Physiology

For the scientific journal, seePhysiology(journal).

Oil painting depictingClaude Bernard,the father of modern physiology, with his pupils

Physiology(/ˌfɪziˈɒlədʒi/;fromAncient Greekφύσις(phúsis)'nature, origin', and-λογία(-logía)'study of')is thescientificstudy offunctionsandmechanismsin aliving system.As asubdisciplineofbiology,physiology focuses on howorganisms,organ systems,individualorgans,cells,andbiomoleculescarry outchemicalandphysicalfunctions in a living system.According to the classes oforganisms,the field can be divided intomedical physiology,animal physiology,plant physiology,cell physiology,andcomparative physiology.

Central to physiological functioning arebiophysicalandbiochemicalprocesses,homeostaticcontrol mechanisms, andcommunicationbetween cells.Physiological stateis the condition of normal function. In contrast,pathologicalstaterefers toabnormal conditions,including humandiseases.

TheNobel Prize in Physiology or Medicineis awarded by theRoyal Swedish Academy of Sciencesfor exceptional scientific achievements in physiology related to the field ofmedicine.

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:

• Anatomyis 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.
• Biochemistryis 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.
• Biophysicsis 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.
• Geneticsis 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.
• Evolutionary biologyis 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:

• based on thetaxastudied:human physiology,animal physiology,plant physiology,microbial physiology, viral physiology
• based on thelevel of organization:cell physiology,molecular physiology,systemsphysiology, organismal physiology,ecological physiology,integrative physiology
• based on the process that causes physiological variation:developmentalphysiology,environmental physiology,evolutionary physiology
• 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

Main article:Cell physiology

Although there are differences betweenanimal,plant,and microbial cells, the basic physiological functions of cells can be divided into the processes ofcell division,cell signaling,cell growth,andcell metabolism.

Subdisciplines by taxa

Plant physiology

Main article:Plant physiology

Plant physiology is a subdiscipline ofbotanyconcerned with the functioning of plants. Closely related fields includeplant morphology,plant ecology,phytochemistry,cell biology,genetics,biophysics,andmolecular biology.Fundamental processes ofplant physiologyincludephotosynthesis,respiration,plant nutrition,tropisms,nastic movements,photoperiodism,photomorphogenesis,circadian rhythms,seed germination,dormancy,andstomatafunction andtranspiration.Absorption of water by roots, production of food in the leaves, and growth of shoots towards light are examples of plant physiology.

Animal physiology

Main article:Biology § Animal form and function

Human physiology

Main article:Human body § 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 thehuman bodyalive 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.Homeostasisis 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.Change inbehavioras a result of these substances is often used to assess the health of individuals.

Much of the foundation of knowledge in human physiology was provided byanimal experimentation.Due to the frequent connection between form and function, physiology andanatomyare intrinsically linked and are studied in tandem as part of a medical curriculum.

Subdisciplines by research objective

Comparative physiology

Main article:Comparative physiology

Involvingevolutionary physiologyandenvironmental 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 inclassical Greece,at the time ofHippocrates(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 inChina,Indiaand elsewhere. Hippocrates incorporated the theory ofhumorism,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 whichGalenwould later expand. The critical thinking ofAristotleand his emphasis on the relationship between structure and function marked the beginning of physiology inAncient Greece.LikeHippocrates,Aristotle took to the humoral theory of disease, which also consisted of four primary qualities in life: hot, cold, wet and dry.Galen (c. 130–200 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 inmedicine.

Early modern period

Jean Fernel(1497–1558), a French physician, introduced the term "physiology".Galen,Ibn al-Nafis,Michael Servetus,Realdo Colombo,Amato LusitanoandWilliam Harvey,are credited as making important discoveries in thecirculation of the blood.Santorio Santorioin 1610s was the first to use a device to measure thepulserate (thepulsilogium), and athermoscopeto measure temperature.

In 1791Luigi Galvanidescribed the role of electricity in nerves of dissected frogs. In 1811,César Julien Jean Legalloisstudied respiration in animal dissection and lesions and found the center of respiration in themedulla oblongata.In the same year,Charles Bellfinished work on what would later become known as theBell–Magendie law,which compared functional differences between dorsal and ventral roots of thespinal cord.In 1824,François Magendiedescribed the sensory roots and produced the first evidence of the cerebellum's role inequilibrationto complete the Bell–Magendie law.

