Figure 7.

Chemo-electro-mechanical coupling in the human heart. Spatio-temporal evolution of the fiber contraction λ_ff, the transmembrane potential ϕ, the intracellular sodium, potassium, and calcium concentrations c_Na, c_K, and c_Ca, and the calcium concentration in the sarcoplasmic reticulum $c_{\text{Ca}}^{\text{sr}}$ during the rapid depolarization phase of the cardiac cycle. Changes in the individual ion concentrations initiate an increase in the transmembrane potential ϕ from -86 mV to +20 mV. Changes in the intracellular calcium concentration c_Ca initiate a mechanical contraction λ_ff of up to 10-15%. During the contraction phase, the apex moves rapidly towards the base and the heart undergoes a clockwise rotation around its long axis.