>The general characteristics of the nervous system from the point of view of cybernetics are as follows. Living organism is a unique cybernetic machine capable of self-government. This function is performed by the nervous system. Self-government requires 3 links: link - the flow of information, which occurs through a specific input information channel and is accomplished as follows:
A. The message arising from the source of information arrives at the receiving end of the information channel - receptor. Receptor- this is an encoding device that receives a message and processes it into a signal - afferent signal, as a result of which external irritation turns into a nerve impulse.
B. Afferent signal is transmitted further along the information channel, which is afferent nerve.
There are 3 types of information channels, 3 inputs to them: external inputs - through the senses (exteroceptors); internal entrances: a) through the organs of plant life (viscera) - interoceptors; b) through the organs of animal life (soma, the body itself) - proprioceptors. Link II - information processing. It is performed by a decoding device, which consists of the cell bodies of afferent neurons of the nerve ganglia and nerve cells of the gray matter of the spinal cord, cortex and subcortex of the brain, forming the nervous network of the gray matter of the central nervous system. III link - management. It is achieved by transmitting efferent signals from the gray matter of the spinal cord and brain to the executive organ and is carried out through efferent channels, i.e. efferent nerves with an effector at the end.
There are 2 types of executive bodies:
1. Executive organs of animal life- voluntary muscles, mainly skeletal.
2. Executive organs of plant life- involuntary muscles and glands.
In addition to this cybernetic scheme, modern cybernetics has established the generality of the feedback principle for the control and coordination of processes occurring both in modern machines and in living organisms; from this point of view, in the nervous system one can distinguish the feedback of the working organ with the nerve centers, the so-called reverse afferentation. This name refers to the transmission of signals from the working organ to the central nervous system about the results of its work at any given moment. When the centers of the nervous system send efferent impulses to the executive organ, a certain working effect (movement, secretion) occurs in the latter. This effect stimulates nerve (sensitive) impulses in the executive organ, which afferent pathways come back to the spinal cord and brain and signal that the working organ is performing a certain action at the moment. This is the essence "reverse afferentation", which, figuratively speaking, is a report to the center on the execution of orders on the periphery. Thus, when the hand grasps an object, the eyes continuously measure the distance between the hand and the target and send their information in the form of afferent signals to the brain. In the brain there is a short circuit to efferent neurons, which transmit motor impulses to the muscles of the hand, which produce the actions necessary for grasping an object. The muscles simultaneously influence the receptors located in them, which continuously send sensitive signals to the brain, informing about the position of the hand at any given moment. Such two-way signaling along reflex chains continues until the distance between the hand and the object is equal to zero, that is, until the hand takes the object.
Consequently, self-checking of the organ’s functioning is carried out all the time, possible thanks to the mechanism "reverse afferentation", which has the character of a closed circle in the sequence: center (device that sets the action program) - effector (motor) - object (working organ) - receptor (receiver) - center.
P.K. Anokhin proposed a model of the organization and regulation of a behavioral act, in which there is a place for all basic mental processes and states. She got the name of the model functional system. Its general structure is shown in Fig. …………
On the left of this diagram, called “situational afferentation,” a set of various influences is presented to which a person finds himself in a particular situation. Many of the incentives associated with it may turn out to be insignificant, and only a few of them are likely to arouse interest - indicative reaction. These factors are depicted in the diagram under the name “trigger stimulus”.
Before inducing behavioral activity, environmental afferentation and triggering stimulus
must be perceived, i.e. subjectively reflected by a person in the form sensations And perceptions, whose interaction with past experience (memory) gives rise to an image. Once formed, the image itself does not cause behavior. It must be correlated with motivation and the information that is stored in memory.
Comparing the image with memory and motivation through consciousness leads to making a decision, to the emergence in a person’s mind of a plan and program of behavior: several possible options for action that, in a given environment and in the presence of a given trigger stimulus, can lead to the satisfaction of an existing need.
In c.s.s. the expected outcome of actions is presented in the form of a kind of neural model - acceptor of the action result. When it is set and the action program is known, the process of implementing the action begins.
From the very beginning of the execution of an action, the will is included in its regulation, and information about the action is transmitted through reverse afferentation to the central nervous system, where it is compared with the acceptor of the action, giving rise to certain emotions. After some time, information about the parameters of the result of an action that has already been performed also appears there.
If the parameters of the performed action do not correspond to the action acceptor (the set goal), then a negative emotional state arises, which creates additional motivation to continue the action and repeat it according to the adjusted program until the result obtained coincides with the set goal (the action acceptor). If this coincidence occurs on the first attempt to perform the action, then a positive emotion arises that stops it.
The theory of the functional system of P. Kanokhin places emphasis in resolving the issue of the interaction of physiological and psychological processes and phenomena. It shows that both play an important role in the joint regulation of behavior, which cannot be fully scientifically explained either on the basis of knowledge of the physiology of higher nervous activity alone, or on the basis of exclusively psychological concepts.
Brain and psyche
A.R. Luria proposed to identify three anatomically relatively autonomous brain blocks that ensure the normal functioning of the corresponding groups of mental phenomena. The first is a block of brain structures that support a certain level of activity. It includes nonspecific structures of different levels: the reticular formation of the brain stem, the structures of the midbrain, its deep parts, the limbic system, the mediobasal parts of the cortex of the frontal and temporal lobes of the brain. The overall level of activity and selective activation of individual substructures, necessary for the normal implementation of mental functions, depend on the work of this block.
The second block is associated with cognitive mental processes, perception, processing and storage of various information coming from the senses: vision, hearing, touch, etc. Its cortical projections are mainly located in the posterior and temporal parts of the cerebral hemispheres. The third block covers the anterior parts of the cerebral cortex. It is associated with thinking, programming, higher regulation of behavior and mental functions, and their conscious control.
