To help us understand homeostasis in living organisms, let us first look at a non-living system. We will use a temperature control system for a room which has many similar features to homeostatic mechanisms.

The room shown in Figure 1 below has a temperature sensor mounted on a wall. The temperature sensor is connected to a temperature control box. The temperature control box has a knob which allows the desired temperature for the room to be set. The desired temperature is called the ‘set point’. When the room temperature is lower than the set point, a heater is switched on.
Test this by clicking on the <GO> button in Figure 1 above, and watch what happens in the room.

Figure 1

Did you notice that the heater turns on and warms up the room? The room temperature keeps rising until it reaches the set point. The temperature controller then switches off the heater.

Homeostatic mechanisms tend to maintain a property which is important to an organism as close as possible to a particular value called the set point.
(In humans the set point for body temperature is 37°C.)

On a hot day, the temperature in the room may rise above the set point. The heater is of no use in this situation. However, a cooler could also be attached to the temperature controller so that it is switched on when the room temperature rises above the set point.

Look at Figure 2 below and click on the <GO> button to watch what now happens in the room.

Figure 2

Did you see the room temperature drop down to the set point causing the cooler to be switched off by the temperature controller?

Click on the <GO> button in Figure 3 below to review what happens to the temperature control system during different weather conditions.

Figure 3