Human life takes place in interaction with 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 the sensitive ones located along the periphery of the body to the center of the nervous system: or. Most of the signals go exactly to the brain, more precisely, to its cortex.
Receptors that perceive irritation are located both in the sense organs and in the internal organs. When information comes from outside, it is necessary for orientation in space and making decisions about future action and is called situational afferentation.
Internal signals provided by the interoception of physiology or nerve endings located inside the body provide information about the state of the body itself, allowing you to feel “malfunctions” that indicate health problems in time.
In psychology, afferentation refers to the flow of nerve impulses from the sense organs and internal organs human to the central nervous system.
The process of perception begins with stimulation of sensitive neurons.
Any signal can serve as its source:
- stream of light;
- sound vibrations;
- airborne chemicals;
- thermal radiation and others.
Neurons convert irritation into a nerve impulse that enters afferent neurons. The latter are located mainly 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, and is involved, providing a given position of the human eye even in the dark, this phenomenon is provided automatically and affects coordination.
The posterior roots of the spinal cord and cranial nerves perceive the received information and transmit it further to afferent neurons or to the upper sections of the central nervous system responsible for a particular type of impulse. Help in this process are special centers in the brain stem that analyze impulses and distribute them according to the type of perception.
The second stage of the reflex arc includes the analysis and processing of information, as a result of which an action is called, which may consist of:
- muscle contraction;
- release of a secret;
- the release of hormones into the blood and so on.
The result of the action has a significant influence on the formation of the reflex in the future. Physiology defines this as a reverse afferentation, due to which the assessment of the expediency of an action occurs.
The role of the back afferent link is to ensure the effectiveness of the reflex. If it has no meaning (does not provide security, 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 the recipe is based on the principle that the reverse afferentation coincides with the action acceptor. In this case, a stable connection is formed, physiologically provided by a system of neurons fastened together.
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 back afferentation is to create an effective reflex.
Afferentation modified
A person's perception of irritation does not always occur objectively. It may be affected by:
- environmental conditions;
- body condition;
- mental changes;
- the action of certain substances.
Therefore, incoming information can be changed. Under such conditions, the body reacts differently, which is called altered afferentation.
Periods of special sensitivity to the limitation of afferentation is the time during which a person 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 reaction of the body changes. Narcotic substances change a person's perception of the world around, affects his behavior.
A long-term change in afferentation occurs with sensory disorders, when a person cannot perceive the stimulus 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. It is involved in the process of formation of reflexes, which greatly simplifies the work of the nervous system. However, under the influence of certain factors, it can acquire altered forms, presenting incorrect information to a person.
Any change in the result is controlled by the corresponding receptors. Afferent impulses arising in the receptors of the functional system enter the corresponding nerve centers along afferent pathways. It is called "reverse afferentation", as it constantly signals the state of a useful adaptive result of a functional system. Under the influence of reverse afferentation, executive mechanisms are selectively involved in the functional system, aimed at restoring what is required for metabolism or social activities result. The reverse afferentation is thus the core basis by which all stages of behavior are evaluated to achieve a useful result and which determines the processes of self-regulation of each functional system. With its help, the central nervous system can regulate the adaptive reactions of the whole organism in accordance with the needs of the organism and environmental conditions. The presence of a back afferent link makes each functional system a cyclic self-regulating organization.
Dynamics of the functional system. The central link of the functional system of any level of organization is beneficial for the body adaptive result. The deviation of this result from the level that ensures the normal vital activity of the organism is immediately perceived by the receptor apparatus and selectively mobilizes special nervous apparatus through nervous and humoral feedback afferentation. The latter, through executive mechanisms, including vegetative reactions and behavior, return a useful adaptive result to the level necessary for normal metabolism. All these processes proceed continuously with constant informing of the center of the functional system about the achievement or non-achievement of a useful adaptive result.
Cybernetic properties of functional systems. In functional systems, general cybernetic properties are manifested, including regulation by the final effect and information exchange. In cybernetics, regulation by the final effect is known to be called feedback. Feedbacks were discovered by N. Wiener in technical devices, and P.K. Anokhin discovered them in living organisms in the form of "reverse afferentation", which was a recognized priority of Russian science in the field of physiological cybernetics.