There is a problem associated with the block representation of brain structures, which is called the problem localization of mental functions, those. more or less accurate representation of them in individual brain structures. There are two different points of view on solving this problem. One was called localizationism, the other anti-localizationism.
According to localizationism Every, even the most elementary, mental function, every psychological property or state of a person is uniquely connected with the work of a limited area of the brain, so that all mental phenomena, as on a map, can be located on the surface and in the deep structures of the brain in very specific places. Indeed, at one time more or less detailed maps of the localization of mental functions in the brain were created, and one of the last such maps was published in the 30s of the 20th century.
Subsequently, it turned out that various disorders of mental processes are often associated with the same brain structures, and vice versa, lesions of the same areas of the brain often lead to loss of various functions. These facts ultimately undermined faith in localizationism and led to the emergence of an alternative doctrine - anti-localizationism. Supporters of the latter argued that the work of the entire brain as a whole, all its structures, is practically connected with every mental phenomenon, so that we can talk about a strict somatotopic representation (localization) of mental functions in the central nervous system. there are no sufficient reasons.
In anti-localizationism, the problem under discussion found its solution in the concept functional organ by which they began to understand the intravital system of temporary connections between individual parts of the brain that ensures the functioning of the corresponding property, process or state. Various links of such a system can be interchangeable, so the structure of functional organs in different people can be different.
However, antilocalizationism could not fully explain the fact of the existence of a more or less definite connection between certain mental and brain disorders, for example, visual impairments with damage to the occipital parts of the cerebral cortex, speech and hearing with damage to the temporal lobes of the cerebral hemispheres, etc. In this regard, neither localizationism nor anti-localizationism has so far managed to achieve a final victory over each other, and both teachings continue to coexist, complementing each other in their weak positions.
Reverse afferentation is information about the results of a completed action that enters the central nervous system. The concept was introduced by P.K. Anokhin within the framework of the theory of functional systems, as a clarifying term “sensory correction” by N.A. Bernstein. Thanks to O. a. the results of actions and their correction are continuously monitored. In the functional system, three types of O. a. are distinguished: 1) from receptors that record the final result; 2) from receptors of executive organs; 3) from the results of behavioral activity. O. a. can also be carried out humorally (through liquid media, blood, lymph, etc.).
Trainer's Dictionary. V. V. Gritsenko.
See what “Reverse afferentation” is in other dictionaries:
REVERSE AFFERENCE- (from Latin afferens, gender afferentis bringing). The physiological mechanism of delivery to the central nervous system of information about the parameters of the achieved useful adaptations, results in the purposeful activity of the body.... ... Veterinary encyclopedic dictionary
reverse afferentation- the process of correcting behavior based on information received by the brain from the outside about the results of ongoing activities. The term was introduced by P.K. Anokhin as a clarification of the term sensory correction proposed by N.A. Bernstein...
Reverse afferentation- the process of correcting behavior based on information received by the brain from the outside about the results of ongoing activities... Dictionary-reference book on philosophy for students of medical, pediatric and dental faculties
AFFERENTATION- [from lat. afferens, afferentis bringing] the flow of nerve impulses coming from extero and interoreceptors to the central nervous system (see Reverse afferentation, Situational afferentation, Trigger afferentation); (cf. efferentation) ...
Feedback- – 1. in technology – information about the flow of processes in the system; for example, the speedometer signals the speed of the car; 2. in cybernetics – information used by the system in self-regulation processes; for example, the refrigerator turns on itself or... ... Encyclopedic Dictionary of Psychology and Pedagogy
AFFERENTATION- (in psychophysiology) (from the Latin affero - I bring, I deliver) - a term denoting the transfer of nervous excitement from the peripheral. sensory neurons to the central ones. Higher animals and humans have a center. afferent neurons are located in the brain... ... Philosophical Encyclopedia
reverse afferentation- a term proposed by P.K. Anokhin to designate the principle of operation of the functional systems of the body, which consists in the constant assessment of a useful adaptive result by comparing its parameters with the parameters of the result acceptor... ... Large medical dictionary
reverse afferentation- the process of signaling the degree of success of the first reflex responses of the central nervous system to environmental irritations. The term a.o. introduced by the Soviet physiologist P.K. Anokhin, he also developed the theory of reverse afferentation, it deepens the provisions of I.P... Encyclopedic Dictionary of Psychology and Pedagogy
REVERSE AFFERENTATION- the principle of operation of the functional systems of the body, which consists in the constant assessment of a useful adaptive result by comparing its parameters with the parameters of the “acceptor of action results” (The term “A. o.” was proposed by P.K. Anokhin) ... Psychomotorics: dictionary-reference book
Application. Some problems of streamlining modern medical terminology- The above-described centuries-old history of the emergence and development of medical terminology, which has many multilingual sources, as well as the given examples of complex relationships between the etymology, structure and semantics of terms, probably... ... Medical encyclopedia
Subject of physiology.
Physiology studies the vital functions of the body and its individual parts: cells, tissues, organs, systems.
sections of physiology:
1. general physiology studies general processes in the body.
2. private physiology - the functions of individual cells, organs and physiological systems. It distinguishes the physiology of muscle tissue, the physiology of the heart, etc.;
3. Evolutionary physiology - studies changes occurring during the process of evolution
4. in human physiology. age, clinical physiology, labor and sports physiology, aviation and space.
The task of physiology is to understand the operation of the machine of the human body, to determine the significance of each of its parts, to understand how these parts are connected, how they interact and how their interaction produces a result - the overall work of the body" (Pavlov).
