Models Of Membrane Excitability

Abstract

In this chapter we will examine models of the onset and propagation of a traveling action potential, including the powerful phenomenological model, the Hodgkin and Huxley (HH) model. 1 This milestone work, based on quantitative interpretation of experimental data, has determined the direction of progress in electrophysiology for decades, led to numerous experimental discoveries and spawned many related models. We will review its assumptions, the way its equations are interpreted and the predictions this model has produced. While a successful phenomenological model is a great step forward, it is not the solution of the problem. The HH and related models, based as they are on macroscopic measurements, cannot be expected to explain what is happening at the molecular level. Still, it was not long before speculative models of the workings of the ion channel molecules began to appear. A scientific problem is solved only when the behavior of the system can be derived from a priori principles, and that still remains to be done for the processes underlying nerve and muscle excitability.