The term Physiology was originally derived from the Greek root with the Latin equivalent Physiologia, which denoted natural knowledge. Physiology is, therefore, the discipline that deals with bodily functions and their control. It is, however, only concerned with the normal.

The goal of physiology is to explain the physical and chemical factors that are responsible for the origin, development, and progression of life. Each type of life, from the very simple virus to the largest tree or to the complicated human being, has its own functional characteristics. Therefore, the vast field of physiology can be divided into viral physiology, bacterial physiology, cellular physiology, plant physiology, human physiology, and many more subdivisions.

In human physiology, we are concerned with the specific characteristics and mechanisms of the human body that make it a living being. The very fact that we remain alive is almost beyond our own control, for hunger makes us seek food and fear makes us seek refuge. Sensations of cold make us provide warmth. Thus, the human being is actually an automaton, and the fact that we are sensing, feeling, and knowledgeable beings is part of this automatic sequence of life; these special attributes allow us to exist under widely varying conditions.