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Old 07-31-2011
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Question Membrane potential measured inside or outside?

I am a little confused on how membrane potential is measured? inside or outside of cell? when a negative sign is given in front of the votage, what does it mean? e.g. -90 mV
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Old 07-31-2011
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nice video!
http://www.cvphysiology.com/Arrhythmias/A007.htm

btw, is the inside relative to the outside!
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Old 07-31-2011
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Thanks so much, Bebix, you are outstanding!
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Old 08-01-2011
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Resting membrane potential
is expressed as the measured potential difference across the cell membrane in
millivolts (mV).
is, by convention, expressed as the intracellular potential relative to the extracellular
potential. Thus, a resting membrane potential of
-70 mV means 70 mY,
cell negative.

1.
The resting membrane potential is established by diffusion potentials that
result from concentration differences of permeant ions.

2. Each permeable ion attempts to drive the membrane potential toward its
equilibrium potential.
Ions with the highest permeabilities, or conductances,
will make the greatest contributions to the resting membrane potential, and
those with the lowest permeabilities will make little or no contribution.

3. For example,
the resting membrane potential of nerve is -70 mV, which is close
to the calculated K+ equilibrium potential of
-85 mV, but far from the calculated
Na+ equilibrium potential of
+65 mV. At rest, the nerve membrane is far more
permeable to K+ than to Na+.

4. The Na+-K+ pump contributes only indirectly
to the resting membrane potential
by maintaining, across the cell membrane, the Na+ and K+ concentration
gradients that then produce diffusion potentials. The direct electrogenic contribution
of the pump (3 Na+ pumped out of the cell for every 2 K+ pumped into

the cell) is small.

BRS Physiology , hope this helps !
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