Physiology (; )
Central to physiological functioning are biophysics and biochemical processes, homeostasis control mechanisms, and cell signaling between cells.
The Nobel Prize in Physiology or Medicine is awarded by the Royal Swedish Academy of Sciences for exceptional scientific achievements in physiology related to the field of medicine.
Foundations
Because physiology focuses on the functions and mechanisms of living organisms at all levels, from the molecular and cellular level to the level of whole organisms and populations, its foundations span a range of key disciplines:
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Anatomy is the study of the structure and organization of living organisms, from the microscopic level of cells and tissues to the macroscopic level of organs and systems. Anatomical knowledge is important in physiology because the structure and function of an organism are often dictated by one another.
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Biochemistry is the study of the chemical processes and substances that occur within living organisms. Knowledge of biochemistry provides the foundation for understanding cellular and molecular processes that are essential to the functioning of organisms.
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Biophysics is the study of the physical properties of living organisms and their interactions with their environment. It helps to explain how organisms sense and respond to different stimuli, such as light, sound, and temperature, and how they maintain homeostasis, or a stable internal environment.
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Genetics is the study of heredity and the variation of traits within and between populations. It provides insights into the genetic basis of physiological processes and the ways in which genes interact with the environment to influence an organism's phenotype.
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Evolutionary biology is the study of the processes that have led to the diversity of life on Earth. It helps to explain the origin and adaptive significance of physiological processes and the ways in which organisms have evolved to cope with their environment.
Subdisciplines
There are many ways to categorize the subdisciplines of physiology:
[Moyes, C.D., Schulte, P.M. Principles of Animal Physiology, second edition. Pearson/Benjamin Cummings. Boston, MA, 2008.]
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based on the taxon studied: human physiology, animal physiology, plant physiology, microbial physiology, viral physiology
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based on the level of organization: cell physiology, molecular physiology, systems physiology, organismal physiology, ecological physiology, integrative physiology
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based on the process that causes physiological variation: developmental physiology, environmental physiology, evolutionary physiology
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based on the ultimate goals of the research: applied physiology (e.g., medical physiology), non-applied (e.g., comparative physiology)
Subdisciplines by level of organisation
Cell physiology
Although there are differences between
animal,
plant, and microbial cells, the basic physiological functions of cells can be divided into the processes of
cell division,
cell signaling,
cell growth, and
Metabolism.
Subdisciplines by taxa
Plant physiology
Plant physiology is a subdiscipline of
botany concerned with the functioning of plants. Closely related fields include
plant morphology,
plant ecology,
phytochemistry,
cell biology,
genetics,
biophysics, and molecular biology. Fundamental processes of
plant physiology include
photosynthesis, respiration,
plant nutrition,
,
nastic movements,
photoperiodism, photomorphogenesis,
,
Germination,
dormancy, and
function and
transpiration. Absorption of water by roots, production of food in the leaves, and growth of shoots towards light are examples of plant physiology.
Animal physiology
Human physiology
Human physiology is the study of how the human body's systems and functions work together to maintain a stable internal environment. It includes the study of the nervous, endocrine, cardiovascular, respiratory, digestive, and urinary systems, as well as cellular and exercise physiology. Understanding human physiology is essential for diagnosing and treating health conditions and promoting overall wellbeing.
It seeks to understand the mechanisms that work to keep the
human body alive and functioning,
through scientific enquiry into the nature of mechanical, physical, and biochemical functions of humans, 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 within systems. The endocrine and nervous systems play major roles in the reception and transmission of signals that integrate function in animals.
Homeostasis is a major aspect with regard to such interactions within plants as well as animals. 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 that occurs in a variety of ways, both electrical and chemical.
Changes in physiology can impact the mental functions of individuals. Examples of this would be the effects of certain medications or toxic levels of substances.
Much of the foundation of knowledge in human physiology was provided by Animal testing. Due to the frequent connection between form and function, physiology and anatomy are intrinsically linked and are studied in tandem as part of a medical curriculum.
Subdisciplines by research objective
Comparative physiology
Involving evolutionary physiology and environmental physiology, comparative physiology considers the diversity of functional characteristics across organisms.
