Lecture 4. Nervous and humoral regulation, main differences. General principles organization of the humoral system. Main humoral agents: hormones, neurotransmitters, metabolites, dietary factors, pheromones. Principles of the influence of hormones on behavior and psyche. The concept of receptors in target tissues. The principle of feedback in the humoral system.
"Humoral" means "liquid". Humoral regulation– this is regulation with the help of substances carried by body fluids: blood, lymph, cerebrospinal fluid, intercellular fluid and others. A humoral signal, in contrast to a nervous one: is slow (spreads with the blood flow, or more slowly), and not fast; diffuse (distributed throughout the body), rather than directed; long-term (lasts from several minutes to several hours), rather than short-term.
In reality, a single neurohumoral regulation system functions in the animal body. Its division into nervous and humoral is made artificially, for the convenience of research: the nervous system is studied using physical methods(registration of electrical parameters), and humoral – chemical.
The main groups of humoral factors: hormones and dietary factors (everything that enters the body with food and drink), as well as pheromones that regulate social behavior.
There are four types of influence of humoral factors on the functions of the body, including the psyche and behavior. Organizing influence - only at certain stages of development a certain factor is necessary, and the rest of the time its role is small. For example, iodine deficiency in the diet of young children causes a lack of hormones thyroid gland, which leads to cretinism. Induction– the humoral factor causes changes in functions, despite other regulatory factors, and its effect is proportional to the dose. Modulation– the humoral factor influences functions, but its effect depends on other regulatory factors (both humoral and nervous). Most hormones and all pheromones modulate human behavior and psyche. Security– a certain level of the hormone is necessary for the implementation of the function, but multiple increases in its concentration in the body do not change the manifestation of the function. For example, male sex hormones organize maturation of the reproductive system in the embryo and in the adult provide reproductive function.
Hormones are biologically active substances that are produced by specialized cells, distributed throughout the body by fluids or diffusion, and interact with target cells. Almost all internal organs contain cells that produce hormones. If such cells are combined into a separate organ, it is called an endocrine gland, or endocrine gland.
The function of each hormone depends not only on the secretory activity of the corresponding gland. After entering the blood, hormones are bound by special transport proteins. Some hormones are secreted and transported in forms devoid of biological activity, and they are converted into biologically active substances only in target tissues. In order for a hormone to change the activity of a target cell, it must bind to a receptor - a protein in the membrane or cytoplasm of the cell. Disruption at any stage of hormonal signal transmission leads to a deficiency in the function regulated by this hormone.
The secretion of hormones increases or decreases under the influence of both nervous and humoral factors. Inhibition of secretory activity occurs either under the influence of certain factors or through a negative feedback mechanism. During feedback, part of the output signal (in in this case, hormone) enters the input of the system (in this case, the secretory cell). Due to feedback loops within the endocrine system, hormonal therapy is very dangerous: administration of large doses hormonal drug not only enhances regulated functions, but also inhibits, up to complete shutdown, the production of this hormone within the body. Uncontrolled use of anabolic steroids not only accelerates the growth of muscle tissue, but also inhibits the synthesis and secretion of testosterone and other male sex hormones.
Hormones, like other humoral factors, influence the psyche and behavior in various ways. The main thing is direct interaction with the neurons of the brain. Some humoral factors (steroids) freely penetrate into the brain through the blood-brain barrier (BBB). Other substances - under no circumstances (adrenaline, norepinephrine, serotonin, dopamine). The third group (glucose) requires special carriers. Thus, the permeability of the BBB is another factor that regulates the effectiveness of humoral regulation.
Lecture 5. The main endocrine glands and their hormones. Hypothalamus, pituitary gland. Adrenal medulla, adrenal cortex. Thyroid. Pancreas. Sex glands. Epiphysis
Vasopressin and oxytocin are synthesized in the hypothalamus and secreted in the posterior pituitary gland. In the hypothalamus, the so-called liberins, for example, corticoliberin (CRH) and gonadoliberin (LH-RG), are synthesized and secreted into the anterior pituitary gland. They stimulate the synthesis and secretion of so-called tropins (ACTH, LH). Tropins act on peripheral glands. For example, ACTH stimulates the synthesis and secretion of glucocorticoids (cortisol) in the adrenal cortex. In the adrenal medulla, under the influence of nervous stimulation, adrenaline is synthesized and secreted. The thyroid gland synthesizes and secretes triiodothyronine; in the pancreas - insulin and glucagon. In the gonads of male and female sex steroids. Melatonin is synthesized in the pineal gland, the synthesis of which is regulated by illumination.
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Test questions for topic 3
1. “Nikanor Ivanovich poured a glass of lafitnik, drank, poured a second one, drank, picked up three pieces of herring on a fork... and at that time they rang, and Pelageya Antonovna brought in a steaming saucepan, at one glance at which one could immediately guess what was in it, in “Thicker than the fiery borscht, there is something tastier in the world - marrow bone.” (Bulgakov M. The Master and Margarita.).
Comment on the character’s behavior using the categories “needs” and “motivation”. Indicate what are the humoral factors in organizing the behavior of the characters. Answer - why is it customary to drink an aperitif (vodka before dinner)?
2. Why is a salt-free diet recommended for premenstrual syndrome?
3. Why do students who have a baby study worse than before giving birth?
4. What are the features of the hormones of the hypothalamus (using the example of corticoliberin and gonadoliberin)?
5. What are the features of the hormones of the anterior pituitary gland (using ACTH as an example)?
6. As is known, hormones affect the psyche by affecting: 1) metabolism; 2) internal organs; 3) directly to the central nervous system; 4) to the central nervous system through the peripheral nervous system.
How do the following hormones influence behavior?
Adrenalin;
Corticoliberin;
GnRH;
Vasopressin;
Oxytocin;
Progesterone;
Cortisol?
7. Which path of influence is not indicated in the previous question? (hint: "Cortisol affects the psyche...")
8. Promoters of vegetarianism believe that a vegetarian diet improves a person’s moral nature. What do you think about it? How does human and animal behavior change with a vegetarian diet?
9. What are the stages of hormonal signal transmission?
10. What is feedback? What is its role in regulating body functions?
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1. Ashmarin I.P. Riddles and revelations of the biochemistry of memory. - L.: Ed. Leningrad State University, 1975
2. Drzhevetskaya I. A. Fundamentals of the physiology of metabolism and the endocrine system. - M.:, Higher School, 1994
3. Leninger A. Fundamentals of biochemistry. vols.1–3. -, M.:, Mir, 1985
4. Chernysheva M. P. Animal hormones. - St. Petersburg:, Glagol, 1995
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Topic 4. Stress
Lecture 6. Specific and nonspecific adaptation. Works by W. Cannon. Sympathoadrenal system. Works by G. Selye. Pituitary-adrenal system. Nonspecificity, systematicity and adaptability of stress. Stress is like novelty.
Stress is a nonspecific systemic adaptive reaction of the body to novelty.
The term “stress” was introduced by Hans Selye in 1936. He showed that the body of rats reacts in a similar way to a variety of damaging influences.
