A schematic diagram of the mathematical model of the mouse early embryonic (E9-E11) cardiomyocyte. The SL components are background Ca²⁺ current (I_Cab), I_CaL, I_CaT, NCX, I_K1, I_KDR, NaK-ATPase, I_f, and I_Na. The SR components are Ca²⁺ pump (SERCA), RyR, and IP₃R. Ca²⁺ diffuses radially in the cytosol and is buffered to troponin and calmodulin in cytosol and to calreticulin in the SR. The model also includes dynamic cytosol Na⁺ and K⁺ concentrations. The compartments are not in scale.