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. Author manuscript; available in PMC: 2016 Feb 26.
Published in final edited form as: Cell. 2015 Feb 26;160(5):816–827. doi: 10.1016/j.cell.2015.02.010

Figure 1. Stock and flow model of homeostasis.

Figure 1

(A) Stock and flow model highlights two types of variables in homeostasis: Stock is quantity of a regulated variable - a parameter that is maintained by homeostasis. Flows are the processes that change the value of the stock. Some, but not all flows are controlled variables and targets for homeostatic control signals (graphically represented here as dials). Clouds represent ‘sources’ and ‘sinks’ for regulated variable that are extrinsic to the homeostatic system.

(B) A physiologic example of stock and flow model: dietary glucose uptake, hepatic glucose production, or glucose uptake into adipose and muscle are flows that maintain the stock of blood glucose.