What is homeostasis?

Homeostasis is the maintenance of the internal environment to a constant state, despite changes to the external environment. Examples of conditions in the body which must be kept constant include body temperature, blood glucose concentration and carbon dioxide concentration.

Homeostasis is achieved by the body using negative feedback. This is the reversal of a change in the body's internal environment to an optimum level. On a basic level, negative feedback takes place via a standard pathway:

Stimulus --> Receptor --> Communication pathway (cell signalling) --> Effector --> Response