Theoretical foundations of age-related physiology (developmental physiology) of the child. Maryana Bezrukikh - Age physiology: (Physiology of child development)

MM. Bezrukikh, V.D. Sonkin, D.A. farber

Age physiology: (Physiology of child development)

Tutorial

For students of higher pedagogical educational institutions

Reviewers:

doctor of biological sciences, head. Department of Higher Nervous Activity and Psychophysiology of St. Petersburg University, Academician of the Russian Academy of Education, Professor A.S. Batuev;

Doctor of Biological Sciences, Professor I.A. Kornienko

FOREWORD

Elucidation of the patterns of child development, the specifics of the functioning of physiological systems at different stages of ontogenesis and the mechanisms that determine this specificity is necessary condition ensuring the normal physical and mental development of the younger generation.

The main questions that parents, educators and psychologists should have in the process of raising and educating a child at home, in kindergarten or at school, at a consultative appointment or individual lessons, are what kind of child he is, what are his features, what option of training with him will be the most effective. Answering these questions is not at all easy, because this requires deep knowledge about the child, the patterns of his development, age and individual characteristics. This knowledge is also extremely important for developing the psychophysiological foundations for organizing educational work, developing mechanisms for adaptation in a child, determining the impact of innovative technologies on him, etc.

Perhaps, for the first time, the importance of a comprehensive knowledge of physiology and psychology for a teacher and educator was highlighted by the famous Russian teacher K.D. Ushinsky in his work "Man as an object of education" (1876). “The art of education,” wrote K.D. Ushinsky, - has the peculiarity that it seems familiar and understandable to almost everyone, and even an easy matter to others - and the more understandable and easier it seems, the less a person is familiar with it theoretically and practically. Almost everyone admits that parenting requires patience; some think that it requires an innate ability and skill, that is, a habit; but very few have come to the conclusion that, in addition to patience, innate ability and skill, special knowledge is also needed, although our numerous wanderings could convince everyone of this. It was K.D. Ushinsky showed that physiology is one of those sciences in which "facts are stated, compared and grouped, and those correlations of facts in which the properties of the object of education, i.e., a person, are found." Analyzing the physiological knowledge that was known, and this was the time of the formation of age physiology, K.D. Ushinsky emphasized: “From this source, which is just opening up, education has almost not yet scooped.” Unfortunately, even now we cannot talk about the wide use of age-related physiology data in pedagogical science. The uniformity of programs, methods, textbooks is a thing of the past, but the teacher still does not take into account the age and individual characteristics of the child in the learning process.

At the same time, the pedagogical effectiveness of the learning process largely depends on how the forms and methods of pedagogical influence are adequate to the age-related physiological and psychophysiological characteristics of schoolchildren, whether the conditions for organizing the educational process correspond to the capabilities of children and adolescents, whether the psychophysiological patterns of the formation of basic school skills - writing and reading, as well as basic motor skills in the process of classes.

The physiology and psychophysiology of a child is a necessary component of the knowledge of any specialist working with children - a psychologist, educator, teacher, social educator. “Upbringing and education deals with a holistic child, with his holistic activity,” said the well-known Russian psychologist and teacher V.V. Davydov. - This activity, considered as a special object of study, contains in its unity many aspects, including ... physiological "(V.V. Davydov" Problems of developmental education. - M., 1986. - P. 167).

age physiology- the science of the features of the life of the body, the functions of its individual systems, the processes occurring in them, and the mechanisms of their regulation at different stages of individual development. Part of it is the study of the physiology of the child in different age periods.

A textbook on age-related physiology for students of pedagogical universities contains knowledge about human development at those stages when the influence of one of the leading factors of development, education, is most significant.

The subject of age physiology (physiology of child development) as academic discipline are the features of the development of physiological functions, their formation and regulation, the vital activity of the organism and the mechanisms of its adaptation to the external environment at different stages of ontogenesis.

Basic concepts of age physiology:

organism - the most complex, hierarchically (subordinately) organized system of organs and structures that ensure vital activity and interaction with the environment. The basic unit of an organism is cell . A collection of cells that are similar in origin, structure and function forms the cloth . Tissues form organs that perform specific functions. Function - specific activity of an organ or system.

Physiological system - a set of organs and tissues related by a common function.

Functional system - dynamic association of various organs or their elements, whose activities are aimed at achieving a specific goal (beneficial result).

As for the structure of the proposed textbook, it is built in such a way that students have a clear idea of the patterns of development of the body in the process of ontogenesis, the features of each age stage.

We tried not to overload the presentation with anatomical data and at the same time considered it necessary to give basic ideas about the structure of organs and systems at different stages of age development, which is necessary for understanding the physiological patterns of organization and regulation of physiological functions.

The book consists of four sections. Section I - "Introduction to developmental physiology" - reveals the subject of developmental physiology as an integral part of developmental physiology, gives an idea of the most important modern physiological theories of ontogenesis, introduces basic concepts, without which it is impossible to understand the main content of the textbook. In the same section, the most general idea of the structure of the human body and its functions is given.

Section II - "The Organism and the Environment" - gives an idea of the main stages and patterns of growth and development, the most important functions of the body that ensure the interaction of the body with the environment and its adaptation to changing conditions, the age development of the body and characteristic features stages of individual development.

Section III - "The Organism as a Whole" - contains a description of the activities of systems that integrate the body into a single whole. First of all, it is the central nervous system, as well as the autonomic nervous system and the system of humoral regulation of functions. The main patterns of age-related development of the brain and its integrative activity are the key aspect of the content of this section.

Section IV - "Stages of Child Development" - contains a morphophysiological description of the main stages of child development from birth to adolescence. This section is most important for practitioners who work directly with the child, for whom it is important to know and understand the basic morphological and functional age-related characteristics of the child's body at each stage of its development. To understand the contents of this section, it is necessary to master all the material presented in the previous three. This section concludes with a chapter that examines the impact of social factors on child development.

At the end of each chapter are questions for independent work students, which allow you to refresh the memory of the main provisions of the studied material that require special attention.

INTRODUCTION TO AGE PHYSIOLOGY

Chapter 1

The relationship of age physiology with other sciences

By the time of birth, the child's body is still very far from a mature state. A human cub is born small, helpless, it cannot survive without the care and care of adults. It takes a long time for it to grow and become a full-fledged mature organism.

age physiology

1. The subject of age physiology. Communication of age physiology with other biological disciplines. The value of age physiology for pedagogy, psychology, medicine and physical education.

Age physiology is a science that studies the patterns of formation and features of the functioning of the body in the process of ontogenesis.

The structure and functions of any organ are inextricably linked. It is impossible to know the functions of the body, its organs, tissues and cells without knowing their structure. Therefore, physiology is closely related to the achievements of human anatomy, histology and cytology. The basic patterns of life are inherent in the entire world of animals. But in the process of evolution, the forms of manifestation of these regularities changed and became more complicated. To study the life of any organism, it is necessary to understand the history of its species development - phylogenesis (the historical development of the organism). Therefore, in age-related physiology, the data of evolutionary doctrine are widely used, and the main stages in the development of various organs of animals are traced. From this, the connection between age-related physiology and evolutionary physiology becomes clear.

