Physiological processes in the human body proceed in a coordinated manner due to the existence of certain mechanisms of their regulation.
The regulation of various processes in the body is carried out with the help of nervous and humoral mechanisms.
Humoral regulation carried out with the help of humoral factors ( hormones), which are carried by blood and lymph throughout the body.
nervous regulation is carried out using nervous system.
Nervous and humoral methods of regulation of functions are closely related. The activity of the nervous system is constantly influenced by chemicals brought with the bloodstream, and the formation of most chemicals and their release into the blood is under constant control of the nervous system.
The regulation of physiological functions in the body cannot be carried out with the help of only nervous or only humoral regulation - this is a single complex neurohumoral regulation functions.
Recently, it has been suggested that there are not two regulatory systems (nervous and humoral), but three (nervous, humoral and immune).
Nervous regulation
Nervous regulation- this is the coordinating influence of the nervous system on cells, tissues and organs, one of the main mechanisms of self-regulation of the functions of the whole organism. Nervous regulation is carried out with the help of nerve impulses. Nervous regulation is fast and local, which is especially important in the regulation of movements, and affects all (!) Systems of the body.
The reflex principle underlies the nervous regulation. Reflex is a universal form of interaction of the body with the environment, it is the body's response to irritation, which is carried out through the central nervous system and is controlled by it.
The structural and functional basis of the reflex is the reflex arc - a series-connected chain of nerve cells that provides a response to irritation. All reflexes are carried out due to the activity of the central nervous system - the brain and spinal cord.
Humoral regulation
Humoral regulation is the coordination of physiological and biochemical processes carried out through the liquid media of the body (blood, lymph, tissue fluid) with the help of biologically active substances (hormones) secreted by cells, organs and tissues during their life.
Humoral regulation arose in the process of evolution earlier than nervous regulation. It became more complicated in the process of evolution, as a result of which the endocrine system (endocrine glands) arose.
Humoral regulation is subordinate to nervous regulation and together with it constitutes a single system of neurohumoral regulation of body functions, which plays an important role in maintaining the relative constancy of the composition and properties of the internal environment of the body (homeostasis) and its adaptation to changing conditions of existence.
immune regulation
Immunity is a physiological function that ensures the body's resistance to the action of foreign antigens. Human immunity makes it immune to many bacteria, viruses, fungi, worms, protozoa, various animal poisons, and protects the body from cancer cells. The task of the immune system is to recognize and destroy all foreign structures.
The immune system is the regulator of homeostasis. This function is carried out through the development autoantibodies, which, for example, can bind excess hormones.
The immunological reaction, on the one hand, is an integral part of the humoral one, since most physiological and biochemical processes are carried out with the direct participation of humoral mediators. However, often the immunological reaction is targeted and thus resembles nervous regulation.
The intensity of the immune response, in turn, is regulated in a neurophilic way. The work of the immune system is corrected by the brain and through the endocrine system. Such nervous and humoral regulation is carried out with the help of neurotransmitters, neuropeptides and hormones. Promediators and neuropeptides reach the organs of the immune system along the axons of the nerves, and hormones are secreted by the endocrine glands unrelatedly into the blood and thus delivered to the organs of the immune system. Phagocyte (cell of immunity), destroys bacterial cells
Form start
Watching the work of your body, you noticed that after running, the frequency of breathing and heart rate increases. After eating, the amount of glucose in the blood increases. However, after some time, these indicators supposedly acquire their original values on their own. How does this regulation take place?
Humoral regulation(lat. humor - liquid) is carried out with the help of substances that affect the metabolic processes in cells, as well as the functioning of organs and the body as a whole. These substances enter the bloodstream, and from it - into the cells. Thus, an increase in the level of carbon dioxide in the blood increases the frequency of respiration.
Some substances, such as hormones, perform their function even if their concentration in the blood is very low. Most hormones are synthesized and released into the blood by the cells of the endocrine glands, which form the endocrine system. Traveling with blood throughout the body, hormones can enter any organ. But the hormone affects the functioning of the organ only if the cells of this organ have receptors for this particular hormone. The receptors are combined with hormones, and this entails a change in the activity of the cell. So, the hormone insulin, joining the receptors of the liver cell, stimulates the penetration of glucose into it and the synthesis of glycogen from this compound.
