The role of excitation contraction coupling in cardiac muscle mechanics

Force (F) and shortening of the myocardium during the heartbeat are determined by the amount of Ca/sup ++/ bound to Troponin-C following Ca/sup ++/ release by the sarcoplasmic reticulum (SR) which is triggered by the cardiac action potential. Troponin-C competes during this process both with other ligands in the cytoplasm of the cardiac myocyte and with the Ca/sup ++/ extrusion from the cell as well as Ca/sup ++/ re-uptake by the SR. In this discussion we address the factors that influence the main determinants of power output by the cardiac muscle.