The need for teachers and educators to know the age characteristics of the functioning of the child's body has been repeatedly emphasized by scientists.

The first thing a teacher should know is the structure and life of the human body and its development. Without this, it is impossible to be a good teacher, to properly raise a child.

The pedagogical effectiveness of upbringing and education is closely dependent on the extent to which the anatomical and physiological characteristics of children and adolescents are taken into account, periods of development that are characterized by the greatest susceptibility to the effects of certain factors, as well as periods of increased sensitivity and reduced body resistance. Knowledge of the physiology of the child is necessary in physical education to determine effective methods teaching motor actions in the classroom physical education, to develop methods for the formation of motor skills, the development of motor qualities, to determine the content of physical education and health work at school.

Age features development of the stomach, pancreas, intestines.

Abdominal digestion is known to be carried out mainly by enzymes. pancreas , but in newborns it is poorly developed. The mass of the gland is 2-4 g, by the end of 1 year it reaches 10-12 g (in adults - 60-115 g).

Granulocytes of the pancreas of the newborn are slightly reactive to stimulants. The development of the secretion of various enzymes proceeds heterochronously. The transition to mixed and especially artificial feeding significantly increases the secretion and release of pancreatic enzymes. At the age of 2 years, the secretion of proteases, lipases and carbohydrases is well stimulated.

Regulation of pancreatic secretion is carried out by nervous and humoral mechanisms. In the regulation of the secretion of the duodenum, the importance of the nature of nutrition is especially great. This influence, which is formed with the transition to definitive nutrition, is heterochronous for the secretion of various enzymes. Bile plays an important role in intestinal digestion.

A number of major metabolic pathways are common to most cells and organisms. These pathways, which result in the synthesis, destruction and interconversion of the most important metabolites, as well as the accumulation of chemical energy, are called intermediate metabolism. Here is a highly simplified diagram of these processes.

Heterotrophs, such as animals and fungi, depend on obtaining organic matter from food. Because most of these nutrients (proteins, carbohydrates, nucleic acids and lipids) cannot be utilized directly, they are first degraded to smaller fragments in a catabolic way (red arrows in the diagram). The resulting metabolites (collectively sometimes referred to as the "metabolite pool") are then catabolized to release free energy or used in anabolic pathways (blue arrows) to synthesize more complex molecules. Of the numerous metabolites, only the three most important representatives are represented here - pyruvate, acetyl-CoA and glycerol. These three compounds are the link between the metabolism of proteins, carbohydrates and lipids. The metabolic pool also includes intermediate metabolites of the citrate cycle (6). This cyclic pathway plays both a catabolic and anabolic role, that is, it is amphibolic (see p.). The end products of the breakdown of organic matter in animals are carbon dioxide (CO 2), water (H 2 O) and ammonia (NH 3). Ammonia is converted into urea and in this form is excreted from the body. The most important form of storage of chemical energy in cells is adenosine triphosphate (ATP, see p.). Energy must be expended on the formation of ATP, i.e., the reaction is endoergic. At the same time, when ATP is broken down into ADP and phosphate, free energy is released. Due to exoergic hydrolysis. Most 3. use this energy to synthesize new necessary compounds and do work.

Metabolism consists of two independent opposite processes:

Catabolism - the breakdown of incoming substances; directed downward, accompanied by the release of energy, which accumulates in the form of ATP;
anabolism - the synthesis of complex molecules from simpler ones; directed upwards, accompanied by the expenditure of energy.

At a young age, the predominance of anabolic processes (growth) over catabolic ones is characteristic. This is especially pronounced after birth and continues until about 18-19 years. During this period, the growth of organs and tissues ends, the full formation of the whole organism begins, and the processes of creation and decay come into balance.

With age, the processes of catabolism begin to predominate, which leads to a decrease (up to a complete cessation) in the production and content in the body of many of the most important substances for life. For example, the synthesis of coenzyme Q10 or levocarnitine stops, and so on. The result is the appearance of various age-related diseases, the loss of vital energy, a decrease in the capabilities of internal organs and muscle strength.

Replenishment of the deficiency of such substances is currently possible with correct use high-quality biologically active additives (bad).

Factors that determine the age-related dynamics of energy metabolism.

In extreme old age (the phase of regressive development), there is a decrease in body weight, as well as a decrease in the linear dimensions of the human body, the main metabolism drops to low values. Moreover, the degree of decrease in basal metabolism at this age correlates, according to various researchers, with how old people show signs of decrepitude and lost working capacity.

As for sex differences in the level of basal metabolism, they are found in ontogeny already from 6-8 months. At the same time, the basal metabolism in boys is higher than in girls. Such relationships persist during puberty, and by old age they are smoothed out.

In ontogeny, not only average value energy metabolism, but also significantly change the possibility of increasing this level in conditions of intense, for example, muscle activity.

In early childhood, the lack of functional maturity of the musculoskeletal, cardiovascular and respiratory systems limits the adaptive capabilities of the energy metabolism reaction when physical activity. AT adulthood adaptive capacity, as well as muscle strength, reach a maximum. In old age, the possibilities of a compensatory increase in the level of respiration and energy exchange under stress are exhausted due to a decrease in VC, the coefficient of oxygen utilization by tissues, and a decrease in the functions of the cardiovascular system.

An increase in skeletal muscle tone with insufficient activity of the vagus nerve center during the first year of life contributes to an increase in energy metabolism. The role of age-related restructuring of the activity of skeletal muscles in the dynamics of energy metabolism is especially clearly distinguished in the study of gas exchange in people. different ages at rest and during physical activity. For progressive growth, an increase in metabolism at rest is characterized by a decrease in the level of basal metabolism and an improvement in energy adaptation to muscle activity. During the period of the stable phase, a high exchange of functional rest is maintained and the exchange during work increases significantly, reaching a stable, minimum level of basal metabolism. And in the regressive phase, the difference between the exchange of functional rest and the main exchange continuously decreases, the rest time lengthens. Changes in the nature of the central regulators of metabolism - the nervous and endocrine systems - are essential in the age-related dynamics of metabolism.

Many researchers believe that the decrease in the energy metabolism of the whole organism during ontogenesis is primarily due to quantitative and qualitative changes in metabolism in the tissues themselves, the magnitude of which is judged by the ratio between the main mechanisms of energy release - anaerobic and aerobic. This allows us to find out the potential capabilities of tissues to generate and use the energy of macroergic bonds. Tissue respiration is currently being studied using the polarographic method, by O 2 tension in tissues, or by oxygenometry, by the degree of blood oxygenation. Using these methods, Ivanov (1973) showed that the amount of oxygen exchange in the tissues of the subcutaneous tissue in people in extreme old age (90-106 years) is reduced compared to subjects aged 19-32 years, while the conditions for oxygen diffusion to tissues worsen. With age, a kind of restructuring of the bioenergy of the heart muscle also occurs, it oxidizes energetically more efficient fatty acids less and less and retains the ability to oxidize energetically less valuable glucose at the same level. Thus, the bioenergetics of the heart in old age changes dramatically at the subcellular level. With age, parallel changes occur in the system of generation and use of macroergic compounds (ATP and creatine phosphate). For example, the concentration of ATP and CP in the muscles of white rats reaches a maximum value in adulthood and falls in old age; these shifts reflect the functional changes in skeletal muscles throughout life.

