Fig. 1

Diagram of model components and fluxes. The bulk endoplasmic/sarcoplasmic reticulum [ Ca²⁺] is represented by c _{e r/s r} , the bulk cytosolic and external [ Ca²⁺] is c _cyt and c _ext respectively. Ca²⁺ channels are located on the ER/SR membrane forming release sites. The domain [ Ca²⁺] (\(c_{cyt}^{d}\) and \(c_{er/sr}^{d}\)) are rapidly changed by the release currents (J _rel ) when the number of open channels changes. Other fluxes considered in this model are: diffusion from cytosolic domain to the bulk cytosol (J _cyt ), diffusion from the bulk ER/SR to the luminal side domains (J _{e r/s r} ), a passive leak from the ER/SR to the cytosol (J _leak ), the SERCA pump flux that re-sequesters Ca²⁺ in to the ER/SR (J _pump ) and fluxes across the plasma membrane (J _pm )