Potassium

[tchristifulli]

I'm refreshing on SA node potential and I can't wrap my mind around something. For one why is potassium labeled K+ if it has a cell voltage of -92?
Secondly how does potassium leaving the cell drive is back down to phase 0?

 

[tchristifulli]

I mean phase 4

 

[EMT B]

Since potassium remains in the cell against its concentration gradient, it requires about -92mV of force to keep it in the cell, as the extracellular forces want to move the potassium out, while the potassium wants to stay in. That is not to say that potassium has a charge of -92. Potassium has a charge of +1

http://www.austincc.edu/emeyerth/mempot1.htm

 

[Ewok Jerky]

dont confuse ion charge (molecular) with membrane potentials (cellular).

 

[CriticalCareIFT]

K+ is always a cation, that -92 is not referring to K+ charge. It's resting membrane potential on the cardiac cell, and is around -90mv internally polarized negatively at the resting state.

 

[Christopher]

I'm refreshing on SA node potential and I can't wrap my mind around something. For one why is potassium labeled K+ if it has a cell voltage of -92?
Secondly how does potassium leaving the cell drive is back down to phase 0?

A net outward flow of positive ions results in a negative membrane potential.

This is like looking at a positive wave going away from you on an ECG.

The cell sits at -90mV due to some inward flow of Na+ and Ca2+, which keeps the cell from being dominated by K+'s gradient.

I'm actually giving a lecture on this very topic this month for con ed (if you're in Southeastern NC for some bizarre reason).

I highly recommend you review this series of Khan Academy videos. It seriously will answer ALL of your questions related to this topic!

 

[EMT B]

he was actually asking about those videos and was confused at one point in the video.