Presentation on the topic "features of the nervous system in old age." Features of the nervous system in children Age-related changes in the central nervous system presentation
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Arteries and microvasculature After the birth of a child, as the age increases, the circumference, diameter, thickness of the walls of the arteries and their length increase. The level of origin of arterial branches from the main arteries and even the type of their branching also change. The diameter of the left coronary artery is greater than the diameter of the right coronary artery in people of all age groups. The most significant differences in the diameter of these arteries are observed in newborns and children aged 10-14 years.
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The length of the arteries increases in proportion to the growth of the body and limbs. The arteries supplying the brain develop most intensively up to 3-4 years of age, surpassing other vessels in rates. The anterior cerebral artery grows most rapidly in length. With age, the arteries that supply the internal organs and the arteries of the upper and lower extremities also lengthen. So, in newborn infants, the inferior mesenteric artery has a length of 5-6 cm, and in adults - 16-17 cm.
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Formation, growth, tissue differentiation of intraorgan blood vessels (small arteries and veins) in various human organs proceed unevenly in ontogenesis. The walls of the arterial section of intraorganic vessels, in contrast to the venous, have three shells at the time of birth: outer, middle and inner. After birth, the length of intraorganic vessels, their diameter, the number of intervascular anastomoses, and the number of vessels per unit volume of the organ increase. This process proceeds most intensively in the first year of life in the period from 8 to 12 years.
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Veins of the systemic circulation With age, the diameter of the veins, their cross-sectional area and length increase. For example, the superior vena cava is short in children due to the high position of the heart. In the first year of a child's life, in children 8-12 years old and in adolescents, the length and cross-sectional area of the superior vena cava increase. In people of mature age, these indicators almost do not change, and in the elderly and old people, due to senile changes in the structure of the walls of this vein, an increase in its diameter is observed.
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After birth, the topography of the superficial veins of the body and limbs changes. So, newborns have dense subcutaneous venous plexuses, large veins are not contoured against their background. By the age of 1-2 years, the larger large and small saphenous veins of the leg are clearly distinguished from these plexuses, and on the upper limb, the lateral and medial saphenous veins of the arm. The diameter of the superficial leg veins increases rapidly from the neonatal period to 2 years: the diameter of the great saphenous vein is almost 2 times, the diameter of the small saphenous vein is 2.5 times.
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The movement of blood through the vessels Blood is constantly moving along a closed vascular system in a certain direction due to the rhythmic contractions of the heart, this living muscular pump that pumps blood from the veins to the arteries. In a healthy person, the amount of blood flowing to the heart is equal to the amount flowing out. The speed of blood flow through arteries, capillaries, veins is different and depends on the width of the lumen of these vessels. Through the capillaries of the systemic circulation, blood flows slowly at a speed of 0.5 mm 1 s. The slow movement of blood through the capillaries contributes to the exchange processes between the blood and the tissues adjacent to the capillary. These metabolic processes take place on a huge area - 6300 m2. This is the total surface of the capillary walls in the human body.
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Blood pressure in blood vessels Blood pressure is the pressure that blood exerts on the walls of blood vessels. Blood pressure depends on the force with which blood was ejected into the aorta during ventricular systole, and on the resistance of small vessels (arterioles, capillaries) to blood flow. The most important condition for blood flow through the vessels is different pressure in the veins and arteries (blood pressure in the aorta is 120, and in the veins - 3-8 mm Hg). Blood moves from an area of higher pressure to an area of lower pressure.
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Due to the rhythmic work of the heart, the blood pressure in the arteries fluctuates. During ventricular systole and ejection of blood into the aorta, the pressure in the arteries increases, and during diastole it decreases. The highest pressure during ventricular systole is called systolic pressure, the lowest pressure during diastole is called diastolic pressure. In healthy adults, the maximum (systolic) pressure is 110-120 mm Hg. Art., and the minimum (diastolic) - 70-80 mm Hg. Art.
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In children, due to the greater elasticity of the walls of the arteries, blood pressure is lower than in adults. In the elderly and senile age, with a decrease in the elasticity of the walls of blood vessels, pressure rises. The difference between the maximum and minimum pressure is called pulse pressure. Its normal value is 40-50 mm Hg. Art.
