An important part of the brain is the hypothalamus: what it is and what it is responsible for, the causes of pathological changes, the diagnosis and treatment of diseases. Functions and hormones of the hypothalamus, its structure and effect on the body

Hypothalamus, what is it, and what is it responsible for, this main organ of the endocrine system? It is called the endocrine brain, it is present in amphibians and mammals, and they need it to regulate the functions of the organs of the hormonal system. Scientists claim that this ancient brain organ allowed amphibians and mammals to survive on earth as a species. The hypothalamus is responsible for the preservation of youth, life extension, mental and physical unity of the representative of the species. It is his well-coordinated work that makes a person harmonious and energetic, and violations in his work lead to premature old age.

The hypothalamus is located in the brain, representing a part of the diencephalon.

Its location is at the bottom of the third ventricle of the brain. This is a nerve formation capable of producing hormones. The hypothalamus occupies a small place in the brain. Its weight is only 5 g, but this mass is enough to combine the nervous and endocrine regulatory mechanisms into a common neuroendocrine system. It controls the activity of the human endocrine system with the help of neurons that produce hormones that affect the production of hormones of another important hormonal organ - the pituitary gland.

The hypothalamus does not have a strictly limited place. This part of the brain is considered as part of a network of neurons that stretches from the midbrain to the deep parts of the forebrain, including the olfactory system. Its position is limited from above by the thalamus, from below by the midbrain, and in front of it is the optic chiasm. Behind is the pituitary gland, which is connected with the hypothalamus by the pituitary stalk and participates with it in the processes that regulate metabolism.

The structure of the hypothalamus is designed so that it can receive all the information it needs and instantly respond to signals, regulating the production of hormones by the organs of internal secretion.

The hypothalamus is conditionally divided into 3 zones:

• periventricular;
• medial;
• lateral.

The periventricular zone is a thin strip adjacent to the third ventricle, at the bottom of which the hypothalamus is located.

In the medial zone, several nuclear regions are distinguished, located in the anteroposterior direction. The medial part of the hypothalamus, to a greater extent, has bilateral connections with the lateral zone and independently receives signals from some parts of the brain. It is an intermediate link between the nervous and endocrine systems.

In this area there are special neurons that perceive the most important parameters of blood and cerebrospinal fluid. They monitor the internal state of the body and control the water and electrolyte composition of the plasma, blood temperature and the content of hormones in it.

In the lateral hypothalamus, neurons are randomly located around the medial forebrain bundle, which goes to the anterior centers of the diencephalon. The bundle consists of long and short fibers directed in different directions from the center. These fibrous tissues are involved in the implementation of the afferent and efferent connections of the hypothalamus, through which the central one communicates with other parts of the brain.

Its nerve and secretion-producing cells look like nuclei and are arranged in pairs. The nuclei of the hypothalamus regulate the connections between neurons and are responsible for the connection between sections of the brain and. The nuclei of the hypothalamus represent accumulations of nerve cells in the anterior, posterior and intermediate regions and form more than 30 pairs located on the right and left sides of the third ventricle. The nuclei of the hypothalamus produce a neurosecretion, which is transported through the processes of these cells to the area of ​​the neurohypophysis, increasing or inhibiting the production of hormones.

Part of the nuclei, connecting with the pituitary gland, form connections that regulate the production of hormones that have a vasoconstrictive and antidiuretic effect. The same connections are responsible for the mechanisms that stimulate the contractility of the muscles of the uterus, increase lactation, and inhibit the development and function of the corpus luteum. The hormones secreted by these important representatives of the endocrine system affect the change in the tone of the smooth muscles of the gastrointestinal tract.

Organ functions

The processes occurring in the hypothalamus are responsible for the functioning of the autonomic nervous and endocrine systems necessary to maintain homeostasis. This is the name of the body's ability to maintain the constancy of the internal environment and ensure the preservation of the functions responsible for life, excluding automatic respiratory movements, heart rhythm and blood pressure. The functions of the hypothalamus are designed to maintain important vital parameters. They are responsible for body temperature, acid-base balance, energy balance, regulating them in a small range and keeping them near optimal physiological values.

The functions of the hypothalamus extend to the organization of the behavior of the population and its preservation as a species. It forms various aspects of behavior and is responsible for the instincts of self-preservation, which contribute to the preservation of mankind as a biological species. In case of changes and stressful situations, it regulates the state of the internal and external environment, forcing the functioning of such mechanisms as:

• appetite;
• care for offspring;
• memory;
• food-procuring behavior;
• sexual behavior;
• reproduction;
• sleep and wakefulness;
• emotions.

The body, thanks to the hypothalamus, is able to ensure the viability of a person who is in extreme conditions. It controls the constancy of the internal environment in case of sudden changes in the living conditions of the individual. The normal work of the hypothalamus allows people to survive in the most difficult conditions of life, when strength is running out.

Causes of Pineal Gland Disorders

Under what circumstances can a part of the brain, deeply hidden in the cranium, be significantly affected? Pathological changes in the hypothalamus are mostly observed in women. The cause of malfunctions is the peculiarity of the vessels of the hypothalamic region, which have a high degree of permeability. When the body is damaged by toxins and viruses, there is always a danger that the infection can affect the brain and easily penetrate the endocrine gland through the bloodstream. Disorders in the work of the hypothalamus cause various life situations. It can be:

• a brain tumor;
• flu;
• various viral neuroinfections;
• malaria;
• rheumatism;
• chronic tonsillitis;
• closed craniocerebral injury;
• vascular diseases;
• chronic intoxication.

Brain injury, in which the hypothalamus is destroyed, leads to death. The destruction of the nerve pathways between the midbrain and the medulla oblongata causes disturbances in the processes of thermoregulation, which leads to the rapid extinction of life.

When to See a Doctor

Violation of the activity of the hypothalamus due to squeezing it with a brain tumor leads to disruption of the work of many systems and organs. Especially women at the age of 30-40 suffer from violations, when their reproductive functions begin to fade, and the endocrine system begins to fail.

They develop hyperprolactinemia, in which the production of the hormone prolactin increases. Disorders of the hypothalamus cause menstrual dysfunction.

From the improper functioning of the pineal gland, the actions of the pituitary gland are inhibited, which causes disturbances in the production of the hormone cortisone. Very often, dysfunction in the functioning of the thyroid gland begins from this.

If a violation in the work of the organ occurs in childhood, then the patient stops growing, and the child does not develop secondary sexual characteristics. The development of diabetes insipidus directly indicates the pathology of the hypothalamus.

The presence of pathologies in the pineal gland leads to dysfunctions of the nervous system and the organ of vision. Patients may find:

• atherosclerosis;
• a sharp increase in body weight;
• myocardial dystrophy;
• hematopoietic pathology.

In patients who were healthy yesterday, with damage to the hypothalamus, the following pathological disorders appear:

• vegetative;
• endocrine;
• exchange;
• trophic.

If a person suspects signs and symptoms of damage to the hypothalamus, he should seek medical help from an endocrinologist or neurologist.

The structure of the brain is very complex and not fully understood. Modern science, despite the fact that it has quite a lot of information about the functions and anatomy of the brain, in all likelihood, is still very far from understanding all the processes that occur in it. Hypothalamus - what is it, how is it arranged, what hormones does it produce and what are they for? This article will focus on the important and mysterious gland of the human body.

Development (of the hypothalamus) begins in the early period of embryogenesis, in the process of brain development, a portion of the diencephalon is formed from the anterior and posterior cerebral bladder.

The hypothalamus is one of the divisions of the diencephalon, which regulates a large number of functions that occur in the body. It is very closely connected with the pituitary gland, and together they are involved in the regulation of the precise work of many organs and systems, while forming the hypothalamic-pituitary complex. Where is the hypothalamus located, what is its structure and functions, what hormones does it produce, and much more will be discussed later. Below is a diagram of the hypothalamic-pituitary system.

