Real spine geometries show size dependence for calcium dynamics. (a) Spines similar to the idealized geometries were selected from a reconstructed dendrite (Wu et al., 2017). Representative filopodia-shaped spines, thin spines, and mushroom spines were selected and labeled with their volume and shape. Scale bars, 0.5 μm. (b) Snapshots at 15 and 30 ms for a single seed for a filopodia-shaped spine (i), thin spine (ii), and mushroom spine (iii). (c) Calcium transients as means and SD, along with variance over time for the realistic spines of different shapes: (i and ii) filopodia-shaped spines, (iii and iv) thin spines, and (v and vi) mushroom spines. The realistic spines are labeled with their volumes.