2 main methods:
observation is the collection and description of facts. This method has a place in cellular and experimental physiology. An experiment studies a process or phenomenon under strictly specified conditions. The experiment can be acute and chronic: 1 - acute experience is carried out during operations, allowing you to study some function in a short period of time. Disadvantages: anesthesia, trauma, blood loss can distort the normal function of the body. 2 – a chronic experiment allows one to study the functions of the body over a long period of time under conditions of normal interaction with the environment. History of the development of physiology. Initially, ideas about the functions of the body were formed on the basis of the works of scientists of Ancient Greece and Rome: Aristotle, Hippocrates, Gallen, etc., as well as scientists from China and India. Physiology became an independent science in the 17th century, when, along with the method of observing the activity of the body, the development of experimental research methods began. This was facilitated by the work of Harvey, who studied the mechanisms of blood circulation; Descartes, who described the reflex mechanism. In the 19th-20th centuries. physiology is developing intensively. Thus, studies of tissue excitability were carried out by K. Bernard and Lapik. Significant contributions were made by scientists: Ludwig, Dubois-Reymond, Helmholtz, Pfluger, Bell, Langley, Hodgkin and domestic scientists: Ovsyanikov, Nislavsky, Zion, Pashutin, Vvedensky. Ivan Mikhailovich Sechenov is called the father of Russian physiology. Of outstanding importance were his works on the study of the functions of the nervous system (central or Sechenov inhibition), breathing, fatigue processes, etc. In his work “Reflexes of the Brain” (1863), he developed the idea of the reflex nature of processes occurring in the brain, including thinking processes. Sechenov proved the determination of the psyche by external conditions, i.e. its dependence on external factors. The experimental substantiation of Sechenov’s provisions was carried out by his student Ivan Petrovich Pavlov. He expanded and developed the reflex theory, studied the functions of the digestive organs, the mechanisms of regulation of digestion and blood circulation, and developed new approaches to conducting physiological experiments “methods of chronic experience.” For his work on digestion, he was awarded the Nobel Prize in 1904. Pavlov studied the basic processes occurring in the cerebral cortex. Using the method of conditioned reflexes he developed, he laid the foundations of the science of higher nervous activity. In 1935, at the world congress of physiologists I.P. Pavlov was called the patriarch of physiologists of the world
Classification of reflexes. Reflex arc. Reverse afferentation, the meaning of its elements.
A reflex is the body’s response to a stimulus with the participation of the nervous system. There are classifications of reflexes:
Based on the method of evocation, a distinction is made between unconditioned reflexes and conditioned reflexes. There are exteroceptive reflexes (skin), interoceptive reflexes (internal organs), proprioceptive reflexes (receptors of muscles, tendons, joints). Depending on the levels of brain structure, spinal, boulevard, mesencephalic, diencephalic, and cortical reflex reactions are distinguished.
According to their biological purpose, reflexes are divided into food, defensive, sexual, etc. The nervous system works on the principle of reflection: stimulus - response. To implement any reflex, a reflex arc and the integrity of all its links are necessary. A reflex arc is a chain of neurons through which a nerve impulse passes from the receptor to the working organ. The reflex arc consists of 5 links: a receptor that perceives external or internal influences; sensitive (centripetal, afferent) neuron, interneuron lying in the central nervous system,
motor neuron (centrifugal, efferent), Working organ. Reverse afferentation - information from the executive organ to the central nervous system, where the analysis of what should be and what happened in response to the action of the stimulus takes place. Based on this analysis, corrective impulses are sent from the center to the performing organ and to the receptors. The term was first proposed by Anokhin
Classification of nerve fibers. 2 Laws of conduction of excitation along nerves. 3Mechanism for conducting nerve impulses along unmyelinated and myelinated nerve fibers
1. The function of rapid transmission of excitation to and from a nerve cell is performed by its processes - dendrites and axons, i.e. nerve fibers. Depending on their structure, they are divided into pulpy, having a myelin sheath, and non-pulpy. This membrane is formed by Schwann cells. They contain myelin. It performs isolating and trophic functions. Areas where the membrane is not covered with myelin are called nodes of Ranvier.
Functionally, all nerve fibers are divided into three groups:
Type A fibers are thick fibers that have a myelin sheath. This group includes 4 subtypes: Aα - these include motor fibers of skeletal muscles and afferent nerves coming from muscle spindles (stretch receptors). Aβ - afferent fibers coming from proprioceptors. Aγ - efferent fibers going to muscle spindles.
Aδ - afferent fibers from temperature and pain receptors of the skin. Group B fibers are thin myelinated fibers that are preganglionic fibers of the autonomic efferent pathways. Group C fibers, non-myelinated postganglionic fibers of the autonomic nervous system.2 The conduction of excitation along the nerves obeys the following laws: The law of anatomical and physiological integrity of the nerve. The first is disrupted by cutting, the second by the action of substances that block conduction, for example novocaine. Law of two-way conduction of excitation. It spreads in both directions from the site of irritation. In the body, most often excitation goes through afferent pathways to the neuron, and through efferent pathways it goes from the neuron. This type of distribution is called orthodromic.
Law of isolated conduction. Excitation is not transmitted from one nerve fiber to another, which is part of the same nerve trunk. Law of non-decremental implementation. Excitation is carried through the nerves without attenuation.
Parathyroid glands.