Description of the hypothalamus

The hypothalamus is located in the intermediate part of the brain and consists of a large number of nuclei. This is an extremely important human organ, which has a direct connection with the central nervous system. The hypothalamus is located below the thalamus, hence its name. This organ is separated from the thalamus by a barrier, but its boundaries are rather blurred, since some of its cells spread to neighboring departments.

What is the hypothalamus? It is a subcortical structure, about the size of a pea, but of great importance. To clearly explain the functions of the hypothalamus, we can give a simple example. The person did not have time to have breakfast in the morning and his stomach growls, gradually the hunger intensifies, and the person cannot concentrate on anything at all, since his thoughts are only occupied with food.

Discomfort intensifies, and the person, leaving everything, begins to eat any food that comes across to him. This whole process is under the control of the hypothalamus. Simply put, if this gland ceased to take part in the work of the body, people simply would not know when they need to eat, and simply starved to death. Naturally, this is a very simple example, and the functions of the hypothalamus are much more extensive.

The structure of the hypothalamus

The structure (hypothalamus) is quite complex, its nuclei are nerve cells and neurosecretory cells, which have 32 pairs. Until the end, the anatomy of this organ has not yet been studied, however, scientists continue to study the work of the hypothalamus. The nerve cells of the nuclei do not perform a secretory function, but hormones are produced in the neurosecretory cells, which are called hypothalamic hormones or neurohormones.

The divisions of the hypothalamus are not clearly represented, but are divided into anterior, middle, and posterior. Their function is different - in the nuclei of the anterior and middle sections, the parasympathetic and autonomic nervous systems of the body are regulated. In the posterior region, the sympathetic system is regulated. Thus, the hypothalamus has a connection with the central nervous system.

The physiology of the hypothalamus is extremely interesting - its vessels have increased permeability, so even large polypeptides can penetrate into them. This feature of the structure determines the sensitivity of the gland to various changes in the internal environment of the body. What else is remarkable about the histology and physiology of such an important gland as the hypothalamus? Its histological structure differs from other parts of the brain in that it has the most powerful circulatory system and simply a huge number of capillaries.

Functions of the hypothalamus

The function of the hypothalamus is to shape the eating and drinking behavior of a person, and it also controls other physiological needs of a person and the aggression of people. Simply put, this gland is the center of emotions. If some of its sections are stimulated, then a person develops negative emotions - anxiety, fear, when other sections are simulated, irritation occurs, and when the third sections are irritated, a feeling of euphoria, joy and pleasure appears.

Considering the hypothalamus, its functions can be reduced to the following:

• regulation of sleep and wakefulness;
• regulation of the temperature balance of the body - physical processes are under the control of the front section, and the rear section is responsible for chemical ones;
• centers (hypothalamus) ensure the supply and distribution of energy;
• gland performs control of metabolic processes;
• the central area of ​​hematopoiesis is also located in this gland.

It is this gland that gives impetus to the synthesis of hormones in the pituitary gland. Moreover, each tropic hormone is accompanied by hypothalamic hormones, they are called liberins.

When it produces liberins, the synthesis of pituitary hormones occurs, which are necessary for the endocrine function to work properly. When tropic hormones are produced in sufficient quantities, the process of liberin synthesis is inhibited, other hormones of the hypothalamus, called statins, are responsible for this process.

The subconscious mind, about which psychotherapists talk so much, is also directly related to the hypothalamus. Absolutely everything that a person has read, seen or heard does not disappear into nowhere, but remains in the deep layers of the psyche, and has an impact on the functioning of the body in the psycho-emotional sense. In addition, it is believed that aging and the hypothalamus are also closely related. Having understood what the hypothalamus is responsible for, you can proceed to the analysis of its hormones.

hypothalamic hormones

Libirins and statins were mentioned above, however, these are not all hormones of the hypothalamus, the following neurohormones have now been studied:

1. Gonadoliberins- Hormones of the hypothalamus, which are responsible for the synthesis of sex hormones. In addition, these hormones are involved in the formation of sexual desire, as well as regulate the menstrual cycle and the release of a mature egg. Gonadoliberin deficiency causes hormonal deficiency and female infertility.
2. Somatoliberin- this is a hormone responsible for the release of growth substances, iron most actively produces this hormone in childhood, and with its deficiency, dwarfism develops.
3. Corticoliberin- this hormone provokes the synthesis of anticorticotropic pituitary hormones. With its lack, the adrenal glands suffer.
4. Prolactoliberin actively produced during pregnancy and lactation.
5. Dopamine, somastatin, melanostatin Hormones that suppress the production of tropic pituitary hormones.
6. Melanoiberin- a hormone involved in the synthesis of melanin.
7. Thyroliberin controls thyroid-stimulating hormones.

What processes control the synthesis of neurohormones? This control is carried out by the nervous system, and in some cases it affects the hormones and the cells of the pituitary gland as well. The table below shows the classification of hormones.

The role of the hypothalamus in vegetative

Its role in the regulation of vegetative functions is great. When the nuclei of the anterior part of the gland are irritated, sympathetic effects are observed in the work of the organs; when the nuclei of the middle part are irritated, the sympathetic influence weakens. However, such a distribution of functionality is not absolute, and both structures of the hypothalamus are capable of influencing sympathetic and parasympathetic. Thus, the anatomical features of the hypothalamic regions functionally complement each other and compensate.

Due to the fact that the hypothalamus has a close connection with the cerebral cortex, it controls the function of blood circulation, respiration, peristalsis, endocrine work of the body and other processes that are influenced by vegetative.

Pathologies of the hypothalamus

There is such a thing as hypothalamic syndrome - this is a complex of problems and diseases of a vegetative and endocrine nature that occur during pathological processes in the hypothalamus.

Pathological processes in the hypothalamic region of the brain may be caused by the following reasons:

• a brain tumor located near the hypothalamus and exerting pressure on it;
• traumatic brain injury affecting the hypothalamic region;
• neurointoxication;
• vascular diseases;
• neuroinfections of viral and bacterial origin;
• stress, strong mental stress;
• hormonal changes;
• congenital pathologies.

Hypothalamic syndrome is manifested by increased weakness, intolerance to changing weather conditions, emotional disorders, a tendency to allergies, sweating, tachycardia, sleep disturbance, blood pressure surges, and so on.

In most cases, the hypothalamic syndrome is complicated by hirsutism, gynecomastia, menstrual irregularities, uterine bleeding, and polycystic ovaries. The main symptom of the hypothalamic syndrome is the presence of frequent vegetative paroxysms, which can lead not only to a decrease in performance, but even to its complete loss.

Other pathologies of the hypothalamus:

• hypopituitarism - violations in the functionality of the gonads that inhibit a person's puberty, and also cause problems with libido, potency, body weight and growth;
• neurogenic diabetes insipidus;
• tertiary hypothyroidism;
• growth and development disorders.

With pathologies and diseases of the hypothalamus, a person may experience personality changes, memory impairment, emotional shifts, and manic outbursts. Endocrinologists, gynecologists and neurologists will help improve the patient's condition.

The hypothalamus is part of the diencephalon and is part of the limbic system. This is a complexly organized part of the brain that performs a number of vegetative functions, is responsible for the humoral and neurosecretory supply of the body, emotional behavioral reactions and other functions.

Morphologically, about 50 pairs of nuclei are distinguished in the hypothalamus, topographically divided into 5 large groups: 1) preoptic group or area, which includes: periventricular, preoptic nucleus, medial and lateral preoptic nuclei, 2) anterior group: supraoptic, paraventricular and suprachiasmatic nuclei, 3) middle group: ventromedial and dorsomedial nuclei, 4) outer group: lateral hypothalamic nucleus, nucleus of the gray tubercle, 5) posterior group: posterior hypothalamic nucleus, periforical nucleus, medial and lateral nuclei of the mammillary (mamillary) bodies.

