Figure 1.

Schematics showing mechanoenergetics coupling and whole-body cardiovascular system. A. Model of oxidative phosphorylation used to compute metabolite concentration from basal ATP hydrolysis rate under normal and failing-heart conditions. B. Schematics of the cross-bridge kinetic model. The state N is a non-permissible XB state where myosin heads cannot bind with actin (as in the absence of cytosolic Ca²⁺), while P is a permissible XB state during which myosin heads can bind with actin molecules. The transition from state N to P depends on thick-thin filament overlap and Ca²⁺ concentration. The states $A_1^T$ and A₂ represent loosely and strongly bound cross-bridge attached state; $A_3^T$ is the strongly bound (post-ratcheted or post-powerstroke) state. C. Schematics of the CVS model used to simulate Frank-Starling curves. Diodes represent inlet/outlet valves and ensure one-way blood flow. C_PA, C_PV, C_SA, C_Ao and C_SV represent lumped compliances of pulmonary artery, pulmonary vein, systemic artery and systemic vein. R_pul, R_sys and R_Ao represent vascular resistances. RV and LV represent right and left ventricular cavities.