In the 1820s, the French physiologistHenri Milne-Edwardsintroduced 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 ofAdam 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 orsystems(called by him asappareils).

In 1858,Joseph Listerstudied the cause of blood coagulation and inflammation that resulted after previous injuries and surgical wounds. He later discovered and implementedantisepticsin the operating room, and as a result, decreased death rate from surgery by a substantial amount.

The Physiological Societywas founded in London in 1876 as a dining club.The American Physiological Society(APS) is a nonprofit organization that was founded in 1887. The Society is, "devoted to fostering education, scientific research, and dissemination of information in the physiological sciences."

In 1891,Ivan Pavlovperformed 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 theCell theoryofMatthias SchleidenandTheodor Schwann.It radically stated that organisms are made up of units called cells.Claude Bernard's (1813–1878) further discoveries ultimately led to his concept ofmilieu interieur(internal environment),which would later be taken up and championed as "homeostasis"by American physiologistWalter B. Cannonin 1929. By homeostasis, Cannon meant "the maintenance of steady states in the body and the physiological processes through which they are regulated."In other words, the body's ability to regulate its internal environment. William Beaumont was the first American to utilize the practical application of physiology.

Nineteenth-century physiologists such asMichael Foster,Max Verworn,andAlfred Binet,based onHaeckel'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 ascell biology.

Late modern period

In the 20th century, biologists became interested in how organisms other than human beings function, eventually spawning the fields ofcomparative physiologyandecophysiology.Major figures in these fields includeKnut Schmidt-NielsenandGeorge Bartholomew.Most recently,evolutionary physiologyhas become a distinct subdiscipline.

In 1920,August Kroghwon the Nobel Prize for discovering how, in capillaries, blood flow is regulated.

In 1954,Andrew Huxleyand Hugh Huxley, alongside their research team, discovered the sliding filaments inskeletal 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?).If physiology is perhaps less visible nowadays than during the golden age of the 19th century,it is in large part because the field has given birth to some of the most active domains of today's biological sciences, such asneuroscience,endocrinology,andimmunology.Furthermore, physiology is still often seen as an integrative discipline, which can put together into a coherent framework data coming from various different domains.

Notable physiologists

Main article:List of physiologists

Women in physiology

Initially, women were largely excluded from official involvement in any physiological society. TheAmerican Physiological Society,for example, was founded in 1887 and included only men in its ranks.In 1902, the American Physiological Society electedIda Hydeas the first female member of the society.Hyde, a representative of theAmerican Association of University Womenand a global advocate for gender equality in education,attempted to promote gender equality in every aspect of science and medicine.

Soon thereafter, in 1913,J.S. Haldaneproposed that women be allowed to formally joinThe Physiological Society,which had been founded in 1876.On 3 July 1915, six women were officially admitted:Florence Buchanan,Winifred Cullis,Ruth C. Skelton,Sarah C. M. Sowton,Constance Leetham Terry,andEnid M. Tribe.The centenary of the election of women was celebrated in 2015 with the publication of the book "Women Physiologists: Centenary Celebrations And Beyond For The Physiological Society." (ISBN978-0-9933410-0-7)

Prominent women physiologists include:

• Bodil Schmidt-Nielsen,the first woman president of theAmerican Physiological Societyin 1975.
• Gerty Cori,along with husbandCarl Cori,received the Nobel Prize in Physiology or Medicine in 1947 for their discovery of thephosphate-containing form ofglucoseknown asglycogen,as well as its function withineukaryoticmetabolicmechanisms for energy production. Moreover, they discovered theCori cycle,also known as the Lactic acid cycle,which describes how muscle tissue converts glycogen into lactic acid vialactic acid fermentation.
• Barbara McClintockwas rewarded the 1983 Nobel Prize in Physiology or Medicine for the discovery ofgenetic transposition.McClintock is the only female recipient who has won an unshared Nobel Prize.
• Gertrude Elion,along withGeorge HitchingsandSir James Black,received the Nobel Prize for Physiology or Medicine in 1988 for their development of drugs employed in the treatment of several major diseases, such asleukemia,someautoimmune disorders,gout,malaria,andviral herpes.
• Linda B. Buck,along withRichard Axel,received the Nobel Prize in Physiology or Medicine in 2004 for their discovery ofodorant receptorsand the complex organization of theolfactory system.
• Françoise Barré-Sinoussi,along withLuc Montagnier,received the Nobel Prize in Physiology or Medicine in 2008 for their work on the identification of theHuman Immunodeficiency Virus(HIV), the cause ofAcquired Immunodeficiency Syndrome(AIDS).
• Elizabeth Blackburn,along withCarol W. GreiderandJack W. Szostak,was awarded the 2009 Nobel Prize for Physiology or Medicine for the discovery of the genetic composition and function oftelomeresand the enzyme calledtelomerase.