The neurons of the hypothalamus are particularly sensitive to the composition of the blood washing them: changes in pH, pCO 2 ro 2 the content of catecholamines, potassium and sodium ions. The supraoptic nucleus contains osmoreceptors. The hypothalamus is the only brain structure that lacks the blood-brain barrier. Neurons of the hypothalamus are capable of neurosecretion of peptides, hormones, mediators.

Epinephrine-sensitive neurons were found in the posterior and lateral hypothalamus. Adrenoreceptive neurons can be located in the same nucleus of the hypothalamus along with cholinergic and serotonin receptor neurons. Administration of epinephrine or norepinephrine to the lateral hypothalamus elicits an eating response, while administration of acetylcholine or carbocholine produces a drinking response. The neurons of the ventromedial and lateral nuclei of the hypothalamus are highly sensitive to glucose due to the presence of "glucoreceptors" in them.

The conduction function of the hypothalamus

The hypothalamus has afferent connections with the olfactory brain, basal ganglia, thalamus, hippocampus, orbital, temporal and parietal cortex.

Efferent pathways are represented by: mamillo-thalamic, hypothalamic-thalamic, hypothalamic-pituitary, mamillo-tegmental, hypothalamic-hippocampal tracts. In addition, the hypothalamus sends impulses to the autonomic centers of the brain stem and spinal cord. The hypothalamus has close connections with the reticular formation of the brain stem, which determines the course of the body's vegetative reactions, its eating and emotional behavior.

Own functions of the hypothalamus

The hypothalamus is the main subcortical center that regulates autonomic functions. Irritation of the anterior group of nuclei imitates the effects of the parasympathetic nervous system, its trophotropic effect on the body: pupil constriction, bradycardia, lowering blood pressure, increased secretion and motility of the gastrointestinal tract. The supraoptic and paraventricular nuclei are involved in the regulation of water and salt metabolism through the production of antidiuretic hormone.

Stimulation of the posterior group of nuclei has ergotropic effects, activates sympathetic effects: pupil dilation, tachycardia, increased blood pressure, inhibition of motility and secretion of the gastrointestinal tract.

The hypothalamus provides mechanisms for thermoregulation. So, the nuclei of the anterior group of nuclei contain neurons responsible for heat transfer, and the posterior group - for the process of heat production. The nuclei of the middle group are involved in the regulation of metabolism and eating behavior. In the ventromedial nuclei there is a center of saturation, and in the lateral nuclei there is a center of hunger. The destruction of the ventromedial nucleus leads to hyperphagia - increased food intake and obesity, and the destruction of the lateral nuclei - to the complete refusal of food. In the same core is the center of thirst. In the hypothalamus there are centers of protein, carbohydrate and fat metabolism, centers of regulation of urination and sexual behavior (suprachiasmatic nucleus), fear, rage, the sleep-wake cycle.

The regulation of many body functions by the hypothalamus is carried out due to the production of pituitary hormones and peptide hormones: liberins, stimulating the release of anterior pituitary hormones, and statins - hormones that inhibit their release. These peptide hormones (thyroliberin, corticoliberin, somatostatin, etc.) through the portal vascular system of the pituitary gland reach its anterior lobe and cause a change in the production of the corresponding adenohypophysis hormone.

The supraoptic and paraventricular nuclei, in addition to their participation in water-salt metabolism, lactation, uterine contraction, produce hormones of a polypeptide nature - oxytocin And antidiuretic hormone (vasopressin), which, with the help of axonal transport, reach the neurohypophysis and, cumulating in it, have a corresponding effect on water reabsorption in the renal tubules, on vascular tone, and on contraction of the pregnant uterus.

The suprachiasmatic nucleus is related to the regulation of sexual behavior, and pathological processes in the region of this nucleus lead to accelerated puberty and menstrual irregularities. The same nucleus is the central driver of circadian (circadian) rhythms of many functions in the body.

The hypothalamus is directly related, as noted above, to the regulation of the sleep-wake cycle. At the same time, the posterior hypothalamus stimulates wakefulness, the anterior - sleep, and damage to the posterior hypothalamus can cause pathological Sopor.

The hypothalamus and pituitary gland produce neuropeptides related to the antinoticeptive (pain) system, or opiates: enkephalins And endorphins.

The hypothalamus is part of the limbic system involved in emotional behavior.

D. Olds, implanting electrodes into some nuclei of the rat hypothalamus, observed that when some nuclei were stimulated, a negative reaction occurred, while others were positive: the rat did not move away from the pedal that closed the stimulating current, and pressed it to exhaustion (experiment with self-irritation). It can be assumed

live that she irritated the "pleasure centers". Irritation of the anterior hypothalamus provoked a picture of rage, fear, a passive-defensive reaction, and the posterior hypothalamus provoked an active aggression, an attack reaction.

Abstract on the topic:

Hypothalamus. Physiology of the hypothalamus.

Completed by: Andreeva Julia 4207

Hypothalamus

The hypothalamus is the outer subcortical center of the autonomic nervous system. This hypotuberous region of the diencephalon has long been an important object of various scientific studies.

Currently, the method of electrode implantation is widely used to study various brain structures. Using a special stereotaxic technique, electrodes are inserted through a burr hole in the skull into any given area of ​​the brain. The electrodes are insulated throughout, only their tip is free. By including electrodes in the circuit, it is possible to irritate certain zones narrowly locally.

In this work, some theoretical and physiological aspects of this region of the diencephalon are considered.

General functions of the hypothalamus.

In vertebrates, the hypothalamus is the main nerve center responsible for regulating the internal environment of the body.

Phylogenetically, this is a rather old part of the brain, and therefore, in terrestrial mammals, its structure is relatively the same, in contrast to the organization of such younger structures as the neocortex and limbic system.

The hypothalamus controls all major homeostatic processes. While a decerebrated animal can be saved quite easily, special intensive measures are required to maintain the life of an animal with a removed hypothalamus, since such an animal has destroyed the main homeostatic mechanisms.

The principle of homeostasis lies in the fact that under a wide variety of conditions of the body associated with its adaptation to dramatically changing environmental conditions (for example, under thermal or cold effects, during intense physical activity, and so on), the internal environment remains constant and its parameters fluctuate only within very narrow limits. The presence and high efficiency of homeostasis mechanisms in mammals, and in particular in humans, provide the possibility of their vital activity under significant changes in the environment. Animals unable to maintain some parameters of the internal environment are forced to live in a narrower range of environmental parameters.

For example: The ability of frogs to thermoregulate is so limited that in order to survive in the conditions of winter cold, they have to sink to the bottom of reservoirs where the water will not freeze. On the contrary, many mammals can live as freely in winter as in summer, despite significant temperature fluctuations.

From this it is clear that due to the weak development of homeostasis mechanisms, these animals are less free in their life activity, and if the hypothalamus is removed, homeostatic processes are consequently disturbed, then special intensive measures are necessary to maintain the life activity of this animal.

Functional anatomy of the hypothalamus.

Location of the hypothalamus. The hypothalamus is a small region of the brain weighing about 5 grams. The hypothalamus does not have clear boundaries, and therefore it can be considered as part of a network of neurons stretching from the midbrain through the hypothalamus to the deep regions of the forebrain, closely related to the phylogenetically old olfactory system. The hypothalamus is the ventral part of the diencephalon, it lies below (ventral to) the thalamus, forming the lower half of the wall of the third ventricle. The lower border of the hypothalamus is the midbrain, and the upper border is the end plate, anterior commissure and optic chiasm. Lateral to the hypothalamus is the optic tract, internal capsule, and subthalamic structures.

The structure of the hypothalamus. In the transverse direction, the hypothalamus can be divided into three zones: 1) Periventricular; 2) medial; 3) Lateral.

The periventricular zone is a thin strip adjacent to the third ventricle. In the medial zone, several nuclear regions are distinguished, located in the anteroposterior direction. The preoptic region phylogenetically belongs to the forebrain, but it is usually referred to as the hypothalamus.

