Calcium movement in nerve fibres

Abstract

Given the existence of a difference in electrical potential between the interior of a nerve cell and the media surrounding it, where the cytoplasm is some 70 mV negative (Hodgkin, 1958), it must be expected that any positively charged ion to which the cell membrane is permeable is more concentrated in the cell interior. For monovalent cations such as Na and divalent cations such as Ca and Mg this is not the case in the majority of the cells such as the squid giant axon. In other words, nerve cells maintain a lower intracellular concentration of these ions, as compared with their concentration in the extracellular fluid. For Mg, Ca and Na ions, this lower internal concentration must, in the steady state, be effected by some membrane based mechanism which consumes energy.