See also

• Outline of physiology
• Biochemistry
• Biophysics
• Cytoarchitecture
• Defense physiology
• Ecophysiology
• Exercise physiology
• Fish physiology
• Insect physiology
• Human body
• Molecular biology
• Metabolome
• Neurophysiology
• Pathophysiology
• Pharmacology
• Physiome
• American Physiological Society
• International Union of Physiological Sciences
• The Physiological Society
• Brazilian Society of Physiology

Bibliography

Human physiology

• Hall, John (2011).Guyton and Hall textbook of medical physiology(12th ed.). Philadelphia, Pa.: Saunders/Elsevier.ISBN978-1-4160-4574-8.
• Widmaier, E.P., Raff, H., Strang, K.T.Vander's Human Physiology.11th Edition, McGraw-Hill, 2009.
• Marieb, E.N. Essentials of Human Anatomy and Physiology. 10th Edition, Benjamin Cummings, 2012.

Animal physiology

• Hill, R.W., Wyse, G.A., Anderson, M.Animal Physiology,3rd ed. Sinauer Associates, Sunderland, 2012.
• Moyes, C.D.,Schulte, P.M.Principles of Animal Physiology,second edition. Pearson/Benjamin Cummings. Boston, MA, 2008.
• Randall, D., Burggren, W., and French, K.Eckert Animal Physiology: Mechanism and Adaptation,5th Edition. W.H. Freeman and Company, 2002.
• Schmidt-Nielsen, K.Animal Physiology: Adaptation and Environment.Cambridge & New York: Cambridge University Press, 1997.
• Withers, P.C.Comparative animal physiology.Saunders College Publishing, New York, 1992.

Plant physiology

• Larcher, W.Physiological plant ecology(4th ed.). Springer, 2001.
• Salisbury, F.B, Ross, C.W.Plant physiology.Brooks/Cole Pub Co., 1992
• Taiz, L., Zieger, E.Plant Physiology(5th ed.), Sunderland, Massachusetts: Sinauer, 2010.

Fungal physiology

• Griffin, D.H.Fungal Physiology,Second Edition. Wiley-Liss, New York, 1994.

Protistan physiology

• Levandowsky, M. Physiological Adaptations of Protists. In:Cell physiology sourcebook: essentials of membrane biophysics.Amsterdam; Boston: Elsevier/AP, 2012.
• Levandowski, M., Hutner, S.H. (eds).Biochemistry and physiology of protozoa.Volumes 1, 2, and 3. Academic Press: New York, NY, 1979; 2nd ed.
• Laybourn-Parry J.A Functional Biology of Free-Living Protozoa.Berkeley, California: University of California Press; 1984.

Algal physiology

• Lobban, C.S., Harrison, P.J.Seaweed ecology and physiology.Cambridge University Press, 1997.
• Stewart, W. D. P. (ed.).Algal Physiology and Biochemistry.Blackwell Scientific Publications, Oxford, 1974.

Bacterial physiology

• El-Sharoud, W. (ed.).Bacterial Physiology: A Molecular Approach.Springer-Verlag, Berlin-Heidelberg, 2008.
• Kim, B.H., Gadd, M.G.Bacterial Physiology and Metabolism.Cambridge, 2008.
• Moat, A.G., Foster, J.W., Spector, M.P.Microbial Physiology,4th ed. Wiley-Liss, Inc. New York, NY, 2002.

External links

• The dictionary definition ofphysiologyat Wiktionary
• Works on the topicPhysiologyatWikisource
• Media related toPhysiologyat Wikimedia Commons
• physiologyINFO.org– public information site sponsored by theAmerican Physiological Society