Physiology is the study of how various biological components work independently and together to enable organisms, from animals to microbes, to function. This scientific discipline covers a wide variety of functions from the cellular and subcellular level to the interaction of organ systems that keep more the complex biological machines of humans running.

Physiological studies are aimed at answering many questions. Physiologists investigate topics ranging from precise mloecular studies of how food is digested to more general studies of how thought processes relate to electrical and biochemical patterns found in the brain (a branch of this discipline known as neurophysiology). It is often physiology-related investigations that uncover the origins of diseases.

Human (or mammalian) physiology is the oldest branch of this science dating back to at least 420 B.C. and the time of Hippocrates, the father of medicine. Modern physiology first appeared in the seventeenth century when scientific...