CC BY
20
Askaryants Vera Petrovna, docent, the Department of Pharmacology and Normal physiology Tashkent Pediatric Medical Institute, Tashkent E-mail: [email protected]
TO THE QUESTION OF THE ROLE OF THE HYPOTHALAMUS IN STRESS
Abstract: Based on the literature review one can say the importance of studying the function of brain centers. Keywords: body, categories, hypothalamus, component.
The hypothalamus is a compartment of the diencepha-lon occupied by the control of homeostasis set points. There are vegetative nerve centers that set a thermostatic setpoint, a massostatoussetpoint, as well as barostatic and other centers for maintaining the body's balance constants.
Undoubtedly, conscious decisions mature in the highest parts of the central nervous system. But it is the hypothalamus that gives our actions the character of passion, which changes the individual fate, and sometimes the fate of entire ethnic groups. Such concepts, passionarity, duty (according to Selye, "voluntarily adopted a code of conduct") and other categories that link human biology with its history are closely related to the role of the hypothalamus in the body.
The hypothalamus is the main element of the limbic system, coordinating biologically expedient behavior, determining what is pleasant and desirable, and what is unpleasant and disgusting for individuals in sensations and behavioral reactions. It is here that the affective component of sensations and reactions is formed. This has a huge impact on cravings, preferences, value setting.
Near the centers of hunger and thirst, in the lateral parts of the hypothalamus there is a center of rage (anger), irritation of which provokes an aggressive emotional-vegetative-motor reaction and severe stress.
Not far from it, in the periventricular nuclei there is a punishment center, irritation of which provokes fear, displeasure, causes severe pain and an active avoidance reaction, and upon prolonged exposure leads to such severe debilitating stress that it can result in the death of the animal. This hypothalamic center is closely connected with similar formations in the gray matter surrounding the sylvium aqueduct of the midbrain, in the amygdala and hippocampus, which is responsible for some functions of memory and learning. Electrical stimulation of the medial and lateral nuclei of the amygdala and ventral hippocampus enhances the stress response. The center of punishments transmits activating effects to the center of rage, which makes possible an active external response of the animal, defense and avoidance. Stress provoked by irritation of the punishment center, is particularly strong and pathogenic in nature, easily leads to distress
and pathological changes in the internal organs of the type of "exhaustion" or "painful adaptation" Coordinated by the center of anger why either turns out to be impossible or limited. These are not merely general behavioral considerations dictated by observations of individuals suffering from unreacted emotions. There are data of quantitative measurements of the level of activation of vegetative functions and the degree of damage to the internal organs in animals subjected to experiments based on a special model of stress - painful effects in conditions of complete immobilization. It does not occur, the realization of the reaction of rage and there is no proper release of endogenous opiates, with their anti-pain and antistress regenerative activity, and the destructive potential of stress turns inward. Mobilization of vegetative functions is excessive and prolonged. The described situation is in the behavioral physiology of the name "excerpts". Exposure, that is, stimulation of the center of punishments while braking the reaction of rage, gives the most severe and pathogenic stress. The pathogenicity of stress caused by stimulation of this area of the hypothalamus, is further enhanced if stress is accompanied by an extended stage of anxiety. Additional experimental effects that increase stress are "the introduction of signals that notify in advance of the imminent painful strike, striking at random, not too short periods of time".
This experimental situation is evidently reproduced in real life, with social inhibition of the human being's ability to realize a defensive reaction or when a ban is imposed on its implementation. This leads to the fact that the most pathogenic situation creates a social stress of hopelessness and the dependence of the individual on the source of stress. Wise Japanese psychologists, trying to prevent such situations in production, decorated offices and factories with dolls - stuffed bosses, taking on the blows of angry subordinates.
The main center of pleasure (or reward, satisfaction) is also in the hypothalamus, along the central bundle of nerve fibers in the ventromedial and lateral nuclei and is represented by noradrenergic neurons. It soothes stress. Having the ability to self-stimulate this center, animals have an irresistible attraction for this and prefer such self-satisfaction to food, sex and any other means of obtaining pleasure. Such an obsessive
TO THE QUESTION OF THE ROLE OF THE HYPOTHALAMUS IN STRESS
pattern of behavior is reminiscent of the actions of fanatics and drug addicts. The pleasure center is closely connected with the centers of saturation and sexual desire, but not only with them.
