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  Physiology (Greek phusis, ‘nature’ + ology) is the study of the function of the biological processes within living organisms. It is broken down into the study of the function of particular organs: thus endocrinology is the study of hormone function. The concept of homeostasis is central to the science of physiology. Homeostasis is the regulation of the internal environment within certain parameters, and is not only a requirement for the perpetuation of physiological processes but is their responsibility. Investigation of homoestatic systems involves the biochemical (see biochemistry) study of metabolism under a variety of conditions to reveal how each system responds, in isolation and in the context of the whole organism. The study of function was of interest to ancient scientists such as Aristotle (384 - 322 BCE) and Galen (129 - 200 CE), though their approaches and theories were very different from those of the modern physiologist. The Hippocratic school of medicine proposed the humoral theory of disease (see humours) which was influential for 2,000 years, along with ideas such as the tidal flow of blood. These misconceptions, and the willingness of later philosophers to recapitulate the suppositions of the ancient Greeks, held back the development of medicine and ensured that practices such as phlebotomy (blood-letting) remained popular through the Middle Ages.

The publication in 1628 of William Harvey\'s observations concerning the circulation of blood represented a major step toward the foundation of modern physiology, though all his observations were anatomical. In the 18th century, Albrecht von Haller defined physiology as anatomy in motion, and thus established the principle that living organisms must be observed during physiological studies. At around the same time Antoine-Laurent Lavoisier was applying the principles of chemistry to living organisms to reveal the similarities between respiration and combustion. The pioneering French physiologist and pharmacologist François Magendie (1783 - 1855) studied physiology in living animals and it was one of his students, Claude Bernard, who, in the 19th century, proposed the concept of the internal environment of an organism. Physiology began to be separated from the study of anatomy and grew as an experimental discipline in its own right. RB

See also mechanism.Further reading Margaret Stanier, Physiological Processes.



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