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The role of IM. Sechenova and I.P. Pavlova in creating modern physiology of the brain

THEM. Sechenov (Fig. 54) was a broad-range physiologist. His research concerned many aspects of physiological science. However, he showed particular interest in the physiology of muscles and nerves.

At the end of St. Petersburg University I.M. Sechenov finally chooses physiology as his specialty and goes to improve abroad. There he works with famous physiologists of that time - I. Muller, E.G. Dubois-Reymond, C. Bernard, K.F.V. Ludwig, G. Helmholtz. Already at the beginning of his scientific activity abroad, I.M. Sechenov is distinguished by the desire for the independence of research, performed in an original and thorough manner.

Upon his return from abroad Sechenov actively develops his scientific activities at the Department of Physiology of the Medical and Surgical Academy in St. Petersburg. At that time, he was particularly interested in the physiology of the nervous system.

In 1862, Sechenov discovered the presence of central inhibition in the brain, proving this in a simple but convincing experiment. The hemisphere was removed from the frog, but the diencephalon (visual tubercles) was left. Placing salt crystals on the visual tubercles, it caused a sharp slowdown in the formation of an arc of the flexion reflex. This discovery brought Sechenov worldwide fame. Soon he publishes his wonderful treatise, “Reflexes of the brain,” in which he shows that psychic phenomena are by nature reflexes of the brain. Mental activity, Sechenov claims, is impossible without external irritations of the senses. All acts of conscious and unconscious life by the mode of origin are reflexes. In daily conscious life, a person cannot refuse to influence him from outside through the senses and from feelings coming from his own body. They support his whole mental life. Thus, Sechenov confirms the position that the content of the human psyche is the material world, reflected in the form of sensations, ideas, concepts.

Merits I.M. Sechenov in front of Russian and world science is huge and undeniable. K.A. Timiryazev called Sechenov the father of Russian physiology, who created the school of Russian physiologists. Among Sechenov's students there were a number of prominent scientists, such as V.V. Pashutin, B.F. Verigo, SV Kravkov, V.Ya. Danilevsky, M.N. Shaternikov. Of particular note is the name of one of Sechenov’s talented students - N.E. Vvedensky, whose studies on the physiology of the nerve

muscle fibers can be called classic. Vvedensky proposed a peculiar concept about the nature of inhibition and created the doctrine of parabiosis.

However, I.M. Sechenov expressed a number of provisions on the strict conditioning of the brain, without relying on any large experimental material. Experimentally, the laws underlying the higher nervous activity were obtained by I.P. Pavlov and his school.

The role of I.P. Pavlova (Fig. 55), one of the largest natural scientists of the late XIX - early XX century., Is truly huge. He managed to create a completely new section in science, and, moreover, one of the most difficult ones - the physiology of the cerebral hemispheres. Prior to Pavlov’s work, the physiology of the brain as a harmonious scientific knowledge system did not exist. The works devoted to the physiology of the brain and nerves were very fragmented.
Pavlov’s greatest merit is that, having created his original method of conditioned reflexes, having studied the physiological mechanisms of cortical activity with his help, he synthesized the entire experience of the past, verified and clarified a number of points with numerous, exceptionally accurate experiments.

Thus, Pavlovian physiology is characterized by the breadth of scientific thought and a comprehensive study of the subject, it is aimed at generalizing the mass of factual material, as a result of which it is mainly synthetic in nature. Previous studies that developed various particular questions of neurophysiology were of an analytical nature and could not rise to the level of a broad generalization of the facts found. What was needed was a brilliant swing of Pavlovian thought in order to bring into the orderly system a mass of extracted, sometimes contradictory facts, obtained as a result of past experience and own experiments, amazing in their perfection, to create a new doctrine of the higher nervous activity of animals and humans.

The doctrine of higher nervous activity associated with the names of I.M. Sechenova and I.P. Pavlova, built on a reflex principle. Reflex refers to the response of the body to environmental stimulation through the nervous system. Recognizing that the existence of organisms is possible only in conjunction with the external environment, Pavlov pointed out that the interaction is carried out using special connections, or reflexes. Reflex, according to Pavlov, is a connection that is established between one or another agent of the external environment with one or another activity of the body, carried out through a system of nerve receptors.

The basis of reflex theory are the following basic principles:

1. The principle of determinism is that each phenomenon has its own reason, a certain impetus, an occasion for its development. Hence, a truly scientific study of a phenomenon should first of all clarify the causes of its origin.

2. The principle of structurality. Arguing that the physiological basis of higher nervous activity is the formation of nerve connections (conditioned reflexes) that reflect the outside world, Pavlov, at the same time, timed the formation of conditioned reflexes to the structures and systems of the brain, which in each nervous act enter into new functional relationships.

3. The principle of analysis and synthesis. The cerebral cortex receives countless irritations of the external world, as well as impulses from the internal environment (internal organs). This makes it necessary to first differentiate the complex of incoming stimuli, which occurs through analysis. At the same time, for the regulation of all processes occurring in the body, for the creation of appropriate forms of adaptation to the external environment, it is necessary to generalize the irritations identified by the analysis, i.e. synthesis. Thus, by analysis, the nervous connection can be divided into large fractions. Synthesis, on the other hand, brings together many bonds into an integrated functional system. Analysis and synthesis are the main physiological mechanism of cortical activity. In his experiments, I.P. Pavlov combined the methods of analysis and synthesis and achieved the depth and comprehensiveness of the study of the subject.
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The role of IM. Sechenova and I.P. Pavlova in creating modern physiology of the brain

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