A remarkable feature of this center is its close connection and even anatomical overlap with the center of anger. Moderate stimulation of the centers of rage may be accompanied by a positive affective component. Obviously, this is necessary for neurosecretory and vegetative provision of the protective effect of emotional discharge in case of the threat of distress. But isn't this what makes some individuals angry or even sadistic? According to B. S. Egelmen and P. Kotton(l993), chronic stress alters the neurochemical characteristics of the intermediate brain of rats, steadily increasing their intrahypothalamic tyrosine hydroxylase activity and lowering the ^-adrenoreceptor content in the brain. This correlates with aggressive behavior. It is assumed that aggression allows rats to use anti-stress mechanisms and adapt to chronic stress. Aggressive this doctrine, which treats aggressive behavior as biologically rational for certain situations, has been called "neurocalvinism." K. Lorenz substantiated the evolutionary expediency of the mechanisms ofaggression in the classic work "The so-called evil: the nature of aggression" by the fact that this form of behavior contributes to the establishment of social hierarchical, territorial and marital relations in animals. Additional centers of awards are located in the amygdala, septum, optic tubercle, subcortical nuclei and lid of the midbrain. Electrical stimulation of the lateral part of the basal nucleus of the almond-shaped complex and its corticomedial nuclei, as well as the dorsal part of the midbrain, soothes the stress response. Stimulation of the basal nuclei of the amygdala activates it. The nuclei of the hippocampus have an anti-stress effect.
In turn, the hippocampus is an obligatory switching station for all sensory projections of the new cortex, with the exception of the olfactory, which gives it the ability to control stress responses in response to a variety of sensory stimuli, for example, visual and auditory.
Interestingly, in the case of single combat, positive and negative stimuli and, therefore, centers of satisfaction and displeasure in experimental animals conquer invariably the latter, the stressful effects of which influence behavior more strongly than the anti-stress action of the center of rewards. It is very important that repeated effects of the stressor cause desensitization and addiction to it, as the stressor becomes a routine factor, it causes more and more weak stress and less and less cortical electrophysiological response. It is very important that repeated effects of the stressor cause desensiti-zation and addiction to it, as the stressor becomes a routine factor, it causes more and more weak stress and less and less cortical electrophysiological response. However, if the stressor acts with reinforcement by stimulating the reward center or punishment center, then there is no response fading. In this
regard, stress stimulates memory especially, short-term. According to some data, ACTH and vasopressin are even in the hippocampus and other parts of the central nervous system the neurotransmitters of memory centers. These data point to the important role of stress in its associated hypothalamic changes in reinforcement and training.
The neurochemical aspects of the regulatory functions of the foothill region can be characterized as follows.
Hypothalamic neurosecretory cells of a person secrete the following main groups of biostimulants.
Liberins (i.e., neuroendocrine stimulants of production of pituitary peptides with an identified structure).Liberins include thyroliberin, which is also a weak prolactoliberin (tripep-tide), lyuliberin (decapeptide, which is both follyliberin, that is, common gonadoliberin), somatoliberin (44 amino acids), and the key stress liberalin - corticoliberin and releasing factors (stimulants). hormones with not exactly established structure). A non-characterized peptide that stimulates the production of the melanocyte-stimulating hormone MSH is called MSH-RF.
Statins (peptides with an established chemical structure that inhibit the production of pituitary hormones by a neuroendocrine method) and inhibiting factors (similar peptides whose structure is not deciphered). This group includes somatostatin, this neuropeptide inhibits many different functions and is sometimes referred to as pangibin. It is fundamentally important that statins (like liberins) can act not only by neuroendocrine transgipofizarnnym way, but also through the cerebrospinal fluid and systemic blood flow (thyroliberin, somatostatin, CRF), paracrine - within the hypothalamus and as neurotransmitters in peptide syndrome.