Table of contents of the topic "Neurology - the doctrine of nervous system.":>General characteristics of the nervous system in terms of cybernetics is 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: a link is the flow of information that occurs through a certain input channel of information and is performed as follows:
A. The message arising from the source of information arrives at the receiving end of the information channel - receptor. Receptor is an encoder that takes 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 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 sense organs (exteroceptors); internal entrances: a) through the organs of plant life (innards) - interoceptors; b) through the organs of animal life (soma, own body) - proprioceptors. II link - information processing. It is performed by a decoding device, which consists of the cell bodies of the afferent neurons of the nerve ganglions and the nerve cells of the gray matter of the spinal cord, cortex and subcortex of the brain, which form the nervous network of the gray matter of the central nervous system. III link - management. It is achieved by the transmission of 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. through 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 general principle feedback to control and coordinate processes occurring both in modern automata and in living organisms; from this point of view, in the nervous system one can distinguish between the feedback of the working organ with the nerve centers, the so-called back afferentation. This name means the transmission of signals from the working body 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 induces nerve (sensory) impulses in the executive organ, which afferent pathways come back to the spinal cord and brain and signal that the working body 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 fulfillment of an order on the periphery. Thus, when taking an object with the hand, 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 circuit to the efferent neurons that transmit motor impulses to the muscles of the hand, which produce the actions necessary to take the subject of the action. Muscles simultaneously act on 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 the chains of reflexes continues until the distance between the hand and the object is zero, that is, until the hand takes the object.
Consequently, self-checking of the work of the organ is carried out all the time, which is possible due to the mechanism "reverse afferentation", which has the character of a vicious circle in the sequence: center (device that sets the program of action) - effector (motor) - object (working organ) - receptor (receiver) - center.
Physiology subject.
Physiology - studies the vital activity of the body and its individual parts: cells, tissues, organs, systems.
sections of physiology:
1. general physiology studies the 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 the changes that occur in the process of evolution
4. in human physiology. age, clinical physiology, physiology of labor and sports, aviation and space.
The task of physiology is to understand how the machine works. human body, to determine the meaning of each of its parts, to understand how these parts are connected, how they interact, and how the result is obtained from their interaction - the overall work of the organism ”(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 allows you to study some function in a short period of time. Disadvantages: anesthesia, trauma, blood loss can pervert the normal function of the body. 2 - a chronic experiment allows for a long time to study the functions of the body in conditions of its normal interaction with the environment. History of development of physiology. Initially, ideas about the functions of the body were formed on the basis of the work of scientists Ancient Greece and Rome: Aristotle, Hippocrates, Gallen, and others, 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 and 20th centuries physiology is developing rapidly. So, studies of tissue excitability were carried out by K. Bernard, Lapik. A significant contribution was 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's inhibition), respiration, fatigue processes, etc. In his work "Reflexes of the Brain" (1863), he developed the idea of the reflex nature of the processes occurring in the brain, including thought processes. Sechenov proved the determinism of the psyche external conditions, i.e. its dependence on external factors. An 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, blood circulation, developed new approaches to conducting physiological experience "methods of chronic experience". For work on digestion in 1904 he was awarded Nobel Prize. Pavlov studied the main processes occurring in the cerebral cortex. Using the method of conditioned reflexes developed by him, he laid the foundations of the science of higher nervous activity. In 1935, at the World Congress of Physiologists I.P. Pavlov was named the patriarch of the 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 involving NS. There are classifications of reflexes:
According to the method of evoking, unconditioned reflexes and conditioned reflexes are distinguished. There are exteroceptive reflexes (skin), interoceptive reflexes (internal organs), proprioceptive reflexes (receptors of muscles, tendons, joints). Depending on the levels of brain structure, there are spinal, tabular, mesencephalic, diencephalic, cortical reflex reactions.
According to their biological purpose, reflexes are divided into food, defensive, sexual, etc. The nervous system works on the principle of reflection: stimulus - response. For the implementation of 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, intercalary neuron, lying in the central nervous system,
motor neuron (centrifugal, efferent), working organ. Reverse afferentation is 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 organ of the performer and to the receptors. The term was first proposed by Anokhin
Classification of nerve fibers. 2Laws of conduction of excitation along the nerves. 3Mechanism of nerve impulse conduction along unmyelinated and myelinated nerve fibers
1. The function of rapid transmission of excitation to and from the nerve cell is performed by its processes - dendrites and axons, i.e. nerve fibers. Depending on the structure, they are divided into fleshy, having a myelin sheath, and non-fleshless. This membrane is formed by Schwann cells. They contain myelin. It performs isolating and trophic functions. Areas where the sheath 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 proprioreceptors. Aγ - efferent fibers going to the 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 violated during transection, the second - by the action of substances blocking the conduction, for example, novocaine. The law of bilateral conduction of excitation. It spreads in both directions from the site of irritation. In the body, most often, excitation goes to the neuron along the afferent paths, and away from the neuron along the efferent paths. Such propagation is called orthodromic.