History
The classical era
The study of human physiology as a medical field originates in
classical Greece, at the time of
Hippocrates (late 5th century BC).
Outside of Western tradition, early forms of physiology or anatomy can be reconstructed as having been present at around the same time in
China,
[Helaine Selin, Medicine Across Cultures: History and Practice of Medicine in Non-Western Cultures (2003), p. 53.] India
and elsewhere. Hippocrates incorporated the theory of
humorism, which consisted of four basic substances: earth, water, air and fire. Each substance is known for having a corresponding humor: black bile, phlegm, blood, and yellow bile, respectively. Hippocrates also noted some emotional connections to the four humors, on which
Galen would later expand. The critical thinking of
Aristotle and his emphasis on the relationship between structure and function marked the beginning of physiology in
Ancient Greece. Like
Hippocrates, Aristotle took to the humoral theory of disease, which also consisted of four primary qualities in life: hot, cold, wet and dry.
Galen (–200 AD) was the first to use experiments to probe the functions of the body. Unlike Hippocrates, Galen argued that humoral imbalances can be located in specific organs, including the entire body.
His modification of this theory better equipped doctors to make more precise diagnoses. Galen also played off of Hippocrates' idea that emotions were also tied to the humors, and added the notion of temperaments: sanguine corresponds with blood; phlegmatic is tied to phlegm; yellow bile is connected to choleric; and black bile corresponds with melancholy. Galen also saw the human body consisting of three connected systems: the brain and nerves, which are responsible for thoughts and sensations; the heart and arteries, which give life; and the liver and veins, which can be attributed to nutrition and growth.
Galen was also the founder of experimental physiology.
And for the next 1,400 years, Galenic physiology was a powerful and influential tool in
medicine.
Early modern period
Jean Fernel (1497–1558), a French physician, introduced the term "physiology".
Galen,
Ibn al-Nafis,
Michael Servetus,
Realdo Colombo,
Amato Lusitano and
William Harvey, are credited as making important discoveries in the circulation of the blood.
Santorio Santorio in 1610s was the first to use a device to measure the
pulse rate (the
pulsilogium), and a
thermoscope to measure temperature.
In 1791 Luigi Galvani described the role of electricity in the nerves of dissected frogs. In 1811, César Julien Jean Legallois studied respiration in animal dissection and lesions and found the center of respiration in the medulla oblongata. In the same year, Charles Bell finished work on what would later become known as the Bell–Magendie law, which compared functional differences between dorsal and ventral roots of the spinal cord. In 1824, François Magendie described the sensory roots and produced the first evidence of the cerebellum's role in equilibration to complete the Bell–Magendie law.
In the 1820s, the French physiologist Henri Milne-Edwards introduced the notion of physiological division of labor, which allowed to "compare and study living things as if they were machines created by the industry of man." Inspired in the work of Adam Smith, Milne-Edwards wrote that the "body of all living beings, whether animal or plant, resembles a factory ... where the organs, comparable to workers, work incessantly to produce the phenomena that constitute the life of the individual." In more differentiated organisms, the functional labor could be apportioned between different instruments or systems (called by him as appareils).
In 1858, Joseph Lister studied the cause of blood coagulation and inflammation that resulted after previous injuries and surgical wounds. He later discovered and implemented in the operating room, and as a result, decreased the death rate from surgery by a substantial amount.
The Physiological Society was founded in London in 1876 as a dining club.
In 1891, Ivan Pavlov performed research on "conditional responses" that involved dogs' saliva production in response to a bell and visual stimuli.
In the 19th century, physiological knowledge began to accumulate at a rapid rate, in particular with the 1838 appearance of the Cell theory of Matthias Schleiden and Theodor Schwann.
Nineteenth-century physiologists such as Michael Foster, Max Verworn, and Alfred Binet, based on Haeckel's ideas, elaborated what came to be called "general physiology", a unified science of life based on the cell actions,[ later renamed in the 20th century as cell biology.]