Age features of higher nervous activity.

Higher nervous activity represents the integrative ability of the higher parts of the brain to provide an individual behavioral adaptation of a person to changing conditions of the internal and external environment. The theory of higher nervous activity is built on the following basic basis:

1. on the concepts of reflex theory,

2. on the theory of reflection,

3. on the theory of systemic activity of the brain.

Development of conditioned reflexes. A child is born with a certain set of innate, unconditioned reflex reactions. From the second day of life, he begins to develop conditioned connections. For example, on the 2-5th day, a reaction to the position for feeding is formed, an orienting reflex occurs. From the 6th day, a leukocyte conditioned reflex reaction to food intake appears. On the 7-15th day of a child's life, conditioned reflexes to sound and vestibular stimuli appear. At 2 months, reflexes can be developed from any analyzer. In the second year of life, the child develops a large number of conditioned reflexes to the ratio of the size, severity, distance of objects. In the process of formation of a conditioned reflex, four stages are distinguished:

The stage of a non-specific reaction, which is characterized by the appearance of an orienting reaction to a stimulus;

the stage of inhibition, at which the child's activity is inhibited under the action of a conditioned signal;

The stage of an unstable conditioned reflex, when conditioned stimuli do not always cause a response;

stage of a stable conditioned reflex.

With age, the rate of development of conditioned reflexes increases. The systems of conditional connections developed in the early and before school age(up to 5 years), are especially durable and retain their value throughout life.

External unconditional braking. External unconditional inhibition appears in a child from the first days of life. At 6-7 years of age, the importance of external inhibition for higher nervous activity decreases and the role of internal inhibition increases.

Internal braking. Internal inhibition appears in a child approximately from the 20th day after birth in the form of a primitive form of differential inhibition. Fading inhibition appears at 2-2.5 months, conditioned inhibition is observed at 2.5-3 months, and delayed inhibition - from 5 months.

dynamic stereotype. In early childhood, stereotypes are of particular importance. They facilitate the adaptation of children to the environment, are the basis for the formation of habits and skills. In children under three years of age, stereotypes are easily developed and help the child develop the conditioned reflexes necessary for life with their help.

Speech development. The development of speech is the process of development of the second signal system. The terms of development of sensory and motor speech do not coincide. The development of sensory speech precedes the development of motor speech. Even before the child begins to speak, he already understands the meaning of the words. In the formation of speech, the following stages are distinguished:

1. Preparatory stage, or the stage of pronunciation of individual sounds and syllables (from 2-4 to 6 months);

2. The stage of the emergence of sensory speech, that is, the manifestation of the first signs of a conditioned reflex to the word, to its meaning (6-8 months);

3. The stage of the emergence of motor speech, that is, the pronunciation of meaningful words (10-12 months).

Up to 2 months, the child's vocabulary is 10-12 words, by 18 months - 30-40 words, by 24 months - 200-300 words, by 36 months - 500-700, in some cases - up to 1500 words. By the age of 6-7, the ability to internal (semantic) speech appears.

Development of thinking. Visual-effective thinking is formed in preschool and primary school age. Verbal-logical thinking manifests itself by the age of 8-9, reaching development by the age of 14-18.

Behavior Development. The behavioral act is carried out according to two principles:

on the principle of reflex, that is, from stimulus to action;

· according to the principle of self-regulation – when one or another physiological indicator deviates from the level that ensures normal life activity, a behavioral reaction is activated, which restores homeostasis.

Sensory, motor, central and some neurohumoral mechanisms are involved in the organization of behavior. Sensor systems provide recognition of stimuli of the external and internal environment. Motor systems implement the motor program in accordance with sensory information. Central systems connect sensory and motor systems to ensure the adaptive behavior of the whole organism in accordance with changing environmental conditions and on the basis of dominant motivation.

For a person, the most important behavior is communicative behavior. The formation of communicative behavior requires visual, acoustic, olfactory and tactile information.

Eye contact for a child is very important for establishing relationships with others. A child aged 1-1.5 weeks distinguishes well common features presented objects, and it is they, and not their form, that are the most essential for him.

Acoustic contact is carried out in the form of a speech dialogue. It is believed that the child reacts to the sounds of speech from birth. In infants 4-5 months old, an "revitalization complex" of maximum strength and duration, including "cooing", is observed in the speech of an adult.

· Tactile sensitivity provides perception of external stimuli in a wide range, so for newborns and young children it is of great cognitive importance. Especially effective are tactile contacts in the first trimester of life.

With age, the role of vision and hearing in ensuring communicative behavior increases. The first communicative interactions occur even before the birth of a child in the "mother-fetus" system. The connection between the mother and the fetus is carried out through tissue contacts. After birth, the mother-child relationship continues in the mother-child system. Already from the 3rd day after birth, a newborn is able to distinguish the smell of milk and the body of his mother from the smell of other people. After the 3rd month of life, the child switches to interactions with other family members. Starting from 2-2.5 years old, children can create groups of 3-4 people. Moreover, boys interact more often than girls. In the presence of mothers, children prefer interaction with adults.

14. Analytical and synthetic activity in different periods of human ontogenesis.

The physiological basis of the processes of higher nervous activity is the analytical and synthetic activity of the cerebral cortex.

Analytical activity of the cortex of the brain lies in its ability to separate, isolate and distinguish between individual stimuli, that is, to differentiate them.

Synthetic activity of the cortex of the cerebral hemispheres is manifested in the unification, generalization of the excitation that occurs in its various parts from the action of various stimuli.

Analysis and synthesis of specific signals are first signal system man and animals. Second signal system- these are nervous processes that occur in the hemispheres of the human brain as a result of the perception of signals from the surrounding world in the form of speech designations. The second signaling system is the basis human thinking, it is socially conditioned. Outside of society, without communication with other people, it does not develop. The first and second signal systems are inseparable from each other, they function together and determine the unity of the higher nervous activity of a person.

15. Qualitative differences in human GNI. Development of the second signal system.

The main laws of higher nervous activity include:

1) the formation of new temporary connections when a neutral stimulus is reinforced with an unconditioned one;

2) the extinction of temporary connections when the conditioned stimulus is not reinforced by the unconditioned one;

3) irradiation and concentration of nervous processes;

4) mutual induction of nervous processes;

5) the formation of complex dynamic systems of reflexes, the so-called dynamic stereotypes.