The Law of Isolated Conduct. Excitation is not transmitted from one nerve fiber to another, which is part of the same nerve trunk. Law of non-decrement holding. Excitation is conducted along the nerves without attenuation.
Parathyroid glands.
A person has 2 pairs of parathyroid glands located on the back surface or submerged inside the thyroid gland. The main, 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 demineralization of the bone and an increase in the calcium content 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, an 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 calcium reabsorption. Influencing calcium metabolism, parathyroid hormone simultaneously affects the metabolism of phosphorus in the body: it inhibits the reabsorption of phosphates and enhances 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, then this leads to a decrease in the secretion of parathyroid hormone. A decrease in the level of calcium in the blood causes an increase in the production of parathyroid hormone. Removal of the parathyroid glands in animals or their hypofunction in humans leads to an increase in neuromuscular excitability, which is manifested by fibrillar twitches of single muscles, turning into spastic contractions of muscle groups, mainly the limbs, face and neck. 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, 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 Item. 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. The 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 into trypsin and chymotrypsin under the action of enterokinase. The volume of secretion of acinar cells is small, and the amount of pancreatic juice is mainly determined by the secretion of duct cells, in which the liquid part of the secret is produced, its ionic composition and quantity change due to reabsorption and ion exchange. There are three phases of secretion of pancreatic juice: 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; secretion of pancreatic juice begins 1-2 minutes after a meal. Irritation of the nuclei of the anterior and intermediate hypothalamic regions stimulates secretion, and the posterior one 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 has 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 a large amount of pancreatic juice, it ensures the creation of a neutral environment. Cholecystokinin - a polypeptide hormone of the upper small intestine, stimulates the secretion of pancreatic juice, rich in digestive enzymes and depleted in bicarbonates.
On secretory function of the Item. hormones of the thyroid and parathyroid glands, adrenal glands.
Endocrine(incretory) function of the Item. 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 lowering it. Glucagon has the opposite effect. Its main physiological role is to regulate blood glucose levels by increasing it; in addition, it affects the 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. The 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 a cholecystokinin antagonist 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 adrenal norepinephrine 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 excreted during starvation.
Indirect hormones. 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 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 pituitary gland and chromaffin cells of the adrenal glands. It enhances filtration, 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 capillary wall of the glomerulus decreases. As a result, the filtration rate is reduced. At the same time, angiotensin II stimulates the release of aldosterone by the adrenal glands. Aldosterone enhances tubular sodium reabsorption and water reabsorption. There is a delay of water and sodium in the body. The action of angiotensin is accompanied by an increase in the synthesis of antidiuretic hormone from 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 androgens and estrogens in the blood. The first are formed in the adrenal glands, the second - in the ovaries.
45 . Sex glands. Male and female sex hormones and their physiological role in sex formation and regulation of reproductive processes. In the male gonads (testicles) there are processes of spermatogenesis and the formation of male sex hormones - androgens. Spermatogenesis is carried out due to the activity of spermatogenic epithelial cells, which are contained in the seminiferous tubules. Androgen production occurs in the 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 increase, the male type of hair appears, and the tone of the voice changes. In addition, testosterone enhances protein synthesis (anabolic effect), which leads to an acceleration of growth processes, physical development, and an increase in muscle mass. Testosterone accelerates the formation of the protein matrix of the bone, enhances the deposition of calcium salts in it. As a result, bone growth, thickness and strength increase. With hyperproduction of testosterone, metabolism accelerates, the number of red blood cells increases in the blood. The secretion of testosterone is regulated by the luteinizing hormone of the adenohypophysis. With an increase in the content of testosterone in the blood, the production of luteinizing hormone is inhibited by a negative feedback mechanism. A decrease in the production of both gonadotropic hormones - follicle-stimulating and luteinizing, also occurs when the processes of spermatogenesis are accelerated. 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 features of a man.
