Numerical simulations illustrating the mechanism of a stronger reduction of CL by βAR stimulation (βARs) in square lattice versus uniform random spatial distribution. Traces of membrane potential (V_m) are shown on the top panels. The stronger effect in the lattice case is due to its stronger effect on CRU recruitment (N_CRU, middle) and its attendant activation of I_NCX (bottom). Disorder in CRU positions substantially shortens the CL in basal state, but simultaneously decreases the effect of stimulation.