resting potential and K+ [HAPP-L]

["Pat Bowne" <Pat.Bowne@xxxxxxxxxxx>]

I switched texts this year and now I'm confused about something I thought I understood. 

I understood, and all my texts agree, that opening the K+ channels and allowing K+ to diffuse out of the cell would hyperpolarize the cell, lowering its resting potential.

But my new text has a question in it about what will happen if you remove K+ from the intracellular fluid. It explains that removing K+ will decrease the concentration gradient and therefore less K+ will diffuse out of the cell, so the cell will be HYPOpolarized. This makes sense mathematically, when I plug the values into the Nernst equation; a decrease in intracellular K+ has the same depolarizing effect as an increase in extracellular K+.

BUT if that is the case, how could opening K+ channels hyperpolarize a cell? When K+ channels open and K+ diffuses out of the cell, internal K+ decreases AND external K+ increases, and you ought to have a doubled depolarizing effect!

Help!

Patricia S. Bowne
Biology Department
Alverno College
3401 S. 39th St.
Milwaukee, WI  53234

pat.bowne@xxxxxxxxxxx 


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