Hyperpolarization of Neurons

bruce raoul parnas brp at neuron.arc.nasa.gov
Fri Apr 29 11:02:22 EST 1994

In article <jstream-290494094838 at girch45.med.uth.tmc.edu>, jstream at girch1.med.uth.tmc.edu (Rifle River) writes:
|> In article <2potfp$gpi at news.arc.nasa.gov>, brp at neuron.arc.nasa.gov (bruce
|> raoul parnas) wrote:
|> > Actually, the negative resting potential derives even more from the Nernst
|> > potentials for the various ions present internally and externally.
|> Bruce, this is an excellent statement and it gets to the heart of the
|> reason
|> why the potential is negative (i/o).
|> > The
|> > resting potential would be negative even in the absence of any sort
|> > of pump mechanism.
|> However, this statement might be contradicted by some "sticklers".
|> Using, ouabain to inhibit the Na/K pump the squid  giant axon can
|> maintain its normal resting potential and it can fire action potentials
|> repeatedly (I don't recall the exact number but I think it was thousands).
|> However, without the Na/K pump the ion gradients will eventually be
|> depleted upon repetitive firing.  Therefore, one could conclude that
|> the Na/K pump is necessary, in the long run, for proper resting potential
|> and for repeated firing of action potentials.

I think this is completely true. I was thinking in the more "abstract"
rather than the "actual" sense. It was more of a cause-effect. The way
I see it, the ionic concentrations and resulting Nernst potential are
the "cause" of the observed "effect" (the negative rest potential. The
Na/K pumps are certainly necessary to maintain this situation because,
as you mention, the ionic concentration gradient would eventually
run down without some form of active maintenance.

So, I guess I would ammend the above to read

"The resting potential would be negative even in the absence of any sort
of pump mechanism, but it would not remain so in this situation"

|> +++++++++++++++                  
|> Rifle River                      
|> jstream at girch1.med.uth.tmc.edu    

dr bruce parnas
brp at psychomo.arc.nasa.gov
/usr/local/Std.Disclaimer:  The opinions expressed here are mine and
not those of NASA, but you probably could have guessed that.

It's not my fault.  Not all of us here at NASA are Rocket Scientists

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