Endocrine system ensures the growth and development of the body, its individual parts and organs with the help of hormones. It is involved in the regulation of metabolism and adapts it to the needs of the body, constantly changing.
Nervous regulation. Unlike the system of humoral regulation, which responds mainly to changes in the internal environment, the nervous system responds to events occurring both inside the body and outside it. With the help of the nervous system, the body responds to any impact very quickly. Such reactions to the action of stimuli are called reflexes.
Immune regulation is provided by the immune system, the task of which is to create immunity - the body's ability to resist the action of external and internal enemies. They are bacteria, viruses, various substances that disrupt the normal functioning of the body, as well as its cells, dead or reborn. The main fighting forces of the immune regulation system are certain blood cells and special substances contained in it.
Human organism- self-regulating system. The task of self-regulation is to support all chemical, physical and biological indicators of the body's work within certain limits. So, the body temperature of a healthy person can vary between 36-37 ° C, blood pressure 115/75-125/90 mm Hg. Art., the concentration of glucose in the blood - 3.8-6.1 mmol / l. The state of the body, in which all parameters of its functioning remain relatively constant, is called homeostasis (Greek homeo - similar, stasis - state). The work of the regulatory systems of the body, acting in constant interconnection, is aimed at maintaining homeostasis.
Connection of the nervous, humoral and immune regulatory systems
The vital activity of the body is regulated, acting in concert, by the nervous, humoral and immune systems. These systems complement each other, forming a single mechanism of neurohumoral-immune regulation.
Neurohumoral Interactions. Any complex action of the organism on an external stimulus - whether it is tasks in control work or a meeting with an unfamiliar dog in the yard of one's house - begins with the regulatory influences of the central nervous system.
Excitation of the reticular formation brings all the structures of the central nervous system into a state of readiness for action. Activation of the limbic system evokes a particular emotion—surprise, joy, anxiety, or fear—depending on how the stimulus is judged. At the same time, the hypothalamus is activated and hypothalamic-pituitary system. Under their influence, the sympathetic nervous system changes the mode of operation of the internal organs, the adrenal medulla and thyroid glands increase the secretion of hormones. The production of glucose by the liver increases, the level of energy metabolism in cells increases. There is a mobilization of the body's internal resources necessary to effectively respond to the stimulus acting on the body.
The activity of the nervous system may be subject to humoral influences. In this case, information about changes in the state of the body with the help of humoral factors is transmitted to the structures of the nervous system. It, in turn, stimulates reactions aimed at restoring homeostasis.
Everyone felt hungry and knows how a person acts when he wants to eat. How does the feeling of hunger arise, is it a manifestation of food motivation? The hunger and satiety centers are located in the hypothalamus. With a decrease in glucose concentration and an increase in insulin levels, the neurons that are sensitive to their content in the blood are activated, and we feel that we are hungry. Information from the hypothalamus goes to the cerebral cortex. With her participation, eating behavior is formed, that is, a set of actions aimed at finding and absorbing food.
The feeling of fullness occurs when the level of glucose and fatty acids in the blood rises, and insulin levels decrease. All these signals activate the saturation center of the hypothalamus, food motivation disappears - eating behavior is inhibited.
Let us give another example of the relationship between the system of humoral and nervous regulation. With the onset of puberty, the production of sex hormones increases in the body. Sex hormones affect the structures of the nervous system. In the hypothalamus there are centers whose neurons are connected with the sex hormone testosterone and are responsible for sexual reflexes. Due to the action of testosterone in women and men, sexual desire arises - one of the most important human motivations, without which the implementation of reproductive function is impossible.
Neuroimmune Interactions. The immune system, destroying foreign agents and damaged cells of the body itself, thereby regulates the state of its internal environment. There is a relationship between the immune system and the nervous system.
