Ionic diffusion in membranes : I. A kinetic model for the squid axon conductances.

A fundamental approach to calculate the diffusion of ions through membranes is introduced. The membran eis considered as a heterogeneous structure with molecules that can have a selective affinity for a certain class of diffusing ions. To diffuse through a membrane an ion must become associated with, or dissolved into, at least one component of that membrane. Diffusion is produced by thermal jumps from one molecular site to another. It is assumed that the electric field can change the binding properties between ions and membrane molecules. The kinetics of the conductances are calculated from the chemical kinetic theory. The calculations are compared to the squid axon data and the unknown parameters are adjusted to fit the data curves. The results are very satisfactory. The calculated activation energies correspond to the measuredQ 10 in the squid axon. The calculated and measured action potentials are quite similar.