Optimisation of Ionic Models to Fit Tissue Action Potentials: Application to 3D Atrial Modelling

Figure 2

Generic ionic model structure. (a) Equivalent Markov state diagram of ionic currents. O represents the open or conducting state for the ionic channel, and C₀₀, C₀₁, and C₁₀ are the closed states. 𝑝 and 𝑞 are two gating variables governing the kinetics. ○ Open gate, ● Closed gate. (b) Typical profile of rate variable (𝛼 or 𝛽) as a function of membrane potential. Each rate is defined by three parameters: 𝑘, a maximum plateau value, 𝐸₅₀, the membrane potential at half the maximum value, and 𝑠, which is related to the slope at the 𝐸₅₀, such that 𝛼́(𝐸₅₀)=−𝑘𝑠_𝛼/4 and 𝛽́(𝐸₅₀)=−𝑘𝑠_𝛽/4. (c) Typical steady-state profile for 𝑝 and 𝑞 as a function of transmembrane potential for a transiently activating inward current. (d) Typical steady-state profile of 𝑝 and 𝑞 for a sustained outward current, as a function of transmembrane potential.

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