Before revision:  Assuming  the activation sensors are independent and the activation variable m has a faster relaxation than the inactivation variable h, the open state probability during the action potential may be expressed as m(t) ^3 h(t) , and the  kinetic equations may be  reduced to rate equations for activation, and  fast and slow inactivation that describe spike frequency adaptation  in the neural membrane, a repetitive bursting oscillation and a cardiac action potential with a plateau oscillation.
After revision:  Assuming the activation sensors are independent and the activation variable m has a faster relaxation than the inactivation variable h, the open state probability during the action potential may be expressed as m(t) but may be approximated by a voltage-dependent function , and the kinetic equations may be reduced to rate equations for activation, and fast and slow inactivation that describe spike frequency adaptation in the neural membrane, a repetitive bursting oscillation and a cardiac action potential with a plateau oscillation.