Lymphocytes that mature in the organs of the immune system have receptors for mediators of the sympathetic and parasympathetic nervous systems. Consequently, these cells are able to perceive signals coming from the nerve centers and respond to them. The hypothalamus receives humoral signals about the penetration of the antigen into the body and activates the autonomic nervous system. Impulses pass through the sympathetic neurons that innervate the lymphoid tissues of the immune system, and the mediator norepinephrine is released. Under its influence, the number of T-lymphocytes increases, which inhibit the activity of B-lymphocytes. Parasympathetic neurons, when excited, release the mediator acetylcholine, which accelerates the maturation of B-lymphocytes. So, the sympathetic nervous system is able to suppress the immune response, and the parasympathetic - to stimulate it.
Homework
2. Prepare for the test "Nervous system".
1. Deviation control - a cyclic mechanism, in which any deviation from the optimal level of the regulated indicator mobilizes all the devices of the functional system to restore it at the previous level. Regulation by deviation implies the presence of a channel in the system complex negative feedback, providing a multidirectional influence: strengthening incentive management mechanisms in case of weakening process indicators or weakening incentive mechanisms in case of excessive strengthening of process indicators. For example, with an increase in blood pressure, regulatory mechanisms are activated that ensure a decrease in blood pressure, and with low blood pressure, opposite reactions are activated. Unlike negative feedback, positive
Feedback, which is rare in the body, has only a unidirectional, enhancing effect on the development of the process, which is under the control of the control complex. Therefore, positive feedback makes the system unstable, unable to ensure the stability of the regulated process within the physiological optimum. For example, if blood pressure were regulated according to the principle of positive feedback, in the case of a decrease in blood pressure, the action of regulatory mechanisms would lead to an even greater decrease in it, and in the case of an increase, to an even greater increase in it. An example of a positive feedback is the increased secretion of digestive juices in the stomach after a meal, which is carried out with the help of hydrolysis products absorbed into the blood.
2. Lead control lies in the fact that the regulatory mechanisms are switched on before a real change in the parameter of the regulated process (indicator) on the basis of information entering the nerve center of the functional system and signaling a possible change in the regulated process in the future. For example, thermoreceptors (temperature detectors) located inside the body provide temperature control of the internal regions of the body. Skin thermoreceptors mainly play the role of environmental temperature detectors. With significant deviations in the ambient temperature, the prerequisites for a possible change in the temperature of the internal environment of the body are created. However, normally this does not happen, since the impulse from the thermoreceptors of the skin, continuously entering the hypothalamic thermoregulatory center, allows it to make changes in the work of the effectors of the system. up to the moment of a real change in the temperature of the internal environment of the body. Increased lung ventilation during exercise begins before an increase in oxygen consumption and accumulation of carbonic acid in human blood. This is due to afferent impulses from the proprioreceptors of actively working muscles. Consequently, proprioceptor impulses act as a factor organizing the restructuring of the functioning of the functional system, which maintains the optimal level of P 02 , P ss, 2 for metabolism and the pH of the internal environment ahead of time.
The advance control can be implemented using the mechanism conditioned reflex. It is shown that the conductors of freight trains in winter have a sharp increase in heat production as they move away from the departure station, where the conductor was in a warm room. On the way back, as we get closer
to the station, the production of heat in the body is clearly reduced, although in both cases the conductor was subjected to equally intense cooling, and all the physical conditions for heat transfer did not change (A.D. Slonim).
Due to the dynamic organization of regulatory mechanisms, functional systems provide exceptional stability of the body's metabolic reactions, both at rest and in a state of increased activity in the environment.
Read also:
|
The nervous system provides the relationship between individual organs and organ systems and the functioning of the body as a whole. It regulates and coordinates the activity of various organs, adapts the activity of the whole organism as an integral system to the changing conditions of the external and internal environment. With the help of the nervous system, the perception and analysis of various stimuli from the environment and internal organs, as well as responses to these stimuli, are carried out. At the same time, it should be borne in mind that all the completeness and subtlety of the organism's adaptation to the environment are carried out through the interaction of nervous and humoral mechanisms of regulation.
