Structural complexity, circuit models, and ion accumulation.

Changes in ion concentration can be expected to accompany natural activity in any preparation with infolded membranes or narrow spaces between cells. Such preparations have complex electrical properties because some of the membranes are isolated by the resistance of the solution in narrow extracellular spaces. Analyses of the diffusional and electrical consequences of these structural complexities are intimately related: both require morphometric measurement and theoretical analysis of the the structure. The measured properties of complex tissues, either diffusional or electrical, depend on the properties of many membranes and intra- and extracellular compartments. Fitting a structural theory to one type of experimental data separates some of the measured properties of the tissue into the properties of its components. Fitting electrical data alone give many electrical parameters of the tissue components. Fitting diffusional data alone may give some of the permeability and diffusional parameters of the tissue components. A complete understanding of ion accumulation probably requires a concomitant analysis of elctrical properties.