From the ventromedial region of the hypothalamus, the pituitary stalk begins, connecting to the adeno- and neurohypophysis. The front of this leg is called the median eminence. The processes of many neurons of the preoptic and anterior regions of the hypothalamus, as well as the ventromedial and infundibular nuclei, terminate there (Fig. 1 - numbers: 1, 4, 5); here, hormones are released from these processes, which enter through the system of portal vessels to the anterior pituitary gland. The totality of nuclear zones, which contain similar hormone-producing neurons, is called the pituitary region. (Fig. 1 - the area marked with a broken line).

The processes of the neurons of the supraoptic and paraventricular nuclei (Fig. 1 - numbers 2 and 3) go to the posterior pituitary gland (these neurons regulate the formation and release of oxytocin and ADT, or vasopressin). It is impossible to link the specific functions of the hypothalamus with its individual nuclei, with the exception of the supraoptic and paraventricular nuclei.

There are no separate nuclear regions in the lateral hypothalamus. The neurons of this zone are diffusely located around the medial bundle of the forebrain, which runs in a rastral-caudal direction from the lateral formations of the base of the limbic system to the anterior centers of the diencephalon. This bundle consists of long and short ascending and descending fibers.

Afferent and efferent connections of the hypothalamus. The organization of afferent and efferent connections of the hypothalamus indicates that it serves as an important integrative center for somatic, vegetative and endocrine functions.

The lateral hypothalamus forms bilateral connections with the upper parts of the brain stem, the central gray matter of the midbrain, and with the limbic system. Sensitive signals from the surface of the body and internal organs enter the hypothalamus along the ascending spinobulboreticular pathways, which lead to the hypothalamus, either through the thalamus or through the limbic region of the midbrain. The remaining afferent signals enter the hypothalamus through polysynaptic pathways, which are not yet fully identified.

The efferent connections of the hypothalamus with the vegetative and somatic nuclei of the brain stem and spinal cord are formed by polysnappy pathways that run as part of the reticular formation.

The medial hypothalamus has bilateral connections with the lateral one, and, in addition, it directly receives signals from some other parts of the brain. In the medial region of the hypothalamus, there are special neurons that perceive the most important parameters of blood and cerebrospinal fluid: that is, these neurons monitor the state of the internal environment of the body. They can sense, for example, blood temperature, plasma water and electrolyte composition, or blood hormone levels.

Through the nervous mechanisms, the medial region of the hypothalamus controls the activity of the neurohypophysis, and through the hormonal mechanisms, the adenohypophysis. Thus, this area serves as an intermediate link between the nervous and endocrine systems.

The hypothalamus and the cardiovascular system.

With electrical stimulation of almost any part of the hypothalamus, reactions from the cardiovascular system can occur. These reactions, mediated primarily by the sympathetic system, as well as by the branches of the vagus nerve leading to the heart, indicate the importance of the hypothalamus for the regulation of hemodynamics by external nerve centers.

Irritation of any part of the hypothalamus may be accompanied by opposite changes in blood flow in different organs (for example, an increase in blood flow in skeletal muscles and a simultaneous decrease in blood vessels in the skin). On the other hand, opposite reactions of the vessels of any organ can occur when different zones of the hypothalamus are stimulated. The biological significance of such hemodynamic shifts can be understood only if they are considered in connection with other physiological reactions accompanying irritation of the same subthalomic zones. In other words, the hemodynamic effects of stimulation of the hypothalamus are part of the general behavioral or homeostatic responses for which this center is responsible.

An example is food and protective behavioral reactions that occur when electrical stimulation of limited areas of the hypothalamus. During defensive behavior, blood pressure and blood flow in the skeletal muscles increase, and blood flow in the intestinal vessels decreases. Eating behavior increases blood pressure and blood flow in the intestines, and blood flow in the skeletal muscles decreases. Similar changes in hemodynamic parameters are also observed during other reactions that occur in response to irritation of the hypothalamus, for example, during thermoregulatory reactions or sexual behavior.

The lower parts of the brain stem are responsible for the mechanisms of regulation of hemodynamics in general (that is, blood pressure in the systemic circulation, cardiac output and blood distribution), acting on the principle of tracking systems. These departments receive information from arterial baro- and chemoreceptors and mechanoreceptors of the atria and ventricles of the heart and send signals to various structures of the cardiovascular system via sympathetic and parasympathetic efferent fibers. Such bulbar self-regulation of hemodynamics, in turn, is controlled by the higher parts of the brain stem, and in particular the hypothalamus. This regulation is carried out due to neural connections between the hypothalamus and preganglionic autonomic neurons. The higher nervous regulation of the cardiovascular system from the side of the hypothalamus is involved in all complex autonomic reactions, for which simple self-regulation is not enough to control, such regulations include: thermoregulation, regulation of food intake, protective behavior, physical activity, and so on.

Adaptive reactions of the cardiovascular system during work. The mechanisms of adaptation of hemodynamics during physical work are of theoretical and practical interest. During exercise, cardiac output increases (mainly as a result of an increase in the heart rate) and at the same time blood flow in skeletal muscles increases. At the same time, blood flow through the skin and abdominal organs is reduced. These adaptive circulatory reactions occur almost simultaneously with the start of work. They are carried out by the central nervous system through the hypothalamus.

In a dog with electrical stimulation of the lateral region of the hypothalamus at the level of the mamillary bodies, exactly the same vegetative reactions occur as when running on a treadmill. In animals under anesthesia, electrical stimulation of the hypothalamus may be accompanied by locomotor acts and increased respiration. By small changes in the position of the irritating electrode, autonomic and somatic reactions independent of each other can be achieved. All these effects are eliminated with bilateral lesions of the corresponding zones; in dogs with such lesions, the adaptive reactions of the cardiovascular system to work disappear, and when running on a treadmill, such animals quickly get tired. These data indicate that groups of neurons responsible for the adaptation of hemodynamics to muscular work are located in the lateral region of the hypothalamus. In turn, these sections of the hypothalamus are controlled by the cerebral cortex. It is not known whether such regulation can be carried out by an isolated hypothalamus, since this requires that special signals from skeletal muscles arrive at the hypothalamus.

The hypothalamus and behavior.

Electrical stimulation of small areas of the hypothalamus is accompanied by the appearance in animals of typical behavioral reactions, which are as diverse as the natural species-specific behaviors of a particular animal. The most important of these reactions are defensive behavior and flight, feeding behavior (consumption of food and water), sexual behavior and thermoregulatory reactions. All these behavioral complexes ensure the survival of the individual and the species, and therefore they can be called homeostatic processes in the broadest sense of the word. Each of these complexes includes somatic, vegetative and hormonal components.

With local electrical stimulation of the caudal ring, an awake cat develops defensive behavior, which manifests itself in such typical somatic reactions as arching the back, hissing, spreading fingers, releasing claws, as well as autonomic reactions - rapid breathing, pupil dilation and piloerection in the back and tail . Arterial pressure and blood flow in the skeletal muscles thus increase, and blood flow in the intestine decreases. Such autonomic reactions are mainly associated with the excitation of adrenergic sympathetic neurons. Defensive behavior involves not only somatic and autonomic reactions, but also hormonal factors.

When the caudal hypothalamus is stimulated, pain stimuli cause only fragments of defensive behavior. This suggests that the neural mechanisms of defensive behavior are located in the posterior part of the hypothalamus.

Eating behavior, also associated with the structures of the hypothalamus, is almost the opposite of defensive behavior in its reactions. Eating behavior occurs with local electrical stimulation of the zone located 2-3 mm dorsal to the zone of defensive behavior. In this case, all the reactions characteristic of an animal in search of food are observed. Approaching the bowl, the animal with artificially induced feeding behavior begins to eat, even if it is not hungry, and at the same time chews even inedible objects.