A person has 2 pairs of parathyroid glands, located on the back surface or embedded inside the thyroid gland. The chief, or oxyphilic, cells of these glands produce parathyroid hormone, or parathyrin, or parathyroid hormone (PTH). Parathyroid hormone regulates calcium metabolism in the body and maintains its level in the blood. In bone tissue, parathyroid hormone enhances the function of osteoclasts, which leads to bone demineralization and increased calcium levels in the blood plasma (hypercalcemia). In the kidneys, parathyroid hormone enhances calcium reabsorption. In the intestine, an increase in calcium reabsorption occurs due to the stimulating effect of parathyroid hormone on the synthesis of calcitriol, the active metabolite of vitamin D3. Under the influence of parathyroid hormone, it is activated in the liver and kidneys. Calcitriol increases the formation of calcium-binding protein in the intestinal wall, which promotes the reabsorption of calcium. Influencing calcium metabolism, parathyroid hormone simultaneously affects phosphorus metabolism in the body: it inhibits the reabsorption of phosphates and increases their excretion in the urine (phosphaturia). The activity of the parathyroid glands is determined by the calcium content in the blood plasma. If the concentration of calcium in the blood increases, this leads to a decrease in the secretion of parathyroid hormone. A decrease in calcium levels in the blood causes increased production of parathyroid hormone. Removal of the parathyroid glands in animals or their hypofunction in humans leads to increased neuromuscular excitability, which is manifested by fibrillary twitching of single muscles, turning into spastic contractions of muscle groups, mainly the limbs, face and back of the head. The animal dies from tetanic convulsions. Hyperfunction of the parathyroid glands leads to demineralization of bone tissue and the development of osteoporosis. Hypercalcemia increases the tendency to stone formation in the kidneys, contributes to the development of disturbances in the electrical activity of the heart, and the occurrence of ulcers in the gastrointestinal tract
42. Endocrine function of the pancreas and its role in the regulation of metabolism.
Exocrine (exocrine, or excretory) function of the pancreas. consists in the secretion into the duodenum of juice containing a set of enzymes that hydrolyze all the main groups of food polymers, the main of which are lipase, a-amylase, trypsin and chymotrypsin. Secretion of inorganic and organic components of pancreatic juice occurs in different structural elements of the pancreas. The main enzymes of pancreatic juice are secreted in an inactive form (trypsinogen, chymotrypsinogen) and are activated only in the duodenum, turning under the action of enterokinase into trypsin and chymotrypsin. The volume of secretion from acinar cells is small, and the amount of pancreatic juice is mainly determined by the secretion of ductal cells in which the liquid part of the secretion is produced, its ionic composition and quantity change due to reabsorption and ion exchange. There are three phases of pancreatic juice secretion: complex-reflex, gastric and intestinal. The complex reflex phase occurs under the influence of conditioned reflex (the sight and smell of food) and unconditioned reflex (chewing and swallowing) stimuli; The secretion of pancreatic juice begins 1-2 minutes after eating. Irritation of the nuclei of the anterior and intermediate hypothalamic regions stimulates secretion, and the posterior region inhibits it. The secretion of pancreatic juice in the gastric phase is associated with the influence of the vagus nerve, as well as the action of gastrin secreted by the stomach. The main phase of pancreatic juice secretion is intestinal: it is of a humoral nature and depends on the release of two intestinal hormones - secretin and cholecystokinin (pancreozymin). Secretin is a peptide hormone that stimulates the secretion of large amounts of pancreatic juice, it ensures the creation of a neutral environment. Cholecystokinin is a polypeptide hormone of the upper small intestine that stimulates the secretion of pancreatic juice, rich in digestive enzymes and depleted in bicarbonates.
On the secretory function of the pancreas. hormones of the thyroid and parathyroid glands and adrenal glands influence.
Endocrine(incretory) function of pancreas. consists in the production of a number of polypeptide hormones entering the blood; it is carried out by the cells of the pancreatic islets. The physiological significance of insulin is to regulate carbohydrate metabolism and maintain the required level of glucose in the blood by reducing it. Glucagon has the opposite effect. Its main physiological role is to regulate blood glucose levels by increasing it; in addition, it affects metabolic processes in the body. Somatostatin inhibits the release of gastrin, insulin and glucagon, the secretion of hydrochloric acid by the stomach and the entry of calcium ions into the cells of the pancreatic islets. Pancreatic polypeptide, more than 90% of which is produced by the PP cells of the pancreatic islets and the exocrine part of the pancreas, is an antagonist of cholecystokinin in its effect.
43-44. Physiology of the adrenal glands. The role of hormones of the cortex and medulla in the regulation of body functions.
Adrenaline and norepinephrine from the adrenal glands act like sympathetic nerves, i.e. increase the frequency, strength of contractions, excitability and conductivity of the heart muscle. Significantly increase energy metabolism. A large number of them are released during fasting.
Hormones of indirect action. ACTH and adrenal corticosteroids gradually increase vascular tone and increase blood pressure. Adrenal glucocorticoids stimulate the breakdown of proteins. Somatotropin, on the contrary, enhances protein synthesis. Mineralocorticoids regulate the sodium-potassium balance. Natriuretic hormone or atriopeptide. It is formed mainly in the left atrium when it is stretched, as well as in the anterior lobe of the pituitary gland and chromaffin cells of the adrenal glands. It enhances filtration and reduces sodium reabsorption. As a result, the excretion of sodium and chlorine by the kidneys increases and daily diuresis increases. Under the influence of renin, the arterioles of the kidneys narrow and the permeability of the glomerular capillary wall decreases. As a result, the filtration rate decreases. At the same time, angiotensin II stimulates the release of aldosterone by the adrenal glands. Aldosterone enhances tubular sodium reabsorption and water reabsorption. Water and sodium retention occurs in the body. The action of angiotensin is accompanied by increased synthesis of antidiuretic hormone of the pituitary gland. An increase in water and sodium chloride in the vascular bed, with the same content of plasma proteins, leads to the release of water into the tissues. Renal edema develops. This occurs against the background of high blood pressure.
In the female body, the emergence of sexual motivation is due to the accumulation of both androgens and estrogens in the blood. The former are formed in the adrenal glands, the latter in the ovaries.