Non-specificity stress means that the body's response does not depend on the modality of the stimulus. In the reaction to any stimulus there are always two components: specific and stress. It is obvious that the body reacts differently to pain, noise, poisoning, good news, unpleasant news, social conflict. But all these stimuli also cause changes in the body that are common to all of the above and many other influences. G. Selye attributed such changes to: 1) enlargement of the adrenal cortex, 2) reduction of the thymus (lymphoid organ), 3) ulceration of the gastric mucosa. In the present, the list of stress reactions has been significantly expanded. Selye's triad is observed only with prolonged exposure to an unfavorable factor.
Systematicity stress means that the body reacts to any impact in a complex manner, i.e. the response involves not only the adrenal cortex, thymus and mucosa. Changes always occur in the behavior of a person or animal, in the physiological and biochemical parameters of the body. Changes in just one parameter—heart rate, or hormone levels, or motor activity—does not mean that the body is demonstrating a stress response. Perhaps we are observing a reaction specific only to a given stimulus.
Stress is adaptive body reaction. All manifestations of a stress response are aimed at enhancing the adaptive capabilities of the body and, ultimately, survival. Therefore, periodic moderate stress is good for health. Stress becomes life-threatening when it becomes uncontrollable (see the section “Uncontrollable Stress and Depression.” The danger of stress, in addition to those cases when it becomes uncontrollable, is determined by the fact that stress is an evolutionarily ancient mechanism. The stress response, in all major features characteristic of humans have been described in lampreys. This group of animals arose approximately 500 million years ago. All these hundreds of millions of years, the main danger for living beings was the possibility of being eaten or, at least, being seriously damaged. Therefore, the stress response is directed to prevent the consequences of blood loss, in particular to mobilize reserves of cardio-vascular system, which is fraught with heart attack and stroke. In addition, stress includes inhibition of the processes of growth, nutrition and reproduction. These important functions can be realized when the animal escapes from a predator. Therefore, chronic stress leads to disruption of these functions. In the modern world, people experience stress caused mainly by social stimuli. Obviously, in the event of an unscheduled call to the authorities, there is no point in preparing for blood loss, but in our body blood pressure rises and all processes in the stomach are inhibited.
Stress develops in the body when the stimulus is new for the body. G. Selye himself believed that animals and people react to all situations with stress. Obviously, in this case, the concept of stress becomes redundant, since it will be equivalent to the concept of life. Sometimes stress is understood as a reaction to damaging influences. But it is well known that stress also accompanies joyful events in our lives. Moreover, many people structure their lives as a constant search for “thrills”, i.e. stressful situations. Another common idea is that stress is a reaction to strong influences. Of course, people who survived natural, man-made, or social disasters experienced extreme stress. At the same time, there is also the “stress of everyday life”, which is well known to any resident big city. Many small events that require us to react in some way ultimately lead to the formation of a stagnant stress response.
Thus, we call stress a reaction not to any, not to harmful, not to strong events, but to those that we encounter for the first time, to which the body has not yet had time to adapt, i.e. stress is a reaction to novelty. If the same stimulus is repeated regularly, i.e. As the novelty of the situation decreases, the stress response of the body decreases. At the same time, the specific reaction intensifies. For example, as a result of regular diving in cold water a person is “hardened”, his body reacts intensively to cooling. Such a person is not afraid of any drafts. But his likelihood of getting sick from overheating is the same as that of an “unhardened” person. And the stress component of the reaction to ice water in such people does not decrease over time.
Lecture 7. Measuring stress. Basic physiological and biochemical manifestations of stress. Quantitative characteristics stress. Sensitivity. Reactivity. Sustainability. Displaced activity is a behavioral stress response. Conditions for the occurrence of displaced activity. Types of displaced activity. Using stress in practice for psychological testing.
The stress response is triggered by two neurohumoral systems, which both have their final link in the adrenal gland. 1) From the brain, through the spinal signal, it enters the adrenal medulla, from which adrenaline is released into the blood. Ego functions duplicate the functions of the sympathetic nervous system. 2) The signal about a new situation enters the hypothalamus, where corticotropic hormone (CRH) is produced, which affects the anterior pituitary gland, in which the synthesis and secretion of adrenocorticotropic hormone (ACTH) increases. ACTH in the bloodstream stimulates the synthesis and secretion of glucocorticoid hormones in the adrenal cortex. The main glucocorticoid in humans is cortisol (hydrocortisone).
Inhibition of the endocrine component of the stress response occurs due to negative feedback: cortisol reduces the synthesis and secretion of both CRH and ACTH. Negative feedback is the only mechanism for inhibiting stress, therefore, when it is disturbed, even a weak stress stimulus leads to a persistent increase in the secretion of CRH, ACTH and cortisol, which is detrimental to the body (see sections “Uncontrolled stress and depression” and “Psychosomatotypes”). There are several hormones that attenuate the stress-induced increase in glucocorticoid synthesis and secretion. In particular, male sex hormones synthesized in the adrenal cortex reduce the magnitude of the stress response. But there is no factor inhibiting the stress response, with the exception of the negative feedback mechanism.
Cortisol increases blood glucose levels. But its main significance is different, since several other hormones (there are seven in total) also increase the glucose content in the blood and enhance its consumption by tissues. Cortisol is the only factor that increases the transport of glucose into the central nervous system through the BBB (see section “Humoral System”). Neurons are able to obtain energy for their vital functions, unlike cells of other tissues, only from glucose. Therefore, a lack of glucose has the most detrimental effect on brain functions. The main symptom of insufficient function of the adrenal cortex is complaints of general weakness, which is caused by insufficient nutrition of the brain.
In addition, cortisol suppresses inflammation. Inflammation not only develops when foreign agents such as infection enter the body. Inflammatory foci occur constantly in the body as a result of the breakdown of body tissues - natural or caused by traumatic injuries.
In addition to adrenaline, CRH, ACTH and cortisol, many other hormones are involved in the stress response. All of them are psychotropic agents, i.e. influence the psyche and behavior.
KRG increases anxiety. It is noteworthy that the nature of its effect on anxiety is induction (see section “Humoral system”). ACTH improves memory processes and reduces anxiety. This hormone does not induce, but only modulates mental processes. Cortisol not only enhances the transport of glucose into the brain, but also, interacting directly with neurons, provides the hiding reaction - one of the two main behavioral reactions under stress (see section “Psychosomatotypes”). Adrenaline does not affect the psyche and behavior. The widespread idea among non-specialists about its effect on the psyche (“Add adrenaline to the blood!”) is false. Adrenaline does not penetrate the BBB, therefore, cannot affect the functioning of neurons.
Pleasant sensations, often resulting from stress, are caused by a group of other hormones called endogenous opiates. They bind to the same receptors in the brain as plant opiates, hence the name. Endogenous opiates include endorphins (endogenous morphines), synthesized in the anterior pituitary gland, and enkephalins (from encephalon - brain), synthesized in the hypothalamus. The two main functions of endogenous opiates are analgesia and euphoria.