In the study of autonomic reactions, it can be found that such behavior is accompanied by increased salivation, increased motility and blood supply to the intestine, and a decrease in muscle blood flow. All these typical changes in vegetative functions during eating behavior serve as a preparatory stage for eating. During eating behavior, the activity of the parasympathetic nerves of the gastrointestinal tract increases.

Principles of organization of the hypothalamus.

Data from systematic studies of the hypothalamus using local electrical stimulation indicate that there are nerve structures in this center that control a wide variety of behavioral responses. In experiments using other methods - for example, destruction or chemical irritation - this position was confirmed and expanded.

Example: aphagia (refusal of food) that occurs when the lateral regions of the hypothalamus are damaged, electrical stimulation of which leads to eating behavior. The destruction of the medial areas of the hypothalamus, the irritation of which inhibits eating behavior (satiation centers), is accompanied by hyperphagia (excessive food intake).

Areas of the hypothalamus whose stimulation leads to behavioral responses overlap widely. In this regard, it has not yet been possible to isolate functional or anatomical clusters of neurons responsible for a particular behavior. Thus, the nuclei of the hypothalamus, detected using neurohistological methods, only approximately correspond to areas whose irritation is accompanied by behavioral reactions. Thus, nerve formations that ensure the formation of integral behavior from individual reactions should not be considered as clearly defined anatomical structures (which the existence of such terms as “hunger center” and “satiety center” could suggest).

The neural organization of the hypothalamus, through which this small formation is able to control many vital behavioral responses and neurohumoral regulatory processes, remains a mystery.

It is possible that the groups of hypothalamic neurons responsible for the performance of any function differ from each other in afferent and efferent connections, mediators, the location of dendrites, and the like. It can be assumed that numerous programs are embedded in the little-studied nerve circuits of the hypothalamus. Activation of these programs under the influence of nerve signals from the overlying parts of the brain (for example, the limbic system) and signals from receptors and the internal environment of the body can lead to various behavioral and neurohumoral regulatory responses.

Functional disorders in people with damage to the hypothalamus

In humans, disorders of the hypothalamus are associated mainly with neoplastic (tumor), traumatic or inflammatory lesions. Such lesions can be very limited, affecting the anterior, intermediate, or posterior hypothalamus. These patients have complex functional disorders. The nature of these disorders is determined, among other things, by the severity (for example, with injuries), or the duration (for example, with slowly growing tumors) of the process. With limited acute lesions, significant functional disorders can occur, while with slowly growing tumors, these disorders begin to appear only with a far advanced process.

The table lists the complex functions of the hypothalamus and the violations of these functions. Disorders of perception, memory, and the sleep/wake cycle are due in part to damage to the ascending and descending tracts that connect the hypothalamus to the limbic system.

List of used literature.

Human physiology. Volume 1, edited by acad. P.G. Kostyuk. "Mir", 1985.

Vorobieva G.A., Gubar L.V., Safyannikova S.B., Anatomy and Physiology.

Ermolaev II, Age physiology.

Fomin A.B., Human Physiology, “Enlightenment”, 1995.

HYPOTHALAMUS [hypothalamus(BNA, JNA, PNA); Greek, hypo- + thalamos room; syn.: hypothalamic region, hypothalamic region, hypothalamic region] - a section of the diencephalon, located downward from the thalamus under the hypothalamic groove and representing an accumulation of nerve cells with numerous afferent and efferent connections.

Story

Starting from the middle of the 19th century. G.'s influence on various aspects of the organism's vital activity was studied (adaptation processes, sexual functions, metabolic processes, thermoregulation, water-salt metabolism, etc.).

The big contribution to G.'s studying was brought by domestic scientists. In the 30s of the 20th century. A. D. Speransky et al. conducted experiments on animals by applying a glass bead or a metal ring to the substance of the brain in the region of the Turkish saddle, as a result, hemorrhages and ulcers occurred in the stomach and intestines.

H. N. Burdenko and B. N. Mogilnitsky described the occurrence of a perforated gastric ulcer during neurosurgical intervention in the region of the third ventricle. A special place is occupied by studies conducted by N. I. Grashchenkov in the study of theoretical and wedge, aspects of G.'s role in various disorders of the nervous system and internal organs.

In 1912, Aschner (V. Aschner) observed atrophy of the gonads in dogs after the destruction of G. In 1928, Sharrer (V. Scharrer) discovered the secretory activity of the hypothalamic nuclei. Holweg and Junkman (W. Hohlweg, K. Junkman, 1932) established the localization of the sexual center in G., electrical stimulation to-rogo in the experiments of Harris (G. W. Harris, 1937) caused ovulation in rabbits. In 1950, Hume and Wittenstein (D. M. Hume, G. J. Wittenstein) showed the effect of hypothalamic extracts on the secretion of adrenocorticotropic hormone. In 1955 Guillemin and Rosenberg (R. Guillemin, V. Rosenberg) found in G. so-called. releasing factor - corticotropin (corticotropin-releasing factor). In subsequent years, the localization of the nuclei of some G., responsible for the regulation of metabolism and the secretion of individual pituitary hormones, was shown (see).

Embryology, anatomy, histology

G. is a phylogenetically ancient formation that exists in all chordates. However, the designation of this part of the brain as a hypothalamus cannot be used in relation to cyclostomes and transversestomes, since the visual tubercles first form at the amphibian stage. In birds, the G. has a relatively small size, but the differentiation of its nuclei is quite well expressed. It receives mainly impulses from the olfactory centers, the striatum, which forms most of the forebrain in birds.

G. reaches its highest development in mammals. In a human embryo at the age of 3 months. on the inner surface of the thalamus there are two furrows dividing it into three parts: the upper one is the epithalamus, the middle one is the thalamus and the lower one is the hypothalamus. In further embryonic development, a finer differentiation of the G.'s nuclei is revealed and its numerous connections are formed. The anterior border of G. is the optic chiasm (chiasma opticum), the terminal plate (lamina terminalis) and the anterior commissure (commissura ant.). The posterior border runs behind the lower edge of the mastoid bodies (corpora mamillaria). Anteriorly, the cell groups of G. without interruption pass into the cell groups of the plate of the transparent septum (lamina septi pellucidi). Despite the small sizes of G., its cytoarchitectonics differs in considerable complexity. In G. the gray matter consisting of hl is well developed. arr. from small cells. In some areas, there are groups of cells that form separate G.'s nuclei (Fig. 1). The number, topography, size, shape, and degree of differentiation of these nuclei vary in different vertebrates; in mammals, 32 pairs of nuclei are usually distinguished. Between adjacent nuclei there are intermediate nerve cells or their small groups, therefore fiziol. not only nuclei, but also some internuclear hypothalamic zones may be of importance. According to the grouping in G., three unsharply demarcated areas of accumulation of nuclei are conventionally distinguished: anterior, middle, and posterior.

In the middle region of G., around the lower edge of the third ventricle, there are gray-tuberous nuclei (nucll. tuberales), arcuately covering the funnel (infundibulum). Above and slightly lateral to them lie large superior medial and inferior medial nuclei. The nerve cells that make up these nuclei are not uniform in size. Small nerve cells are localized on the periphery, and larger ones occupy the middle of the nuclei. The nerve cells of the superior medial and inferior medial nuclei differ from each other in the structure of the dendrites. In the cells of the superior medial nuclei, the dendrites are characterized by the presence of a large number of long spines, the axons are highly branched and have numerous synaptic connections. Serotuberous nuclei (nucll. tuberales) are clusters of small nerve cells of a fusiform or triangular shape, localized around the base of the funnel. The processes of the nerve cells of these nuclei are determined in the proximal part of the pituitary stalk to the median eminence, where they end in axovasal synapses on the loops of the primary capillary network of the pituitary gland. These cells give rise to the fibers of the tuberohypophyseal bundle.

