On the Reversible Abrupt Structural Changes in Nerve Fibers Underlying Their Excitation and Conduction Processes

The cortical gel layer of nerve fibers has the properties of a cationexchanger. Hence, this layer can, and actually does, undergo a reversible abrupt structural change when monovalent cations (e.g. Na+) are substituted for the divalent counter-ions (e.g. Ca2+). This structural change brings about a sudden rise in the water content of the layer which in turn produces a large enhancement of cation mobilities accompanied by a shift of ion-selectivity in favor of hydrophilic cations. Based on these grounds, it is argued that the electrophysiological processes known as “nerve excitation and conduction” are, basically, manifestations of abrupt structural changes in the cortical gel layer. In recent studies, we have shown that several aspects of the excitation phenomena can actually be reproduced by using synthetic polyanionic hydrogels in place of living nervous tissues. It is noted that these studies of synthetic model systems lead us to a better understanding of the process of divalent-monovalent cation-exchange in natural and artificial polyanionic gels.