Understanding the electrical behavior of the action potential in terms of elementary electrical sources

A conceptof major importance in human electrophysiology studies is the processby which activation of an excitable cell results in a rapid rise and fallof the electrical membrane potential, the so-called action potential.Hodgkin and Huxley proposed a model to explain the ionic mecha-nisms underlying the formation of action potentials. However, thismodel is unsuitably complex for teaching purposes. In addition, theHodgkin and Huxley approach describes the shape of the actionpotential only in terms of ionic currents, i.e., it is unable to explain theelectrical significance of the action potential or describe the electricalfield arising from this source using basic concepts of electromagnetictheory. The goal of the present report was to propose a new model todescribe the electrical behaviour of the action potential in terms ofelementary electrical sources (in particular, dipoles). The efficacy ofthis model was tested through a closed-book written exam. Theproposed model increased the ability of students to appreciate thedistributed character of the action potential and also to recognize thatthis source spreads out along the fiber as function of space. Inaddition, the new approach allowed students to realize that theamplitude and sign of the extracellular electrical potential arising fromthe action potential are determined by the spatial derivative of thisintracellular source. The proposed model, which incorporates intuitivegraphical representations, has improved students’ understanding ofthe electrical potentials generated by bioelectrical sources and hasheightened their interest in bioelectricity.