Stress is quantitatively characterized by three main parameters: sensitivity, magnitude of reaction and resistance. Sensitivity (the value of the reaction threshold) and the magnitude of the reaction are the parameters of all reactions of the body. Much more interesting and important is the third value, stability, which is determined by the speed with which the system, in this case, the stress system, returns to its original parameters after the stimulus that caused its activation has ceased to act. It is the low resistance of the stress system of the body that causes numerous violations of its functions. With low stability, even weak stimuli cause inadequately prolonged tension in the stress system with all the adverse consequences: tension in the cardiovascular system, inhibition of the digestive and reproductive function. The stability of a stressor system does not depend on its sensitivity and magnitude of the reaction.
Behavior under stress is characterized by so-called biased activity. Since stress is a reaction to novelty, in a situation where it is not possible to find a key stimulus (see section “Behavioral Act”), but the motivation is strong, the first available behavior program is used. In this case, a person or animal demonstrates displaced activity - behavior that is clearly inadequate, i.e. which cannot satisfy the current need.
Displaced activity has one of the following forms: mosaic activity (fragments from different behavioral programs), redirected activity (for example, family violence) and displaced activity itself, in which a behavioral program of a different motivation is used (for example, eating behavior in case of troubles at work).
One of the common forms of displaced activity is grooming - the behavior of cleaning the skin (fur, feathers). The intensity of grooming is often used to assess the degree of stress in experiments and observations of animals. Grooming has great importance and as a response that reduces the effects of stress (see section “Uncontrollable Stress and Depression”).
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Test questions for topic 4.
1. The “Anti-stress” food supplement consists of free amino acids. Why is this supplement recommended for use after stress?
2. What others pharmacological agents, recommended for preventing the harmful consequences of stressful situations, do you know? What is their mechanism of action?
3. What is the similarity and difference between the behavior of a woman combing her hair and a man scratching his bald spot? To answer, use the categories of the concepts “needs”, “humoral factors”, “hormones”, “stress”.
4. Does craving for extreme sports depend on hormones? If yes, then from which ones?
6. Does the desire to visit a steam room in a bath depend on hormones? If yes, then from which ones?
7. What is the difference between displaced and redirected activity?
8. How does a redirected response differ from a mosaic response?
9. List stress hormones.
10. What hormones inhibit the stress response?
1. Cox T. Stress. - M.: Medicine, 1981
2. Selye G. At the level of the whole organism. - M.: Science, 1972
Our body is a huge multicellular system. Each cell is a miniature carrier of life, which has subordinated its own freedom to the activity of the organism as a whole. Each cell of the body contains genetic information sufficient for the entire organism to reproduce. This information is recorded in the structure of deoxyribonucleic acid (DNA) and is contained in genes located in the nucleus. Along with the nucleus, a very important component of the cell is the membrane, which determines its specialization. So, muscle cells perform the function of contraction, nerve cells produce electrical signals, gland cells secrete secretions. Cells of the “same specialty” are combined into groups called tissues (for example, muscle, nervous, connective tissue, etc.). Tissues form organs. Organs as individual components are included in systems (for example, bone, circulatory, muscle), which perform a single function in the body. Chemical analysis shows that any living organism consists of the same elements that are often found in inanimate nature, in the inorganic world. The French chemist G. Bertrand calculated that the body of a person weighing 100 kg contains: oxygen - 63 kg, carbon - 19 kg, nitrogen - 5 kg, calcium - 1 kg, phosphorus - 700g, sulfur - 640g, sodium 250g, potassium - 220g, chlorine – 180g, magnesium – 40g, iron – 3g, iodine – 0.03g, fluorine, bromine, manganese, copper – even less. It is easy to notice that living and nonliving things are built from the same elements. But in living organisms they are combined into special chemical compounds - organic matter.
There are three large groups these substances: squirrels(these are 20 amino acids, of which 8 are essential and must be supplied with food; first of all, they are a building material, and then a source of energy, their energy value is as follows: 1 g of protein - 42 kcal); fats(this is both a building material and an energy source: 1g - 9.3 kcal); carbohydrates(this is, first of all, the main source of energy: 1g - 4.1 kcal). Here we should point out the possibility of mutual transitions (conversions) of proteins, fats and carbohydrates into each other during biochemical reactions inside the body. Entering the body with food along with inorganic substances (water, salts), vitamins and inhaled oxygen, they participate in metabolism.
Metabolism- a basic biological process that is characteristic of all living things and is a complex chain of redox biochemical reactions with the participation of oxygen (aerobic phase) and without the temporary participation of oxygen (anaerobic phase), consisting in the assimilation and processing in the body of food coming from environment substances, the release of chemical energy, its transformation into other types (mechanical, thermal, electrical) and the release into the external environment of their decay products (carbon dioxide, water, ammonia, urea, etc.)
We see that this exchange is a two-pronged process associated with the constant breakdown of substances, which is accompanied by the release and consumption of energy (the process dissimilation) and their constant renewal and replenishment of energy (the process assimilation).
Research has shown that cellular molecules are continuously broken down and synthesized again. It is estimated that in humans, half of all tissue proteins are broken down and rebuilt within every 80 days.
Muscle proteins are replaced more slowly, being replaced every 180 days. We observe these processes during the growth of nails and hair. In a growing and developing organism, the processes of assimilation prevail over the processes of dissimilation. It is as a result of this that substances accumulate and the body grows. In a mature adult organism, these processes are in dynamic equilibrium. However, any increase in the activity of the body (for example, muscle) leads to an increase in the processes of dissimilation. Therefore, in order for the body to maintain a balance between the intake and expenditure of substances and energy, it is necessary to strengthen the assimilation processes, due, first of all, to increasing the supply of nutrients to it.
For example, the nutrition of people actively involved in physical education, sports or work should provide the body with 1.5-2 times more energy than the nutrition of those not involved in these types of activities. It should always be remembered that excess nutrients are deposited in the body in the form of excess adipose tissue.
If the processes of dissimilation begin to prevail over the processes of assimilation, exhaustion of the body occurs and, ultimately, its death due to the destruction of vital tissue proteins.
Along with the metabolic process, two other integral processes of the entire living process are realized: reproduction(ensuring the conservation of the species) and adaptation(adaptation to unchanging conditions of the external and internal environment of the body). In order not to die, the body reacts to the influence of the external environment adaptively, and this entails changes in the body itself. For example, cooling leads to increased oxidative processes, which in turn causes an increase in heat production. Systematic intense muscle activity leads to increased formation of muscle proteins and increased muscle mass, as well as an increase in the content of substances in the muscles that serve as sources of energy for muscle activity.
Any living organism can exist if only the composition of its body is maintained within certain, usually quite narrow limits. Constancy of the internal environment ( homeostasis:“homeo” – similar, “stasis” – state) – a fundamental biological law. The law of development of the human body, written in its genetic code, is also immutable. The first law, as it were, excludes development, while the second requires it. Is this contradiction another challenge for the regulatory system? There are two mechanisms of regulation - humoral and nervous. The humoral or chemical mechanism of regulation is evolutionarily more ancient. Its essence is that in different cells and organs in the course of life, substances that differ in their chemical nature and physiological effects are formed. Most of them have enormous biological activity, that is, the ability to cause significant changes in function in very small concentrations. Entering the tissue fluid and then into the blood, they are carried throughout the body and affect all cells and tissues.