The neuroanatomical substrate for the formation and extinction of temporary connections, differentiation and integration of stimuli is the cerebral cortex. In the subcortical regions of the brain are the nerve centers of the most important unconditioned reflexes, which form the basis for the formation of a conditioned reflex. The subcortical sections provide a high level of activity of the nerve cells of the cerebral cortex, thereby creating the necessary conditions for the formation of temporary connections and their differentiation. At the same time, the functioning of the subcortical regions of the brain is controlled by the cortex, which stimulates and inhibits the development of their activity.

The qualitative difference between the higher nervous activity of man and animals is due to the fact that a person has become more complex in the mechanisms of his mental activity, since a special stimulus has appeared - the word.

(PHYSIOLOGY OF CHILD DEVELOPMENT)

Tutorial

For students of higher pedagogical educational institutions

M.M. Bezrukikh I (1, 2), III (15), IV (18-23),

V.D. Sonkin I (1, 3), II (4-10), III (17), IV (18-22),

D.A. Farber I (2), III (11-14, 16), IV (18-23)

Reviewers:

doctor of biological sciences, head. Department of Higher Nervous Activity and Psychophysiology, St. Petersburg University, Academician of the Russian Academy of Education,

Professor A. S. Batuev; Doctor of Biological Sciences, Professor I.A. Kornienko

Bezrukikh M. M. and etc.

Age physiology: (Physiology of child development): Proc. allowance for students. higher ped. studies, institutions / M. M. Bezrukikh, V. D. Sonkin, D. A. Farber. - M.: Publishing Center "Academy", 2002. - 416 p. ISBN 5-7695-0581-8

The textbook presents modern concepts of human ontogenesis, taking into account the latest achievements in anthropology, anatomy, physiology, biochemistry, neuro- and psychophysiology, etc. The morphological and functional features of the child at the main stages of age development, their connection with the processes of socialization, including education and upbringing, are considered. The book is illustrated with a large number of diagrams, tables, drawings that facilitate the assimilation of the material, questions for self-examination are proposed.

AGE PHYSIOLOGY 1

Tutorial 1

FOREWORD 3

Section I INTRODUCTION TO AGE PHYSIOLOGY 7

Chapter 1

Chapter 2. THEORETICAL FOUNDATIONS OF AGE PHYSIOLOGY 18

(PHYSIOLOGY OF DEVELOPMENT) 18

Chapter 3. GENERAL PLAN OF THE STRUCTURE OF THE ORGANISM 28

Section II ORGANISM AND ENVIRONMENT 39

Chapter 4. GROWTH AND DEVELOPMENT 39

Chapter 5. ORGANISM AND ITS HABITAT 67

Chapter 6. INTERNAL ENVIRONMENT OF THE ORGANISM 82

Chapter 7. METABOLISM (METABOLISM) 96

Chapter 8. SYSTEM OF OXYGEN SUPPLY OF THE ORGANISM 132

Chapter 9. PHYSIOLOGY OF ACTIVITY AND ADAPTATION 162

Chapter 10

Section III THE ORGANISM AS A WHOLE 199

Chapter 11. NERVOUS SYSTEM: SIGNIFICANCE AND STRUCTURAL AND FUNCTIONAL ORGANIZATION 199

Chapter 12

Chapter 13. REGULATION OF THE FUNCTIONAL STATE OF THE BRAIN 219

Chapter 14. INTEGRATIVE ACTIVITY OF THE BRAIN 225

Chapter 15. CENTRAL MOVEMENT REGULATION 248

Chapter 16

Chapter 17

Section IV STAGES OF CHILD DEVELOPMENT 297

Chapter 18. INFANTITY (from 0 to 1 year) 297

Chapter 19. EARLY AGE 316

(FROM 1 YEAR TO 3 YEARS) 316

Chapter 20. PRESCHOOL 324

(FROM 3 TO 6-7 YEARS) 324

Chapter 21

Chapter 22

Chapter 23. SOCIAL FACTORS OF DEVELOPMENT AT DIFFERENT STAGES OF ONTOGENESIS 369

LITERATURE 382

FOREWORD

Elucidation of the patterns of child development, the specifics of the functioning of physiological systems at different stages of ontogenesis and the mechanisms that determine this specifics, is a necessary condition for ensuring the normal physical and mental development of the younger generation.

Perhaps, for the first time, the importance of a comprehensive knowledge of physiology and psychology for a teacher and educator was highlighted by the famous Russian teacher K.D. Ushinsky in his work “Man as an Object of Education” (1876). “The art of education,” wrote K.D. Ushinsky, “has the peculiarity that it seems familiar and understandable to almost everyone, and even an easy matter to others, and the more understandable and easier it seems, the less a person is theoretically familiar with it. and practically. Almost everyone admits that parenting requires patience; some think that it requires an innate ability and skill, i.e. skill; but very few have come to the conclusion that, in addition to patience, innate ability and skill, special knowledge is also needed, although our numerous wanderings could convince everyone of this. It was K.D. Ushinsky who showed that physiology is one of those sciences in which “facts are stated, compared and grouped together, and those correlations of facts in which the properties of the object of education, i.e., a person, are found.” Analyzing the physiological knowledge that was known, and this was the time of the formation of age-related physiology, K.D. Ushinsky emphasized: “From this source, just opening, education almost did not draw yet.” Unfortunately, even now we cannot talk about the wide use of age-related physiology data in pedagogical science. The uniformity of programs, methods, textbooks is a thing of the past, but the teacher still does not take into account the age and individual characteristics of the child in the learning process.

The physiology and psychophysiology of a child is a necessary component of the knowledge of any specialist working with children - a psychologist, educator, teacher, social pedagogue. “Upbringing and education deals with a holistic child, with his holistic activity,” said the well-known Russian psychologist and teacher V.V. Davydov. - This activity, considered as a special object of study, contains in its unity many aspects, including ... physiological (V.V. Davydov "Problems of developmental education." - M., 1986. - P. 167).

Age physiology is the science of the features of the life of the body, the functions of its individual systems, the processes that take place in them, and the mechanisms of their regulation at different stages of individual development. Part of it is the study of the physiology of the child in different age periods.

The subject of developmental physiology (physiology of child development) as an academic discipline is the features of the development of physiological functions, their formation and regulation, the vital activity of the organism and the mechanisms of its adaptation to the external environment at different stages of ontogenesis.

Basic concepts of age physiology:

An organism is the most complex, hierarchically (subordinately) organized system of organs and structures that ensure vital activity and interaction with the environment. The elementary unit of the organism is the cell. A collection of cells that are similar in origin, structure and function forms a tissue. Tissues form organs that perform specific functions. A function is a specific activity of an organ or system.

Physiological system - a set of organs and tissues related by a common function.

A functional system is a dynamic association of various organs or their elements, the activity of which is aimed at achieving a specific goal (useful result).

Section II - "The Organism and the Environment" - gives an idea of the main stages and patterns of growth and development, the most important functions of the body that ensure the interaction of the body with the environment and its adaptation to changing conditions, the age development of the body and the characteristic features of the stages of individual development.

