Membrane Potential Laboratory
The interactive model presented below simultaneously plots membrane potentials
as predicted by the
- Nernst Equilibrium Relationship for K+, and the
- Goldman, Hodgin, Katz (GHK) equation.
The Nernst relationship for K+ is
$$E_k=60\textrm{log}\frac{[K^+]_o}{[K^+]_i} (mV)$$
and is depicted by the "blue" curve where
- [K+]o varies from 0.1 to 140.0 mM along the X axis and
- [K+]i is set by the investigator.
The GHK relationship is
$$V_m=60\textrm{log}\frac{[K^+]_o + \alpha[Na^+]_o}{[K^+]_i + \alpha[Na^+]_i} (mV)$$
It is depicted by the "orange" curve where
- [K+]o varies from 0.1 to 140.0 mM and
- [K+]i and alpha are set by the investigator.
- [Na+]o is set to 145 mM.
- [Na+]i is set to 17 mM.
Experiment with altering [K+]i and/or alpha to
see how changes in these values alter the membrane potential for any given
value of [K+]o.