Physiology is the science of the functioning of living systems. It is a subcategory of biology. In physiology, the scientific method is applied to determine how organisms, organ systems, organs, cells and biomolecules carry out the chemical or physical function that they have in a living system. The word physiology is from Ancient Greek: φύσις, physis, "nature, origin"; and -λογία, -logia, "study of".
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Human physiology is the science of the mechanical, physical, and biochemical functions of humans in good health, their organs, and the cells of which they are composed. The principal level of focus of physiology is at the level of organs and systems. Most aspects of human physiology, and animal experimentation has provided much of the foundation of physiological knowledge. Anatomy and physiology are closely related fields of study: anatomy, the study of form, and physiology, the study of function, are intrinsically tied and are studied in tantem as part of a medical curriculum.
Human physiology dates back to at least 420 B.C. and the time of Hippocrates,[1] the father of medicine. The critical thinking of Aristotle and his emphasis on the relationship between structure and function marked the beginning of physiology in Ancient Greece, while Claudius Galenus (c. 126-199 A.D.), known as Galen, was the first to use experiments to probe the function of the body. Galen was the founder of experimental physiology.[2] The ancient Indian books of Ayurveda, the Sushruta Samhita and Charaka Samhita, also had descriptions on human anatomy and physiology. The medical world moved on from Galenism only with the appearance of Andreas Vesalius and William Harvey.[3]
During the Middle Ages, the ancient Greek and Indian medical traditions were further developed by Muslim physicians, most notably Avicenna (980-1037), who introduced experimentation and quantification into the study of physiology in The Canon of Medicine. Many of the ancient physiological doctrines were eventually discredited by Ibn al-Nafis (1213–1288), who was the first physician to correctly describe the anatomy of the heart, the coronary circulation, the structure of the lungs, and the pulmonary circulation, for which he is considered the father of circulatory physiology.[4] He was also the first to describe the relationship between the lungs and the aeration of the blood, the cause of pulsation,[5] and an early concept of capillary circulation.[6]
Following from the Middle Ages, the Renaissance brought an increase of physiological research in the Western world that triggered the modern study of anatomy and physiology. Andreas Vesalius was an author of one of the most influential books on human anatomy, De humani corporis fabrica.[7] Vesalius is often referred to as the founder of modern human anatomy.[8] Anatomist William Harvey described the circulatory system in the 17th century,[9] demonstrating the fruitful combination of close observations and careful experiments to learn about the functions of the body, which was fundamental to the development of experimental physiology. Herman Boerhaave is sometimes referred to as a father of physiology due to his exemplary teaching in Leiden and textbook Institutiones medicae (1708).
In the 18th century, important works in this field were by Pierre Cabanis, a french doctor and physiologist.
In the 19th century, physiological knowledge began to accumulate at a rapid rate, most notably in 1838 with the Cell theory of Matthias Schleiden and Theodor Schwann, which radically stated that organisms are made up of units called cells. Claude Bernard's (1813–1878) further discoveries ultimately led to his concept of milieu interieur (internal environment), which would later be taken up and championed as "homeostasis" by American physiologist Walter Cannon (1871–1945).
In the 20th century, biologists also became interested in how organisms other than human beings function, eventually spawning the fields of comparative physiology and ecophysiology.[10] Major figures in these fields include Knut Schmidt-Nielsen and George Bartholomew. Most recently, evolutionary physiology has become a distinct subdiscipline[11].
The biological basis of the study of physiology, integration refers to the overlap of many functions of the systems of the human body, as well as its accompanied form. It is achieved through communication which occurs in a variety of ways, both electrical and chemical.
In terms of the human body, the endocrine and nervous systems play major roles in the reception and transmission of signals which integrate function. Homeostasis is a major aspect with regards to the interactions within an organism, humans included.
There is an abundance of universities that allow students to major in physiology.[12][13] It is considered one of the fastest growing majors for undergraduate students.
The highest honor awarded in physiology is the Nobel Prize in Physiology, awarded since 1901 by the Royal Swedish Academy of Sciences.
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