Homeostasis is one of the fundamental characteristics of living things.It is the maintenance of the internal environment within tolerable limits. Electro-Magnetic Stimulation has been shown to assist normal body function by facilitating homeostasis.

The internal environment of a living organism's body features body fluids in multicellular animals. The body fluids include blood plasma, tissue fluid and intracellular fluid.The maintenance of a steady state in these fluids is essential to living things as the lack of it harms the genetic material.

With regard to any parameter, an organism may be a conformer or a regulator. Regulators try to maintain the parameter at a constant level, regardless of what is happening in its environment. Conformers allow the environment to determine the parameter. For instance, endothermic animals maintain a constant body temperature, while ectothermic animals exhibit wide variation in body temperature.

This is not to say that conformers may not have behavioural adaptations that allow them to exert some control over the parameter in question. For instance, reptiles often sit on sun-heated rocks in the morning to raise their body temperatures.

An advantage of homeostatic regulation is that it allows the organism to function more effectively. For instance, ectotherms   tend to become sluggish at low temperatures, whereas endotherms are as active as always. On the other hand, regulation requires energy. One reason snakes are able to eat just once a week is that they use much less energy for maintaining homeostasis.

Homeostasis in the human body

All sorts of factors affect the suitability of the human body fluids to sustain life; these include properties like temperature, salinity, and acidity and the concentrations of nutrients such as glucose, various ions, oxygen, and wastes, such as carbon dioxide and urea. Since these properties affect the chemical reactions that keep bodies alive, there are built-in physiological mechanisms to maintain them at desirable levels.

Many external factors can affect homeostasis and create an imbalance. For example, extremes of temperature or lack of oxygen can disturb the internal enviroment. Any factor that causes an imbalance is refered to as stress.

Stress may also originate internally. For example a low blood-sugar level, pain or unpleasant thoughts can all affect homeostasis.

When homeostasis is disrupted illness may occur. If homeostasis is not restored, the imbalance may eventually be fatal.