Half the class correctly answers the question. You decide to throw them a softball question on the quiz/exam:įor a typical cell at rest, what happens to the membrane potential if the extracellular potassium concentration is increased? Then, you show one of the things that many students dread the most. indeed, the most important processes in our lives. These are phenomena that underlie every thought, every emotion, every action. You connect these ideas to the basis of the action potential, highlighting that these electrical events are intimately coupled to subsequent chemical and mechanical events. You show carefully constructed animations of ions moving across the membrane (or not) depending on the permeability of the membrane to those ions. You explain that biologically-relevant ions carry electrical charge and that they're distributed in different concentrations inside and outside the cell. It's time to introduce them to a conceptual cornerstone in physiology. Imagine that you're teaching a class filled with budding young minds. There are few concepts in physiology that cause as much initial bewilderment as how membrane potentials work.