The referenced video gives a detailed insight into the Equiibrium Potential Equations - Nernst Equation and Goldman–Hodgkin– Katz Equation. You do not want to miss out on this one for attaining maximum knowledge! Timeline: 00:30 Electrochemical Gradient 01:30 Equilibrium and Nernst Equation 04:00 Nernst Equation for Sodium 04:50 Reference to Membrane Potential 06:33 GHK Equation 08:22 Membrane Permeability Changes 12:30 Values and Application