The group of nuclei of the posterior region consists of scattered large cells, among which clusters of small cells lie. This section also includes the nuclei of the mastoid body (nucll. corporis mamillaris), which protrude on the lower surface of the diencephalon in the form of hemispheres (paired in primates and unpaired in other mammals). The cells of these nuclei are efferent nerve cells and give rise to one. from the main projection systems from G. to the medulla oblongata and spinal cord. The largest cell cluster forms the medial nucleus of the mastoid body. Anterior to the mastoid bodies, the bottom of the third ventricle protrudes in the form of a gray tubercle (tuber cinereum), formed by a thin plate of gray matter. This protrusion extends into a funnel, passing in the distal direction into the pituitary stalk and further into the posterior lobe of the pituitary gland. The funnel is delimited from the gray mound by an indistinct furrow. The expanded upper part of the funnel - the median eminence - has a special structure and a kind of vascularization). From the funnel cavity, the median eminence is lined with ependyma, followed by a layer of nerve fibers of the hypothalamic-pituitary bundle and thinner fibers originating from the nuclei of the gray tubercle. The outer part of the median eminence is formed by supporting neuroglial (ependymal) fibers, between which numerous nerve fibers lie. Deposition of neurosecretory granules is observed in and around these nerve fibers. In the outer layer of the median eminence there is a network of capillaries that provides blood supply to the adenohypophysis. These capillaries form loops that rise into the thickness of the median eminence towards the nerve fibers that descend to these capillaries.

G. includes nuclei formed by nerve cells that do not have a secretory function, and nuclei consisting of neurosecretory cells. Secretory nervous cells are concentrated hl. arr. directly next to the walls of the third ventricle. By their structural features, these cells resemble cells of the reticular formation (see). Fiziol, the data indicate that cells of this type produce physiologically active substances that promote the release of triple hormones from the pituitary gland and are called hypothalamic neurohormones (see).

Neurosecretory cells are concentrated in the anterior region of G., where they form the oversight (nucl. supraopticus) and paraventricular (nucl. paraventricularis) nuclei on each side. The supervisory nucleus is located in the posterolateral region from the beginning of the optic tract. It is formed by a group of cells lying along the angle between the wall of the third ventricle and the dorsal surface of the optic chiasm. The paraventricular nucleus consists of large and medium-sized nerve cells, has the form of a plate lying between the fornix and the wall of the third ventricle, begins in the region of the optic chiasm and gradually rises backwards and upwards in an oblique direction.

Between both of these nuclei are numerous single neurosecretory cells or their groups. In the paraventricular nucleus, large neurosecretory cells are concentrated mainly in the expanded posterior part (large cell part), and smaller neurons predominate in the narrowed anterior part of this nucleus. The area of ​​the supraventricular and paraventricular nuclei is characterized by abundant vascularization. The axons of the neurons of the paraventricular and supervisory nuclei, forming the hypothalamic-pituitary bundle, reach the posterior lobe of the pituitary gland, where they form contacts with the capillaries. In the posterior pituitary gland, neurohormones accumulate and enter the bloodstream. The main feature of neurosecretory cells is the presence of specific (elementary) granules contained in different quantities both in the area of ​​perikaryons and in processes - axons and dendrites (see Hypothalamo-pituitary system). The neurosecretory cells of the oversight and paraventricular nuclei are similar in shape and structure, but a certain differentiation is allowed; cells of the oversight nucleus produce predominantly antidiuretic hormone (see Vasopressin), and periventricular - oxytocin (see). Thus, G. is formed by a complex of neuroconductive and neurosecretory cells. In this regard, the regulatory influences of G. are transmitted to effectors, including the endocrine glands, not only with the help of hypothalamic neurohormones, which are carried in the bloodstream and, therefore, act humorally, but also through efferent nerve fibers.

G. is closely connected with neighboring structures of the brain through pathways. G. is connected with a forebrain by a medial beam, fibers to-rogo arise in an olfactory bulb, a head of a caudate kernel, an amygdala and a front part of a parahippocampal crinkle (gyrus parahippocampalis).

G. has a well-developed and very complex system of afferent and efferent pathways. G.'s afferent pathways are divided into six groups: 1) the medial bundle of the forebrain, which connects the septum and preoptic region with almost all G.'s nuclei; 2) the arch which is system of the afferent fibers connecting bark of a hippocampus (see) with G.; the main part of the fibers of the arch goes to the nuclei of the mastoid body, the other - to the septum and to the lateral preoptic region, the third - to other nuclei of G.; 3) thalamo-pituitary fibers, connecting mainly the medial and intralamellar nuclei of the thalamus (see) with G.; 4) mastoid-cover bundle, in Krom there are fibers ascending from the midbrain (see) to G.; some of these fibers end in the preoptic region and septum; 5) posterior longitudinal bundle (fasciculus longitudinalis dorsalis), which carries impulses from the brainstem to G.; the system of fibers of the posterior longitudinal bundle and mastoid bodies provides a connection between the reticular formation of the midbrain with G. and the limbic system (see); 6) the pallido-hypothalamic pathway connecting the strio-pallidar system with G. Indirect cerebellar-hypothalamic connections, optic-hypothalamic pathways, and vagosupraoptic connections have also been established.

G.'s efferent pathways are divided into three groups: 1) bundles of fibers of the periventricular system (fibrae periventriculares), originating in the posterior hypothalamic nuclei, first go together through the periventricular zone; some of them terminate in the postero-medial thalamic nuclei; most of the fibers of the periventricular system go to the lower part of the brain stem, as well as to the reticular formation of the midbrain and the spinal cord (G.'s reticular tract); 2) the mastoid bundles, originating in the nuclei of the mastoid body of G., are divided into two bundles: the mastoid-thalamic (fasc. mamillothalamicus), going to the anterior nuclei of the thalamus, and the mastoid-covering bundle (fasc. mamillotegmentalis), going to the nuclei of the midbrain ; 3) the hypothalamic-pituitary tract - the shortest, but clearly defined bundle of axons of G. neurons; these fibers originate in the supraventricular and paraventricular nuclei and go through the pituitary stalk to the neurohypophysis. The majority of G.'s functions, in particular the control of visceral functions, is carried out through these afferent ways. In addition to afferent and efferent connections, G. has a commissural pathway. Thanks to him, the medial hypothalamic nuclei of one side come into contact with the medial and lateral nuclei of the other side.

The main source of arterial blood supply to the nuclei of G. are the branches of the arterial circle of the brain, which provide an isolated abundant blood supply to individual groups of nuclei of G. G.'s vessels are highly permeable to large molecular protein compounds. The relationship between G. and the adenohypophysis is carried out through the vessels of the portal system, which has its own characteristics (see the Hypothalamo-pituitary system).

Physiology

G. occupies a leading position in the implementation of the regulation of many functions of the whole organism, and above all the constancy of the internal environment (see Homeostasis). G. - the highest vegetative center, carrying out complex integration and adaptation of the functions of various internal systems to the integral activity of the organism. It is essential in maintaining the optimal level of metabolism (protein, carbohydrate, fat, water and mineral) and energy, in regulating the temperature balance of the body, the activity of the digestive, cardiovascular, excretory, respiratory and endocrine systems. Under the control of G. are such glands of internal secretion as the pituitary, thyroid, genital, pancreas, adrenal glands, etc.

