  Recent studies have revealed the complex structure of nerve signals in axons.
There is experimental evidence that the propagation of an electrical signal
(action potential) is accompanied by mechanical and thermal effects. In this
paper, first an overview is presented on experimental results and possible
mechanisms of electromechanophysiological couplings which govern the signal
formation in axons. This forms a basis for building up a mathematical model
describing an ensemble of waves. Three physical mechanisms responsible for
coupling are (i) electric-lipid bi-layer interaction resulting in the
mechanical wave in biomembrane; (ii) electric-fluid interaction resulting in
the mechanical wave in the axoplasm; (iii) electric-fluid interaction resulting
in the temperature change in axoplasm. The influence of possible changes in
variables which could have a role for interactions are analysed and the concept
of internal variables introduced for describing the endothermic processes. The
previously proposed mathematical model is modified reflecting the possible
physical explanation of these interactions.
