leak channels that allow the slightly negative charge.

So I haven't really started reviewing neurobio, but this doesn't make sense from what I already know: action potentials cause depolarization, which means sodium rushes into the cell and potassium out. Why would potassium go into the cell if there is a leak channel already that allows it to be at equilibrium?

 

[MedPR]

3 sodiums out, and 2 potassiums in for 1 ATP. Cells with the resting membrane potential also have potassium leak channels that allow the slightly negative charge.

So I haven't really started reviewing neurobio, but this doesn't make sense from what I already know: action potentials cause depolarization, which means sodium rushes into the cell and potassium out. Why would potassium go into the cell if there is a leak channel already that allows it to be at equilibrium?

Depolarization doesn't really involve potassium "rushing out" of the cell. During depol, both the sodium voltage gated channels and the potassium channels are opening, but the sodium channels open way faster than the potassium channels, so more sodium moves in than potassium moves out.

Remember that interstitial fluid has a higher concentration of sodium and intracellular fluid has a higher concentration of potassium.

When the potassium channels are finally completely open, the sodium channels are closing/have closed and the cell is depolarized (+70mv in nervous cells I think). Now potassium starts to move out of the cell due to its concentration gradient as well as the newly created electron/charge gradient created by the sodium.

Eventually the potassium channels close and the Na/K ATP-ase stabilizes the membrane potential and sets it back to the resting potential.

I'm not exactly sure how to answer your question because I don't know when K+ goes into the cell passively..?

 

[chiddler]

I'm not exactly sure how to answer your question because I don't know when K+ goes into the cell passively..?

?

you answered it very well xD

thank you.