physiology

(fĭzēŏl`əjē), study of the normal functioning of animals and plants during life and of the activities by which life is maintained and transmitted. It is based fundamentally on the activities of protoplasm. The study of function is usually undertaken along with a study of structure (see anatomyanatomy
, branch of biology concerned with the study of body structure of various organisms, including humans. Comparative anatomy is concerned with the structural differences of plant and animal forms.
..... Click the link for more information. ), the two being intimately related. Since the discovery of the cell structure of tissues, the science of physiology has undergone rapid development. It includes the study of vital activities in cells, tissues, and organs—of processes such as contractility of muscle tissue, coordination through the nervous system, feeding, digestion, excretion, respiration, circulation, reproduction, and secretion. Virtually every specialized field in the biological sciences (e.g., embryology, pathology, botany, zoology) involves a consideration of the physiological aspects of its subject. The study of human physiology was stimulated by the development of medicine, and it embraces many chemical and physical principles. Plant physiology includes also the study of photosynthesis and transpiration. A separate and specialized branch, plant physiology arose from attempts to apply the findings of animal physiology to plants and in its turn contributed to the development of general physiology, especially in the study of cells.

Physiology

in animals and man, the branch of science dealing with the life processes and individual systems, organs, and tissues of organisms, as well as with the regulation of physiological functions. Physiology also studies the interaction of living organisms with the environment and their behavior under different conditions.

Classification. Physiology is the most important branch of biology and includes a number of largely independent but closely related disciplines, among them general physiology, applied physiology, and the physiology of specific structures.

General physiology studies the physiological principles common to different species, the reactions of living organisms to stimuli, and the processes of excitation and inhibition. The electric phenomena occurring in the living organism, that is, its bioelectrical potentials, are investigated by electrophysiology. The phylogenetic development of physiological processes in different species of invertebrate and vertebrate animals is the concern of comparative physiology. Comparative physiology is in turn the basis of evolutionary physiology, which studies the origin and evolution of the life processes in relation to the general evolution of the organic world.

Developmental physiology studies the formation and development of physiological functions in the course of ontogeny, from the fertilization of the egg cell until death, and is closely associated with evolutionary physiology. The study of the evolution of functions is closely related to that of ecological physiology, which investigates the functioning of physiological systems in relation to the surrounding habitat, that is, it investigates the physiological basis of adaptation to a variety of environmental factors.

The physiology of specific structures investigates the life processes in individual groups or species of animals, for example, farm animals, birds, and insects, the properties of such specialized tissues as nerve and muscle tissue and of such organs as the kidneys and heart, and the ways in which these structures form specialized functional systems.

Applied physiology studies the general and specific principles that control the functioning of living organisms, and of man in particular, in relation to various aspects of life. Branches of applied physiology include the physiology of labor, sports physiology, the physiology of nutrition, aviation physiology, space physiology, and underwater physiology.

Physiology is also subdivided into normal and pathological physiology. Normal physiology primarily studies the functioning of the healthy organism, its interaction with the environment, and the mechanisms by which it resists and adapts to a variety of factors. Pathological physiology studies the altered functions of the diseased organism, the processes of compensation and adaptation in disease, and the mechanisms of recovery and rehabilitation. A branch of pathological physiology is clinical physiology, which studies the origin and activity of such functions as blood circulation, digestion, and higher nervous activity during disease in animals and man.

Relation to other sciences. As a branch of biology, physiology is closely related to such morphological sciences as anatomy, histology, and cytology, since morphology and physiology are interdependent. Physiology makes extensive use of the principles and methods of physics, chemistry, cybernetics, and mathematics. The chemical and physical processes occurring in the organism are studied in conjunction with biochemistry, biophysics, and bionics, and evolutionary laws are studied in conjunction with embryology. The physiology of higher nervous activity is associated with ethology, psychology, physiological psychology, and pedagogy. The physiology of farm animals has direct significance for livestock breeding, zootechny, and veterinary science. Physiology is most closely associated with medicine, which utilizes the achievements of physiology to diagnose, treat, and prevent a variety of diseases. Clinical medicine, in turn, provides physiology with new areas of investigation. The data established by physiological studies constitute part of the foundation of the natural sciences and are widely used in philosophy to substantiate the materialist world outlook.

Research methods. Progress in physiology depends directly on improvements in research methods. In I. P. Pavlov’s words, “Science moves by fits and starts and depends on advances in methodology. With every methodological advance, we as it were climb one step higher” (Poln. sobr. soch., vol. 2, book 2, 1951, p. 22). The study of the functions of the living organism is based both on physiological methods as such and on the methods of physics, chemistry, mathematics, and cybernetics. Consequently, physiological processes may be studied at different levels, among them the cellular and molecular levels. The principal methods of studying the physiological processes of living organisms are observation and different types of experimentation performed on animals. However, an experiment performed on an animal under artificial conditions is not absolute in value and its results cannot be unqualifiedly extrapolated to man and animals living in natural conditions.

