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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 3. Homeostatic units.

Figure 3

(A) System stock, Plant stock and Storage stock each represent homeostatic units that are connected by flows. Each of the stocks is monitored by a specialized Controller, which regulates the flows into and out of the stock. Homeostatic system is thus hierarchically organized into ‘nested’ homeostatic units.

(B) Physiologic example of nested homeostatic units: System stock (blood glucose) is monitored by System Controller (pancreatic β-cells), Plant stock (glucose in skeletal muscle) is monitored by Plant specific Controller (e.g., AMPK) and Storage stock (muscle glycogen) is presumably monitored by a glycogen sensor, which is currently unknown. Each of the Controllers regulates the flows into and out of the corresponding stock.