Fig. (1). Cardiocyte calcium-induced calcium-release.

Ca²⁺ influx through sarcolemmal LTCCs triggers a large release of SR-stored Ca²⁺ by RyR2 which then triggers Ca²⁺-sensitive myofilament contraction. Contraction is terminated by Ca²⁺ uptake into the SR via SERCA2 or expulsion of Ca²⁺ into the extracellular space by NCX and PMCA. Blue circles represent Ca²⁺ while green circles represent Na⁺. Width of blue arrows is roughly proportional to the relative degree of Ca²⁺ flux.