45. Sex glands. Male and female sex hormones and their physiological role in the formation of sex and regulation of reproductive processes. In the male gonads (testes), the processes of spermatogenesis and the formation of male sex hormones - androgens - occur. Spermatogenesis is carried out due to the activity of spermatogenic epithelial cells, which are contained in the seminiferous tubules. Androgen production occurs in interstitial cells. Androgens include several steroid hormones, the most important of which is testosterone. The production of this hormone determines the adequate development of male primary and secondary sexual characteristics (masculinizing effect). Under the influence of testosterone during puberty, the size of the penis and testicles increases, a male type of hair appears, and the tone of the voice changes. In addition, testosterone enhances protein synthesis (anabolic effect), which leads to accelerated growth processes, physical development, and increased muscle mass. Testosterone accelerates the formation of the protein matrix of the bone and enhances the deposition of calcium salts in it. As a result, bone growth, thickness and strength increase. With overproduction of testosterone, metabolism accelerates and the number of red blood cells in the blood increases. Testosterone secretion is regulated by luteinizing hormone of the adenohypophysis. With an increase in testosterone levels in the blood, the production of luteinizing hormone is inhibited through a negative feedback mechanism. A decrease in the production of both gonadotropic hormones - follicle-stimulating and luteinizing hormones - also occurs with the acceleration of spermatogenesis processes. The lack of male sex hormones also leads to certain neuropsychic changes, in particular to the lack of attraction to the opposite sex and the loss of other typical psychophysiological traits of a man.
Female reproductive glands. The female reproductive glands (ovaries) produce estrogen and progesterone. The secretion of these hormones is characterized by a certain cyclicity associated with changes in the production of pituitary gonadotropins during the menstrual cycle. The secretion of gonadotropins is inhibited by high levels of female sex hormones in the blood. During pregnancy, the secretion of estrogen increases significantly due to the hormonal activity of the placenta. The most active representative of this group of hormones is β-estradiol. Progesterone is a hormone of the corpus luteum; its production increases at the end of the menstrual cycle. The main purpose of progesterone is to prepare the endometrium for implantation of a fertilized egg. Under the influence of estrogens, the development of primary and secondary female sexual characteristics is accelerated. During puberty, the size of the ovaries, uterus, vagina, and external genitalia increases. The processes of proliferation and growth of glands in the endometrium intensify. Estrogens accelerate the development of mammary glands and affect the development of the bone skeleton by increasing the activity of osteoblasts. The action of these hormones leads to an increase in protein biosynthesis; The formation of fat also increases, the excess of which is deposited in the subcutaneous tissue, which determines the external features of the female figure. Under the influence of estrogens, female-type hair growth develops: the skin becomes thinner and smoother, as well as well-vascularized.
Insufficient secretion of female sex hormones leads to the cessation of menstruation, atrophy of the mammary glands, vagina and uterus.
46. Blood, its quantity, properties and functions. Blood composition. Basic physiological blood constants.
Blood, lymph, tissue fluid. the internal environment of the body in which many homeostasis processes take place. Blood is a liquid tissue and, together with the hematopoietic and storage organs (bone marrow, lymph nodes, spleen), forms the physiological blood system. The adult body contains about 4-6 liters of blood or 6-8% of body weight. The main functions of blood are:
1. Transport, it includes: a. respiratory - transport of breath. gases O2 and CO2 b. trophic - transfer of nutrients, vitamins, microelements; V. excretory - transport of metabolic products to the excretory organs;
d. thermoregulatory - removal of excess heat from internal organs and brain to the skin; d. regulatory - transfer of hormones and other substances.2. Homeostatic. A. maintaining the pH of the internal environment of the body; b. maintaining the constancy of ionic and water-salt balance, osmotic pressure.
H. Protective function. Provided by specific immune antibodies contained in the blood. antiviral and antibacterial. c-you, the phagocytic activity of leukocytes. 4.Hemostatic Fx. The blood has an enzyme coagulation system that prevents bleeding. Blood consists of plasma and formed elements suspended in it: red blood cells, leukocytes and platelets. The ratio of the volume of formed elements and plasma is called hematocrit. Normally, formed elements occupy 42-45% of blood volume, and plasma - 55-58%. The specific gravity of whole blood is 1.052-1.061 g/cm3. Its viscosity is 4.4-4.7 poise, and the osmotic division is 7.6 atm. Most of the osmotic pressure is due to Na, K, and Cl present in the plasma. Solutions whose osmotic pressure is higher than the osmotic pressure of blood are called hypertonic. If the osmotic pressure of the solution is lower than that of blood, it is called hypotonic (0.3%. NaCl).
47. Physiological mechanisms for maintaining a constant acid-base balance.
Blood buffer systems. Parameters of acid-base balance. Provided by lungs and kidneys. Housing and communal services, liver With the help of the lungs, carbonic acid is removed from the blood. The body produces 10 moles of carbonic acid every minute. Blood acidification does not occur because bicarbonates are formed from it. In the capillaries of the lungs, carbonic acid is again formed from carbonic acid anions and protons, which, under the influence of the enzyme carbonic anhydrase, is broken down into carbon dioxide and water. They are running out of steam. Non-volatile organic and inorganic acids are released from the blood through the kidneys. They are excreted both in a free state and in the form of salts. Under physiological conditions of the kidney, urine has an acidic reaction (pH = 5-7). The kidneys are involved in the regulation of acid-base homeostasis through the following mechanisms: Secretion of hydrogen ions formed from carbonic acid into the urine.
The formation of bicarbonates, which enter the blood and increase its alkaline reserve.
Synthesis of ammonia, the cation of which can bind with a cation, hydrogen. Reabsorption of bicarbonates in the tubules from primary urine into the blood. Filtration of excess acidic and alkaline compounds into the urine. The importance of the digestive organs for maintaining acid-base balance is small. In particular, protons are released in the stomach in the form of hydrochloric acid. The pancreas and glands of the small intestine contain bicarbonates. But at the same time, protons and bicarbonates are reabsorbed into the blood. As a result, the blood reaction does not change. The acid-base balance of the blood is characterized by several indicators: the current pH. This is the actual pH value of the blood. Normal pH = 7.35-7.45.