Female gonads. The female gonads (ovaries) produce estrogen and progesterone. The secretion of these hormones is characterized by a certain cyclicity associated with a change in the production of pituitary gonadotropins during the menstrual cycle. The secretion of gonadotropins is inhibited by a high content of female sex hormones in the blood. During pregnancy, the secretion of estrogens 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 corpus luteum hormone; its production increases at the end of the menstrual cycle. The main purpose of progesterone is to prepare the endometrium for the 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 increase. The processes of proliferation and growth of glands in the endometrium are enhanced. Estrogens accelerate the development of the mammary glands, affect the development of the bone skeleton by enhancing the activity of osteoblasts. The action of these hormones leads to an increase in protein biosynthesis; the formation of fat is also enhanced, the excess of which is deposited in the subcutaneous base, which determines the external features of the female figure. Under the influence of estrogens, female-type hair develops: the skin becomes thinner and smoother, as well as well vascularized.
Insufficient secretion of female sex hormones entails the cessation of menstruation, atrophy of the mammary glands, vagina and uterus.
46. Blood, its quantity, properties and functions. The composition of the blood. Basic physiological constants of blood.
Blood, lymph, tissue fluid yavl. the internal environment of the body, in which many processes of homeostasis take place. Blood is a liquid tissue and together with hematopoietic and depositing organs (bone marrow, lymph nodes, spleen) forms the physiological blood system. In the body of an adult, about 4-6 liters of blood or 6-8% of body weight. The main functions of the blood are:
1. Transport, it includes: a. respiratory - transport breathe. gases O2 and CO2 b. trophic - the transfer of nutrients, vitamins, microelements; in. excretory - transport of metabolic products to the excretory organs;
d. thermoregulatory - removal of excess heat from the internal organs and brain to the skin; e. regulatory - the transfer of hormones and other substances.2. Homeostatic. a. maintaining the pH of the internal environment of the body; b. maintaining a constant ionic and water-salt balance, osmotic pressure.
Z. Protective function. It is provided by immune antibodies contained in the blood, specific. antiviral and antibacterial. in-you, phagocytic activity of leukocytes. 4.Hemostatic Fx. The blood has an enzymatic coagulation system that prevents bleeding. Blood consists of plasma and shaped elements suspended in it: erythrocytes, leukocytes and platelets. The ratio of the volume of formed elements and plasma is called hematocrit. Normally, formed elements occupy 42-45% of the 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 and K, Cl 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 the blood, it is called hypotonic (0.3%. NaCl).
47. Physiological mechanisms for maintaining a constant acid-base balance.
Buffer systems of the blood. Parameters of acid-base balance. Provided by lungs, kidneys. Utilities, 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 anions and protons are again formed carbonic acid, which, under the influence of the enzyme carbonic anhydrase, is split into carbon dioxide and water. They breathe out. Through the kidneys, non-volatile organic and inorganic acids are excreted from the blood. They are excreted both in the 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 that enter the blood and increase its alkaline reserve.
Synthesis of ammonia, the cation of which can bind to the cation, hydrogen. Reabsorption in the tubules from the primary urine into the blood of bicarbonates. Filtration of excess acid and alkaline compounds into the urine. The importance of the digestive organs to maintain 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 bicarbonates. But at the same time, both protons and bicarbonates are reabsorbed into the blood. As a result, the reaction of the blood does not change. The acid-base balance of the blood is characterized by several indicators Actual pH. This is the actual pH value of the blood. Normal pH = 7.35-7.45.
Partial voltage CO2 (PC02). Milking arterial blood 36-44 mm. rt. Art. Standard blood bicarbonate (SB). The content of bicarbonate (bicarbonate) anions at normal saturation of hemoglobin with oxygen. The value is 21.3 - 24.3 mol / l. Actual blood bicarbonate (AB). True concentration of bicarbonate anions. Normally, it practically does not differ from the standard one. Buffer bases (BB). The total sum of all buffering anions under standard conditions. 40-60 mol/l.
A shift in the reaction of the blood to the acid side is called acidosis, to the alkaline side is called alkalosis. These pH changes can be respiratory and non-respiratory or metabolic. Respiratory changes in the reaction of the blood are due to changes in the content of carbon dioxide. Non-respiratory - bicarbonate anions. Changes in pH can be compensated and uncompensated. If the reaction of the blood does not change, then these are compensated alkalosis and acidosis. Shifts are compensated by buffer systems, primarily bicarbonate. Therefore, they are observed in a healthy body. With a lack or excess of buffer components, partially compensated acidosis and alkalosis occur, but the pH does not go beyond the normal range. If the blood reaction is less than 7.29 or more than 7.56, uncompensated acidosis and alkalosis are observed. The most formidable 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 the electrolyte composition, artificial ventilation, etc.