Section IV - "Stages of child development" - contains a morpho-physiological description of the main stages of child development from birth to adolescence. This section is most important for practitioners who work directly with the child, for whom it is important to know and understand the basic morphological and functional age-related characteristics of the child's body at each stage of its development. To understand the contents of this section, it is necessary to master all the material presented in the previous three. This section concludes with a chapter that examines the impact of social factors on child development.

At the end of each chapter, there are questions for independent work of students, which allow you to refresh the memory of the main provisions of the studied material that require special attention.

Section I INTRODUCTION TO AGE PHYSIOLOGY

Chapter 1

The relationship of age physiology with other sciences

The section of physiological science that studies the biological patterns and mechanisms of growth and development is called age physiology. The development of a multicellular organism (and the human body consists of several billion cells) begins at the moment of fertilization. The entire life cycle of an organism, from conception to death, is called individual development, or ontogenesis.

Patterns and features of the life of the organism on early stages ontogenesis are traditionally the subject of research age physiology (physiology of child development).

The physiology of child development concentrates its interest on those stages that are of greatest interest to the educator, teacher, school psychologist: from birth to morphofunctional and psychosocial maturation. Earlier stages related to intrauterine development are explored by science embryology. Later stages, from reaching maturity to old age, study normal physiology and gerontology.

Man in his development obeys all the basic laws established by Nature for any developing multicellular organism, and therefore developmental physiology is one of the sections of a much broader field of knowledge - developmental biology. At the same time, in the dynamics of human growth, development and maturation, there are many specific, special features that are unique to the species Homo sapience (the Homo sapience). In this plane, developmental physiology is closely intertwined with science anthropology which aims at the comprehensive study of man.

A person always lives in the specific conditions of the environment with which he interacts. Continuous interaction and adaptation to the environment is the general law of the existence of living things. Man has learned not only to adapt to the environment, but also to change the world around him in the necessary direction. However, this did not save him from the influence of environmental factors, and at different stages of age development, the set, strength of action and the result of the influence of these factors may be different. This determines the relationship of physiology with ecological physiology, which studies the impact on a living organism of various environmental factors and ways of adapting the organism to the action of these factors.

During periods of intensive development, it is especially important to know how environmental factors act on a person, how various risk factors influence. This has traditionally received increased attention. And here the physiology of development closely interacts with hygiene, since it is the physiological laws that most often act as the theoretical foundations of hygiene requirements and recommendations.

The role of living conditions, and not only "physical", but also social, psychological, in the formation of a healthy and adapted person is very great. A child should be aware of the value of his health from early childhood, possess the necessary skills to preserve it.

Formation of the value of health and a healthy lifestyle is the task of pedagogical valeology, which draws factual material and basic theoretical provisions from developmental physiology.

Finally, developmental physiology is the natural science basis pedagogy. At the same time, the physiology of development is inextricably linked with the psychology of development, since for each person his biological and personal make up a single whole. No wonder any biological damage (illness, injury, genetic disorders, etc.) inevitably affects the development of the individual. The teacher should be equally well versed in the problems of developmental psychology and physiology of development: only in this case his activity will bring real benefit to his students.

AGE PHYSIOLOGY- a section of physiology that studies the features of the age-related development of the functions of animal and plant organisms from their inception to the cessation of individual existence (death). V. f. explores in each period of ontogenesis (see) the functions of the whole organism, its cells, tissues and functional systems.

The main tasks of V. f.: a) the study of the characteristics of the ontogeny of the organism and its individual systems inherent in each age (see); b) revealing the main factors that determine the general pattern of age-related changes in organisms. The solution of these problems and the creation of a full-fledged theory of ontogenesis (taking into account the characteristics of aging inherent in individual systematic groups of organisms) will facilitate finding ways to control the vital processes of the human body at all stages of ontogenesis (increase in physical and mental abilities, etc.). These tasks closely bring V. f. with pedagogy and pediatrics (see), with gerontology (see) and geriatrics (see). Besides, V. f. is closely connected with biochemistry, molecular biology, biophysics, anatomy, histology and other biol, sciences.

In most lower forms of animals, the main periods of life are the embryonic, larval, and adult stages (in insects, development is accompanied by metamorphosis). In higher vertebrates, periods of ontogeny are close to those of humans.

At the person, on morfol, classifications of VV Bunak (1965), distinguish the following main periods of ontogenesis: prenatal (embryonic, prefetal and fetal phases), infantile, teenage, youthful, adult, elderly, senile and late senile. According to fiziol, the classification of I. A. Arshavsky (1967), a person distinguishes between antenatal ontogenesis with the actual embryonic, or germinal (1 week), embryonic (5 weeks) and fetal (32 weeks) periods and postnatal ontogenesis with the following periods: neonatal (8 days), lactotrophic form of nutrition (5-6 months), combination of lactotrophic form of nutrition with complementary foods (from 6 to 11-12 months), preschool age(from 1 year to 2.5-3 years old), preschool age (from 3 to 7 years old), adolescence (from 7 to 12-13 years old), prepubertal (from 12-13 to 17-18 years old), puberty ( from 18 to 50-60 years old), elderly (from 60 to 75 years old), old age (from 75 to 90 years old), macrobiotic (over 90 years old).

The founder of the domestic V. f. and gerontology can be considered I. I. Mechnikov, who created the theory of aging as a consequence of the struggle of parenchymal and connective tissues in the body and intoxication of the body with the products of decay of proteins in the intestine (“Etudes on Human Nature”, 1903; “Etudes of Optimism”, 1907). His work served as the basis for the study of the problem of aging and death. The idea of death as a result of the depletion of a hypothetical "nuclear substance" (I. R. Tarkhanov, 1891) is consonant with the later concept of J. Lev (1906).

S. I. Metalnikov considered the imperfection of the division of the nuclear apparatus of cells to be the cause of aging. A deep study of the early ontogenesis of c.s.s. and analyzers in humans were carried out by V. M. Bekhterev in 1884-1897. and P.F. Lesgaft in 1884-1909. Problems of comparative physiology and morphology of age development were developed by Preyer (1885) and E. Babak (1902). The founder of national pediatrics, NP Gundobin In the period from 1891 to 1907, he created a multilateral doctrine of the development of the child. Minot (Ch. S. Minot, 1908) put forward the idea of death as a consequence of the weakening of the differentiation of cells and tissues to old age.

Especially intensively in our country V. f. began to develop in the Soviet period. I. P. Pavlov and M. K. Petrova (1936) showed the role of a “breakdown” in c. n. in premature aging of the body. A. A. Bogomolets in 1912-1946 developed and substantiated the theory of the stimulating role of connective tissue for longevity, proposed the use of antireticular cytotoxic serum (ACS) to excite the vital activity of an aging organism, created the theory of colloidoclasic shock as the basis for hemotherapy of aging. II Shmalgauzen (1926) discovered the patterns of growth and differentiation of developing organisms and aging as a consequence of the cessation of growth when maximum differentiation is reached.