In acute experiments, organs and tissues are artificially isolated, organs are removed and artificially stimulated, and bioelectric potentials are derived from such organs. Chronic experiments facilitate the repeated study of a single phenomenon. Methods used in chronic experiments include the creation of fistulas, the placing of organs under a skin flap, the creation of heterogenous anastomoses between nerves, organ transplantation, and the implantation of electrodes.

Complex forms of behavior are studied by chronic experiments using the conditioned reflex or by instrumental methods combined with stimulation of the brain and the recording of bioelectric activity through implanted electrodes. The use of numerous long-term implanted electrodes and of the microelectrode technique for diagnostic and therapeutic purposes has advanced the study of the neurophysiology of the human brain. The recording of local changes in bioelectric and metabolic processes by plotting such changes on graphs has promoted an understanding of the structure and functioning of the brain. Investigations of higher nervous activity have been facilitated by using modifications of the classical conditioned reflex and by using modern electrophysiological methods. Clinical and functional tests on man and animals are another form of physiological experiment. Other physiological research methods include the artificial introduction in animals of such pathological processes as cancer, hypertension, exophthalmic goiter, and peptic ulcer; the use of artificial models and automatic electronic devices that simulate the functioning of the brain and the memory; and artificial prostheses.

Improved methods of research have radically altered experimental techniques and the recording of data. Electronic transformers have replaced mechanical systems, and the functions of man and animals are studied with great accuracy by means of electroencephalography, electrocardiography, electromyography, and especially biotelemetry. The use of stereotaxic apparatus provides information about the inner structures of the brain. Both automatic photography with electron-beam tubes and recording by means of electronic instruments are methods widely used to register physiological processes. In another widely used method, the results of physiological experiments are recorded on magnetic and punched tape and are then processed in a computer. The use of the electron microscope to study the nervous system provides accurate information on the structure of interneuronal contacts and their characteritics in different brain systems.

History. In ancient times the earliest information on physiology was obtained from the empirical observations of naturalists and physicians and particularly through the dissection of animal and human cadavers. For many centuries the accepted views concerning the body and its functions were those of Hippocrates and Aristotle (fifth and fourth centuries B.C., respectively). Substantial progress in the development of physiology took place after the introduction of vivisection by the Roman physician Galen (second century A.D.). In the Middle Ages, advances in medicine stimulated the development of biology, and the overall progress achieved in the sciences during the Renaissance contributed to the development of physiology.

Physiology as a science was founded by the English physician W. Harvey, whose discovery of the blood circulation in 1628, in the words of F. Engels, “made a science of [the] physiology (of man and animals)” (Dialektika prirody, 1969, p. 158). Harvey was the first to describe the systemic and pulmonary circulation of the blood and to determine that the heart was the source of blood circulation in the body: he proved that the blood flows from the heart through the arteries and returns to it through the veins. The foundations for the discovery of the blood circulation had been laid by the Belgian anatomist A. Vesalius, the Spanish physician M. Servetus (1553), and the Italian anatomists R. Colombo (1551) and G. Fallopio. The Italian biologist M. Malpighi, who wrote the first description of the capillaries (1661), confirmed the correctness of Harvey’s description of the blood circulation.

The formulation of the reflex principle in the early 17th century by the French philosopher R. Descartes and in the 18th century by the Czech physician G. Prochaska was a major advance in physiology that helped determine its subsequent materialist trend. According to this principle, any activity of the organism is a response, or reflex, to external influences that is mediated by the central nervous system. Descartes believed that the sensory nerves were propulsive mechanisms that became tense when stimulated and opened valves on the surface of the brain. “Animal spirits” emerging through these valves proceeded to the muscles and caused them to contract. The discovery of reflexes was the first step in the undermining of the idealist and ecclesiastical viewpoint on the behavior mechanisms of living organisms. Subsequently, in the words of P. K. Anokhin, “the reflex principle as dealt with by Sechenov became a weapon in the cultural revolution of the 1860’s, and 40 years later Pavlov used it to revolutionize current theories concerning the psyche” (Ot Dekarta do Pavlova, 1945, p. 3).

Methods of research that utilized the achievements of physics and chemistry were introduced into physiology in the 18th century. The concepts and methods of mechanics were widely applied. As early as the late 17th century, the Italian naturalist G. A. Borelli used the laws of mechanics to explain the movements of animals and the mechanisms of respiratory movements. He also applied the laws of hydraulics to the study of the blood circulation. The English chemist S. Hales determined the intensity of blood pressure in 1733, and the French naturalist R. Reaumur and the Italian naturalist L. Spallanzani studied the chemical mechanisms of digestion. The French chemist A. Lavoisier, while studying the phenomena of oxidation, attempted to explain the respiratory process by means of the principles of chemistry. The Italian anatomist L. Galvani discovered “animal electricity,” that is, the bioelectric phenomena in the organism.