Late modern period
In the 20th century, biologists became interested in how organisms other than human beings function, eventually spawning the fields of comparative physiology and ecophysiology.
In 1920, August Krogh won the Nobel Prize for discovering how, in capillaries, blood flow is regulated.
In 1954, Andrew Huxley and Hugh Huxley, alongside their research team, discovered the sliding filaments in skeletal muscle, known today as the sliding filament theory.
Recently, there have been intense debates about the vitality of physiology as a discipline (Is it dead or alive?).
Notable physiologists
Women in physiology
Initially, women were largely excluded from official involvement in any physiological society. The American Physiological Society, for example, was founded in 1887 and included only men in its ranks.
Soon thereafter, in 1913, J.S. Haldane proposed that women be allowed to formally join The Physiological Society, which had been founded in 1876.
Prominent women physiologists include:
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Bodil Schmidt-Nielsen, the first woman president of the American Physiological Society in 1975.
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Gerty Cori,
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Barbara McClintock was rewarded the 1983 Nobel Prize in Physiology or Medicine for the discovery of genetic transposition. McClintock is the only female recipient who has won an unshared Nobel Prize.
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Gertrude Elion,
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Linda B. Buck,
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Françoise Barré-Sinoussi,
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Elizabeth Blackburn,
See also
Bibliography
Human physiology
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Widmaier, E.P., Raff, H., Strang, K.T. Vander's Human Physiology. 11th Edition, McGraw-Hill, 2009.
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Marieb, E.N. Essentials of Human Anatomy and Physiology. 10th Edition, Benjamin Cummings, 2012.
Animal physiology
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Hill, R.W., Wyse, G.A., Anderson, M. Animal Physiology, 3rd ed. Sinauer Associates, Sunderland, 2012.
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Moyes, C.D., Patricia Schulte Principles of Animal Physiology, second edition. Pearson/Benjamin Cummings. Boston, MA, 2008.
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Randall, D., Burggren, W., and French, K. Eckert Animal Physiology: Mechanism and Adaptation, 5th Edition. W.H. Freeman and Company, 2002.
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Schmidt-Nielsen, K. Animal Physiology: Adaptation and Environment. Cambridge & New York: Cambridge University Press, 1997.
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Withers, P.C. Comparative animal physiology. Saunders College Publishing, New York, 1992.
Plant physiology
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Larcher, W. Physiological plant ecology (4th ed.). Springer, 2001.
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Salisbury, F.B, Ross, C.W. Plant physiology. Brooks/Cole Pub Co., 1992
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Taiz, L., Zieger, E. Plant Physiology (5th ed.), Sunderland, Massachusetts: Sinauer, 2010.
Fungal physiology
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Griffin, D.H. Fungal Physiology, Second Edition. Wiley-Liss, New York, 1994.
Protistan physiology
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Levandowsky, M. Physiological Adaptations of Protists. In: Cell physiology sourcebook: essentials of membrane biophysics. Amsterdam; Boston: Elsevier/AP, 2012.
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Levandowski, M., Hutner, S.H. (eds). Biochemistry and physiology of protozoa. Volumes 1, 2, and 3. Academic Press: New York, NY, 1979; 2nd ed.
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Laybourn-Parry J. A Functional Biology of Free-Living Protozoa. Berkeley, California: University of California Press; 1984.
Algal physiology
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Lobban, C.S., Harrison, P.J. Seaweed ecology and physiology. Cambridge University Press, 1997.
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Stewart, W. D. P. (ed.). Algal Physiology and Biochemistry. Blackwell Scientific Publications, Oxford, 1974.
Bacterial physiology
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El-Sharoud, W. (ed.). Bacterial Physiology: A Molecular Approach. Springer-Verlag, Berlin-Heidelberg, 2008.
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Kim, B.H., Gadd, M.G. Bacterial Physiology and Metabolism. Cambridge, 2008.
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Moat, A.G., Foster, J.W., Spector, M.P. Microbial Physiology, 4th ed. Wiley-Liss, Inc. New York, NY, 2002.
External links
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physiologyINFO.org – public information site sponsored by the American Physiological Society