The regulation of the triple functions of the pituitary gland is carried out by the release of hypothalamic neurohormones entering the pituitary gland through the portal vascular system. Between G. and a hypophysis there is a feedback (fig. 2), by means of a cut their secretory function is regulated. The principle of feedback (feedback relation) is that with an increase in the secretion of hormones by the endocrine glands, the secretion of G.'s hormones decreases (see Neurohumoral regulation). The secretion of triple pituitary hormones a leads to a change in the functions of the endocrine glands, the secret of which enters the bloodstream and, in turn, can act on the hypothalamus. Seven hypothalamic neurohormones activating and three inhibiting the release of triple pituitary hormones were found in the hypothalamus. They are widely used in the clinic to diagnose diseases of the endocrine glands. It is generally accepted that the anterior region of G. is directly involved in the regulation of the release of gonadotropins. Most researchers consider the center that regulates the thyrotropic function of the pituitary gland to be an area located in the anterobasal part of the brain, below the paraventricular nucleus, extending from the supraventricular nuclei in front to the arcuate nuclei posteriorly. The localization of areas that selectively control the adrenocorticotropic function of the pituitary gland has not been studied enough. A number of researchers connect the regulation of ACTH with the posterior region of G. The Hungarian school of J. Szentagothai connects the regulation of ACTH with the premamillary region. The maximum concentration of ACTH - releasing factor is found in the area of ​​medial emission. Localization of areas G., participating in the regulation of other tropic hormones of the pituitary gland, remains unclear. Functional isolation and differentiation of the hypothalamic zones according to their participation in the control of the tropic functions of the pituitary gland cannot be carried out quite clearly.

Numerous studies have shown that the anterior region of G. has a stimulating effect on sexual development, and the posterior region of G. has an inhibitory effect. In patients with pathology of the hypothalamic region, there is a violation of the functions of the reproductive system: sexual weakness, menstrual irregularities. There are many cases of rapid puberty as a result of excessive irritation of the area of ​​the gray tubercle by the tumor. At the adiposogenital syndrome connected with defeat of tuberal area of ​​G., violations of sexual function are observed.

G. is important in maintaining optimal; temperature of the body scheme (see Thermoregulation).

The mechanism of heat loss is associated with the function of the anterior region of G. The destruction of the posterior regions of G. causes a decrease in body temperature.

G. regulates the function of the sympathetic and parasympathetic parts of the autonomic nervous system, their coordination. The back area of ​​G. participates in regulation of activity of a sympathetic part of century. n. s., and the middle and anterior ones - of the parasympathetic section, since stimulation of the anterior and middle regions of the G. causes parasympathetic reactions (slowing of the heartbeat, increased intestinal motility, bladder tone, etc.), and irritation of the posterior region causes sympathetic reactions (increased heartbeat, etc.). There are reciprocal links between these centers. However, it is difficult to clearly distinguish between centers in G..

The study of the hypothalamic level of regulation of eating behavior showed that it is carried out as a result of reciprocal interactions of two food centers: the lateral and ventromedial hypothalamic nuclei. Activation of neurons of lateral G. causes formation of food motivation. With the bilateral destruction of this section of G., food motivation is completely eliminated, and the animal may die from exhaustion. Increased activity of the ventro-medial nucleus of G. reduces the level of food motivation. With the destruction of this core, the level of food motivation significantly increases, hyperphagia, polydipsia and obesity are observed.

Vasomotor reactions of hypothalamic origin are closely related to the state of c. n. With. Various types of arterial hypertension (see Arterial hypertension), developing after G.'s stimulation, are due to the combined influence of the sympathetic department of c. n. With. and release of adrenaline from the adrenal glands. However, in this case, the influence of the neurohypophysis cannot be excluded, especially in the genesis of persistent hypertension, which is confirmed by experimental data, when arterial hypertension caused by stimulation of the posterior region of the brain decreases after electrical destruction of the medial emission. The regional vasomotor reactions that develop after the destruction of the preoptic region differ from the general vasomotor reactions observed after stimulation of the posterior region of G.

G. is one of the main structures involved in the regulation of the change of sleep and wakefulness (see Sleep). A wedge, by researches it is established that the symptom of a lethargic sleep at epidemic encephalitis is caused by damage of G. G.'s damage caused a dream and in an experiment. The posterior region of the brain is of decisive importance for maintaining the state of wakefulness. Extensive destruction of the middle region of the brain led to a state of prolonged sleep in animals. Sleep disturbance in the form of narcolepsy is explained by damage to the rostral part of the reticular formation of the midbrain and G. Experimental data have been obtained (P.K. Anokhin, 1958), indicating that sleep, as a result of inhibition of cortical activity, develops as a result of the release of hypothalamic formations that remain active during the entire period of sleep.

G. is under the regulating influence of a cerebral cortex. The neurons of the cortex, receiving information about the initial state of the organism and the environment, have a downward influence on all subcortical structures, including the centers of G., regulating the level of their excitation. The cerebral cortex has an inhibitory effect on the functions of G. Acquired cortical mechanisms suppress many emotions and primary impulses that are formed with the participation of G. Therefore, decortication often leads to the development of an “imaginary rage” reaction (dilated pupils, piloerection, tachycardia, increased intracranial pressure, salivation and etc.).

From fiziol, the point of view has a number of features, and first of all it concerns its participation in formation of behavioral reactions of an organism important for preservation of a constancy of the internal environment. G.'s irritation leads to the formation of purposeful behavior - eating, drinking, sexual, aggressive, etc. G. plays a major role in the formation of the body's main drives (see Motivation).

The metabolism of G. neurons is selectively sensitive to the content of certain substances in the blood, and with any change in their content, these cells enter a state of excitation. Hypothalamic neurons are sensitive to the slightest deviations in the pH of the blood, the tension of carbon dioxide and oxygen, the content of ions, especially potassium and sodium, etc. Thus, cells selectively sensitive to changes in the osmotic pressure of the blood were found in the supraoptic nucleus of G., in the ventromedial nucleus - glucose content , in the anterior hypothalamus - sex hormones. Thus, G.'s cells function as receptors that perceive changes in homeostasis and have the ability to transform humoral changes in the internal environment into a nervous process, biologically colored excitation. G.'s centers are characterized by the expressed selectivity of excitation depending on various changes of structure of blood (fig. 3). G.'s cells can be selectively activated not only by a change in certain blood constants, but also by nerve impulses from the corresponding organs associated with this need. G.'s neurons, which have selective reception in relation to changing blood constants, work according to a trigger type (see Trigger mechanisms). Excitation in these G.'s cells does not occur immediately, as soon as any constant of the blood changes, but after a certain period of time, when their excitability rises to a critical level. Thus, the cells of the motivational centers of G. characterize the frequency of work. If the change in the blood constant is maintained for a long time, then in this case the excitability of the G. neurons quickly rises to a critical value and the state of excitation of these neurons is maintained at a high level all the time while there is a change in the constant that caused the development of the excitation process. Constant impulsation of G.'s neurons is eliminated only when the irritation that caused it disappears, i.e., the content of one or another blood factor is normalized. Functioning of trigger, G.'s mechanisms is considerably extended in time. Excitation of some G.'s cells can occur periodically after a few hours, as, for example, with a lack of glucose, others - after several days or even months, as, for example, when the content of sex hormones changes. G.'s neurons not only perceive changes in blood parameters, but also transform them into a special nervous process that forms the behavior of the organism in the environment, aimed at satisfying internal needs.

G.'s extensive connections with other structures of the brain contribute to the generalization of excitations that arise in the cells of the brain. First of all, excitation from the G. spreads to the limbic structures of the brain and through the nuclei of the thalamus to the anterior sections of the cerebral cortex. The zone of distribution of the ascending activating influences of G. depends on the strength of the initial irritation of the G. centers. With increased excitation of the G. centers, the apparatuses of the reticular formation are activated. All these ascending activating influences of the hypothalamic centers, excited by the internal need of the organism, determine the emergence of a state of motivational excitation.

The descending influences of G. provide regulation of functions of hl. arr. through in. n. With. But at the same time, the hormones of the pituitary gland are also an important component in the implementation of the descending influences of G.. Thus, both ascending and descending influences of G. are carried out in a nervous and humoral way (see Neurohumoral regulation). Great attention is paid to descending influences of G. in connection with G. Selye's concept of the “stress” reaction (see Adaptation syndrome, Stress). The existence of inhibitory influences of various G. nuclei on mono- and polysynaptic spinal reflexes has been established. When the complex of mamillary nuclei is irritated, in some cases there is an increase in the activity of motor neurons of the spinal cord.