A. V. Palladii clarified the biochemical basis of differentiation in early ontogenesis. A. V. Nagorny and his students I. N. Bulankin and V. N. Nikitin created the theory of the fading usefulness of protoplasm self-renewal as the basis of ontogenesis, the doctrine of the initial progressive and then regressive significance of the increase in protoplasm structuredness for the life of the organism (works 30-70 th years). D.F. Chebotarev and V.V. Frolkis since the 50s. study the ontogeny of the functional systems of the body and the features of its adaptation in old age. V. V. Frolkis (1975) put forward the regulatory-adaptive theory of aging, according to which the violation of regulations is considered as the most important attribute of aging. PK Anokhin and his school actively studied the patterns of development of functions in ontogenesis and created a theory of systemogenesis (see), in accordance with the cut, selective and accelerated maturation of morphol, formations provides the body with the ability to adapt to environmental factors.

Foreign scientists Korenchevsky (V. Korenchevsky, from 1925 to 1961) and K. Parkhon (40-60s) showed colloid-chemical and endocrine conditioning of aging. Binet (L. Binet) iF. Burlier (F. Bourliere) in the 50th, and also Shock (N. W. Shock, from 1942 to 1975) investigated fiziol, and patofiziol. changes in the organs and systems of the aging organism. F. Vertsar, Curtis (N. J. Curtis) and Bjorksten (J. Bjorksten) found that the increase in intermolecular bonds in the cell genome and collagen of the intercellular substance of the connective tissue of the body can be the leading cause of aging (works of 50-70 years). A. Comfort (from 1963 to 1975) found patterns of extinction of populations of vertebrate species in ontogeny.

Researches in the field of V. f. at various levels of organization of living matter made it possible to establish the quantitative and qualitative features of the age-related development of macromolecular structures of cells and their individual organelles, the nature of the relationship between cells and tissues inherent in each age, as well as the peculiarity of age-related changes in metabolic processes in tissues and functional systems of the body - in early youth, an increase , and then, towards old age, a slow decrease in the intensity of metabolic processes. When studying age-related changes in neurohumoral regulation and functional capabilities of the whole organism of humans and animals, their qualitative features at each stage of ontogenesis, the presence of high lability and plasticity, combined with the "vulnerability" of the child's body and significant adaptive capabilities of the aging organism, were revealed. Special attention V. t. devotes to the study of the functional characteristics of various periods of the age development of the organism and the factors that determine them, i.e., the definition of objective physiol., biochemical, and biophysic characteristics ("passports"), age standards. The problems of imprinting (see Instinct), the characteristics of the organism during puberty (see), neuroendocrine shifts during periods of female and male menopause (see Menopause), complex adaptive changes in the aging human body (see Old age, aging) are being deeply developed. . Under laboratory conditions, the possibilities of prolonging life and increasing the ability of full-fledged self-renewal of protoplasm at all stages of ontogenesis are being studied.

Bibliography: Arshavsky I. A. Essays on age physiology, M., 1967, bibliogr.; Bogomolets A. A. Life extension, Kyiv, 1940; Bunak VV Allocation of stages of ontogenesis and chronological boundaries of age periods, Owls. Pedagogy, No. 11, p. 105, 1965; Age physiology, ed. V. N. Nikitina, L., 1975; Comfort A. Biology of aging, trans. from English, M., 1967, bibliography; Nagorny A. V., Nikitin V. N. and B at l and N to and N I. N. Problem of aging and longevity, M., 1963; Nikitin V. N. Domestic work on age physiology, biochemistry and morphology, Kharkov, 1958; Par-x about N K. I. Age biology, trans. from Romanian, Bucharest, 1959; Frolkis VV Aging and biological possibilities of an organism, M., 1975; Burger M. Altern und Krankheit, als Problem der Biomorphose, Lpz., 1960; Curtis H. J. Biological mechanisms of aging, Springfield, 1966.

Current page: 1 (total book has 12 pages) [accessible reading excerpt: 8 pages]

Yuri Savchenkov, Olga Soldatova, Sergey Shilov
Age physiology (physiological characteristics of children and adolescents). Textbook for universities

Reviewers:

Kovalevsky V. A. , Doctor of Medical Sciences, Professor, Head of the Department of Childhood Psychology, Krasnoyarsk State Pedagogical University. V. P. Astafieva,

Manchuk V. T. , MD, Corresponding Member RAMS, Professor of the Department of Polyclinic Pediatrics, KrasSMU, Director of the Research Institute of Medical Problems of the North, Siberian Branch of the Russian Academy of Medical Sciences

Introduction

The child's body is an extremely complex and at the same time very vulnerable socio-biological system. It is in childhood that the foundations of the health of the future adult are laid. An adequate assessment of the physical development of a child is possible only if the characteristics of the corresponding age period are taken into account, and the vital signs of this child are compared with the standards of his age group.

Age physiology studies the functional features of the individual development of the body throughout its life. Based on the data of this science, methods of teaching, educating and protecting the health of children are being developed. If the methods of education and training do not correspond to the capabilities of the body at any stage of development, the recommendations may turn out to be ineffective, cause a negative attitude of the child to learning, and even provoke various diseases.

As the child grows and develops, almost all physiological parameters undergo significant changes: blood counts, the activity of the cardiovascular system, respiration, digestion, etc. change. Knowledge of various physiological parameters characteristic of each age period is necessary to assess the development of a healthy child.

In the proposed publication, the features of the age-related dynamics of the main physiological parameters of healthy children of all age groups are summarized and classified according to systems.

The manual on age-related physiology is an additional educational material on the physiological characteristics of children of different ages, which is necessary for assimilation by students who study at pedagogical higher and secondary specialized educational institutions and are already familiar with the general course of human physiology and anatomy.

Each section of the book provides short description the main directions of ontogenesis of indicators of a particular physiological system. In this version of the manual, the sections "Age characteristics of higher nervous activity and mental functions", "Age characteristics of endocrine functions", "Age characteristics of thermoregulation and metabolism" are significantly expanded.

This book contains descriptions of numerous physiological and biochemical parameters and will be useful in practical work not only future teachers, defectologists, child psychologists, but also future pediatricians, as well as already working young professionals and high school students who want to replenish their knowledge of the physiological characteristics of the child's body.

Chapter 1
Age periodization

Patterns of growth and development of the child's body. Age periods of child development

A child is not an adult in miniature, but an organism, relatively perfect for each age, with its own morphological and functional features, for which the dynamics of their course from birth to puberty is natural.

The child's body is an extremely complex and at the same time very vulnerable socio-biological system. It is in childhood that the foundations of the health of the future adult are laid. An adequate assessment of the physical development of a child is possible only if the characteristics of the corresponding age period are taken into account, and the vital signs of a particular child are compared with the standards of his age group.

Growth and development are often used interchangeably. Meanwhile, their biological nature (mechanism and consequences) is different.

Development is a process of quantitative and qualitative changes in the human body, accompanied by an increase in the level of its complexity. Development includes three main interrelated factors: growth, differentiation of organs and tissues, and shaping.

Growth is a quantitative process characterized by an increase in the mass of an organism due to a change in the number of cells and their size.

