Internal variables used for describing the signal propagation in axons

Abstract

In this paper, the concept of internal variables developed in continuum mechanics is briefly described and then applied to the modelling of temperature change accompanying the propagation of signals in nerve fibres. The internal variable describes the exothermic and endothermic processes and involves the relaxation time measured in experiments. The model is based on using the FitzHugh and Nagumo idea for calculating the action potential with one generalised ion current. In the case of more detailed modelling like the Hodgkin–Huxley approach, sodium and potassium ion currents could be taken into account separately which dictates two internal variables. Such a phenomenological modelling of functional dependencies should be checked by experimental studies.