Aging, Physiology of

a branch of human and animal physiology concerned with the patterns of formation and development of physiological functions during ontogeny—from fertilization of the egg cell to the end of life. It studies the body’s functional characteristics, systems, organs, and tissues at different ages. The life cycle of all animals and man consists of certain stages or periods. For example, mammalian development goes through the following periods: intrauterine (including the phases of embryonal and placental development), first hours after birth, lactation, puberty, maturity, and senescence.

The following age periodization has been proposed (Moscow, 1967) for man: (1) birth (1-10 days); (2) infancy (10 days-1 year); (3) childhood: (a) early (1-3 years), (b) first (4-7 years), and (c) second (8-12 years for boys and 8-11 years for girls); (4) adolescence (13-16 years for boys and 12-15 years for girls); (5) youth (17-21 for boys and 16-20 for girls); (6) adulthood: first period (22-35 for men and 21-35 for women) and second period (36-60 for men and 36-55 for women); (7) middle age (61-74 for men and 56-74 for women); (8) old age (75-90); and (9) advanced old age (90 and older).

I. M. Sechenov (1878) indicated the importance of studying the physiological processes from the ontogenetic stand-point. The first data on the functional characteristics of the nervous system in early ontogeny were obtained by I. R. Tarkhanov (1879) and V. M. Bekhterev (1886). Similar studies were done in other countries as well. The German physiologist W. Preyer (1885) investigated blood circulation, respiration, and other functions of developing mammals, birds, and amphibians, and the Czech biologist E. Babak studied amphibian ontogeny (1909). N. P. Gundobin’s book Peculiarities of Childhood (1906) laid the foundation for a systematic study of the morphology and physiology of the developing human organism.

Research in the field of the physiology of aging expanded considerably in the second half of the 20th century, particularly in the USSR. Information was obtained on the structural and functional developmental characteristics of individual organs and systems: higher nervous activity (L. A. Orbeli, N. I. Krasnogorskii, A. G. Ivanov-Smolenskii, A. A. Volokhov, N. I. Kasatkin, M. M. Kol’tsova, A. N. Kabanov); the cerebral cortex, subcortical structures, and their interrelations (P. K. Anokhin, I. A. Arshavskii, E. Sh. Ayrapetiants, A. A. Markosian, A. A. Volokhov, and others); locomotor apparatus (V. G. Shtefko, V. S. Farfel’, L. K. Semenova); cardiovascular and respiratory systems (F. I. Val’ker, V. I. Puzik, N. V. Lauer, I. A. Arshavskii, V. V. Frol’kis); and blood circulation (A. F. Tur, A. A. Markosian). Effective work was done on neurophysiology and endocrinology in aging, age-related changes in metabolism and energy, cellular and subcellular processes, and also on acceleration—that is, accelerated development of the human body.

Various concepts of ontogeny and aging were formed: by A. A. Bogomolets on the role of the physiology of connective tissue; by A. V. Nagornyi on the significance of intensity of self-renewal of protein (damped curve); by P. K. Anokhin on system genesis—that is, maturation in ontogeny of certain functional systems responsible for adaptive reactions; by I. A. Arshavskii on the role of motor activity in development (energy rule of skeletal muscles); and by A. A. Markosian on the reliability of the biological system that ensures the development and existence of organisms under changing environmental conditions.

Researchers in the physiology of aging use both the techniques employed in physiology and the comparative method—that is, comparing the functioning of various systems at different ages, including middle and old age. The physiology of aging is closely associated with the allied sciences of morphology, biochemistry, biophysics, and anthropology. It is the scientific and theoretical foundation of such branches of medicine as pediatrics, the hygiene of children and adolescents, gerontology, and geriatrics, and of pedagogy, psychology, and physical education as well. Therefore, the study of the physiology of aging is expanding in the various institutions, organized in the USSR in 1918, that are concerned with the health protection of children and in the physiological institutes and laboratories of the Academy of Sciences of the USSR, the Academy of Pedagogical Sciences of the USSR, and the Academy of Medical Sciences of the USSR. In 1970 a course on the physiology of aging was made mandatory in all the departments of pedagogical institutes. The conferences on the morphology, physiology, and biochemistry of aging sponsored by the Institute of the Physiology of Aging of the Academy of Pedagogical Sciences of the USSR plays a major role in coordinating research in the field. The Ninth Conference (Moscow, April 1969) coordinated the work of 247 scientific research and pedagogical institutions of the Soviet Union.