Fig. 3.
Addition of extra feedback to core functions can be used to integrate key signaling characteristics or enhance the robustness of important functions. (A) Combining two negative feedback loops can independently stabilize basal signaling and limit maximal signal output. (B) Adding a negative feedback loop to the oscillator in Fig. 2C can result in sharper spikes, an increased input range over which oscillations occur and an increased output frequency range. (C) A system made up of a dual fast and slow positive feedback loops can exhibit transient or persistent bistable states if the fast or both positive feedbacks are engaged.