Differentiation is the emergence of specialized structures of a new quality from poorly specialized progenitor cells. For example, a nerve cell that is laid down in the neural tube of an embryo (embryo) can potentially perform any nervous function. If a neuron migrating to the visual area of the brain is transplanted into the area responsible for hearing, it will turn into an auditory neuron, not a visual one.

Formation is the acquisition by the body of its inherent forms. For example, the auricle acquires the shape inherent in an adult by the age of 12.

In those cases when intensive growth processes simultaneously occur in many different tissues of the body, the so-called growth spurts are noted. This is manifested in a sharp increase in the longitudinal dimensions of the body due to an increase in the length of the trunk and limbs. In the postnatal period of human ontogenesis, such “leaps” are most pronounced:

in the first year of life, when there is a 1.5-fold increase in length and a 3-4-fold increase in body weight;

at the age of 5–6 years, when, mainly due to the growth of the limbs, the child reaches approximately 70% of the body length of an adult;

13-15 years - pubertal growth spurt due to an increase in the length of the body and limbs.

The development of the organism from the moment of birth to the onset of maturity occurs in constantly changing environmental conditions. Therefore, the development of the organism is adaptive, or adaptive, in nature.

To ensure an adaptive result, various functional systems mature non-simultaneously and unevenly, switching on and replacing each other at different periods of ontogenesis. This is the essence of one of the defining principles of the individual development of an organism - the principle of heterochrony, or the non-simultaneous maturation of organs and systems and even parts of the same organ.

The terms of maturation of various organs and systems depend on their significance for the life of the organism. Those organs and functional systems that are most vital at this stage of development grow and develop faster. By combining individual elements of one or another organ with the earliest maturing elements of another organ participating in the implementation of the same function, the minimum provision of vital functions sufficient for a certain stage of development is carried out. For example, to ensure food intake at the time of birth, the circular muscle of the mouth first matures from the facial muscles; from the cervical - the muscles responsible for turning the head; of the receptors of the tongue - receptors located at its root. By this time, the mechanisms responsible for the coordination of respiratory and swallowing movements and ensuring that milk does not enter the respiratory tract mature. This ensures the necessary actions associated with the nutrition of the newborn: the capture and retention of the nipple, sucking movements, the direction of food along the appropriate paths. Taste sensations are transmitted through the receptors of the tongue.

The adaptive nature of the heterochronous development of body systems reflects another of the general principles of development - the reliability of the functioning of biological systems. The reliability of a biological system is understood as such a level of organization and regulation of processes that is able to ensure the vital activity of an organism in extreme conditions. It is based on such properties of a living system as the redundancy of elements, their duplication and interchangeability, the speed of return to relative constancy and the dynamism of individual parts of the system. An example of the redundancy of elements can be the fact that during the period of intrauterine development, from 4,000 to 200,000 primary follicles are laid in the ovaries, from which eggs are later formed, and only 500–600 follicles mature during the entire reproductive period.

Mechanisms for ensuring biological reliability change significantly in the course of ontogeny. In the early stages of postnatal life, reliability is ensured by a genetically programmed association of links of functional systems. In the course of development, as the cerebral cortex, which provides the highest level of regulation and control of functions, matures, the plasticity of connections increases. Due to this, selective formation of functional systems occurs in accordance with a specific situation.

Another important feature of the individual development of the child's body is the presence of periods of high sensitivity of individual organs and systems to the effects of environmental factors - sensitive periods. These are periods when the system is developing rapidly and it needs an influx of adequate information. For example, for the visual system, light quanta are adequate information, for the auditory system, sound waves. The absence or deficiency of such information leads to negative consequences, up to the unformedness of a particular function.

It should be noted that ontogenetic development combines periods of evolutionary, or gradual, morphofunctional maturation and periods of revolutionary, turning points in development associated with both internal (biological) and external (social) factors. These are the so-called critical periods. The inconsistency of environmental influences with the characteristics and functional capabilities of the organism at these stages of development can have detrimental consequences.

The first critical period is considered to be the stage of early postnatal development (up to 3 years), when the most intensive morphofunctional maturation occurs. In the process further development critical periods arise as a result of a sharp change in social and environmental factors and their interaction with the processes of morphofunctional maturation. These periods are:

the age of the beginning of education (6–8 years), when the qualitative restructuring of the morphofunctional organization of the brain falls on a period of a sharp change in social conditions;

the beginning of puberty is the pubertal period (in girls - 11-12 years old, in boys - 13-14 years old), which is characterized by a sharp increase in the activity of the central link of the endocrine system - the hypothalamus. As a result, there is a significant decrease in the effectiveness of cortical regulation, which determines voluntary regulation and self-regulation. Meanwhile, it is at this time that social requirements for a teenager increase, which sometimes leads to a discrepancy between the requirements and the functional capabilities of the body, which may result in a violation of the physical and mental health of the child.

Age periodization of the ontogeny of a growing organism. There are two main periods of ontogeny: antenatal and postnatal. The antenatal period is represented by the embryonic period (from conception to the eighth week of the intrauterine period) and the fetal period (from the ninth to the fortieth week). Usually pregnancy lasts 38-42 weeks. The postnatal period covers the period from birth to the natural death of a person. According to the age periodization adopted at a special symposium in 1965, the following periods are distinguished in the postnatal development of the child's body:

newborn (1–30 days);

chest (30 days - 1 year);

early childhood (1–3 years);

first childhood (4–7 years);

second childhood (8-12 years old - boys, 8-11 years old - girls);

teenage (13-16 years old - boys, 12-15 years old - girls);

youth (17–21 years old boys, 16–20 years old girls).

Considering the issues of age periodization, it must be borne in mind that the boundaries of the stages of development are very arbitrary. All age-related structural and functional changes in the human body occur under the influence of heredity and environmental conditions, that is, they depend on specific ethnic, climatic, social and other factors.

Heredity determines the potential for physical and mental development individual. So, for example, the short stature of African pygmies (125–150 cm) and the tall stature of the representatives of the Watussi tribe are associated with the characteristics of the genotype. However, in each group there are individuals in whom this indicator may differ significantly from the average age norm. Deviations can occur due to the impact on the body of various environmental factors, such as nutrition, emotional and socio-economic factors, the position of the child in the family, relationships with parents and peers, the level of culture of society. These factors can interfere with the growth and development of the child, or vice versa, stimulate them. Therefore, the indicators of growth and development of children of the same calendar age can vary significantly. It is generally accepted to form groups of children in preschool institutions and classes in secondary schools according to calendar age. In this regard, the educator and teacher must take into account the individual psychophysiological characteristics of development.

Growth and developmental delay, called retardation, or advanced development - acceleration - indicate the need to determine the biological age of the child. Biological age, or developmental age, reflects the growth, development, maturation, aging of the organism and is determined by a combination of structural, functional and adaptive features of the organism.

Biological age is determined by a number of indicators of morphological and physiological maturity:

according to the proportions of the body (the ratio of the length of the body and limbs);

the degree of development of secondary sexual characteristics;

skeletal maturity (the order and timing of ossification of the skeleton);

dental maturity (terms of eruption of milk and molars);

metabolic rate;

features of the cardiovascular, respiratory, neuroendocrine and other systems.

