Hierarchical clustering of ryanodine receptors enables emergence of a calcium clock in sinoatrial node cells

Video 1.
Periodic global calcium waves in a 3-D model of SANCs with initial SR calcium load of 1.15 mM. In this SANC model, couplons were spaced regularly at 0.7-µm spacing longitudinally and azimuthally. RyR cooperativity was set to 3. The cell was “sealed” to calcium by disabling NCX, L-type current, and background current, and voltage clamping at − 65 mV. The cytosolic [Ca²⁺] is coded by red shades from 100 nM (black) to 5,000 nM (saturation). Calcium dynamics is shown within the outer shell of cytosolic voxels (i.e., directly linked to cell surface membrane). See also Fig. 5.