This is the second level of management - supracellular or humoral. Chemical irritants do not have a specific “addressee” and act differently on different cells. The main representatives of humoral regulators are metabolites (metabolic products), hormones (productive endocrine glands), mediators (chemical intermediaries in the transmission of excitation from the nerve fiber to the cells of the working organ). Moreover, the most active of them are metabolites (for example, carbon dioxide) and hormones. These are the most general outline information about the principle of regulation through blood and lymph. In the process of evolution of the animal world, along with the humoral regulation mechanism, a more advanced one arose - nervous.
The entire nervous system is divided into central and peripheral. The central cord includes the brain and spinal cord. Through the peripheral, the brain and spinal cord communicate with all organs. It consists of centripetal neurons, which perceive and transmit stimuli from the external and internal environment of the body to the central nervous system, and centrifugal neurons, which transmit control commands from the central nervous system to all organs. It should be noted the special role of the spinal cord in any motor act, since it is connected by continuous pathways to all skeletal muscles (with the exception of the facial muscles).
The peripheral nervous system is divided into two divisions: somatic and autonomic. The somatic nervous system provides innervation skin body, musculoskeletal system (bones, joints, muscles) and sensory organs. The autonomic nervous system innervates the internal organs, blood vessels and glands, thereby controlling and regulating metabolic processes in the body. This is a vegetative level of control, however, it should be remembered that the regulation of the body’s vital functions is ensured by a harmonious combination of the work of all parts of the nervous system.
The nervous mechanism of regulation is carried out by reflex. A reflex is the body’s response to a particular stimulus in the form of nerve impulses. The formation of reflexes is based on excitation and inhibition in the cerebral cortex, as two opposite sides of a single process of balancing the interaction of the body with the external environment. An unconditioned reflex is an innate, hereditary reaction of the body (for example, withdrawing a hand when receiving an injection). Reflexes that occur under certain conditions as a result of life experience of a given organism are called conditioned. For its formation it is necessary to combine irritation of any sense organ with innate unconditioned reflex. In this case, between nerve cells cerebral hemispheres a new neural connection is established in the brain. Conditioned reflexes- the real masters of our body.
They determine his habits, mood, well-being, etc., the secretion of saliva at the sight or smell of food, your future professional skills, the ability to read, write, and remember, are again provided by them.
Conditioned reflexes, repeated many times during a specific activity, form a dynamic stereotype in the cerebral cortex.
The nervous mechanism of regulation is more advanced than the humoral one. Firstly, the interaction of cells occurs through the nervous system much faster, since the speed of impulse transmission along the nerve pathways reaches 120 m/s, and secondly, nerve impulses always have a specific addressee in mind, that is, they are directed to strictly defined cells. In addition, nervous regulation is more economical and requires minimal energy expenditure, since it is instantly turned on and quickly turned off when the need to coordinate some processes disappears. The nervous system is characterized by a variety of functions and almost unlimited power over physiological processes. Humoral regulation is to a certain extent subject to it. However, emphasizing the power of the nervous system, it should be noted that it always acts in close coordination with the humoral regulatory mechanism. Moreover, various chemical compounds along the humoral pathway affect nerve cells, changing their condition.
So, you see that all levels of control (from cellular to the level of the central nervous system), complementing each other, make the body a single self-developing and self-regulating system. This self-regulation is also possible because there are necessarily feedback connections between the regulated process and the regulatory system.
For example, muscle movements are carried out under the influence of impulses arriving to the muscles from the central nervous system. In turn, any muscle contraction leads to the appearance of a stream of impulses coming from the muscles to the central nervous system, informing it about the intensity of the contraction. This changes the activity of certain nerve centers. Remember how difficult it is to unbutton a coat button with numb fingers. The point is not that in the cold the muscles of the fingers lose the ability to move. Cold blocks nerve endings and causes loss of sensation. Signals about the position of the fingers in space do not reach the central nervous system, which under such conditions cannot coordinate muscle activity. In other words, the reflex is carried out only when the motor nerve, sensory nerve and muscle form a closed electrical circuit.
(From the Latin “humor” - liquid) is carried out due to substances released into the internal environment of the body (lymph, blood, tissue fluid). This is a more ancient regulation system compared to the nervous system.
Examples of humoral regulation:
- adrenaline (hormone)
- histamine (tissue hormone)
- carbon dioxide in high concentration (formed during active physical work)
- causes local expansion of capillaries, more blood flows to this place
- stimulates the respiratory center of the medulla oblongata, breathing intensifies
Comparison with neural regulation
1) Slow: substances move along with the blood (the effect occurs after 30 seconds), and nerve impulses occur almost instantly (tenths of a second).
2) Longer: humoral regulation acts while the substance is in the blood, and the nerve impulse acts for a short time.
3) Larger scale, because chemicals are carried by the blood throughout the body, nervous regulation acts precisely - on one organ or part of an organ.
Tests
1. Humoral regulation of body functions is carried out with the help of
A) chemical substances, coming from organs and tissues into the blood
B) nerve impulses through the nervous system
C) fats that enter the body with food
D) vitamins in the process of metabolism and energy conversion
2. The chemical interaction of cells, tissues, organs and organ systems, carried out through the blood, occurs in the process
A) plastic exchange
B) nervous regulation
B) energy metabolism
D) humoral regulation
3. In the human body, humoral regulation is carried out
A) nerve impulses
B) chemicals that affect organs through the blood
B) chemicals entering the digestive canal
D) odorous substances that enter the respiratory tract
4. The following take part in the humoral regulation of body functions:
A) antibodies
B) hormones
B) enzymes
D) nucleic acids
5) The excitation of the human respiratory center is affected by an increase in concentration
A) oxygen
B) nitrogen
B) hemoglobin
D) carbon dioxide
6. The main humoral regulator of respiration is
A) carbon monoxide
B) pepsin
B) insulin
D) carbon dioxide
7. Substances with the help of which human humoral regulation of functions is carried out,
A) spread at the speed of blood movement
B) instantly reach the executive bodies
B) are found in the blood in high concentrations
D) are not destroyed in the body
8. Humoral regulation compared to nervous regulation
A) faster and longer lasting
B) faster, less lasting
B) less fast, longer lasting
D) less fast and lasting
humoral.
duration of action.
Resting membrane potential. Modern ideas about the mechanism of its origin. Method of its registration.
Resting potential. Resting membrane potential is the electrical potential between inside plasma membrane and outer surface cell membrane. In relation to the outer surface at rest, the inner side of the membrane is always negatively charged. For each type of cell, the resting potential is almost constant. In warm-blooded animals it is: in skeletal muscle fibers - 90 mV, in myocardial cells - 80, in nerve cells and fibers - 60–70, in secretory glandular cells - 30–40, in smooth muscle cells - 30–70 mV. All living cells have a resting potential, but its value is much less (for example, in red blood cells - 7–10 mV).
