Fig. 1.

Scheme of a single cell in the EO model. a Scheme of the ionic dynamics for a single-cell model. Simulated ionic currents (i _x) involved in the AP generation are shown: i _Na fast Na⁺ current, i _pNa persistent Na⁺ current, i _bNa background Na⁺ current, i _NaCa Na⁺/Ca²⁺ exchange (NCX) current, i _CaL Ca²⁺ current via L-type Ca²⁺ channels, i _bCa background Ca²⁺ current, i _to transient outward K⁺ current, i _Kr, i _Ks rapid and slow components of delayed K⁺ current, i _K1 rectifier K⁺ current, i _NaK Na⁺/K⁺ pump current, DS dyadic space, TC terminal cisterns, LR longitudinal reticulum, i _rel Ca²⁺ release flow from the sarcoplasmic reticulum (SR), i _up SERCA pump flow from cytosol to the SR, i _tr Ca²⁺ diffusion between the LR and the TC, CaS Ca²⁺ complexes with calsequestrin, CaTnC Ca²⁺ complexes with TnC, B ₁, B ₂ Ca²⁺ complexes with fast and slow buffer ligands. b Rheological scheme for a single cell model, where a contractile element (CE) is connected to an in-series and parallel passive elastic element (SE, XSE, PE), and a viscous element (VS) is inserted in parallel to the PE. Variables l, l ₁ and l _ex define deformations of PE, CE and XSE, respectively, relative to their slack lengths (see text for details)