The study of physiology in Russia began in the first half of the 18th century. A department of anatomy and physiology was established in the St. Petersburg Academy of Sciences, which was founded in 1725. The department’s chairmen, D. Bernoulli, L. Euler, and J. Weitbrecht, studied the biophysics of the blood circulation. The research of M. V. Lomonosov ascribed great importance to the role of chemistry in physiological processes. The faculty of medicine at Moscow University, which was founded in 1755, played a major role in the development of physiology in Russia; S. G. Zybelin was the first at the university to teach physiology, anatomy, and other medical disciplines. An independent department of physiology at Moscow University, headed by M. I. Skiadan and I. I. Vech’, was founded in 1776. The first academic dissertation on physiology, dealing with respiration, was completed by F. I. Barsuk-Moiseev in 1794. The St. Petersburg Medical and Surgical Academy (now the S. M. Kirov Military Medical Academy), founded in 1798, was later to contribute significantly to the development of physiology in Russia.

Physiology became independent of anatomy in the 19th century. Factors contributing to the development of physiology included advances in organic chemistry, the discovery of the laws of the conservation and transformation of energy and of the cellular structure of the body, and the formulation of the theory of evolution of organic life.

In the early 19th century it was believed that the chemical compounds in the living organism were fundamentally different from inorganic substances and could not be produced outside the body. In 1828 the German chemist F. Wöhler synthesized the organic compound urea from inorganic substances, thus undermining the vitalist doctrine of the uniqueness of the body’s chemical compounds. The German chemist J. von Liebig and later many other scientists synthesized organic compounds occurring in the body and studied their structure, thus making it possible to analyze the chemical compounds involved in the formation of organisms and in metabolism. Studies were conducted on the metabolism and energy of living organisms. The physiologists V. V. Pashutin and A. A. Likhachev (Russia), M. Rubner (Germany), and F. Benedict and W. Atwater (USA) devised methods of direct and indirect calorimetry that measured the energy in foods and the energy released by animals and man at rest and at work. Nutritional standards were established by the German physiologist K. von Voit.

Improved methods of electron stimulation and of mechanically recording physiological processes led to increased knowledge of the physiology of nerve and muscle tissue. The German physiologist E. Du Bois-Reymond invented an induction apparatus, and another German physiologist, K. Ludwig, invented (1847) the kymograph, a floating manometer for recording blood pressure, and instruments for recording the rate of the blood flow. The French physiologist E. Marey, the first to use photography to study movements in organisms, invented an apparatus for recording chest movements. The Italian physiologist A. Mosso introduced a device for studying variations in the volume of organs as modified by the circulation of blood, an instrument for measuring fatigue (the ergograph), and a gravimetric device for studying the circulation of the blood.

The principles governing the action of direct current on excitable tissue were discovered by the German physiologist E. Pflüger and the Russian physiologist B. F. Verigo, and the rate of the conduction of excitation along nerves was determined by the German physician H. von Helmholtz. Helmholtz also laid the foundation of the theory of vision and hearing. By means of the method of telephonic auscultation of an excited nerve, the Russian physiologist N. E. Vvedenskii studied the physiological properties of excitable tissues and confirmed the rhythmic nature of nerve impulses. He proved that the properties of living tissues change both in response to stimulation and during the course of their own activity. In formulating his theory of the optimum and pessimum of stimulation, Vvedenskii was the first to note the reciprocal relations existing in the central nervous system. He was also the first to study inhibition in its genetic relation to excitation and to discover the phases of transition from excitation to inhibition. The studies on the manifestations of electricity in the body begun by the Italian physiologist L. Galvani and the Italian physicist A. Volta were continued by the German physiologists Du Bois-Reymond and L. Hermann and in Russia by Vvedenskii. The Russian physiologists I. M. Sechenov and V. Ia. Danilevskii were the first to record manifestations of electricity in the central nervous system.

The neural regulation of physiological functions was studied by transecting and stimulating different nerves. The German physiologists and brothers E. H. Weber and E. F. Weber discovered the inhibitory action of the vagus nerve on the heart, the Russian physiologist I. F. Tsion proved that the sympathetic trunk accelerates the heartbeat, and I. P. Pavlov discovered that the sympathetic trunk intensifies the heartbeat. A. P. Val’ter in Russia and later C. Bernard in France established the existence of sympathetic vasoconstrictive nerves. Ludwig and Tsion found centropetal fibers proceeding from the heart and aorta that alter cardiac function and vascular tone by means of reflexes. F. V. Ovsiannikov discovered the vasomotor center in the medulla oblongata, and N. A. Mislavskii investigated the previously discovered respiratory center in the medulla oblongata.

Beginning in the 19th century, the nervous system was known to possess a trophic function, that is, to influence metabolism and the nutrition of organs. In 1824 the French physiologist F. Magendie described the pathological changes that occur in tissues after the transection of nerves. Bernard observed changes in the carbohydrate metabolism of a part of the medulla oblongata that had been punctured (diabetic puncture, or Bernard’s puncture). The German physiologist R. Heidenhain discovered that the sympathetic nerves affect the composition of the saliva, and Pavlov detected the trophic action of the sympathetic nerves on the heart.