Nonapeptides (arginyl- and lysyl-vasopressin and oxytocin). These are the first neurohormones found in the hypothalamus and the most quantitatively significant products of its neurosecretion. In addition to the neuroendocrine systemic effect, they have a trans-hypophysial effect, and can also be peptidergic neurotransmitters and paracrine regulators in the CNS.
Vasopressin serves as an important stimulator of ACTH secretion under stress and, like corticoliberin, is released into the pituitary system. Vasopressin has a mitogenic effect on the cells of the glomerular zone of the adrenal cortex. The other nonapeptide, oxytocin, exhibits a weak corticoliberin-like effect. Nonapeptides use receptors and post-receptor mediators other than CRF in adenohypophysis cells and affect not only synthesis, but release of ACTH, therefore the effects of CRF and octapeptide during stress are summed up.
Monoamines, among which the most important place is occupied by dopamine, which functions as an inhibitor of prolactin secretion and also called conditionally "prolactostatin". Its effect has a much stronger effect on the functions of prolactin synthesizing cells of the adenohypophysis than the effects of
all identified and suspected peptide stimulants of prolactino-genesis. Therefore, at the intersection of the pituitary stalk, the production of all the hormones of the adenohypophysis (secondary panhypopituitarism) is inhibited, except for prolactin, the synthesis of which is, on the contrary, disinhibited. The other monoamines of the under-the-hill monoamines act as neurotransmitters and are represented by serotonin, adrenaline, noradrenaline and histamine. Melatonin can be transported here from the pineal gland. Abundantly represented in the foothill and neurons synthesizing GABA. In relation to stress, stimulating the release of corticoliberin and vasopressin, cho-linergic and serotonergic systems are stimulants.
Endogenous opiates represent a special group of widely distributed anti-stress neuropeptides. They are also produced by the hypothalamus, and the hypothalamus, along with the nucleus tractus solitaries in the medulla oblongata, is a unique place for the formation of opioid peptides of all three families - proopiomelanocortin, proenkephalin and proinorphin-neoendorphin. Opiates can act by the neuroendocrine route (released into the blood and cerebrospinal fluid), as well as peptide synaptic mediators and paracrine regulators, in the hypothalamus itself - this is the central nervous system. The main opioid is ^-endorphin.
The hypothalamus produces many other neuropeptides, widely represented in all its nuclei, as well as throughout the body, in the cells of the diffuse endocrine system (apudo-cytes), in particular, also produced by the enteric system of the gastrointestinal tract, secretory cardiomyocytes, jukstaglo-merular kidney complex, other elements scattered in the body of mixed origin. These neuropeptides are often very important for the hypothalamic autonomic functions, but they do not act through the bloodstream, like liberins and statins, but para-crinely - at the adjacent centers of the foothill, or in the mode of synaptic peptide neurotransmitters in the hypothalamus and other parts of the CNS.
Cytokinins can penetrate the hypothalamus through the vascular organ of the end plate and the neurohematic formations of the neurohypophysis. In addition, the cytokines form astroglia of the hypothalamus itself and the surrounding formations.
So, under stress, the hypothalamus is activated by both humoral factors (hypoxia, hypoglycemia, interleukins), reaching it through neurohemal structures, and nerve cholinergic and serotonergic influences emanating from the limbic system and other CNS departments.
References:
1. Gusev E. I., Konovalov A. N., Burd G. S. Neurology and neurosurgery.- M., "Medicine".2000.- 645 p.
2. Shtulman D. R. Levin O. S. Neurology: Reference practitioner. 5th ed. Supplement and Pererab.- M: MEDPress-inform, 2007.-960 p.
3. Badalyan L. O. Children's neurology.- M., 1998.
4. Neurology. National leadership / Ed. E. I. Guseva, A. N. Konovalova, V. I. Skvortsova.- M.: GEOTAR-Media, 2009.
5. Tishevskoy I. A. Anatomy of the central nervous system: Tutorial.- Chelyabinsk: Publishing house of YUrRU, 2000.