Humoral regulation is a method of transmitting regulatory information to effectors through the liquid internal environment of the body using chemical molecules released by cells or specialized tissues and organs. This type of regulation of vital activity can provide both a relatively autonomous local exchange of information about the characteristics of metabolism and the function of cells and tissues, as well as a systemic efferent channel of information communication, which is more or less dependent on the nervous processes of perception and processing of information about the state of the external and internal environment.
The division of the mechanisms of regulation of the vital activity of the body into nervous and humoral is very conditional and can only be used for analytical purposes as a way of studying. In fact, the nervous and humoral mechanisms of regulation are inseparable, since information about the state of the external and internal environment is almost always perceived by the elements of the nervous system - receptors, is processed in the nervous system, where it can be transformed into signals of executive devices of either a nervous or humoral nature.
The control "device" is, as a rule, the nervous system. However, the signals coming through the control channels of the nervous system are transmitted at the ends of the nerve conductors in the form of chemical intermediary molecules entering the microenvironment of cells, i.e. in a humorous way. And the endocrine glands specialized for humoral regulation are controlled by the nervous system.
Thus, we should talk about a single neurohumoral system of regulation of physiological functions.
General plan of the structure of the nervous system.
human nervous system structurally subdivided into central(CNS) and peripheral.
CNS composed of neurons and neuroglial cells peripheral- from the processes of neurons and peripheral nodes - ganglia.
The central nervous system includes the spinal cord and brain, and the peripheral nervous system includes 12 pairs of cranial nerves, 31 pairs of spinal nerves and nerve nodes.
functional the nervous system is divided into somatic that regulates the activity of skeletal muscles and sensory organs and vegetative(sympathetic, parasympathetic), regulating the activity of internal organs, vessels and glands.
Depending on the nature of the innervation of organs and tissues, the nervous system is divided into somatic and vegetative. The somatic nervous system regulates voluntary movements of the skeletal muscles and provides sensitivity. The autonomic nervous system coordinates the activity of internal organs, glands, the cardiovascular system and innervates all metabolic processes in the human body. The work of this regulatory system is not controlled by consciousness and is carried out thanks to the coordinated work of its two departments: sympathetic and parasympathetic. In most cases, activation of these departments has the opposite effect. Sympathetic influence is most pronounced when the body is in a state of stress or intense work. The sympathetic nervous system is a system of alarm and mobilization of reserves necessary to protect the body from environmental influences. It gives signals that activate brain activity and mobilize protective reactions (the process of thermoregulation, immune responses, blood coagulation mechanisms). When the sympathetic nervous system is activated, the heart rate increases, digestion processes slow down, breathing rate increases and gas exchange increases, the concentration of glucose and fatty acids in the blood increases due to their release by the liver and adipose tissue (Fig. 5).
The parasympathetic division of the autonomic nervous system regulates the work of internal organs at rest, i.e. it is a system of current regulation of physiological processes in the body. The predominance of the activity of the parasympathetic part of the autonomic nervous system creates conditions for rest and restoration of body functions. When it is activated, the frequency and strength of heart contractions decrease, digestion processes are stimulated, and the airway clearance decreases (Fig. 5). All internal organs are innervated by both the sympathetic and parasympathetic divisions of the autonomic nervous system. The skin and the musculoskeletal system have only sympathetic innervation.
Fig.5. Regulation of various physiological processes of the human body under the influence of the sympathetic and parasympathetic divisions of the autonomic nervous system
The autonomic nervous system has a sensory (sensitive) component represented by receptors (sensitive devices) located in the internal organs. These receptors perceive indicators of the state of the internal environment of the body (for example, the concentration of carbon dioxide, pressure, the concentration of nutrients in the bloodstream) and transmit this information along the centripetal nerve fibers to the central nervous system, where this information is processed. In response to the information received from the central nervous system, signals are transmitted along the centrifugal nerve fibers to the corresponding working organs involved in maintaining homeostasis.