The reflex theory of nervous activity was further developed in the 19th century. The cerebrospinal reflexes were studied in detail, and the reflex arc was analyzed. The Scottish physiologist C. Bell (1811), Magendie (1817), and the German naturalist J. Müller studied the distribution of motor and sensory fibers in the nerve roots of the spinal cord; their research resulted in the establishment of the Bell-Magendie law. In 1826, Bell hypothesized that afferent influences proceed from muscles during their contraction to the central nervous system, a view that was later developed by A. Fol’kman and A. M. Filomafitskii. The work of Bell and Magendie stimulated research on the localization of functions in the brain and constituted the foundation of subsequent research on physiological systems that function according to the feedback principle.

In 1842 the French physiologist P. Flourens, after studying the role of the different areas of both the brain and individual nerves in voluntary movements, advanced a concept of the plasticity of nerve centers and the dominant role of the cerebral hemispheres in affecting voluntary movements.

An important contribution to the development of physiology was Sechenov’s discovery (1862) of inhibition in the central nervous system. Sechenov demonstrated that under certain conditions stimulation of the brain may cause an inhibitory process that suppresses excitation. Sechenov also discovered the phenomenon of summation in nerve centers. He proved that “all conscious and unconscious acts are reflex in origin” (Izbr. filos, i psikhologich. proizv., 1947, p. 176), thus helping establish a materialist approach to physiology. Influenced by Sechenov’s research, S. P. Botkin and Pavlov introduced the concept of nervism, according to which the nervous system predominates in the regulation of physiological functions and processes in the living organism. The concept of nervism was intended to refute the concept of humoral regulation. The study of the influence of the nervous system on bodily functions has been a major focus of Russian and Soviet physiology.

Beginning in the second half of the 19th century, the role of specific areas of the brain and spinal cord in regulating physiological functions was studied by removing individual parts of the organism. The German physiologists G. Fritsch and E. Hitzig directly stimulated the cerebral cortex in 1870, and another German physiologist, F. Goltz, successfully removed a cerebral hemisphere in 1891. The physiologists V. A. Basov, L. Teary, L. Well, R. Heidenhain and Pavlov studied the functions of the internal organs, particularly those of the digestive organs, by means of experimental surgery. Pavlov formulated the principles governing the functioning of the principal digestive glands, their neural regulation, and the changes occurring in the composition of the digestive juices in relation to the nutritive and nondigestible substances ingested. Pavlov was awarded a Nobel Prize in 1904 for his research in this area, which elucidated the functioning of the digestive apparatus as an integrated system.

A new stage in the development of physiology began in the 20th century, when the earlier, narrowly analytic view of the body’s vital processes gave way to a synthetic view. Soviet and foreign physiology was greatly influenced by the work of Pavlov and his school on higher nervous activity. Pavlov’s discovery of conditioned reflexes created an empirical foundation for the study of the psychological processes governing the behavior of animals and man. Pavlov’s 35 years of research on higher nervous activity elucidated the physiology of the analyzers and established the types of nervous systems as well as the laws governing the formation and inhibition of conditioned reflexes. He described disturbances of higher nervous activity in experimental neuroses, formulated a cortical theory of sleep and hypnosis, and introduced the concept of the first- and second-signal systems. Pavlov’s work formed the materialist basis for later studies on higher nervous activity, as well as the scientific basis of V. I. Lenin’s theory of reflection.

The English neurophysiologist C. Sherrington made a major contribution to the physiology of the central nervous system by formulating the principles governing the integrative activity of the brain: reciprocal inhibition, occlusion, and the convergence of excitation on individual neurons. Sherrington contributed new information on the interdependence of excitation and inhibition and on the nature and impairment of muscle tone, thus providing a foundation for future research.

The Dutch physiologist R. Magnus studied the postural, or righting, reflexes, which ensure the maintenance of body posture and balance. The Soviet physiologist V. M. Bekhterev demonstrated the role of the subcortical structures in eliciting emotional and motor reactions in animals and man. He also discovered the conduction paths of the spinal cord and brain and elucidated the functions of the thalamus. The Soviet physiologist A. A. Ukhtomskii formulated the theory of the dominant as the leading principle of brain function; this served as an important supplement to existing concepts of the inflexibility of reflex acts and their brain centers. Ukhtomskii discovered that excitation of the brain that is caused by a dominant need both inhibits minor reflexes and results in the intensified dominant activity of these reflexes.

The emphasis on physics in research led to substantial advances in physiology in the 19th century. The use of a string galvanometer by the Dutch physiologist W. Einthoven and later by the Soviet physiologist A. F. Samoilov made it possible to record bioelectric potentials in the human heart. Using electronic amplifiers that intensified weak bioelectric potentials hundreds of thousands of times, the American physician H. Gasser, the English physiologist E. Adrian, and the Russian physiologist D. S. Vorontsov recorded the bioelectric potentials of nerve trunks. The Russian physiologist V. V. Pravdich-Neminskii was the first to record the electric manifestations of cerebral activity by means of electroencephalography. His work was continued and developed by the German physician H. Berger. The Soviet physiologist M. N. Livanov used mathematical methods to analyze the bioelectric potentials of the cerebral cortex, and the English physiologist A. Hill recorded heat production in nerves traversed by waves of excitation.

