A model for channel noise,including the effect of diffusion

A model (based on a proposal by Schick (1974), is developed for channels composed of four species; the channels allow conduction when all species are in the correct configuration. Allowance is also made for diffusion resulting from depletion of ions in the neighbourhood of the channel. The result is a series of pulses in which the current falls as ^–1/2 upon closing the channel. The resulting power spectrum is calculated according to the method given by Schick and earlier workers, and is found to be, at least qualitatively, in agreement with many of the features of noise measured for certain types of nerve membranes. The calculations are not linearized, but are carried through numerically.