According to modern membrane theory, the resting potential arises due to the passive and active movement of ions across the membrane.
Passive movement of ions occurs along a concentration gradient and does not require energy. At rest, the cell membrane is more permeable to potassium ions. The cytoplasm of muscle and nerve cells contains 30–50 times more potassium ions than in the intercellular fluid. Potassium ions in the cytoplasm are in a free state and, according to the concentration gradient, diffuse through the cell membrane into the extracellular fluid; they are not scattered in it, but are retained on the outer surface of the membrane by intracellular anions.
Inside the cell there are mainly anions of organic acids: aspartic, acetic, pyruvic, etc. The content of inorganic anions in the cell is relatively small. Anions cannot penetrate the membrane and remain in the cell, located on the inner surface of the membrane.
Since potassium ions have a positive charge and anions have a negative charge, the outer surface of the membrane is positively charged and the inner one is negatively charged. There are 8–10 times more sodium ions in the extracellular fluid than in the cell; their permeability through the membrane is insignificant. The penetration of sodium ions from the extracellular fluid into the cell leads to a slight decrease in the resting potential.
The resting potential is the difference in electrical potential between the inner and outer sides of the membrane when the cell is in a state of physiological rest. His average value is -70 mV (millivolts).
Action potential.
An action potential is a shift in membrane potential that occurs in tissue under the action of a threshold and superthreshold stimulus, which is accompanied by recharging of the cell membrane.
When the action of a stimulus is excited, ion-selective sodium channels open on the cell membrane and sodium from the external environment will enter the cell cytoplasm in an avalanche as a result of the movements of sodium ions in a state of excitation along the concentration gradient inside the sides; the membrane is charged (-). This is the action potential.
Drawing and graph
The doctrine of reflex (R. Descartes, G. Prokhazka), its development in the works of I.M. Sechenov, I.P. Pavlov, P.K. Anokhin. Classification of reflexes. Reflex path, reverse afferentation and its significance. Reflex time. Receptive field of reflex.
The activity of the body is a natural reflex reaction to a stimulus. Reflex is the body’s reaction to irritation of receptors, which is carried out with the participation of the central nervous system. The structural basis of the reflex is the reflex arc.
A reflex arc is a sequentially connected chain of nerve cells that ensures the implementation of a reaction, a response to stimulation.
The reflex arc consists of six components: receptors, afferent (sensitive) path, reflex center, efferent (motor, secretory) path, effector (working organ), feedback.
Reflex arcs can be of two types:
1) simple - monosynaptic reflex arcs (reflex arc of the tendon reflex), consisting of 2 neurons (receptor (afferent) and effector), there is 1 synapse between them;
2) complex – polysynaptic reflex arcs. They consist of 3 neurons (there may be more) - a receptor, one or more intercalary and an effector.
The idea of a reflex arc as an expedient response of the body dictates the need to supplement the reflex arc with another link - a feedback loop. This component establishes a connection between the realized result of the reflex reaction and the nerve center that issues executive commands. With the help of this component, the open reflex arc closed.
Features of a simple monosynaptic reflex arc:
1) geographically close receptor and effector;
2) reflex arc two-neuron, monosynaptic;
3) nerve fibers of group A? (70-120 m/s);
4) short reflex time;
5) muscles contracting according to the type of single muscle contraction.
Features of a complex monosynaptic reflex arc:
1) territorially separated receptor and effector;
2) three-neuron receptor arch (there may be more neurons);
3) the presence of nerve fibers of groups C and B;
4) muscle contraction according to the tetanus type.
Features of the autonomic reflex:
1) the interneuron is located in the lateral horns;
2) the preganglionic nerve pathway begins from the lateral horns, after the ganglion - the postganglionic;
3) the efferent path of the autonomic nervous arch reflex is interrupted by the autonomic ganglion, in which the efferent neuron lies.
The difference between the sympathetic nervous arch and the parasympathetic: the sympathetic nervous arch has a short preganglionic path, since the autonomic ganglion lies closer to spinal cord, and the postganglionic pathway is long.
In the parasympathetic arc, the opposite is true: the preganglionic pathway is long, since the ganglion lies close to the organ or in the organ itself, and the postganglionic pathway is short.
Work metabolism, energy expenditure of the body during various types of labor. Working check. Specifically - the dynamic effect of food. Distribution of the population into groups depending on energy consumption.
Intensity metabolic processes in the body increases significantly under conditions of physical activity. An objective criterion for assessing energy costs associated with physical activity of different professional groups is the physical activity coefficient. It represents the ratio of total energy expenditure to the basal metabolic rate. The direct dependence of the amount of energy consumption on the severity of the load makes it possible to use the level of energy consumption as one of the indicators of the intensity of the work performed
The difference between the body's energy expenditures for performing various types of work and energy expenditures for basal metabolism constitutes the so-called working increase (to the minimum level of energy expenditure). The maximum permissible severity of work performed over a number of years should not exceed the energy consumption of the basal metabolic rate for a given individual by more than 3 times.
^ Mental work does not require as much energy as physical work.
^ The specific dynamic effect of food is an increase in the intensity of metabolism under the influence of food intake and an increase in the body’s energy expenditure relative to the levels of metabolism and energy expenditure that occurred before the meal. The specific dynamic effect of food is due to the expenditure of energy on digestion of food, absorption of nutrients from the blood and lymph gastrointestinal tract, resynthesis of protein, complex lipid and other molecules; influence on metabolism biologically active substances, entering the body as part of food (especially protein) and formed in it during the digestion process.
^ An increase in the body's energy consumption above the level that occurred before a meal appears approximately an hour after a meal, reaching a maximum after three hours, which is due to the development by this time of a high intensity of the processes of digestion, absorption and resynthesis of substances entering the body. The specific dynamic effect of food can last 12-18 hours. It is most pronounced when taking protein foods, which increases the metabolic rate by up to 30%, and less significantly when taking mixed foods, which increases the metabolic rate by 6-15%.
^ The level of total energy consumption, as well as basal metabolism, depends on age: daily energy consumption increases in children from 800 kcal (6 months - 1 year) to 2850 kcal (11-14 years). A sharp increase in energy consumption occurs in adolescent boys aged 14-17 years (3150 kcal). After 40 years, energy consumption decreases and by the age of 80 it is about 2000-2200 kcal/day.
When excitation predominates, inhibitory conditioned reflexes are suppressed, and motor and autonomic excitation appears. When the inhibitory process predominates, positive conditioned reflexes weaken or disappear. Weakness, drowsiness appear, and motor activity is limited. A person’s labor activity is the basis of his existence. Any work takes place in a specific environment, which determines the working conditions. In each type of labor process there are elements of physical labor (in which muscle load is performed) and elements of mental labor. Therefore, any work is divided according to its severity (4-6 groups) and intensity (4-6 groups). As a rule, any work is accompanied by an increase in nervous tension against the background of decreasing muscle effort.
