Ion channels, like most other proteins, are designed to move. To preserve ionic gradients across cell membranes, they are usually closed and open their gates only when called upon to do electric work. Ionic fluxes through open channels are exploited by cells for a variety of tasks, including the generation of explosive action potentials in excitable cells. A singular feature of the ion channels underlying action potentials is that their gates are regulated by the voltage across the plasma membrane.
Membrane potential has two roles in voltage-gated ion channels. It controls the open probability of their gates, especially the so-called activation gate, and it drives ions through open channels. The activation gate in this class of ion channel tends to be highly sensitive to small changes in membrane potential, so much so that a depolarization of only 5 mV can produce a 10-fold increase of...
