Figure 5.
Schematics showing the steady-state signal–response dependency for bistable and monostable systems. A: Hysteresis in a bistable system. When the signal intensity is less than S1 or greater than S2, there is only one stable steady state; two stable steady states coexist when the signal intensity is in the interval (S1, S2). Depending on the direction of change in the signal intensity (indicated by the arrows), the system will be characterized by different signal–response curves (red and green). At S1 and S2, the system undergoes abrupt transitions from the high response level state to the low response level state and vice versa, respectively. B: Irreversibility in a bistable system. At S1, the system undergoes an abrupt transition from the low response level state to the high response level state. However, when the signal intensity shifts from high to low, the system remains in the high response level state. C: Sigmoidal signal–response curve of a monostable system. Regardless of the direction of change in the signal intensity, the signal– response relationship is uniquely defined.