Calcium-induced calcium release

Calcium-induced calcium release (CICR) is a mechanism of calcium release from muscle sarcoplasmic reticulum that was proposed in the 1970s. Originally proposed for skeletal muscle, subsequent research has revealed that it is actually the predominant mechanism in cardiac muscle.

CICR in Excitation-Contraction (EC) Coupling
The mechanism that couples excitation - an action potential in the plasma membrane of the muscle cell - and contraction of heart muscle is an increase in the cell's cystolic calcium concentration. This calcium combines with the regulator protein troponin, initiatin cross-bridge formation between actin and myosin.