Figure 1.

Action potential model. (a) Cell schematic, (b) overall bond graph structure. The bond graph modules Na_channel, NaK, K_channels, LCC, NCX and Ca_buffer contain more detailed aspects of the bond graph structure which are described further in the Methods and electronic supplementary material. Coloured bonds link bond graph modules to the appropriate chemical species. Definitions: I_Na, sodium current; I_K1, time-independent K⁺ current; I_K, time-dependent K⁺ current; I_Kp, plateau K⁺ current; I_LCC, L-type Ca²⁺ current; NCX, Na⁺–Ca²⁺ exchanger; Na/K, Na⁺/K⁺ ATPase; TRPN, troponin; CMDN, calmodulin. (Online version in colour.)