G. is in continuous cyclic interactions with other departments of the subcortex and the cerebral cortex. It is this mechanism that underlies G.'s participation in emotional activity (see Emotions). The special importance of the centers of G. in the activity of the whole organism allowed P. K. Anrkhin and K. V. Sudakov (1968.1971) to suggest a "peyzmaker" (peytsmaker - trigger) role of this brain structure in the formation of biol, motivations. Due to the fact that nervous and humoral signaling about various internal needs is addressed to the hypothalamic regions, they acquire the significance of "pacemakers" of motivational excitations. According to this concept, the hypothalamic "pacemakers" determine the energy basis of motivational excitations due to ascending activating influences.

Neurons of the motivational centers of G. possess various chemical. specificity, the edge is determined by the selective use of special chemicals in their metabolism. substances. And this chem. specificity of G. remains in the ascending influences activating it at all levels, providing high-quality biol, an originality of behavioral acts. Thus, the introduction of adrenolytic substances (chlorpromazine) can selectively block the mechanisms of activation of the cerebral cortex during nociceptive stimulation. Activation of the cerebral cortex during food arousal of hungry animals is selectively blocked by anticholinergic drugs. Neurotropic substances with a specific mechanism of action due to the existence of heterochemical. organizations of the hypothalamic centers can selectively block various mechanisms of hypothalamus involved in the formation of such states of the body as hunger, fear, thirst, etc.

Research methods

Electroencephalographic method. According to the results of an electroencephalographic study, lesions (see Electroencephalography) can be divided into four groups: the first group - the absence of deviations or minimal deviations from the normal EEG; the second group - a sharp decrease in the alpha rhythm up to its disappearance; the third group - the appearance of the theta rhythm on the EEG, especially in connection with repeated afferent stimuli; the fourth group - paroxysmal EEG disturbances in the form of the appearance of changes characteristic of sleep; this type of EEG characterizes diencephalic epilepsy. With the syndromes described above, a comparative evaluation of the EEG does not reveal specificity.

Plethysmographic studies (see. Plethysmography ) reveal a wide range of changes - from the state of autonomic vascular instability and paradoxical reaction to complete areflexia (see), which corresponds to the degree of severity of functional or organic lesions of the G. nuclei. n.a. using the motor method with verbal reinforcement, it was found that in all forms of G.'s pathology, the interaction between the cortex and subcortex is sharply reduced.

In patients with G.'s defeat, regardless of its cause (tumor, inflammation, etc.), the content of catecholamines and histamine in the blood may increase, the alpha-globulin fraction increases and the beta-globulin fraction decreases, the level of excretion of 17-ketosteroids changes. At various forms of G.'s defeat disturbances of skin temperature and sweating are clearly shown.

Pathology

Both functional disorders and irreversible changes in its nuclei occur in the hypothalamus. First of all, it should be noted the possibility of varying degrees of damage to the nuclei (mainly supervising and paraventricular) in diseases of the endocrine glands.

Injuries to the brain, leading to a redistribution of cerebral fluid, can also cause changes in the hypothalamic nuclei located near the ependyma of the bottom of the third ventricle.

Pathomorphologically, these changes relate primarily to neurons and are especially clearly identified when stained according to Nissl (see Nissl method) and Gomory's method. They are expressed by the phenomena of tigrolysis, neuronophagy, vacuolization of protoplasm, and the formation of shadow cells. Due to the increased permeability of the walls of blood vessels during infections and intoxications, the hypothalamic nuclei can be exposed to pathogenic effects of toxins and chemicals. products circulating in the blood. Neurovirus infections are especially dangerous. The most common inflammatory processes of G. are basal meningitis of tuberculous origin and syphilis. Rare forms of G.'s defeat include granulomatous inflammation (Beck's disease), lymphogranulomatosis, leukemia, and vascular aneurysms of various origins. Of G.'s tumors, various types of gliomas, defined as astrocytomas, are most common; craniopharyngeomas, ectopic pinealomas and teratomas, as well as suprasellar pituitary adenomas located above the Turkish saddle, meningiomas and cysts.

Clinical manifestations of dysfunction of the hypothalamus

At G.'s defeat allocate the following main syndromes.

1. Neuro-endocrine manifested by obesity with a characteristic redistribution of subcutaneous adipose tissue (moon-shaped face, thick neck and torso, thin limbs), osteoporosis with a tendency to kyphosis of the spine, back and lower back pain, sexual dysfunction (early amenorrhea in women and impotence in men), growth hair on the face and trunk in women and adolescents, hyperpigmentation of the skin, especially in places of folds, the presence of purple atrophic stripes on the abdomen and thighs (striae distensae), arterial hypertension, periodic edema, general weakness and increased fatigue. A variety of the specified syndrome is Itsenko - Cushing's disease (see).

Other manifestations of the neuroendocrine syndrome are diabetes insipidus (see), pituitary cachexia (see), adipose-genital dystrophy (see), etc.

2. Neurodystrophic syndrome characterized by a change in salt metabolism, destructive changes in the skin and muscles, accompanied by edema and atrophy of the skin, neuromyositis, periodically occurring intra-articular edema; the skin is dry, flaky with stripes of stretching, itching, rashes are observed. Osteomalacia, calcification, bone sclerosis, ulceration, bedsores, bleeding along the gallbladder are also noted. path and in the parenchyma of the lungs, transient edema of the retina.

3. Vegetative-vascular syndrome characterized by the expansion of small veins on the face and body, increased fragility of blood vessels, a tendency to hemorrhage, high permeability of the walls of blood vessels, various vegetative-vascular paroxysms, including migraines, accompanied by an increase or decrease in blood pressure.

4. Neurotic syndrome it is shown by original hysterical reactions and psikhopatol, states, and also disturbances of wakefulness and a dream.

The listed syndromes can manifest themselves both with functional disorders and with organic lesions of the nuclei of the G. If the vegetative-vascular syndrome is observed with functional changes, then neurodystrophic - with severe organic lesions of the nuclei of the middle region of the G., sometimes its anterior and posterior regions. The neuroendocrine syndrome is shown in the beginning as result of functional disturbances of kernels of forward area G., further organic defeats of the mentioned kernels join.

Treatment

In the pathology of the hypothalamic region, three types of treatment are used.

1. X-ray therapy in small doses within (50 r) 6-8 sessions per area G. with the inflammatory nature of the lesion or the presence of a pronounced allergic condition. With a good excretory function of the kidneys, irradiation should be accompanied by the appointment of small doses of diuretics. X-ray therapy is indicated for severe vegetative-vascular syndrome, with neuro-endocrine, in the initial stage of its development.

2. Hormone therapy in the form of mono-therapy or in combination with radiotherapy. The use of cortisone, prednisolone or their derivatives, as well as ACTH should be accompanied by careful monitoring of the hormonal function of the adrenal glands. Preparations of sex hormones of the thyroid gland are also used, and attempts are being made to use ri-leasing hormones.

3. Introduction by the method of ionogalvanization into the nasal mucosa of various chemical. substances at a minimum current strength of 0.3-0.5 a; the duration of the procedure is 10-20 minutes. Usually held up to 30 sessions. For ionogalvanization, 2% calcium chloride solution, 2% vitamin B1 solution, 0.25% diphenhydramine solution, ergotamine or phenamine solution are used. Ionogalvanization is incompatible with radiotherapy. In some cases, drugs are used that reduce intracranial pressure, acting on the processes of inhibition or excitation in the cortex and subcortex (phenobarbital, bromides, caffeine, phenamine, ephedrine). In all cases, a careful individual choice of forms of treatment is necessary.

Operative treatment is carried out at G.'s tumors according to the standard methods of operations on a brain (see).

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B. H. Babichev, S. A. Osipovsky.