Movement of ions through fixed pores in the neural membrane.

A simple configuration is first proposed for the pores used by sodium and potassium ions in moving through the neural membrane. The voltage dependence of the ion current through a system of such pores is then derived from diffusion theory and shown not to agree well with experimental observation. Good agreement is obtained, however, when the end segments of the pores are modified to include constrictions and ion-specific trapping centers.