Fig. 1

Schematic of 3 coupled CRUs with network labels μ−1, μ and μ+1 showing the regions of the the different Ca ²⁺ concentrations: subsarcolemmal space (\(c_{\mathrm {s}}^{\mu }\)), bulk cytsosol (\(c_{\mathrm {i}}^{\mu }\)), unrecruited SR (\(c_{\mathrm {u}}^{\mu })\) and total Ca ²⁺ concentration in the SR (\(c_{\mathrm {j}}^{\mu }\)). The orange bidirectional arrows represent Ca ²⁺ diffusion though the bulk cytosol with time constant τ_c and through the SR with time constant τ_sr, respectively