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Pulse Pulse is the rhythmic vibration of the walls of arteries as blood flows through them. These fluctuations arise due to contractions of the heart (60-70 beats per 1 minute). During systole of the left ventricle, blood is ejected with force into the aorta and stretches its walls. During diastole, the aortic walls, which have elasticity, resilience, return to their original position. These stretches and contractions of the walls of the aorta cause their rhythmic fluctuations. The pulse is determined most often on the radial artery in the lower parts of the forearm, closer to the hand, or on the dorsal artery of the foot at the level of the ankle joint.
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The movement of blood through the veins Through the veins, blood returns to the heart. The movement of blood through the veins is no longer provided by the force of heart contractions, but by other factors. The blood pressure created by the heart in the initial sections of the veins is low, only 10-15 mm Hg. Art. Therefore, the movement of blood through thin-walled veins towards the heart is facilitated by: 1) contraction of the skeletal muscles adjacent to the veins, which compress the veins and thereby push the blood towards the heart; 2) the presence of valves in the veins that prevent the reverse flow of blood and pass it only towards the heart; 3) negative pressure during respiratory movements in the chest cavity, which has a suction effect and helps the movement of blood through the veins to the heart.
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Regulation of the functions of the cardiovascular system The work of the heart, the tone of the walls of blood vessels and the maintenance of a constant blood pressure are regulated by the autonomic nervous system, which is not controlled by our consciousness. In the walls of the aorta, carotid and other arteries, large veins there are sensitive nerve endings - baroreceptors that perceive blood pressure, and chemoreceptors that detect changes in blood composition. Blood vessels in a healthy body are in a somewhat tense state, which is called vascular tone.
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Nerve impulses about the state of the vessels, their tone, are sent along the cardiac nerves to the vasomotor center located in the medulla oblongata. Vasomotor centers are found in the gray matter of the spinal cord. All these centers are controlled from the corresponding parts of the hypothalamus (interbrain). With a decrease in blood pressure in the vessels, impulses from the vasomotor centers increase heart contractions, increase the tone of the vascular walls, the vessels narrow, and the blood pressure in them levels off. With an increase in pressure, the strength and frequency of heart contractions decrease, vascular tone also decreases, the vessels dilate, and pressure normalizes. Thanks to reflex mechanisms, self-regulation of vascular tone and blood pressure in the vessels is carried out.
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Humoral mechanisms are also involved in the regulation of vascular tone (and, accordingly, blood pressure in the vessels). Changes in the chemical composition of the blood affect the excitability and conduction of nerve impulses in the heart, the strength and frequency of heart contractions. With a surge of emotions (joy, fear, anger), adrenal hormones (adrenaline and norepinephrine) are released into the blood, which increase the work of the heart and constrict blood vessels. The pituitary hormone vasopressin also constricts blood vessels. Acetylcholine, histamine and other biologically active substances have a vasodilating effect. In extreme situations, for example, with large blood loss, vascular tone is maintained by the release of blood from the so-called blood depots (skin, liver, etc.). At the same time, with a loss of more than 30% of blood, biological mechanisms are unable to ensure a continuous blood flow, and the body may die.
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age-related features of the nervous system and higher nervous activity
Plan
1. Development of the central nervous system in the process of ontogenesis. one
2. The main stages in the development of higher nervous activity. 6
3. Age features of psychophysiological functions. 9
1. Development of the central nervous system in the process of ontogenesis
The nervous system coordinates and regulates the activity of all organs and systems, ensuring the functioning of the body as a whole; carries out adaptation of the body to changes in the environment, maintains the constancy of its internal environment.
Topographically, the human nervous system is divided into central and peripheral. To central nervous system include the spinal cord and brain. Peripheral nervous system make up the spinal and cranial nerves, their roots, branches, nerve endings, plexuses and nodes that lie in all parts of the human body. According to the anatomical and functional classification, the nervous system is conditionally divided into somatic and autonomic. Somatic nervous system provides innervation of the body - skin, skeletal muscles. autonomic nervous system regulates metabolic processes in all organs and tissues, as well as growth and reproduction, innervates all internal organs, glands, smooth muscles of organs, heart.