The study of excitation in nerves by using the methods of physical chemistry began in the 20th century. The ionic theory of excitation was formulated by the Soviet physiologist V. Iu. Chagovets and developed by the German physiologist J. Bernstein, the German physical chemist W. Nernst, and the Soviet physicist P. P. Lazarev. The membrane theory of excitation was developed by the British researchers P. Boyle, E. Conway, A. Hodgkin, A. Huxley, and B. Katz. The Soviet cytophysiologist D. N. Nasonov established the role of cell proteins in the excitation process. Closely associated with research on excitation is the theory of mediators, that is, chemical transmitters of nerve endings. Important research in this area was conducted by the Austrian pharmacologist O. Loewi, by Samoilov, I. P. Razenkov, A. V. Kibiakov, K. M. Bykov, L. S. Shtern, E. B. Babskii, and Kh. S. Koshtoiants (USSR), by W. Cannon (USA), and by B. Mint (France). Existing views on the integrative activity of the nervous system were developed by the Australian physiologist J. Eccles, who formulated the theory of membrane mechanisms of synaptic transmission.

In the mid-20th century the American neuroanatomist H. Magoun and the Italian physiologist G. Moruzzi discovered the nonspecific activating and inhibitory influences of the reticular formation on different areas of the brain. Their studies significantly altered traditional views on the distribution of excitation in the central nervous system and on the mechanisms of cortical and subcortical interrelationships, sleep and wakefulness, anesthesia, the emotions, and motivations. The Soviet physiologist P. K. Anokhin developed these ideas and described the ascending activating influences exerted by the subcortical formations on the cerebral cortex during different types of biological reactions.

The functions of the limbic system were studied in detail by the American physician P. MacLean and the Soviet physiologist I. S. Beritashvili. The role of the limbic system in the regulation of autonomic processes and in the development of emotions, motivation, and memory, as well as the physiological mechanisms of emotions, were studied by the American researchers P. Bard, P. MacLean, D. Lindsley, and J. Olds, the Italian physician A. Zanchetti, the Swiss researchers W. Hess and R. Hunsperger, and the Soviet researchers Beritashvili, Anokhin, A. V. Val’dman, N. P. Bekhtereva, and P. V. Simonov. The mechanisms of sleep were analyzed by Pavlov, Hess, Moruzzi, the French neurophysiologist M. Jouvet, and the Soviet researchers F. P. Maiorov, N. A. Rozhanskii, Anokhin, and N. I. Grashchenkov.

New theories on the functioning of the endocrine glands were developed in the early 20th century, and the functional disturbances resulting from injury to these glands were elucidated. New views on the internal environment of the organism and on homeostasis, barrier functions, and integrated neurohumoral regulation were formulated by Cannon and the Soviet researchers L. A. Orbeli, Bykov, Shtern, and G. N. Kassil’. Pavlov’s theories on the trophic function of the nervous system were developed by the work of Orbeli and his students A. V. Tonkikh and A. G. Ginetsinskii on the adaptative and trophic functions of the sympathetic nervous system and its influence on the skeletal muscles, sensory organs, and central nervous system. Related studies conducted by A. D. Speranskii’s school dealt with the influence of the nervous system on pathological processes. Bykov and his followers V. N. Chernigovskii, I. A. Bulygin, A. D. Slonim, I. T. Kurtsin, E. Sh. Airapet’iants, A. V. Rikkl’ and A. V. Solov’ev formulated a theory of cortical and visceral physiology and pathology. Bykov elucidated the role of conditioned reflexes in the regulation of internal functions.

The physiology of nutrition had made significant progress by the mid-20th century. The expenditure of energy by persons in different occupations was studied and nutritional standards were developed by the Soviet physiologists M. N. Shaternikov and O. P. Molchanova, the German physiologist C. von Voit, and the American physiologist F. Benedict.

The development of space travel and of underwater research is promoting the study of space and underwater physiology. In the second half of the 20th century the physiology of sensory systems has been studied by the Soviet researchers Chernigovskii, A. L. Byzov, G. V. Gershuni, and R. A. Durinian, the Swedish physiologist R. Granit, and the Canadian physiologist V. Amasian. The Soviet physiologist A. M. Ugolev discovered the mechanism of parietal digestion, and the central hypothalamic mechanisms regulating hunger and satiation were discovered by the American physiologist J. Brobeck and the Indian physiologist B. Anand.

Research on vitamins has continued to develop since the 19th century, when the organism’s need for these substances in order to function normally was established by the Russian pediatrician N. I. Lunin.