Blood and its functions, quantity and composition. Hematocrit Blood plasma and its physicochemical properties. Osmotic blood pressure and its functional role. Regulation of the constancy of blood osmotic pressure.
Hematocrit is the percentage (as a percentage) of the total blood volume that is made up of red blood cells. Normally, this figure is 40-48% for men, 36-42% for women.
Blood is physiological system, which includes:
1) peripheral (circulating and deposited) blood;
2) hematopoietic organs;
3) organs of blood destruction;
4) regulatory mechanisms.
The blood system has a number of features:
1) dynamism, i.e. the composition of the peripheral component can constantly change;
2) lack of independent meaning, since it performs all its functions in constant movement, i.e. it functions together with the circulatory system.
Its components are formed in various organs.
Blood performs many functions in the body:
transport; respiratory; nutritional; excretory; thermoregulatory; protective.
Blood consists of formed elements (45%) and a liquid part or plasma (55%)
Formed elements include red blood cells, leukocytes, platelets
The composition of plasma includes water (90-92%) and dry residue (8-10%)
The dry residue consists of organic and inorganic substances
Organic substances include:
Plasma proteins (total amount 7-8%) - albumins (4.5%), globulins (2-3.5%), fibrinogen (0.2-0.4%)
Non-protein nitrogen-containing compounds (amino acids, polypeptides, urea, uric acid, creatine, creatinine, ammonia)
The total amount of non-protein nitrogen (residual nitrogen) is 11-15 mmol/l (30-40 mg%). If the function of the kidneys, which excrete waste from the body, is impaired, the content of residual nitrogen increases sharply
Nitrogen-free organic substances: glucose 4.4-6.65 mmol/l (80-120 mg%), neutral fats, lipids
Enzymes and proenzymes: some of them are involved in the processes of blood coagulation and fibrinolysis (prothrombin, profibrinolysin), some break down glucogen, fats, proteins, etc.
Inorganic substances in plasma make up about 1% of its composition
These include mainly cations (Na+, Ca2+, K+, Mg2+) and anions (Cl-, HPO42-, HCO3-)
A large number of metabolic products, biologically active substances (serotonin, histamine), hormones enter the blood from the body tissues; they are absorbed from the intestines nutrients, vitamins
Plasma makes up the liquid part of the blood and is a water-salt solution of proteins. It consists of 90–95% water and 8–10% dry matter. The composition of the dry residue includes inorganic and organic substances. Organic includes proteins, nitrogen-containing substances of non-protein nature, nitrogen-free organic components, enzymes.
The physicochemical properties of blood are manifested by a combination of the properties of suspension, colloid and electrolyte solution
1. The properties of the suspension are manifested by the ability of the formed elements to be in suspension and are determined by the protein composition of the blood and the ratio of albumin and globulin fractions
2. Colloidal properties are determined by the amount of plasma proteins and ensure the constancy of the liquid composition of the blood and its volume.
3. Electrolyte properties of blood depend on the content of anions and cations, the amount of which (as well as non-electrolytes with low molecular weight - glucose) determines the value of osmotic pressure (normally 7.3-7.6 atm. or 745-760 kPa)
4. Blood viscosity is determined by proteins and formed elements, mainly red blood cells
5. Relative density (specific gravity) (normally, the specific gravity of blood is 1.05-1.064, plasma - 1.025-1.03)
6. The active reaction of the blood is determined by the concentration of hydrogen ions. To determine the acidity or alkalinity of the environment, they use the hydrogen pH indicator, which is characterized by a high
7. Maintaining the constancy of the active blood reaction is ensured by the activity of the lungs, kidneys, sweat glands, as well as buffer systems
The osmotic pressure of the blood is ensured by the concentration of osmotically active substances in the blood, i.e. it is the pressure difference between electrolytes and non-electrolytes.
Osmotic pressure is a rigid constant, its value is 7.3–8.1 atm. Electrolytes create up to 90–96% of the total osmotic pressure, of which 60% is sodium chloride, since electrolytes have a low molecular weight and create a high molecular concentration. Non-electrolytes make up 4-10% of the osmotic pressure and have a high molecular weight, therefore creating a low osmotic concentration. These include glucose, lipids, and blood plasma proteins. The osmotic pressure created by proteins is called oncotic. With its help, the formed elements are maintained in suspension in the bloodstream. To maintain normal life functions, it is necessary that the osmotic pressure value is always within the acceptable range.
The concept of hemostasis. Vascular-platelet and coagulation hemostasis. Factors and phases of blood coagulation. Platelets and their role in hemocoagulation. Interaction between the coagulation and anticoagulation systems of the blood. Fibrinolysis.
Platelets (red blood platelets) are flat, non-nuclear cells of irregular round shape, the number of which in the blood ranges from 200 to 300 thousand per 1 mm3
They are formed in the red bone marrow by detaching sections of the cytoplasm from megakaryocytes
Platelets circulate in the peripheral blood from 5 to 11 days, after which they are destroyed in the liver, lungs, and spleen
Platelets contain blood clotting factors, serotonin, histamine
Platelets have adhesive and agglutination properties
(i.e., the ability to adhere to foreign and own altered walls, as well as the ability to stick together and at the same time secrete hemostasis factors), affect the tone of microvessels and the permeability of their walls, take part in the process of blood clotting
Hemostasis is a complex set of physiological, biochemical and biophysical processes that prevent the occurrence of bleeding and ensure their stop.
Hemostasis is ensured by the interaction of three systems: vascular, cellular (platelets) and plasma
There are two mechanisms of hemostasis:
1. Primary (vascular-platelet)
2. Secondary (coagulation or blood clotting)
Vascular-platelet hemostasis is ensured by the vascular reaction involving platelets
Damage to small vessels (arterioles, capillaries, venules) is accompanied by their reflex spasm, either due to vegetative or humoral influences
At the same time, biologically active substances (serotonin, norepinephrine) are released from damaged tissues and blood cells, which cause vasoconstriction
After 1-2 hours, platelets begin to stick to the damaged areas of the vascular wall and spread out on them (adhesion)
At the same time, platelets begin to stick together, forming lumps (aggregation)
The resulting aggregates are superimposed on the adherent cells, resulting in the formation of a platelet plug that closes the damaged vessel and stops bleeding
During this reaction, substances that promote blood clotting are released from platelets
The process ends with the compaction of the platelet thrombus, which occurs due to the contractile protein of platelets - thrombostenin
Hemocoagulation is the second most important mechanism of hemostasis, which is activated when larger vessels are damaged, when vascular-platelet reactions are insufficient
At the same time, thrombus formation is ensured by a complex blood coagulation system, with which the anticoagulant system interacts
Blood coagulation occurs in stages (4 stages or phases) as a result of the interaction of plasma blood factors and various compounds contained in the formed elements and tissues
There are 13 blood clotting factors in plasma:
Fibrinogen (I), Prothrombin (II), Thromboplastin (III), Ca+ (IV), Proaccelerin (V), Accelerin (VI), Proconvertin (VII), Antihemophilic globulin A (VIII), Christmas factor (IX), Stewart factor -Prower (X), plasma thromboplastin precursor (XI), Hageman factor (XII), Fibrin-stabilizing factor (XIII)
In phase I, active thromboplastin is formed within 5-10 minutes
In phase II of coagulation (lasts 2-5 seconds), the enzyme thrombin is formed from prothrombin (III) with the participation of active thromboplastin (product of phase I).