Buffer systems are a complex of weak acids and bases that can prevent the reaction from shifting in one direction or another. The blood contains the following buffer systems:
Bicarbonate or bicarbonate. 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 hydrocarbons. 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 hydrophosphate 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 with sodium hydrogen phosphate and sodium dihydrogen phosphate (Na2HPO4 + H2CO3 = NaHCO3 + NaH2PO4) 3. protein buffer system. Proteins are a buffer due to their amphoteric nature (they are either alkaline or acid properties). Although the buffer capacity of the protein system is small, it plays 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 leads to 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. With the dissociation of oxyhemoglobin in the capillaries of tissues 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. Anions of carbonic acid bind to potassium cations in erythrocytes and sodium cations in blood plasma. Potassium and sodium bicarbonates are formed, preserving the buffering capacity of the blood. In addition, reduced hemoglobin can directly bind to carbon dioxide to form carbohemoglobin. It also prevents the blood reaction from shifting to the acid side. The acid-base balance of the blood is characterized by several indicators: Actual pH. This is the actual pH value of the blood. Normal pH \u003d 7.35-7.45. Partial voltage of CO2 (PC02). Milking arterial blood 36-44 mm. rt. Art. Standard blood bicarbonate (SB). The content of bicarbonate (bicarbonate) anions at normal saturation of hemoglobin with oxygen. The value is 21.3 - 24.3 mol / l. Actual blood bicarbonate (AB). True concentration of bicarbonate anions. Normally, it practically does not differ from the standard one. Buffer bases (BB). The total sum of all buffering anions 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 the plasma is 1.025-1.029 g/cm3, the viscosity is 1.9-2.6. Plasma contains 90-92% water and 8-10% solids. The composition of the dry residue includes minerals (about 0.9%), mainly sodium chloride, potassium, magnesium, calcium cations, chloride anions, bicarbonate, phosphate anions. In addition, it contains glucose, as well as protein hydrolysis products - urea, creatinine, amino acids, etc. They are called residual nitrogen. The content of glucose in plasma is 3.6-6.9 mmol/l, residual nitrogen is 14.3-28.6 mmol/l.
Plasma proteins are of particular importance. Their total number is 7-8%. Proteins are composed of several fractions, but highest value have albumins, globulins and fibrinogen. Albumin contains 3.5-5%, globulins 2-3%, fibrinogen 0.3-0.4%. With normal nutrition, about 17 g of albumin and 5 g of globulins are produced daily in the human body.
Plasma albumin functions: 1. Create most of the oncotic pressure, providing normal distribution water and ions between blood and tissue fluid, urination. 2. They serve as a protein reserve of blood, which is 200 g of protein. It is used by the body during protein starvation. 3. Due to the negative charge, they contribute to stabilization and prevent the sedimentation of blood cells. 4. Maintain acid-base balance, being a buffer system. 5. Carry sex hormones, bile pigments and calcium ions. The same functions are performed by other fractions of proteins, 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 carries 90% of the copper ions required by the body.
5. Carry hormones thyroxine and cortisol
6.b-globulin transferrin carries the bulk of the iron.
7.Several b-globulins are blood coagulation factors.
8.g-globulins perform a protective function, being immunoglobulins. With diseases, their number in the blood increases.
Fibrinogen is a soluble protein precursor of fibrin, from which a blood clot forms.
Oncotic (colloidal osmotic) pressure of blood plasma is part of the osmotic pressure created by blood plasma proteins. Normally 25-30 mm Hg. Art. Depends more 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) - the force that ensures the movement of the solvent through a semipermeable membrane that separates solutions with different concentrations of substances. It is determined by the total concentration of various particles of blood plasma (ions and molecules).
49. . Erythrocytes. Their structure and functions. Hemolysis, its types.
Erythrocytes (E) are highly specialized. non-nucleated 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. Due to the shape of the surface E for the diffusion of gases. In addition, it is their plasticity. Due to the high plasticity, they are deformed and easily pass through the capillaries. The old and the pathologist. E plasticity is low. Therefore, they linger in the capillaries of the reticular tissue of the spleen and are destroyed there. Membrane E passes O2 and CO2 molecules well. The membrane contains up to 52% protein. Na / K-ATPase is built into it, removing Na from the cytoplasm and pumping in K ions. The main mass of E is hemoglobin chemoprotein.