Partial voltage of C02 (PC02). Arterial blood yield is 36-44 mm. rt. st. Standard blood bicarbonate (SB). Content of bicarbonate (hydrocarbonate) anions at normal saturation of hemoglobin with oxygen. Value 21.3 - 24.3 mol/l. Current blood bicarbonate (AB). True concentration of bicarbonate anions. Normally, it is practically no different from the standard one. Buffer bases (BB). The total sum of all anions that have buffering properties under standard conditions. 40-60 mol/l.
A shift in the blood reaction to the acidic side is called acidosis, and to the alkaline side - alkalosis. These pH changes can be respiratory, non-respiratory or metabolic. Respiratory changes in blood reaction are caused by changes in carbon dioxide content. Non-respiratory - bicarbonate anions. Changes in pH can be compensated or uncompensated. If the blood reaction does not change, then this is compensated alkalosis and acidosis. Shifts are compensated by buffer systems, primarily bicarbonate. Therefore, they are observed in a healthy body. With a deficiency or excess of buffer components, partially compensated acidosis and alkalosis occur, but the pH does not go beyond normal limits. If the blood reaction is less than 7.29 or more than 7.56, uncompensated acidosis and alkalosis are observed. The most dangerous condition in the clinic is uncompensated metabolic acidosis. It occurs as a result of circulatory disorders and tissue hypoxia, and as a result, increased anaerobic breakdown of fats and proteins, etc. At a pH below 7.0, profound changes in the functions of the central nervous system (coma) occur, cardiac fibrillation occurs, blood pressure drops, breathing is depressed and death can occur. Metabolic acidosis is eliminated by correction of electrolyte composition, artificial ventilation, etc.
Buffer systems are a complex of weak acids and bases that can prevent a reaction from shifting in one direction or another. Blood contains the following buffer systems:
Bicarbonate or hydrocarbonate. It consists of free carbonic acid and sodium and potassium bicarbonates (NaHCO3 and KHCO3). When alkalis accumulate in the blood, they interact with carbonic acid. Bicarbonate and water are formed. If the acidity of the blood increases, then the acids combine with bicarbonates. Neutral salts and carbonic acid are formed. In the lungs it breaks down into carbon dioxide and water, which are exhaled. 2. Phosphate buffer system. 0na is a complex of sodium hydrogen phosphate and sodium dihydrogen phosphate (Na2HPO4), and NaH2PO4). The first exhibits the properties of a base, the second a weak acid. Acids form a neutral salt and sodium dihydrogen phosphate with sodium hydrogen phosphate (Na2HPO4 + H2CO3 = NaHCO3 + NaH2PO4) 3. protein buffer system. Proteins act as buffers due to their amphoteric properties (they exhibit either alkaline or acidic properties). Although the buffer capacity of the protein system is small, it plays an important role in the intercellular fluid. Hemoglobin buffer system of erythrocytes. The most powerful buffer system. Consists of reduced hemoglobin and potassium salt of oxyhemoglobin. The amino acid histidine, which is present in the structure of hemoglobin, has carboxyl and amide groups. The former provide hemoglobin with the properties of a weak acid, the latter a weak base. When oxyhemoglobin dissociates in tissue capillaries into oxygen and hemoglobin, the latter acquires the ability to hide with hydrogen cations. They are formed as a result of the dissociation of carbonic acid formed from carbon dioxide. Carbonic acid anions bind to potassium cations found in red blood cells and sodium cations in the blood plasma. Potassium and sodium bicarbonates are formed, preserving the buffer capacity of the blood. In addition, reduced hemoglobin can directly combine with carbon dioxide to form carbohemoglobin. This also prevents the blood reaction from shifting to the acidic side. The acid-base balance of the blood is characterized by several indicators: Current pH. This is the actual pH value of the blood. Normal pH = 7.35-7.45. Partial voltage of C02 (PC02). Arterial blood yield is 36-44 mm. rt. Art. Standard blood bicarbonate (SB). Content of bicarbonate (hydrocarbonate) anions at normal saturation of hemoglobin with oxygen. Value 21.3 - 24.3 mol/l. Current blood bicarbonate (AB). True concentration of bicarbonate anions. Normally, it is practically no different from the standard one. Buffer bases (BB). The total sum of all anions that have buffering properties under standard conditions. 40-60 mol/l.
48. Composition, properties and significance of blood plasma components, their characteristics and functional significance. Osmotic and oncotic blood pressure, their role.
The specific gravity of plasma is 1.025-1.029 g/cm3, viscosity is 1.9-2.6. Plasma contains 90-92% water and 8-10% dry matter. The dry residue contains minerals (about 0.9%), mainly sodium chloride, potassium, magnesium, calcium cations, chlorine anions, bicarbonate, and phosphate anions. In addition, it contains glucose, as well as protein hydrolysis products - urea, creatinine, amino acids, etc. They are called residual nitrogen. Plasma glucose content is 3.6-6.9 mmol/l, residual nitrogen 14.3-28.6 mmol/l.
Plasma proteins are of particular importance. Their total number is 7-8%. Proteins consist of several fractions, but the most important are albumins, globulins and fibrinogen. Albumin contains 3.5-5%, globulins 2-3%, fibrinogen 0.3-0.4%. With normal nutrition, the human body produces about 17 g of albumin and 5 g of globulins every day.
