The homeostasis is a state of balance of the functions and systems of the body. This process is regulate by the internal environment of the body and their responses to the external stimuli by the equilibrium of the functions and actions of the systems, organs, and cells of the individuals. The homeoatasis needs a constant feedback between the organic and inorganic needs of the organisms to survive the daily life, being the feedback possible because of receptors and effectors mechanisms, controlled by specific structures. The feedback can be either positive to increase the reaction, or negative to reduce that reaction, being the better form to maintain the balance of the body and homeostasis in general.
Example:
A simple example of a homeostatic process is the regulation of the blood pressure, because of a negative feedback loop. When there is a increase in blood pressure detected by the receptors in the blood vessels a message is sent to the brain, the brain in turn seds back a message to the effectors to the heart and blood vessels (that makes the heart rate decrease and the blood vessels dilate (increase their diameter)) causing the overall blood pressure to decrease.