Functions E: O2 transfer from lungs to 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 men's blood contains 4.5-5.0 million Oe (4.5-5.0 * 1012 l). Women - 3.7-4.7 million (3.7-4.7 * 10 liters). Hemolysis - the destruction of the E membrane and the release of hemoglobin into the plasma. As a result, the blood becomes transparent. 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.pathologist. forms E. There are two mechanisms. Intracellular. hemolysis occurs in macrophages of the spleen, bone marrow, and liver cells. Intravascular., in small vessels, from which Hb is transferred with the help of plasma protein to the liver cells. There, the heme of hemoglobin is converted to bilirubin. About 6-7 g of Hb is destroyed per day.
2. Pathological. According to the mechanism of occurrence:
1.Chemical. When exposed to E-s substances, dissolving 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 with mechanical membrane ruptures. 4. Biological. These are hemolytic poisons of bacteria, insects, snakes. As a result of a transfusion of incompatible blood. 5.Osmotic. Occurs if the E-s got into the environment with an osmotic pressure lower than that of the blood. Water enters the E-s, they swell and burst.
50. Varieties 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 formed by four subunits, each of which includes a heme connected to an iron atom and the protein part of a 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, erythrocytes contain hemoglobin of the GI and G2 types. In subsequent periods of intrauterine development and in the first months after birth, the main part is fetal hemoglobin (F-hemoglobin). It has two a- and two g-polypeptide chains in its structure.
One gram of hemoglobin is capable of binding 1.34 ml of oxygen. The combination of hemoglobin with oxygen, which is 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 the capillaries of tissues is called deoxyhemoglobin or reduced (Hb). It has a dark cherry color. From 10 to 30% of carbon dioxide entering the blood from tissues combines with the amide group of hemoglobin. An easily dissociating compound carbhemoglobin (HbCO 2) 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 with carbon monoxide is much higher than with oxygen, and the rate of dissociation 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 monoxide 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 ferric. Therefore, methemoglobin is a very weakly dissociating compound. It does not give oxygen to the tissues.
All hemoglobin compounds have a characteristic spectrum.
Hemoglobin forms a brown compound with hydrochloric acid - hydrochloric hematin. The shape of its crystals depends on the type of blood. The hemoglobin content is determined by the Saly method. Saly's hemometer consists of 3 test tubes. Two of them, located to the side of the central one, are filled with a standard solution of brown hematin hydrochloride. The middle tube is graduated in units of hemoglobin. 0.2 ml of hydrochloric acid is poured into it. Then, 20 µl of blood is collected with a measuring pipette and released into hydrochloric acid. Mix the contents of the tube and incubate for 5 minutes. The resulting solution of hematin hydrochloride is diluted with water until its color is the same as in the side test tubes. The content of hemoglobin 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 with blood loss, intoxication, impaired erythropoiesis, lack of iron, vitamin B 12, etc. In addition, a color index is determined. This is the ratio of hemoglobin in the blood to the number of red blood cells. Normally, its value is 0.85-1.05.
51. Leukocytes, their types. Functions of various types of leukocytes.
Leukocytes are blood cells containing a nucleus. In some leukocytes, the cytoplasm contains granules - granulocytes. In others, granularity is absent - agranulocytes. There are three forms of granulocytes. Eosinophils, basophils, neutrophils. Agranulocytes are subdivided into monocytes and lymphocytes. All granulocytes and monocytes are produced in the red bone marrow. Lymphocytes are also image. from bone marrow stem cells, but multiply in the lymph nodes, appendix, spleen, thymus ..
The principle of subordination of nerve centers (the principle of subordination) manifests itself in the form of a regulatory influence of the higher located nerve centers on the lower ones. So, the motor centers of the brain control the spinal motor neurons. An example of such influence is the phenomenon central braking spinal reflexes discovered by I.M. Sechenov and called Sechenov inhibition. In the experiment of I.M. Sechenov, stimulation of the visual tubercles of a frog with a salt crystal (i.e., irritation of the reticular formation of the midbrain) led to inhibition of spinal motor reflexes caused by immersion of the frog's foot in a weak acid solution. Consequently, the inhibition of the centers of the spinal cord was a consequence of the excitation of the centers of the midbrain. The termination of this inhibitory control during a break in the cerebrospinal pathways causes a sharp increase in the excitability of the spinal centers and hyperreflexia.
