How to Quantify the Electrical Voltage in a Spherical Cow

In order to quantify the electrical voltage in the cell, you have to account for all the ion channels that exist and all the currents that pass through. Some of the models have up to 100 differential equations just for one cell. You can end up having millions of cardiac cells you have to simulate when you go to the or 3D realistic hearts. Sometimes it takes many, many hours to do just a couple of seconds.