Voltage-gated ion channels of excitable tissue have evolved an exquisite sensitivity to membrane potential. The open probability of a typical potassium or sodium channel, for example, may be increased by two orders of magnitude in response to a depolarization of less than 10 mV (Zagotta et al., 1994; Hirschberg et al., 1995). As recognized by Hodgkin and Huxley (1952), this responsiveness to ch...