Functions of plasma albumins: 1. Create most of the oncotic pressure, ensuring normal distribution of water and ions between the blood and tissue fluid, urine formation. 2. Serve as a protein reserve in the blood, which amounts to 200 g of protein. It is used by the body during protein starvation. 3. Thanks to the negative charge, they promote stabilization and prevent sedimentation of blood cells. 4. Maintain acid-base balance, being a buffer system. 5. Transport sex hormones, bile pigments and calcium ions. These same functions are performed by other protein fractions, but to a much lesser extent. They have special functions. Globulins include four subfractions - a 1, a 2, b and g-globulins. Functions of globulins:
1.a-globulins are involved in the regulation of erythropoiesis.
2.Necessary for blood clotting.
3.Participate in the dissolution of a blood clot.
4.a 2 -albumin ceruloplasmin transports 90% of the copper ions needed by the body.
5.Carry the hormones thyroxine and cortisol
6.b-globulin transferrin transports the bulk of iron.
7.Several b-globulins are blood clotting factors.
8.g-globulins perform a protective function, being immunoglobulins. In diseases, their amount in the blood increases.
Fibrinogen is a soluble precursor to the protein fibrin, which forms the blood clot thrombus.
Oncotic (colloid-osmotic) pressure of blood plasma is part of the osmotic pressure created by blood plasma proteins. Normally 25-30 mmHg. Art. Depends largely on albumin. The role of oncotic pressure in the exchange of fluid between blood and tissues: the greater its value, the more water is retained in the vascular bed and the less it passes into the tissues and vice versa, it affects the formation of tissue fluid, lymph, urine and the absorption of water in the intestine.
(osmotic pressure) is the force that ensures the movement of a solvent through a semi-permeable membrane that separates solutions with different concentrations of substances. It is determined by the total concentration of various blood plasma particles (ions and molecules).
49. . Red blood cells. Their structure and functions. Hemolysis, its types.
Red blood cells (E) are highly specialized. anucleate blood cells. The nucleus is lost during maturation. E have the shape of a biconcave disk. On average, their diameter is about 7.5 microns, and the thickness at the periphery is 2.5 microns. Thanks to the shape of the surface E for the diffusion of gases. In addition, this is their plasticity. Due to their high plasticity, they are deformed and easily pass through capillaries. The old ones also have a pathologist. E plasticity is low. Therefore, they are retained in the capillaries of the reticular tissue of the spleen and destroyed there. Membrane E allows O2 and CO2 molecules to pass through well. The membrane contains up to 52% protein. It has a built-in Na/K-ATPase, which removes Na from the cytoplasm and pumps K ions. The bulk of E is the chemoprotein hemoglobin.
Functions of E: Transfer of O2 from the lungs to the tissues.
2. Participation in the transport of CO2 from tissues to the lungs.
3. Transport of water from tissues to the lungs, where it is released in the form of steam. 4. Participate in blood clotting by releasing erythrocyte coagulation factors.
5.Carry amino acids on their surface
6. Participate in the regulation of blood viscosity due to plasticity. One microliter of male blood contains 4.5-5.0 million E (4.5-5.0 * 1012 l). Women -3.7-4.7 million (3.7-4.7 * 10 l). Hemolysis is the destruction of the E membrane and the release of hemoglobin into the plasma. As a result, the blood becomes clear. There are the following types of hemolysis. According to the place of occurrence: 1. Endogenous, (in the body) 2. Exogenous, outside it. By nature: 1. Physiological. It ensures the destruction of old and pathological. forms E. There are two mechanisms. Inside the cell. hemolysis occurs in macrophages of the spleen, bone marrow, and liver cells. Intravascular, in small vessels, from which Hb is transferred to liver cells using plasma protein. There, hemoglobin heme is converted into bilirubin. About 6-7 g of Hb are destroyed per day.
2. Pathological According to the mechanism of occurrence:
1. Chemical. When E-s are exposed to substances that dissolve membrane lipids. These are alcohols, ethers, alkalis, acids, etc. 2. Temperature. At low temperatures, ice crystals form in E-s, breaking their shell. 3. Mechanical. Observed during mechanical membrane ruptures. 4.Biological. These are hemolytic poisons of bacteria, insects, and snakes. As a result of transfusion of incompatible blood. 5.Osmotic. Occurs if E-s are in an environment with an osmotic pressure lower than that of the blood. Water enters the E-s, they swell and burst.
50. Types of hemoglobin, its compounds, their physiological significance. Hemoglobin (Hb) is a chemoprotein found in red blood cells. Its molecular weight is 66,000 daltons. The hemoglobin molecule is made up of four subunits, each of which includes heme, connected to an iron atom, and the protein part of the globin. Heme is synthesized in the mitochondria of erythroblasts, and globin in their ribosomes. In an adult, hemoglobin contains two a- and two b-polypeptide chains (A-hemoglobin). In adulthood, it makes up the bulk of hemoglobin. In the first three months of intrauterine development, red blood cells contain hemoglobin types GI and G2. In subsequent periods of intrauterine development and in the first months after birth, the main part is fetal hemoglobin (F-hemoglobin). Its structure contains two a- and two g-polypeptide chains.
One gram of hemoglobin is capable of binding 1.34 ml of oxygen. The combination of hemoglobin with oxygen formed in the capillaries of the lungs is called oxyhemoglobin (HbO 2). It has a bright scarlet color. Hemoglobin that has given up oxygen in tissue capillaries is called deoxyhemoglobin or reduced (Hb). It has a dark cherry coloration. From 10 to 30% of carbon dioxide entering the blood from tissues combines with the amide group of hemoglobin. An easily dissociable compound, carbhemoglobin (HbCO2), is formed. In this form, part of the carbon dioxide is transported to the lungs. In some cases, hemoglobin forms pathological compounds. Carbon monoxide poisoning produces carboxyhemoglobin (HbCO). The affinity of hemoglobin for carbon monoxide is much higher than for oxygen, and the dissociation rate of carboxyhemoglobin is 200 times less than that of oxyhemoglobin. Therefore, the presence of even 1% carbon monoxide in the air leads to a progressive increase in the amount of carboxyhemoglobin and dangerous carbon poisoning. The blood loses its ability to carry oxygen. Hypoxia of the brain and other tissues develops. In case of poisoning with strong oxidizing agents, such as nitrites, methemoglobin (MetHb) is formed. In this hemoglobin compound, iron becomes trivalent. Therefore, methemoglobin is a very weakly dissociating compound. It does not give oxygen to tissues.