When determining the biological age, the level of mental development of the individual is also taken into account. All indicators are compared with standard indicators characteristic of a given age, gender and ethnic group. At the same time, it is important to take into account the most informative indicators for each age period. For example, in the pubertal period - neuroendocrine changes and the development of secondary sexual characteristics.

To simplify and standardize the average age of an organized group of children, it is customary to consider the age of a child equal to 1 month if his calendar age is in the range from 16 days to 1 month 15 days; equal to 2 months - if his age is from 1 month 16 days to 2 months 15 days, etc. After the first year of life and up to 3 years: 1.5 years include a child with an age of 1 year 3 months to 1 year 8 months and 29 days, to the second years - from 1 year 9 months to 2 years 2 months 29 days, etc. After 3 years at yearly intervals: 4 years includes children aged 3 years 6 months to 4 years 5 months 29 days, etc.

Chapter 2
Excitable tissues

Age-related changes in the structure of a neuron, nerve fiber and neuromuscular synapse

Different types of nerve cells in ontogeny mature heterochronously. Most early, even in the embryonic period, large afferent and efferent neurons mature. Small cells (interneurons) mature gradually during postnatal ontogenesis under the influence of environmental factors.

Separate parts of the neuron also do not mature at the same time. Dendrites grow much later than the axon. Their development occurs only after the birth of a child and largely depends on the influx of external information. The number of dendrite branches and the number of spines increase in proportion to the number of functional connections. The most branched network of dendrites with a large number of spines are neurons of the cerebral cortex.

Myelination of axons begins in utero and occurs in next order. First of all, the peripheral fibers are covered with a myelin sheath, then the fibers of the spinal cord, the brain stem (medulla oblongata and midbrain), the cerebellum, and the last - the fibers of the cerebral cortex. In the spinal cord, motor fibers are myelinated earlier (by 3–6 months of life) than sensitive ones (by 1.5–2 years). Myelination of brain fibers occurs in a different sequence. Here, sensory fibers and sensory areas are myelinated earlier than others, while motor fibers are myelinated only 6 months after birth, or even later. Myelination is generally completed by 3 years of age, although growth of the myelin sheath continues until approximately 9–10 years of age.

Age-related changes also affect the synaptic apparatus. With age, the intensity of the formation of mediators in the synapses increases, the number of receptors on the postsynaptic membrane that respond to these mediators increases. Accordingly, as development increases, the speed of impulse conduction through synapses increases. The influx of external information determines the number of synapses. First of all, synapses of the spinal cord are formed, and then other departments nervous system. Moreover, excitatory synapses mature first, then inhibitory ones. It is with the maturation of inhibitory synapses that the complication of information processing processes is associated.

Chapter 3
Physiology of the central nervous system

Anatomical and physiological features of the maturation of the spinal cord and brain

The spinal cord fills the cavity of the spinal canal and has a corresponding segmental structure. In the center of the spinal cord is located gray matter (accumulation of nerve cell bodies), surrounded by white matter (accumulation of nerve fibers). The spinal cord provides motor reactions of the trunk and limbs, some autonomic reflexes (vascular tone, urination, etc.) and a conductive function, since all sensitive (ascending) and motor (descending) paths pass through it, along which a connection is established between various parts of the CNS.

The spinal cord develops earlier than the brain. In the early stages of fetal development, the spinal cord fills the entire cavity of the spinal canal, and then begins to lag behind in growth and ends at the level of the third lumbar vertebra by the time of birth.

By the end of the first year of life, the spinal cord occupies the same position in the spinal canal as in adults (at the level of the first lumbar vertebra). At the same time, the segments of the thoracic spinal cord grow faster than the segments of the lumbar and sacral regions. The spinal cord grows slowly in thickness. The most intensive increase in the mass of the spinal cord occurs by the age of 3 (4 times), and by the age of 20 its mass becomes like that of an adult (8 times more than that of a newborn). Myelination of nerve fibers in the spinal cord begins with the motor nerves.

By the time of birth, the medulla oblongata and the bridge are already formed. Although the maturation of the nuclei of the medulla oblongata lasts up to 7 years. The location of the bridge differs from adults. In newborns, the bridge is slightly higher than in adults. This difference disappears by 5 years.

The cerebellum in newborns is still underdeveloped. Enhanced growth and development of the cerebellum is observed in the first year of life and during puberty. Myelination of its fibers ends by about 6 months of age. The complete formation of the cellular structures of the cerebellum is carried out by the age of 7–8, and by the age of 15–16 its dimensions correspond to the level of an adult.

The shape and structure of the midbrain in a newborn is almost the same as in an adult. The postnatal period of maturation of midbrain structures is mainly accompanied by pigmentation of the red nucleus and substantia nigra. Pigmentation of the neurons of the red nucleus begins at the age of two and ends by the age of 4. Pigmentation of neurons in the substantia nigra begins from the sixth month of life and reaches a maximum by the age of 16.

The diencephalon includes two major structures: the thalamus, or thalamus, and the hypothalamus, the hypothalamus. Morphological differentiation of these structures occurs in the third month of intrauterine development.

The thalamus is a multinuclear formation associated with the cerebral cortex. Through its nuclei, visual, auditory and somatosensory information is transmitted to the corresponding associative and sensory zones of the cerebral cortex. The nuclei of the reticular formation of the diencephalon activate cortical neurons that perceive this information. By the time of birth, most of its nuclei are well developed. Enhanced growth of the thalamus occurs at the age of four. The size of an adult thalamus reaches 13 years.

The hypothalamus, despite its small size, contains dozens of highly differentiated nuclei and regulates most autonomic functions, such as maintaining body temperature and water balance. The nuclei of the hypothalamus are involved in many complex behavioral responses: sexual desire, feelings of hunger, satiety, thirst, fear and rage. In addition, through the pituitary gland, the hypothalamus controls the work of the endocrine glands, and the substances formed in the neurosecretory cells of the hypothalamus itself are involved in the regulation of the sleep-wake cycle. The nuclei of the hypothalamus mature mainly by the age of 2–3 years, although the differentiation of cells of some of its structures continues up to 15–17 years.

The most intense myelination of fibers, an increase in the thickness of the cerebral cortex and its layers occurs in the first year of life, gradually slowing down and stopping by 3 years in the projection areas and by 7 years in the associative areas. First, the lower layers of the bark ripen, then the upper ones. By the end of the first year of life, as a structural unit of the cerebral cortex, ensembles of neurons, or columns, are distinguished, the complication of which continues up to 18 years. The most intense differentiation of the intercalated neurons of the cortex occurs at the age of 3 to 6 years, reaching a maximum by 14 years. The full structural and functional maturation of the cerebral cortex reaches approximately 20 years.

Theoretical foundations of age-related physiology (developmental physiology) of the child. Maryana Bezrukikh - Age physiology: (Physiology of child development)

Metabolism consists of two independent opposite processes:

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