Fig 2. Illustration of Ca²⁺ clamp protocol.

A–Ca²⁺ clamp protocol illustrated for 9 steps of SR-Ca²⁺, showing traces for: (i) proportion open RyR; (ii) intracellular- (purple) and SR- (blue) Ca²⁺ concentration. B–Snapshots of the spatio-temporal Ca²⁺ dynamics at different SR-Ca²⁺ concentrations, showing: (i) non-propagating sparks; (ii) slow Ca²⁺ wave; (iii) multiple and rapid Ca²⁺ waves; the time range for the snapshots is shown in the square brackets. The data shown are clipped to the first of the two seconds associated with each clamp step in order to clearly visualise the waveforms.