The endocrine system also regulates the activity of tissues and internal organs. This regulation is called humoral and is carried out with the help of special substances (hormones) that are secreted by the endocrine glands into the blood or tissue fluid. Hormones - These are special regulatory substances produced in some tissues of the body, transported with the bloodstream to various organs and affecting their work. While the signals (nerve impulses) that provide nervous regulation propagate at a high speed and it takes fractions of a second to carry out a response from the autonomic nervous system, humoral regulation is much slower, and under its control are those processes of our body that require minutes to regulate. and clock. Hormones are potent substances and cause their effect in very small quantities. Each hormone affects certain organs and organ systems, which are called target organs. Target organ cells have specific receptor proteins that selectively interact with specific hormones. The formation of a complex of a hormone with a receptor protein involves a whole chain of biochemical reactions that determine the physiological action of this hormone. The concentration of most hormones can vary over a wide range, which ensures that many physiological parameters are maintained constant with the constantly changing needs of the human body. Nervous and humoral regulation in the body are closely interconnected and coordinated, which ensures its adaptability in a constantly changing environment.
Hormones play the leading role in the humoral functional regulation of the human body. pituitary and hypothalamus. The pituitary gland (lower cerebral appendage) is a part of the brain related to the diencephalon, it is attached by a special leg to another part of the diencephalon, hypothalamus, and is closely related to it. The pituitary gland consists of three parts: anterior, middle and posterior (Fig. 6). The hypothalamus is the main regulatory center of the autonomic nervous system, in addition, this part of the brain contains special neurosecretory cells that combine the properties of a nerve cell (neuron) and a secretory cell that synthesizes hormones. However, in the hypothalamus itself, these hormones are not released into the blood, but enter the pituitary gland, in its posterior lobe ( neurohypophysis) where they are released into the blood. One of these hormones antidiuretic hormone(ADG or vasopressin), predominantly affects the kidney and the walls of blood vessels. An increase in the synthesis of this hormone occurs with significant blood loss and other cases of fluid loss. Under the action of this hormone, the loss of fluid in the body decreases, in addition, like other hormones, ADH also affects brain function. It is a natural stimulant of learning and memory. Lack of synthesis of this hormone in the body leads to a disease called diabetes insipidus, in which the volume of urine excreted by patients sharply increases (up to 20 liters per day). Another hormone released into the blood in the posterior pituitary gland is called oxytocin. The target for this hormone is the smooth muscles of the uterus, muscle cells surrounding the ducts of the mammary glands and testes. An increase in the synthesis of this hormone is observed at the end of pregnancy and is absolutely necessary for the course of childbirth. Oxytocin impairs learning and memory. Anterior pituitary ( adenohypophysis) is an endocrine gland and secretes a number of hormones into the blood that regulate the functions of other endocrine glands (thyroid gland, adrenal glands, gonads) and are called tropic hormones. For instance, adenocorticotropic hormone (ACTH) acts on the adrenal cortex and under its influence a number of steroid hormones are released into the blood. Thyroid-stimulating hormone stimulates the thyroid gland. growth hormone(or growth hormone) acts on bones, muscles, tendons, internal organs, stimulating their growth. In the neurosecretory cells of the hypothalamus, special factors are synthesized that affect the functioning of the anterior pituitary gland. Some of these factors are called liberals, they stimulate the secretion of hormones by cells of the adenohypophysis. Other factors statins, inhibit the secretion of the corresponding hormones. The activity of neurosecretory cells of the hypothalamus changes under the influence of nerve impulses coming from peripheral receptors and other parts of the brain. Thus, the connection between the nervous and humoral systems is primarily carried out at the level of the hypothalamus.
Fig.6. Scheme of the brain (a), hypothalamus and pituitary gland (b):
1 - hypothalamus, 2 - pituitary gland; 3 - medulla oblongata; 4 and 5 - neurosecretory cells of the hypothalamus; 6 - pituitary stalk; 7 and 12 - processes (axons) of neurosecretory cells;
8 - posterior pituitary gland (neurohypophysis), 9 - intermediate pituitary gland, 10 - anterior pituitary gland (adenohypophysis), 11 - median elevation of the pituitary stalk.
In addition to the hypothalamic-pituitary system, the endocrine glands include the thyroid and parathyroid glands, the adrenal cortex and medulla, pancreatic islet cells, intestinal secretory cells, sex glands, and some heart cells.
