Fig. 1.

Generic signal-response models with DNF. Squares indicate model variables, circles indicate model functions. Arrows between and to components indicate biochemical reactions, arrows on arrows indicate modifying influences and arrows to functions indicate the respective influence on the function. The models differ in design of the delayed negative feedback (DNF) as well as in presence of mass conservation for the component C and auto-inhibitory feedback. a Model with input-inhibition as DNF and without mass conservation. b Model with input-inhibition as DNF and with mass conservation. c Model with output-activation as DNF and without mass conservation. d Model with output-activation as DNF and with mass conservation. In all models the time delay τ is before activation of the response variable R. Dashed lines indicate an alternative auto-inhibitory feedback