Major advances in the study of cardiac functions have been made in the 20th century by E. Starling and T. Lewis (Great Britain), H. Wiggers (USA), and A. I. Smirnov, G. I. Kositskii, and F. Z. Meerson (USSR). Research on blood vessels has been conducted by H. Hering (Germany), C. Heymans (Belgium), V. V. Parin and Chernigovskii (USSR), and E. Neil (Great Britain). Studies on capillary circulation have been made by the Danish physiologist A. Krogh and the Soviet physiologist A. M. Chernukh. The mechanism of respiration and the transfer of gases by the blood have been studied by J. Barcroft and J. Haldane (Great Britain), D. Van Slyke (USA), and E. M. Kreps (USSR). The mechanisms that regulate kidney function have been elucidated by the English physiologist A. Cushny and the American pharmacologist A. Richards. The Soviet physiologists Orbeli and A. I. Karamian systematized the evolutionary laws of neural functions and the physiological mechanisms of behavior. The Canadian pathologist H. Selye formulated (1936) a theory of stress as a nonspecific adaptive reaction to external and internal stimuli that significantly influenced the development of physiology and medicine.

The systemic approach to physiology was widely used beginning in the 1960’s. According to Anokhin’s theory of functional systems, the body’s organs become selectively involved in systemic organizations that facilitate the organism’s adaptation to the environment. Systemic mechanisms of brain activity are studied by a number of Soviet physiologists, including M. N. Livanov and A. B. Kogan.

Recent trends and objectives. A major goal of modern physiology is to elucidate the mechanisms of mental activity in animals and man in order to devise effective means of preventing mental and neurological diseases. Toward this end, research is conducted on the functional differences between the right and left cerebral hemispheres and on the complex neuronal mechanisms of the conditioned reflex. Brain functions in man are studied by means of implanted electrodes, and psychopathological syndromes are artificially induced in animals.

Analysis of the molecular mechanisms of nervous excitation and muscular contraction makes it possible to elucidate the selective permeability of cell membranes, to create laboratory models of such membranes for purposes of research, and to understand the mechanism by which substances are transferred across cell membranes. Such analysis also elucidates the role of neurons, groups of neurons, and glial elements in the integrative activity of the brain, and particularly in the processes of memory. Research on the different levels of the central nervous system elucidates their function in the emergence and maintenance of emotional states. Continued study of the perception, transmission, and analysis of information by the body’s sensory systems will contribute to an understanding of the mechanisms of speech formation and perception and of the recognition of visual images and acoustic and tactile signals.

Another area of study is the physiology of the movements and compensatory mechanisms governing the restoration of motor functions after injury to the musculoskeletal and nervous systems. Research is being conducted on the central mechanisms regulating the body’s autonomic functions, on the adaptive and trophic influences exerted by the autonomic nervous system, and on the structure and functions of the autonomic ganglia. Studies on respiration, blood circulation, digestion, the metabolism of water and salt, thermoregulation, and the activity of the endocrine glands are elucidating the physiological mechanisms of the visceral functions. The implantation of artificial organs such as the heart, kidneys, and liver requires elucidating the mechanisms of their functioning within the organism.

Physiology also deals with problems directly related to medicine, for example, the role of emotional stress in the origin of cardiovascular diseases and neuroses. Developmental physiology and gerontology have become important branches of physiology, and specialists in the physiology of farm animals study ways of increasing productivity.

Also under study are the evolutionary history of the nervous system’s morphological and functional organization and of the body’s somatic and autonomic functions. Other research focuses on ecologically determined physiological changes in man and animals. Scientific and technological progress has made it necessary to investigate man’s adaptation to working and living conditions as well as the effect of such factors as emotional stress and climatic conditions. A major task of physiology is the elucidation of the mechanisms of human resistance to stress. By means of robots and the simulation of physiological functions, man’s adaptation to space and to underwater conditions is investigated. In related studies, conducted with the aid of computers, subjects maintain their own physiological functions at a certain level regardless of the action of external influences. New means are being devised, and existing ones improved, for protection against environmental pollution, electromagnetic fields, barometric and gravitational pressure, and other physical factors.

Scientific institutions and organizations. Major centers of physiological research in the USSR include the I. P. Pavlov Institute of

Table 1. International physiological congresses
	Place	Year
First ...............	Basel	1889
Second ...............	Liège, Belgium	1892
Third ...............	Bern	1895
Fourth ...............	Cambridge, England	1898
Fifth ...............	Turin	1901
Sixth ...............	Brussels	1904
Seventh ...............	Heidelberg	1907
Eighth ...............	Vienna	1910
Ninth ...............	Groningen, The Netherlands	1913
Tenth ...............	Paris	1920
Eleventh ...............	Edinburgh	1923
Twelfth ...............	Stockholm	1926
Thirteenth ...............	Boston	1929
Fourteenth ...............	Rome	1932
Fifteenth ...............	Leningrad-Moscow	1935
Sixteenth ...............	Zürich	1938
Seventeenth ...............	Oxford	1947
Eighteenth ...............	Copenhagen	1950
Nineteenth ...............	Montreal	1953
Twentieth ...............	Brussels	1956
Twenty-first ...............	Buenos Aires	1959
Twenty-second ...............	Leiden, The Netherlands	1962
Twenty-third ...............	Tokyo	1965
Twenty-fourth ...............	Washington, D.C.	1968
Twenty-fifth ...............	Munich	1971
Twenty-sixth ...............	New Delhi	1974
Twenty-seventh ...............	Paris	1977