All hemoglobin compounds have a characteristic spectrum...
Hemoglobin forms a brown compound with hydrochloric acid - hematin hydrochloride. The shape of its crystals depends on the type of blood. Hemoglobin content is determined by Sali's method. Sali's hemometer consists of 3 test tubes. Two of them, located on the side of the central one, are filled with a standard solution of brown hematin hydrochloride. The middle tube is graduated in hemoglobin units. 0.2 ml of hydrochloric acid is poured into it. Then, 20 μl of blood is collected using a measuring pipette and released into hydrochloric acid. Mix the contents of the test tube and leave for 5 minutes. The resulting solution of hematin hydrochloride is diluted with water until its color becomes the same as in the side test tubes. The hemoglobin content is determined by the level of liquid in the middle test tube. Normally, the blood of men contains 132-164 g/l (13.2-16.4 g%) of hemoglobin. In women - 115-145 g/l (11.5-14.5 g%). The amount of hemoglobin decreases due to blood loss, intoxication, disorders of erythropoiesis, lack of iron, vitamin B 12, etc. In addition, the color index is determined. This is the ratio of the hemoglobin content in the blood to the number of red blood cells. Normally, its value is 0.85-1.05.
51. Leukocytes, their types. Functions of different types of leukocytes.
Leukocytes are blood cells containing a nucleus. In some leukocytes, the cytoplasm contains granules - granulocytes. Others have no granularity - agranulocytes. There are three forms of granulocytes: eosinophils, basophils, neutrophils. Agranulocytes are divided into monocytes and lymphocytes. All granulocytes and monocytes are formed in the red bone marrow. Lymphocytes are also an image. from bone marrow stem cells, but multiply in the lymph nodes, appendix, spleen, thymus...
Human life proceeds in interaction with the environment.
He perceives the world around him with the help of his senses, processes the information received and reacts accordingly.
One of the most important elements of interaction is afferentation.
What is afferentation?
In physiology, afferentation is understood as the transfer of nervous excitation from sensitive ones located on the periphery of the body to the center of the nervous system: or. Most signals enter the brain, or more precisely, its cortex.
Receptors that perceive irritation are located both in the sensory organs and in the internal organs. When information comes from the outside, it is necessary for orientation in space and making decisions about future action and is called situational afferentation.
Internal signals provided by interoreception of physiology or nerve endings located inside the body provide information about the state of the body itself, allowing time to sense “problems” that indicate health problems.
In psychology, afferentation refers to the flow of nerve impulses from the sensory organs and internal organs of a person to the central nervous system.
The process of perception begins with irritation of sensory neurons.
Its source can be any signal:
- stream of light;
- sound vibrations;
- chemicals sprayed into the air;
- thermal radiation and others.
Neurons convert stimulation into a nerve impulse that enters afferent neurons. The latter are located predominantly in the ganglia of the spinal cord, only visual and olfactory signals go directly to the brain. This is due to the importance of the information they provide. Here also is involved, ensuring the specified position of a person’s eyes even in the dark; this phenomenon is ensured automatically and affects coordination.
The dorsal roots of the spinal cord and cranial nerves perceive the information received and transmit it further to afferent neurons or to the upper parts of the central nervous system, which are responsible for a specific type of impulse. Special centers in the brain stem help in this process, analyzing impulses and distributing them according to the type of perception.
The second stage of the reflex arc includes the analysis and processing of information, the results of which trigger an action, which may include:
- muscle contraction;
- secretion;
- release of hormones into the blood and so on.
The result of the action has a significant impact on the subsequent formation of the reflex. Physiology defines this as reverse afferentation, due to which the appropriateness of an action is assessed.
The role of the reverse afferentation link is to ensure the effectiveness of the reflex. If it does not make sense (does not provide safety, does not help get food, eliminate pain, and so on), that is, does not contain “reinforcement,” it has no meaning, and then the reflex arc does not close.
The formation of a recipe is based on the principle that reverse afferentation coincides with the action acceptor. In this case, a stable connection is formed, physiologically provided by a system of neurons connected to each other.
In physiology, this is called a reflex; it can be either innate (positive reinforcements accumulated over generations “work” in it) or acquired. They function as long as the connection is confirmed, that is, all elements of the reflex arc are present.
Thus, the role of reverse afferentation is to create an effective reflex.
Afferentation changed
A person’s perception of irritation does not always occur objectively. It may be affected by:
- environmental conditions;
- state of the body;
- mental changes;
- the effect of certain substances.
Therefore, the incoming information may be changed. Under such conditions, the body reacts differently, which is called altered afferentation.
Periods of special sensitivity to the limitation of afferentation are the times during which a person biasedly perceives his body and its relationship with the outside world. For example, in a state of weightlessness, the sensations emanating from the internal organs become different, and accordingly the body’s reaction changes. Drugs change a person’s perception of the world around them and affect their behavior.
A long-term change in afferentation occurs in sensory disorders, when a person cannot perceive irritation correctly, or mental disorders, when sensory neurons work normally, but the processing and transformation of information is impaired.
In this case, the patient needs corrective work or specialized treatment.
Afferentation helps a person perceive himself and the world around him. It participates in the process of forming reflexes, which greatly simplifies the functioning of the nervous system. However, under the influence of certain factors, it can acquire altered forms, presenting the person with incorrect information.