The nervous system develops from the ectoderm, through the stages of the neural strip and the cerebral groove, with the subsequent formation of the neural tube. The spinal cord develops from its caudal part, first 3 and then 5 cerebral vesicles form from the rostral part, from which the final, intermediate, middle, hind and medulla oblongata develop later. Such differentiation of the central nervous system occurs in the third or fourth week of embryonic development.
In the future, the volume of the brain increases more intensively than that of the spinal cord, and by the time of birth it averages 400 g. Moreover, in girls, the mass of the brain is slightly lower than in boys. The number of neurons at birth corresponds to the level of an adult, but the number of branching of axons, dendrites and synaptic contacts increases significantly after birth.
The most intensive mass of the brain increases the first 2 years after birth. Then the rate of its development decreases slightly, but continues to remain high up to 6-7 years. The final maturation of the brain ends by 17-20 years. By this age, its mass in men averages 1400 g, and in women - 1250 g. The development of the brain is heterochronous. First of all, those nervous structures on which the normal vital activity of the organism depends at this age stage mature. Functional usefulness is achieved, first of all, by stem, subcortical and cortical structures that regulate the vegetative functions of the body. These departments approach in their development the brain of an adult already at the age of 2-4 years.
Spinal cord . During the first three months of intrauterine life, the spinal cord occupies the entire length of the spinal canal. In the future, the spine grows faster than the spinal cord. Therefore, the lower end of the spinal cord rises in the spinal canal. In a newborn child, the lower end of the spinal cord is at the level of the III lumbar vertebra, in an adult - at the level of the II lumbar vertebra.
The spinal cord of a newborn is 14 cm long. By the age of 2, the length of the spinal cord reaches 20 cm, and by the age of 10, compared with the neonatal period, it doubles. The thoracic segments of the spinal cord grow fastest. The mass of the spinal cord in a newborn is about 5.5 g, in children of the 1st year - about 10 g. By the age of 3, the mass of the spinal cord exceeds 13 g, by the age of 7 it is approximately 19 g. In a newborn, the central canal is wider than in an adult . A decrease in its lumen occurs mainly during 1-2 years, as well as in later age periods, when an increase in the mass of gray and white matter is observed. The volume of the white matter of the spinal cord increases rapidly, especially due to the own bundles of the segmental apparatus, the formation of which occurs at an earlier time compared to the time of the formation of the pathways.
Medulla . By the time of birth, it is fully developed both anatomically and functionally. Its mass reaches 8 g in a newborn. The medulla oblongata occupies a more horizontal position than in adults and differs in the degree of myelination of the nuclei and pathways, the size of the cells and their location. As the fetus develops, the size of the nerve cells of the medulla oblongata increases, and the size of the nucleus decreases relatively with cell growth. The nerve cells of a newborn have long processes, their cytoplasm contains a tigroid substance. The nuclei of the medulla oblongata are formed early. Associated with their development is the emergence in ontogeny of the regulatory mechanisms of respiration, the cardiovascular, digestive, and other systems.
Cerebellum . In the embryonic period of development, the ancient part of the cerebellum, the worm, is first formed, and then its hemispheres. At the 4-5th month of intrauterine development, the superficial sections of the cerebellum grow, furrows and convolutions form. The cerebellum grows most intensively in the first year of life, especially from the 5th to the 11th month, when the child learns to sit and walk. In a one-year-old child, the mass of the cerebellum increases by 4 times and averages 95 g. After this, a period of slow growth of the cerebellum begins, by the age of 3 the size of the cerebellum approaches its size in an adult. In a 15-year-old child, the mass of the cerebellum is 150 g. In addition, the rapid development of the cerebellum occurs during puberty.
The gray and white matter of the cerebellum develops differently. In a child, the growth of gray matter is relatively slower than that of white matter. So, from the neonatal period to 7 years, the amount of gray matter increases approximately 2 times, and white - almost 5 times. From the nuclei of the cerebellum, the dentate nucleus is formed earlier than others. Starting from the period of intrauterine development and up to the first years of life of children, nuclear formations are better expressed than nerve fibers.