Physiology of the Academy of Sciences of the USSR in Leningrad, the Institute of Higher Nervous Activity of the Academy of Sciences of the USSR in Moscow, the I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry of the Academy of Sciences of the USSR in Leningrad, the P. K. Anokhin Institute of Normal Physiology of the Academy of Medical Sciences of the USSR in Moscow, and the Institute of General Pathology and Pathological Physiology of the Academy of Medical Sciences of the USSR in Moscow. Other important centers of physiological research are the Brain Institute of the Academy of Medical Sciences of the USSR in Moscow, the A. A. Bogomolets Institute of Physiology of the Academy of Sciences of the Ukrainian SSR in Kiev, the Institute of Physiology of the Academy of Sciences of the Byelorussian SSR in Minsk, the I. S. Beritashvili Institute of Physiology in Tbilisi, the L. A. Orbeli Institute of Physiology in Yerevan, the A. I. Karaev Institute of Physiology in Baku, the Institute of Physiology in Tashkent, the Institute of Physiology in Alma-Ata, the A. A. Ukhtomskii Institute of Physiology in Leningrad, the Institute of Neurocybernetics in Rostov-on-Don, and the Institute of Physiology in Kiev.

The I. P. Pavlov All-Union Physiological Society, founded in 1917, has major branches in Moscow, Leningrad, Kiev, and other cities in the USSR. A department of physiology founded within the Academy of Sciences of the USSR in 1963 directs the work of the institutes of physiology attached to the academy and to the All-Union Physiological Society. About ten physiological journals are published. Teaching and research are conducted at sub-departments of physiology at universities and at higher educational institutions of medicine, pedagogy, and agriculture.

Table 2. Physiological congresses held in the USSR
	Place	Year
First ...............	Petrograd	1917
Second ...............	Leningrad	1926
Third ...............	Moscow	1928
Fourth ...............	Kharkov	1930
Fifth ...............	Moscow	1934
Sixth ...............	Tbilisi	1937
Seventh ...............	Moscow	1947
Eighth ...............	Kiev	1955
Ninth ...............	Minsk	1959
Tenth ...............	Yerevan	1964
Eleventh ...............	Leningrad	1970
Twelfth ...............	Tbilisi	1975

International physiological congresses have been held trienni-ally since 1889, with two interruptions of seven and nine years owing to World War I and World War II, respectively. A list of the international physiological congresses is given in Table 1.

The International Union of Physiological Sciences (IUPS), founded in 1970, publishes the IUPS Newsletter. In the USSR, physiological congresses have been held since 1917. A list of the physiological congresses held in the USSR is given in Table 2.

