Figure 5.

Solution diagram for the modified HH cleft model as a function of fractional potassium cleft current F_IK with cleft width fixed w_f = 1. Black curves represent stable steady-state solutions, and blue curves represent stable autorhythmic solutions. (A) Spontaneous autorhythmic solutions exist for 0.62 < F_IK < 0.87. Peak membrane potential V_m decreases and minimal membrane potential increases as F_IK increases until minimal V_m inactivates sodium current and abolishes oscillations. (B) Maximal and minimal cleft potassium concentrations [K]_cl increase when F_IK increases. (C) Potassium currents in the cleft I_K,cl decrease when F_IK increases. (D) Autorhythmic frequency increases in response to increasing F_IK.