The cellular structure of the cerebellar cortex in a newborn differs significantly from that of an adult. Its cells in all layers differ in shape, size and number of processes. In a newborn, Purkinje cells are not yet fully formed, the tigroid substance is not developed in them, the nucleus almost completely occupies the cell, the nucleolus has an irregular shape, and the cell dendrites are underdeveloped. The formation of these cells proceeds rapidly after birth and ends by 3-5 weeks of age. The cellular layers of the cerebellar cortex in a newborn are much thinner than in an adult. By the end of the 2nd year of life, their sizes reach the lower limit of the size in an adult. The complete formation of the cellular structures of the cerebellum is carried out by 7-8 years.
Bridge . In a newborn, it is located higher than in an adult, and by the age of 5 it is located at the same level as in a mature organism. The development of the bridge is associated with the formation of the cerebellar peduncles and the establishment of connections between the cerebellum and other parts of the central nervous system. The internal structure of the bridge in a child does not have distinctive features compared to an adult. The nuclei of the nerves located in it are already formed by the time of birth.
midbrain . Its shape and structure are almost the same as an adult. The nucleus of the oculomotor nerve is well developed. The red nucleus is well developed, its large cell part, which ensures the transmission of impulses from the cerebellum to the motor neurons of the spinal cord, develops earlier than the small cell part, through which excitation is transmitted from the cerebellum to the subcortical formations of the brain and to the cerebral cortex.
In a newborn, the substantia nigra is a well-defined formation, the cells of which are differentiated. But a significant part of the cells of the black substance does not have a characteristic pigment (melanin), which appears from 6 months of life and reaches its maximum development by 16 years. The development of pigmentation is in direct connection with the improvement of the functions of the substantia nigra.
diencephalon . Individual formations of the diencephalon have their own rates of development. The laying of the visual hillock is carried out by 2 months of intrauterine development. At the 3rd month, the thalamus and hypothalamus are differentiated. At the 4-5th month, light layers of developing nerve fibers appear between the nuclei of the thalamus. At this time, the cells are still poorly differentiated. At 6 months, the cells of the reticular formation of the thalamus become clearly visible. Other nuclei of the thalamus begin to form from 6 months of intrauterine life, by 9 months they are well expressed. With age, they further differentiate. The increased growth of the thalamus is carried out at the age of 4, and it reaches the size of an adult by the age of 13.
In the embryonic period of development, the hypothalamic region is laid, but in the first months of intrauterine development, the nuclei of the hypothalamus are not differentiated. Only on the 4-5th month there is an accumulation of cellular elements of the future nuclei, on the 8th month they are well expressed.
The nuclei of the hypothalamus mature at different times, mainly by 2-3 years. By the time of birth, the structures of the gray tubercle are not yet fully differentiated, which leads to imperfection of thermoregulation in newborns and children of the first year of life. The differentiation of the cellular elements of the gray tubercle ends the latest - by the age of 13-17.
The cerebral cortex . Until the 4th month of fetal development, the surface of the cerebral hemispheres is smooth and only an indentation of the future lateral sulcus is noted on it, which is finally formed only by the time of birth. The outer cortical layer grows faster than the inner one, which leads to the formation of folds and furrows. By 5 months of intrauterine development, the main furrows are formed: lateral, central, corpus callosum, parietal-occipital and spur. Secondary furrows appear after 6 months. By the time of birth, the primary and secondary furrows are well defined, and the cerebral cortex has the same type of structure as in an adult. But the development of the shape and size of the furrows and convolutions, the formation of small new furrows and convolutions continues after birth.
By the time of birth, the cerebral cortex has the same number of nerve cells (14-16 billion) as in an adult. But the nerve cells of the newborn are immature in structure, have a simple spindle shape and a very small number of processes. The gray matter of the cerebral cortex is poorly differentiated from the white. The cerebral cortex is relatively thinner, the cortical layers are poorly differentiated, and the cortical centers are underdeveloped. After birth, the cerebral cortex develops rapidly. The ratio of gray and white matter by 4 months is approaching the ratio in an adult.