Back afferent principle
The principle of reverse afferentation lies in the receptor perception of the results of the reflex act and the transmission of information back to the structures of the nerve center, where it is processed and compared with the remaining parameters of excitation. Back afferentation is realized in the form of positive or negative feedback. Thus, with the help of reverse afferentation, the nerve centers continuously monitor the effectiveness, expediency and optimality of reflex activity.
| 2) The main functions of the limbic system: 1) participation in the formation of food, sexual, defensive instincts; 2) regulation of vegetative-visceral functions; 3) formation social behavior; 4) participation in the formation of the mechanisms of long-term and short-term memory; 5) performance of the olfactory function; 6) inhibition of conditioned reflexes, strengthening of unconditioned ones; 7) participation in the formation of the wake-sleep cycle. thalamus à cingulate gyrus cortex à parahippocampal gyrus à hippocampus). This circle has to do with memory and learning processes. The limbic system is related to the regulation of the level of reaction of the autonomous, somatic systems during emotional and motivational activity, the regulation of the level of attention, perception, reproduction of emotionally significant information. The limbic system determines the choice and implementation of adaptive forms of behavior, the dynamics of innate forms of behavior, the maintenance of homeostasis, and generative processes. Finally, it ensures the creation of an emotional background, the formation and implementation of the processes of higher nervous activity. |
The word limbic means borderline. The term was originally used to describe the structures that bound the basal regions. big brain, but with the accumulation of knowledge about the functions of the limbic system, the term "limbic system" has expanded to refer to the entire neural circuit that controls emotional behavior and motivational arousal. The main part of the limbic system is the hypothalamus and related structures. In addition to being involved in the regulation of behavioral responses, these areas control many indicators of the internal environment of the body, such as body temperature, osmolality of body fluids, body weight, and the need for food and fluids. All these functions are called autonomic functions of the brain, and their regulation is closely related to behavior.
Ticket 10
There are the following methods for studying the functions of the central nervous system:
1. The method of transections of the brain stem at various levels. For example, between the medulla oblongata and the spinal cord.
2. The method of extirpation (removal) or destruction of parts of the brain.
3. Method of irritation of various departments and centers of the brain.
4. Anatomical and clinical method. Clinical observations of changes in the functions of the central nervous system in case of damage to any of its departments, followed by a pathoanatomical study.
5. Electrophysiological methods:
a. electroencephalography - registration of brain biopotentials from the surface of the skin of the skull. The technique was developed and implemented in the clinic by G. Berger.
b. registration of biopotentials of various nerve centers; used in conjunction with stereotaxic technique, in which electrodes are inserted into a strictly defined nucleus with the help of micromanipulators.
in. the method of evoked potentials, registration of the electrical activity of brain regions during electrical stimulation of peripheral receptors or other regions;
6. method of intracerebral administration of substances using microinophoresis;
7. chronoreflexometry - determination of the time of reflexes.
The diencephalon consists of the thalamus and hypothalamus, they connect the brain stem with the cerebral cortex.
The thalamus is a paired formation, the largest accumulation of gray matter in the diencephalon.
Topographically, the anterior, middle, posterior, medial and lateral groups of nuclei are distinguished.
By function, they are distinguished:
1) specific:
a) switching, relay. They receive primary information from various receptors. The nerve impulse along the thalamocortical tract goes to a strictly limited area of the cerebral cortex (primary projection zones), due to this, specific sensations arise. The nuclei of the ventrabasal complex receive an impulse from skin receptors, tendon proprioceptors, and ligaments.
The impulse is sent to the sensorimotor zone, the body orientation in space is regulated;
b) associative (internal) nuclei. The primary impulse comes from the relay nuclei, is processed (an integrative function is carried out), transmitted to the associative zones of the cerebral cortex;
2) non-specific nuclei. This is a non-specific way of transmitting impulses to the cerebral cortex, the frequency of the biopotential changes (modeling function);
Physiological role - the highest subcortical integrative center of the autonomic nervous system, which has an effect on:
1) thermoregulation. The anterior nuclei are the center of body output. The posterior nuclei are the center of heat production and the preservation of heat when the temperature drops;
2) pituitary. Liberins promote the secretion of hormones of the anterior pituitary gland, statins inhibit it;
3) fat metabolism. Irritation of the lateral (nutrition center) nuclei and ventromedial (satiation center) nuclei leads to obesity, inhibition leads to cachexia;
4) carbohydrate metabolism. Irritation of the anterior nuclei leads to hypoglycemia, the posterior nuclei to hyperglycemia;
5) the cardiovascular system. Irritation of the anterior nuclei has an inhibitory effect, the posterior nuclei - an activating one;
6) motor and secretory functions of the gastrointestinal tract. Irritation of the anterior nuclei increases motility and secretory function of the gastrointestinal tract, the posterior nuclei - inhibits sexual function;
7) behavioral responses. Irritation of the starting emotional zone (anterior nuclei) causes a feeling of joy, satisfaction, erotic feelings.
