Nernst Potentials & Membrane
Ion concentrations on either side of a semipermeable membrane set the Nernst equilibrium voltage for each species. When several ions permeate with different permeabilities, the Goldman–Hodgkin–Katz equation estimates the zero-current (resting) potential. Sliders expose how extracellular potassium or relative sodium permeability shifts V_m.
Who it's for: Introductory biophysics or physiology students.
Key terms
- Nernst equation
- GHK voltage
- Resting potential
- Permeability
Cl⁻ uses fixed demo concentrations; tune P_K : P_Na : P_Cl to see how resting voltage shifts toward the dominant permeant ion.
Live graphs
How it works
Thermodynamic reversal potentials from concentration ratios, plus a Goldman–Hodgkin–Katz estimate of zero-current voltage when multiple ions permeate.
Frequently asked questions
- Why fix chloride concentrations in the GHK example?
- To keep the control panel tractable; chloride is included with illustrative intracellular/extracellular values so the GHK denominator is well posed.
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