ABSTRACT
The ultramicroscopic membrane that surrounds a neuron and demarcates it from neighboring cells does more than merely contain the cytoplasmic gel. Fluctuations in the permeability characteristics of the membrane are the source of all neuroelectric activity. The membrane accomplishes extraordinary functions because of its ability to pass some ions into or out of the neuron selectively, while barring the movement of others, and to individually vary the permeability to various ions over time. This variable selective and differential permeability to ions at the molecular level is thus the ultimate source of all responses at the behavioral level.