By 9 months, the first three layers of the cortex become more distinct, and by the year the overall structure of the brain is approaching a mature state. The arrangement of the layers of the cortex, the differentiation of nerve cells is basically completed by 3 years. In primary school age and during puberty, the ongoing development of the brain is characterized by an increase in the number of associative fibers and the formation of new neural connections. During this period, the mass of the brain increases slightly.
In the development of the cerebral cortex, the general principle is preserved: phylogenetically older structures are formed first, and then younger ones. On the 5th month, nuclei that regulate motor activity appear earlier than others. At the 6th month, the core of the skin and visual analyzer appears. Later than others, phylogenetically new regions develop: frontal and lower parietal (on the 7th month), then temporo-parietal and parietal-occipital. Moreover, phylogenetically younger sections of the cerebral cortex increase relatively with age, while older ones, on the contrary, decrease.
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Age changes
Age-related changes in the nervous system determine the most important manifestations of aging of the whole human body (shifts in mental and behavioral reactions), a decrease in mental and muscle performance, reproductive ability, adaptation to the environment, etc.
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With aging, there is a decrease in the weight of the brain, thinning of the gyri, expansion and deepening of the furrows, expansion of the ventricular-cisternal system. There is a decrease in the number of neurons and their replacement by glial elements; in some parts of the cerebral cortex, the loss of neurons can reach 25-45% (in relation to their number in newborns). In the spinal ganglions of people aged 70-79 years, the number of nerve cells is 30.4% less than in 40-49-year-olds.
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distraction
In the process of aging, the integrative activity of the nervous system changes: conditioned reflexes are formed more slowly, the mobility and strength of the main nervous processes decrease, the processes of concentration and concentration of attention, memory worsen.
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Lability
Significant age-related shifts occur in the autonomic ganglia. In particular, changes in the perception, processing and transmission of information in nerve cells are associated with a decrease in their lability.
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Rhythms
Elderly people are characterized by a slowdown in the alpha rhythm, but an increase in slow oscillations (theta and delta waves), a decrease in the ability to assimilate imposed rhythms.
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Walking disorders
Gradually, the length of the steps is reduced, the gait becomes slow, the person begins to slouch. All Movements become less fluid. It is difficult for a person to take off his trousers while standing alternately on one and the other leg. Handwriting changes, all movements of the arms and hands lose their dexterity. Undoubtedly, this complex movement disorder is associated with the loss of neurons in the spinal cord, cerebellum and brain, as well as the loss of muscle mass.
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Falls
Falls are a significant threat to life in the elderly without overt neurological symptoms. On average, 30% of these people living in their home fall one or more times a year. Falls have many causes, some of which have just been mentioned in the discussion of gait disorders. An important provoking factor is the age-related decline in vision and vestibular function.
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Status of analyzers
Along with psychological changes, the functioning of the sense organs also changes with age. In older people, the accommodative ability decreases over the years, senile farsightedness often develops, the field of vision narrows, hearing acuity decreases, which can lead to the development of a mild form of hearing loss. In general, these changes do not reach sharp manifestations.
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Diseases
Separately, it is worth mentioning such pathology of the brain as Parkinson's disease. It is based on a violation of subcortical structures, which consists in the lack of certain chemicals, which leads to a violation of the bonds between them. The main manifestation of this disease is the frequently repeated movements of the body (or a separate area), which occur without the will of the patient. It all starts with small twitches of certain muscle groups, which makes it very difficult to perform some actions. For example, writing is broken, objects start to fall out of hands, a person has difficulty dressing.
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Senile dementia is one of the most terrible pathologies of the human brain. One of the causes of dementia is the so-called Alzheimer's disease. After a person passes the mark of 60 years, the risk of developing this disease increases with each subsequent year of his life. Primarily, senile dementia is caused by a decrease in the number of neurotransmitters. A decrease in the level of their content in the body disrupts the activity of many parts of the brain, including those responsible for memory, learning and other cognitive functions. Thus, the external symptoms of Alzheimer's disease appear.
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