Nernst Equation for Cellular Membranes
The Nernst equation is used to determine the potential of an ion of charge across a membrane using both extracellular and intracellular concentrations. It can be written as[more]
, with .
is the equilibrium membrane potential in volts;
is the ideal gas constant;
is the temperature in Kelvin;
is Faraday's constant;
, , , and are the extracellular concentrations of potassium, sodium, chlorine, and calcium ions;
and , , , and are the intracellular concentrations of potassium, sodium, chlorine, and calcium ions.
The default setting of the Demonstration calculates the equilibrium potentials for ions in a mammalian cell.[less]
 D. H. Terman and G. B. Ermentrout, Foundations of Mathematical Neuroscience, New York: Springer, 2010 pp. 2–5.