Effect of Poisson clumping: Clusterization of CRUs and emergence of voids as disorder in CRU locations increases. Left: The cell cylinder surfaces unwrapping to squares with examples of distributions of RyR clusters under the cell membrane with varying degrees of disorder used in our simulations of SAN cell function. 555 CRUs are distributed in each case. SD values of normal distributions used to perturb CRU locations from their perfect square lattice positions are shown in respective labels above each image. Right: Histograms of the respective distributions of nearest neighbor distances with their mean and SD values (in μm).