## Membrane Potential Laboratory

 [K]i mM: Alpha:

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.