How to Use a sodium potassium pump
This is a great video presentation of how Sodium Potassium Pump can maintain a voltage gradient across a cell. It also discusses various things like the differences between positive and negative charges and positive and less positive charges etc. The video tries to explain a lot of things happen within a cell when you fluctuate the voltage of sodium as well as positive and negative ions within a cell. You must watch it yourself to see the changes happen within a cell when you make some changes.