A thermodynamic theory of temperature dependence of the conductivity in voltage clamp experiments on axons

An attempt is made at interpreting, on a physical basis, the results of mechanical and optical measurement of the nerve membrane swelling during excitation. We present a microscopic-scale theoretical description of two independent series of experiments: (1) measurements of the membrane conductivity as a function of depolarizing voltage and temperature, and (2) direct measurements of membrane swelling in the conductive state. The irreversible increase in the membrane resistance is attributed (quantitatively) to a phase transition taking place at temperature T=40°C. The microscopic parameters determined from measurements of transmembrane conductivity, substituted to the formula describing temperature dependence of membrane swelling, give the values in agreement with the direct measurements of swelling.