Thyroid- this is the only human organ that is able to actively absorb iodine and include it in biologically active molecules, thyroid hormones. These hormones affect almost all cells of the human body, their main effects are associated with the regulation of growth and development processes, as well as metabolic processes in the body. Thyroid hormones stimulate the growth and development of all body systems, especially the nervous system. When the thyroid gland is not functioning properly, adults develop a disease called myxedema. Its symptoms are a decrease in metabolism and dysfunction of the nervous system: the reaction to stimuli slows down, fatigue increases, body temperature drops, edema develops, the gastrointestinal tract suffers, etc. A decrease in thyroid levels in newborns is accompanied by more severe consequences and leads to cretinism, mental retardation up to complete idiocy. Previously, myxedema and cretinism were common in mountainous areas where there is little iodine in glacial water. Now this problem is easily solved by adding sodium iodine salt to table salt. An overactive thyroid gland leads to a disorder called Graves' disease. In such patients, the basal metabolism increases, sleep is disturbed, the temperature rises, breathing and heartbeat become more frequent. Many patients have bulging eyes, sometimes a goiter is formed.
adrenal glands- paired glands located at the poles of the kidneys. Each adrenal gland has two layers: cortical and medulla. These layers are completely different in their origin. The outer cortical layer develops from the middle germ layer (mesoderm), the medulla is a modified node of the autonomic nervous system. The adrenal cortex produces corticosteroid hormones (corticoids). These hormones have a wide spectrum of action: they affect water-salt metabolism, fat and carbohydrate metabolism, the body's immune properties, and suppress inflammatory reactions. One of the main corticoids, cortisol, is necessary to create a reaction to strong stimuli that lead to the development of stress. Stress can be defined as a threatening situation that develops under the influence of pain, blood loss, fear. Cortisol prevents blood loss, constricts small arterial vessels, and increases the contractility of the heart muscle. With the destruction of the cells of the adrenal cortex develops Addison's disease. In patients, a bronze skin tone is observed in some parts of the body, muscle weakness develops, weight loss, memory and mental abilities suffer. Tuberculosis used to be the most common cause of Addison's disease, nowadays it's autoimmune reactions (the mistaken production of antibodies to one's own molecules).
Hormones synthesized in the adrenal medulla: adrenalin and norepinephrine. The targets of these hormones are all tissues of the body. Adrenaline and norepinephrine are designed to mobilize all the forces of a person in case of a situation that requires great physical or mental stress, in case of injury, infection, fright. Under their influence, the frequency and strength of heart contractions increase, blood pressure rises, breathing quickens and bronchi expand, and the excitability of brain structures increases.
Pancreas is a gland of a mixed type, it performs both digestive (production of pancreatic juice) and endocrine functions. It produces hormones that regulate carbohydrate metabolism in the body. Hormone insulin stimulates the flow of glucose and amino acids from the blood into the cells of various tissues, as well as the formation in the liver from glucose of the main reserve polysaccharide of our body, glycogen. Another pancreatic hormone glucagon, according to its biological effects, is an insulin antagonist, increasing blood glucose levels. Glucogon stimulates the breakdown of glycogen in the liver. With a lack of insulin develops diabetes, Glucose ingested with food is not absorbed by tissues, accumulates in the blood and is excreted from the body with urine, while tissues are sorely lacking in glucose. The nervous tissue suffers especially strongly: the sensitivity of the peripheral nerves is disturbed, there is a feeling of heaviness in the limbs, convulsions are possible. In severe cases, diabetic coma and death can occur.
The nervous and humoral systems, working together, excite or inhibit various physiological functions, which minimizes deviations of individual parameters of the internal environment. The relative constancy of the internal environment is ensured in humans by regulating the activity of the cardiovascular, respiratory, digestive, excretory systems, and sweat glands. Regulatory mechanisms ensure the constancy of the chemical composition, osmotic pressure, the number of blood cells, etc. Very perfect mechanisms ensure the maintenance of a constant temperature of the human body (thermoregulation).
