this resting potential undergoes rhythmic oscillations, which have been termed "slow waves", and reflect intrinsic activity of slow wave potentials. these slow waves are caused by changes in the distribution of ca, na, k and cl ions between the intracellular and extracellular spaces, which, in turn, reflects the permeability of the plasma membrane to each of those ions. k is the major ion responsible for such changes in ion flux, reflecting changes in various k channels.