Nernst and Goldman (Interactive)

Nernst and Goldman

$$E_r = \frac{RT}{zF}\ln\left(\frac{[\text{Ion}]_\text{out}}{[\text{Ion}]_\text{in}}\right)$$

$$E_m = \frac{RT}{F}\ln\left(\frac{ P_{\text{K}^+}[\text{K}^+]_\text{out} + P_{\text{Na}^+}[\text{Na}^+]_\text{out} + P_{\text{Cl}^-}[\text{Cl}^-]_\text{in}} {P_{\text{K}^+}[\text{K}^+]_\text{in} + P_{\text{Na}^+}[\text{Na}^+]_\text{in} + P_{\text{Cl}^-}[\text{Cl}^-]_\text{out}}\right)$$

Top controls

Temperature (K)

310

Voltage coloration Scope indicators

-65.0 mV

Mode

Goldman Nernst Na⁺ Nernst K⁺ Nernst Cl^-

Concentrations

[Na⁺] out / in

440 / 50

[K⁺] out / in

20 / 400

[Cl^-] out / in

560 / 52

Each ion uses one “membrane” control: top thumb = outside, bottom thumb = inside.

Permeabilities

P_Na (log10)

P_K (log10)

500

P_Cl (log10)

In Goldman mode, permeabilities control the membrane potential. In Nernst modes, permeabilities are ignored (but still visualized as channels).

Reset

Resets concentrations, permeabilities, temperature, and the scope trace.

Top: cell + ions + channels. Bottom: oscilloscope trace.