Phase III (lasts 2-5 seconds) consists of the formation of insoluble fibrin from the fibrinogen protein (I) under the influence of the resulting thrombin
Phase IV (lasts several hours) is characterized by thickening or retraction of the blood clot
At the same time, serum is released from the fibrin polymer with the help of a contractile protein of the blood plate - retractoenzyme, which is activated by calcium ions
The anticoagulant system is represented by natural anticoagulants (substances that inhibit blood clotting)
They are formed in tissues, formed elements and are present in plasma
These include: heparin, antithrombin, antithromboplastin
Heparin is an important natural anticoagulant, produced by mast cells
Its point of application is the reaction of converting fibrinogen into fibrin, which it blocks due to the binding of thrombin
The activity of heparin depends on the content of antithrombin in the plasma, which increases its coagulating abilities
Antithromboplastins are substances that block coagulation factors involved in the activation of thromboplastin
Fibrinolysis is the process of breakdown of fibrin, formed during blood clotting, under the influence of the fibrinolytic system
Tissue activators are released when cells of various organs (except the liver) are damaged in the form of hydrolases, trypsin, urokinase
Activators of microorganisms are streptokinase, staphyllokinase, etc.
Electroencephalography.
Electroencephalography is a method for studying the electrical activity of the brain. The method is based on the principle of recording electrical potentials appearing in nerve cells during their activity. The electrical activity of the brain is small, expressed in millionths of a volt. The study of the biopotentials of the brain is therefore carried out using special, highly sensitive measuring instruments or amplifiers called electroencephalographs (Fig.). For this purpose, metal plates (electrodes) are placed on the surface of the human skull, which are connected by wires to the input of the electroencephalograph. The output of the device is graphic image on paper, fluctuations in the difference in biopotentials of the brain, called an electroencephalogram (EEG).
EEG data turns out to be different in a healthy and sick person. At rest, the EEG of an adult healthy person shows rhythmic fluctuations of two types of biopotentials. Larger oscillations, with an average frequency of 10 per 1 sec. and with a voltage of 50 microvolts are called alpha waves. Other, smaller oscillations, with an average frequency of 30 per 1 sec. and a voltage of 15-20 microvolts are called beta waves. If a person’s brain moves from a state of relative rest to a state of activity, then the alpha rhythm weakens and the beta rhythm increases. During sleep, both the alpha rhythm and the beta rhythm decrease and slower biopotentials appear with a frequency of 4-5 or 2-3 vibrations per 1 second. and a frequency of 14-22 vibrations per 1 second. In children, the EEG differs from the results of studying the electrical activity of the brain in adults and approaches them as the brain fully matures, i.e., by 13-17 years of life.
With various brain diseases, various abnormalities occur on the EEG. Signs of pathology on the resting EEG are: persistent absence of alpha activity (desynchronization of the alpha rhythm) or, conversely, its sharp increase (hypersynchronization); violation of the regularity of fluctuations in biopotentials; as well as the appearance pathological forms biopotentials - high-amplitude slow (theta and delta waves, sharp waves, peak-wave complexes and paroxysmal discharges, etc. Based on these disturbances, a neurologist can determine the severity and, to a certain extent, the nature of a brain disease. For example, if in there is a tumor in the brain or there has been a cerebral hemorrhage, electroencephalographic curves give the doctor an indication of where (in what part of the brain) this damage is located.In epilepsy, the EEG, even in the interictal period, can observe the appearance of sharp waves or peak-wave complexes against the background of normal bioelectrical activity .
Electroencephalography is especially important when the question arises about the need for brain surgery to remove a tumor, abscess or foreign body. Electroencephalography data in combination with other research methods are used to outline a plan for future surgery.
In all cases when, when examining a patient with a central nervous system disease, a neurologist suspects structural lesions of the brain, an electroencephalographic study is advisable. For this purpose, it is recommended to refer patients to specialized institutions where electroencephalography rooms operate.
Basic forms of regulation of physiological functions. The relationship between nervous and humoral regulatory mechanisms.
Physiological regulation is the active control of the body’s functions and its behavior to maintain an optimal level of vital activity, constancy of the internal environment and metabolic processes in order to adapt the body to changing environmental conditions.
Mechanisms of physiological regulation:
humoral.
Humoral physiological regulation uses body fluids (blood, lymph, cerebrospinal fluid, etc.) to transmit information. Signals are transmitted through chemicals: hormones, mediators, biologically active substances (BAS), electrolytes, etc.
Features of humoral regulation: does not have an exact addressee - with the flow of biological fluids, substances can be delivered to any cells of the body;
the speed of information delivery is low - determined by the speed of flow of biological fluids - 0.5-5 m/s;
duration of action.
Nervous physiological regulation for the processing and transmission of information is mediated through the central and peripheral nervous systems. Signals are transmitted using nerve impulses.
Features of nervous regulation: has a precise addressee - signals are delivered to strictly defined organs and tissues; high speed of information delivery - nerve impulse transmission speed - up to 120 m/s; short duration of action.
For normal regulation of body functions, interaction between the nervous and humoral systems is necessary.
Neurohumoral regulation combines all functions of the body to achieve a goal, while the body functions as a single whole. The body is in inextricable unity with the external environment due to the activity of the nervous system, the activity of which is carried out on the basis of reflexes. A reflex is a strictly predetermined reaction of the body to external or internal stimulation, carried out with the obligatory participation of the central nervous system. A reflex is a functional unit of nervous activity.
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Hormones have various effects on the body and its functions.
1. Metabolic influence is the most important, which forms the basis of all other influences. This action of hormones causes changes in tissue metabolism. It occurs due to three main hormonal influences: 1) changes in the permeability of cell membranes and organelles; 2) changes in enzyme activity in the cell; 3) influence on the genetic apparatus of the cell nucleus.
2. Morphogenetic effect of hormones on the growth and development of the body. These processes are carried out due to changes in the genetic apparatus of cells and metabolism. Examples include the effects of growth hormone on body growth and internal organs, sex hormones - on the development of secondary sexual characteristics.
3. The kinetic or triggering effect of hormones is that they trigger some function that they regulate. For example, oxytocin causes contraction of the uterine muscles, adrenaline triggers the breakdown of glycogen in the liver and the release of glucose into the blood.
4. The corrective effect of hormones is that they change the intensity of the functions of organs and tissues, which can be regulated without them. For example, hemodynamics are perfectly regulated by nervous mechanisms, but hormones (adrenaline, thyroxine, etc.) strengthen and prolong nervous influences.
