The soliton theory provides an alternative explanation for the nervous impulse based on cooperative melting transitions in the biomembrane. It relies on reversible electromechanical processes and the thermodynamics of membranes. During the nervous impulse, the membrane is shifted through its transition, with associated changes in heat capacity, compressibility and inherent time-scales. The latent heat of the transition explains the sign and the magnitude of the experimentally observed reversible heat production of the action potential and the observed changes in nerve dimension (shortening and increase in membrane thickness). The dimensional changes give rise to the possibility to excite the nerve mechanically or thermally.
In the transition, one finds fluctuations in the membrane permeability corresponding to spontaneous pore formation, which in a patch clamp experiment are indistinguishable from the quantized current events usually attributed to protein channels. They show most features of protein channels including temperature- and mechano-sensitivity, and voltage-gating. Their characteristic open time scales can be understood in the context of the fluctuation theorems applied to a membrane.
Membrane fluctuations therefore provide an estimate for the most suitable time-scale of membrane excitation. After a perturbation, relaxation processes in artificial membranes may display relaxation time scales up to several seconds. In biomembranes close to transitions, the expected relaxation time scales are expected to be in the millisecond regime. This is also the time scale of the open-lifetimes of membrane pores - and as it happens, the typical lifetime of protein channels. Therefore, we argue that this is also the time-scale of the most effective nerve membrane excitation.