Recent research has shown the importance of the spatial and temporal a
spects of calcium signals, which depend upon regenerative properties o
f the inositol trisphosphate and ryanodine receptors that regulate the
release of calcium from internal stores. Initiation sites have been f
ound to spontaneously release calcium, recognized as 'hot spots' or 's
parks', and can trigger a wave that spreads through a process of calci
um-induced calcium release.