5. The reactogenic effect of hormones is that they are able to change the reactivity of tissue to the action of the same hormone, other hormones or neurotransmitters. For example, folliculin enhances the effect of progesteron on the uterine mucosa, calcium-regulating hormones reduce the sensitivity of the distal nephron to the action of vasopressin. A type of reactogenic action of hormones is a permissive action - the ability of one hormone to ensure the manifestation of the effect of another hormone. For example, the effects of adrenaline require the presence of small amounts of cortisol.
6. Adaptive influence - adapting the intensity of metabolism to the needs of the body in a certain situation. It is especially characteristic of the hormones of the adrenal glands, pituitary gland, and thyroid gland, which bring metabolism into line with the body’s needs. These hormones ensure optimal metabolic rate in each specific situation, creating the necessary conditions for cell activity. The nature of the action of corticosteroids is determined by the initial level of metabolism: if it is low, hormones increase it and vice versa.
Mechanism of action of hormones c Each hormone affects only the organs that are sensitive to it. The organs to which the action of hormones is directed and which have an affinity for it are called target organs. These target organs have specific receptors, which are information molecules that transform the hormonal signal into hormonal action. Hormones carry out their biological effects by binding to these receptors. There are membrane (integral components of plasma membranes) and intracellular (in the cytoplasm, nucleus, mitochondria, i.e. inside cells) receptors.
There are two main mechanisms for implementing hormonal effects at the cellular level: implementation of the effect from the outer surface of the cell membrane; the effect is realized after the hormone penetrates into the cell.
Both of these pathways begin after the interaction of a hormone with its specific receptor.
I. Biological effect of hormones interacting with local receptors lysed on the plasma membrane, is carried out with the participation of second messengers, or transmitters. Depending on what substance performs its function, hormones are divided into the following groups:
hormones that have a biological effect with the participation of cAMP;
hormones that act with the participation of cGMP;
hormones, ext. involving ionized calcium or phosphatidylinositides (inositol triphosphate and diacylglycerol) or both compounds as a second messenger;
hormones that exert their effect by stimulating a cascade of kinases and phosphatases. The mechanisms involved in the formation of second messengers (messengers) are carried out through the activation of adenylate cyclase, guanylate cyclase, phospholipase C, tyrosine kinases, Ca2* channels, etc. The separation of hormones according to the principle of the activating systems of one or another secondary messenger is conditional, since many hormones interact with The receptor activates several secondary messengers simultaneously.
II. The mechanism of action of adrenal hormones, sex hormones, calcitriol, steroid and thyroid hormones is different - the receptors for them are localized intracellularly. These hormones in their own way physical and chemical properties easily penetrate the membrane into the cell and form a hormone-receptor complex in the cytoplasm. After the polypeptide fragment is cleaved from the receptor protein, the hormone-receptor complex enters the nucleus, where it interacts with specific regions of DNA, inducing the synthesis of specific RNA, initiating transcription and the synthesis of proteins and enzymes in ribosomes. All these phenomena require the long-term presence of the hormone-receptor complex in the nucleus. The effects of steroid hormones appear both after a few hours and very quickly. This is explained by steroid hormones the content of cAMP and the amount of ionized calcium in the cell increase
Circulating hormones do not act on all cells (target cells) in the same way; this is due to specific receptor proteins (receptors). The number of receptors localized on the cytoplasmic membrane and in the cytoplasm of the cell is not constant. It is regulated by the action of appropriate hormones. At constant elevated level hormone, the number of its receptors decreases. This phenomenon goes by various names: hyposensitization, refractoriness, tachyphylaxis or tolerance. At the same time, the specificity of the receptors is low and therefore they can bind not only hormones, but also compounds similar to them in structure. For example, cholera toxin can interact with receptors for TSH. Immunoglobulin G, interacting with the TSH receptor, can cause the release of thyroglobulin. The receptors also have limited binding capacity. All this leads to the fact that excess hormones bind to nonspecific cell receptors or, after inactivation, are excreted from the body, which can cause disturbances in hormonal regulation. Some hormones can affect the number of not only their “own” receptors, but also receptors for another hormone. Thus, progesterone reduces, and estrogens increase, the number of receptors for both estrogen and progesterone. Many endocrine glands respond to environmental influences. Their reaction is adaptive in nature, helping the body cope with the influence of the external environment (cold, heat, emotions, stress, etc.). An important factor determining the production of the hormone is the state of the regulated function, i.e. The production of hormones is regulated according to the principle of self-regulation.
95. Humoral regulation. Classification of humoral agents and endocrine glands. Biochemical nature of hormones.
When studying the epithelial tissues of the body in the classification, along with the integumentary epithelium, the glandular epithelium was distinguished, which included the exocrine glands (exocrine) and the internal secretion glands (endocrine). It was indicated that the endocrine glands do not have excretory ducts and secrete their secretion (called a hormone) into the blood or lymph. According to the structure, endocrine glands are divided into two types: follicular, when endocrinocytes form follicles, and trabecular, represented by strands of endocrine cells.
Hormones are substances with high biological activity that regulate the growth and activity of cells in various tissues of the body.
Hormones are characterized by specificity of action on specific cells and organs, called targets. This is due to the presence on target cells of specific receptors that recognize and bind this hormone. Being bound by a receptor, the hormone can affect plasma membrane, on an enzyme located in this membrane, on cellular organelles in the cytoplasm, or on nuclear (genetic) material.
The chemical nature of hormones is different. The vast majority of hormones belong to proteins and amino acid derivatives, some belong to steroids (i.e. cholesterol derivatives).
Endocrine regulation is one of several types of regulatory influences, among which are:
autocrine regulation (within one cell or cells of one type);
paracrine regulation (short-distance, - on neighboring cells);
endocrine (mediated by hormones circulating in the blood);
nervous regulation.
Along with the term “endocrine regulation”, the term “neuro-humoral regulation” is often used, emphasizing the close relationship between the nervous and endocrine systems.
Common to nerve and endocrine cells is the production of humoral regulatory factors. Endocrine cells synthesize hormones and release them into the blood, and neurons synthesize neurotransmitters (most of which are neuroamines): norepinephrine, serotinin and others, released into synaptic clefts. The hypothalamus contains secretory neurons that combine the properties of nerve and endocrine cells. They have the ability to form both neuroamines and oligopeptide hormones. The production of hormones by endocrine organs is regulated by the nervous system.
Classification of endocrine structures
I. Central regulatory formations of the endocrine system:
hypothalamus (neurosecretory nuclei);
pituitary gland (adenohypophysis and neurohypophysis);
II. Peripheral endocrine glands:
parathyroid glands;
adrenal glands (cortex and medulla).
III. Organs that combine endocrine and non-endocrine functions:
gonads (sex glands - testes and ovaries);
placenta;
pancreas.
IV. Single hormone-producing cells, apudocytes.
As in any system, its central and peripheral links have direct and feedback connections. Hormones produced in peripheral endocrine formations can have a regulatory effect on the activity of the central units.
One of the structural features of endocrine organs is the abundance of vessels in them, especially sinusoidal type hemocapillaries and lymphocapillaries, which receive secreted hormones.
