Fig. 3

Examples of supply- and demand- driven homeostatic systems. A, B Demand-driven homeostatic mechanisms equivalent to the abstract models shown in Fig. 2C, D. C, D Supply-driven homeostatic mechanisms analogous to the models in Fig. 2. E, F. For simplicity, actuators and controllers are not shown. Flows regulated by controllers are shown in green, and those governed by actuators in yellow. External flows are shown in blue. Dashed arrows represent the flow of information. Blunt and pointed arrows indicate inhibition and upregulation respectively