Oscillatory isozymes another two-variable model for birhythmicity

6 Oscillatory isozymes another two-variable model for birhythmicity 

In the model of oscillatory isozymes, the product nullcline also 

The system of two oscillatory isozymes can be viewed as the simplest model of coupled biochemical oscillators. Indeed, the number of vari- 

The model based on oscillatory isozymes, which can be extended to a larger number of oscillatory units coupled in parallel, is closer to the neuronal situation than the model of fig. 3.1. Indeed, the situation of two isozymes activated by their common product is somewhat analogous to that of two ion channels carrying the same ionic species and activated in a self-amplified manner by the membrane potential. 

The scenario described above for the origin of birhythmicity is not the only one conceivable. Different routes to birhythmicity exist, as shown by the theoretical study of other models containing two or three variables (Schulmeister Sel kov, 1978 Tracqui et al, 1987 Tracqui, 1993). This question is discussed further in chapter 4, in relation to models based on the coupling between two instability-generating mechanisms. 

---