Model is underconstrained.
The following variables couldn't be defined:
 * V in component membrane
 * i_Ca in component calcium_current
 * i_K in component rapidly_activating_K_current
 * i_K_Ca in component calcium_activated_K_current
 * i_Na_Ca in component Na_Ca_exchanger_current
 * n_infinity in component rapidly_activating_K_current_n_gate
 * tau_n in component rapidly_activating_K_current_n_gate
 * m_infinity in component calcium_current_m_gate
 * V_Na_Ca in component Na_Ca_exchanger_current
 * d/dt V in component membrane
 * d/dt n in component rapidly_activating_K_current_n_gate
 * d/dt Ca_i in component ionic_concentrations
 * d/dt Ca_ret in component ionic_concentrations