During every heartbeat, a change in the electrical potential of cardiac myocytes propagates throughout the heart and leads to a coordinated contraction of the atria and ventricles. The process of converting this electrical stimulus to a mechanical response is called excitation contraction coupling. Calcium ions play an important role in this process, since they are the direct activators of the myofilaments – the motor units of the cardiac muscle.
Mathematical models of cardiac myocytes that describe these functions exist in a large variety and most of them implement a different approach to calcium handling, leading to a different transient and intracellular concentrations. As a consequence, the mechanical response will be different for all of these models.