<P> As organisms age, the efficiency of their control systems becomes reduced . The inefficiencies gradually result in an unstable internal environment that increases the risk of illness, and leads to the physical changes associated with aging . </P> <P> Various chronic diseases are kept under control by homeostatic compensation, which masks a problem by compensating for it (making up for it) in another way . However, the compensating mechanisms eventually wear out or are disrupted by a new complicating factor (such as the advent of a concurrent acute viral infection), which sends the body reeling through a new cascade of events . Such decompensation unmasks the underlying disease, worsening its symptoms . Common examples include decompensated heart failure, kidney failure, and liver failure . </P> <P> Familiar technological homeostatic mechanisms include: </P> <Ul> <Li> A thermostat operates by switching heaters or air - conditioners on and off in response to the output of a temperature sensor . </Li> <Li> Cruise control adjusts a car's throttle in response to changes in speed . </Li> <Li> An autopilot operates the steering controls of an aircraft or ship in response to deviation from a pre-set compass bearing or route . </Li> <Li> Process control systems in a chemical plant or oil refinery maintain fluid levels, pressures, temperature, chemical composition, etc. by controlling heaters, pumps and valves . </Li> <Li> The centrifugal governor of a steam engine, as designed by James Watt in 1788, reduces the throttle valve in response to increases in the engine speed, or opens the valve if the speed falls below the pre-set rate . </Li> </Ul>

Where is the sensing mechanism for the homeostatic control of temperature located