REFERENCES

History
Anokhin, P. K. Ot Dekarta do Pavlova. Moscow, 1945.
Koshtoiants, Kh. S. Ocherki po istorii fiziologii v Rossii. Moscow-Leningrad, 1946.
Lunkevich, V. V. Ot Geraklita do Darvina: Ocherki po istorii biologii, 2nd ed., vols. 1–2. Moscow, 1960.
Maiorov, F. P. Istoriia ucheniia ob uslovnykh refleksakh, 2nd ed. Moscow-Leningrad, 1954.
Razvitie biologii v SSSR. Moscow, 1967.
Istoriia biologii s drevneishikh vremen do nachala XX veka. Moscow, 1972.
Istoriia biologii s nachala XX veka do nashikh dnei. Moscow, 1975.
Collections and monographs
Lazarev, P. P. Sochineniia, vol. 2. Moscow-Leningrad, 1950.
Ukhtomskii, A. A. Sobr. Soch., vols. 1–6. Leningrad, 1950–62.
Pavlov, I. P. Poln sobr. soch., 2nd ed., vols. 1–6. Moscow, 1951–52.
Vvedenskii, N. E. Poln. sobr. soch., vols. 1–7. Leningrad, 1951–63.
Mislavskii, N. A. Izbr. proizv. Moscow, 1952.
Sechenov, I. M. Izbr. proizv., vol. 1. Moscow, 1952.
Bykov, K. M. Izbr. proizv., vols. 1–2. Moscow, 1953–58.
Bekhterev, V. M. Izbr. proizv. Moscow, 1954.
Orbeli, L. A. Lektsii po voprosam vysshei nervnoi deiatel’nosti. Moscow-Leningrad, 1945.
Orbeli, L. A. Izbr. trudy, vols. 1–5. Moscow, 1961–68.
Ovsiannikov, F. V. Izbr. proizv. Moscow, 1955.
Speranskii, A. D. Izbr. trudy. Moscow, 1955.
Beritov, I. S. Obshchaia fiziologiia myshechnoi i nervnoi sistemy, 3rd ed., vols. 1–2. Moscow, 1959–66.
Eccles, J. Fiziologiia nervnykh kletok. Moscow, 1959. (Translated from English.)
Chernigovskii, V. N. Interoretseptory. Moscow, 1960.
Shtern, L. S. “Neposredstvennaia pitatel’naia sreda organov i tkanei: Fiziologicheskie mekhanizmy, opredeliaiushchie ee sostav i svoistva.” Izbr. trudy. Moscow, 1960.
Beritov, I. S. Nervnye mekhanizmy povedeniia vysshikh pozvonochnykh zhivotnykh. Moscow, 1961.
Hoffman, B., and P. Cranefield. Elektrofiziologiia serdtsa. Moscow, 1962. (Translated from English.)
Magnus, R. Ustanovka tela. Moscow-Leningrad, 1962. (Translated from German.)
Parin, V. V., and F. Z. Meerson. Ocherki klinicheskoi fiziologii krovoobrashcheniia, 2nd ed. Moscow, 1965.
Hodgkin, A. Nervnyi impul’s. Moscow, 1965. (Translated from English.)
Gellhorn, E., and G. Loofbourrow. Emotsii i emotsional’nye rasstroistva. Moscow, 1966. (Translated from English.)
Anokhin, P. K. Biologiia i neirofiziologiia uslovnogo refleksa. Moscow, 1968.
Tonkikh, A. V. Gipotalamo-gipofizarnaia oblast’ i reguliatsiia fiziologicheskikh funktsii organizma, 2nd ed. Leningrad, 1968.
Rusinov, V. S. Dominanta. Moscow, 1969.
Eccles, J. Tormoznye puti tsentral’noi nervnoi sistemy. Moscow, 1971. (Translated from English.)
Sudakov, K. V. Biologicheskie motivatsii. Moscow, 1971.
Sherrington, C. Integrativnaia deiatel’nost’ nervnoi sistemy. Leningrad, 1969. (Translated from English.)
Delgado, J. Mozg i soznanie. Moscow, 1971. (Translated from English.)
Ugolev, A. M. Membrannoe pishchevarenie: Polisubstratnye protsessy, organizatsiia i reguliatsiia. Leningrad, 1972.
Granit, R. Osnovy reguliatsii dvizhenii. Moscow, 1973. (Translated from English.)
Asratian, E. A. I. P. Pavlov. Moscow, 1974.
Beritashvili, I. S. Pamiat’pozvonochnykh zhivotnykh, ee kharakteristika i proiskhozhdenie, 2nd ed. Moscow, 1974.
Sechenov, I. M. Lektsii po fiziologii. Moscow, 1974.
Anokhin, P. K. Ocherki po fiziologii funktsional’nykh sistem. Moscow, 1975.
Textbooks and manuals
Koshtoiants, Kh. S. Osnovy sravnitel’noi fiziologii, 2nd ed., vols. 1–2. Moscow, 1950–57.
Fiziologiia cheloveka, 2nd ed. Edited by E. B. Babskii. Moscow, 1972.
Kostin, A. P., A. A. Sysoev, and F. A. Meshcheriakov. Fiziologiia sel’skokhoziaistvennykh zhivotnykh. Moscow, 1974.
Kostiuk, P. G. Fiziologiia tsentral’noi nervnoy sistemy. Kiev, 1971. Kogan, A. B. Elektrofiziologiia. Moscow, 1969.
Prosser, C., and F. Brown. Sravnitel’naia fiziologiia zhivotnykh. Moscow, 1967. (Translated from English.)
Yost, H. Fiziologiia kletki. Moscow, 1975. (Translated from English.)
Manuals of physiology
Fiziologiia sistemy krovi. Leningrad, 1968.
Obshchaia i chastnaia fiziologiia nervnoi sistemy. Leningrad, 1969.
Fiziologiia myshechnoi deiatel’nosti, truda i sporta. Leningrad, 1969.
Fiziologiia vysshei nervnoi deiatel’nosti, parts 1–2. Leningrad, 1970–71.
Fiziologiia sensornykh sistem, parts 1–3. Leningrad, 1971–75.
Klinicheskaia neirofiziologiia. Leningrad, 1972.
Fiziologiiapochki. Leningrad, 1972.
Fiziologiia dykhaniia. Leningrad, 1973.
Fiziologiia pishchevareniia. Leningrad, 1974.
Grachev, I. I., and V. P. Galantsev. Fiziologiia laktatsii. Leningrad, 1973.
Khodorov, B. A. Obshchaia fiziologiia vozbudimykh membran. Leningrad, 1975.
Vozrastnaia fiziologiia. Leningrad, 1975.
Fiziologiia dvizhenii. Leningrad, 1976.
Fiziologiia rechi. Leningrad, 1976.
Lehrbuch der Physiologic. Edited by W. Rüdiger. Berlin, 1971.
Ochs, S. Elements of Neurophysiology. New York-London-Sydney, 1965.
Physiology and Biophysics, 19th ed. Philadelphia-London, 1965.
Ganong, W. F. Review of Medical Physiology, 5th ed. Los Altos, Calif., 1971.

K. V. SUDAKOV

physiology

[‚fiz·ē′äl·ə·jē] (biology) The study of the basic activities that occur in cells and tissues of living organisms by using physical and chemical methods.

physiology

1. the branch of science concerned with the functioning of organisms 2. the processes and functions of all or part of an organism
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noun the branch of the biological sciences dealing with the functioning of organisms

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