Scheme of cellular structures and molecules involved in excitation-contraction coupling in ventricular myocytes. The black stars indicate Ca2+ ions. Solid lines indicate Ca2+ influx into cytosol and dotted lines indicate Ca2+ extrusion pathways. The thickness of the line indicates the relative contribution of each pathway. LTCC = L-type Ca2+ channel, NCX = sodium-calcium exchanger, PLB = phospholamban, RyR = ryanodine receptor, SR = sarcoplasmic reticulum, SERCA = sarcoplasmic reticulum Ca2+ ATPase.