Ticket number 11
1. Functions and role of the hypothalamus in the implementation of autonomic metabolic functions.
2. The concept of instincts. Types of instincts. Forms of learning.
1) The hypothalamus is the highest subcortical center of the autonomic nervous system. In this area there are centers that regulate all vegetative functions, ensure the constancy of the internal environment of the body, as well as regulate fat, protein, carbohydrate and water-salt metabolism.
The hypothalamus is involved in the regulation of almost all autonomic functions. It regulates the cardiovascular system, digestive organs, water-salt, carbohydrate, fat and protein metabolism, urination, the functions of the endocrine glands, and maintains body temperature. Complex reactions occur in the hypothalamus, which are supplemented by a hormonal component.
Excitation of the posterior nuclei of the hypothalamus causes: dilation of the pupils and palpebral fissures, increased heart rate, vasoconstriction and increased blood pressure, inhibition of the motor function of the stomach and intestines, an increase in the blood levels of adrenaline and noradrenaline, an increase in blood glucose.
The responses that occur when different parts of the hypothalamus are irritated have a feature that consists in the participation of many organs of the body in them. The nuclei of the hypothalamus are involved in many, including behavioral reactions. So, the hypothalamus is involved in sexual and aggressive-defensive reactions.
The hypothalamus provides the vegetative component of all the complex reactions of the body, through the implementation of the functions of the sympathetic and parasympathetic divisions of the autonomic nervous system and the secretory functions of the endocrine glands. However, he does not have direct ties with the authorities. It affects through changes in the activity of the spinal and stem centers of the autonomic nervous system.
2) Instinct - a set of innate complex reactions of the body that occur, as a rule, almost unchanged in response to external or internal stimuli. Any instinct consists of a chain of reactions in which the end of one link serves as the beginning of another.
Instincts are classified according to their biological and physiological significance. food, manifested in the form of food production, the capture of food, the accumulation of its reserves, etc .; defensive, consisting of both passive defensive reactions (running away, "freezing", "hiding"), and active defense with the help of teeth, claws, horns, etc.
Man's instincts are largely subordinate to his conscious activity formed in the process of education. Already in the fetal period, individual structures of the nervous system of the embryo mature faster than others, thereby ensuring the readiness of the newborn organism to survive in specific conditions of existence for it.
Learning is the development of adaptive forms of behavior in the process of ontogenesis. In higher animals and humans, instinctive behavior and learning do not exist in behavior on their own, but are intertwined into a single behavioral act.
Passive (reactive) learning takes place in all cases when the body, without making purposeful efforts, reacts to some external factors;
operant learning(from lat. operatio - action) - this is learning, during which the body achieves a useful result with the help of active behavior.
Ticket number 12
1. Physiology of the reticular formation of the brain stem. Influence of RF on various body functions.
The reticular formation (RF) is a network of neurons various types and sizes, having numerous connections with each other, as well as with all the structures of the central nervous system. It is located in the thickness of the gray matter of the medulla oblongata, midbrain and diencephalon and regulates the level of functional activity (excitability) of all nerve centers of these parts of the central nervous system. In the same way, it affects the CBP.
2. Conditioned reflexes. Types of conditioned reflexes.
Conditioned reflexes are acquired, are not inherited, appear to any stimulus, are unstable, can develop and disappear, do not have ready-made reflex arcs, they are formed under certain conditions on the basis of unconditioned reflexes, and are carried out due to the activity of the cerebral cortex. For example, opening the doors of an apartment with a key, turning on the TV with a remote control, brushing your teeth in the morning - in general, almost everything.
Ticket 13
1. Subcortical nuclei (basal ganglia) and their role in regulation
motor functions of the body.
2. Specific features of human GNI. The concept of signal
systems.
1. In addition to the cortex, which forms the surface layers of the telencephalon, the gray matter in each of the cerebral hemispheres lies in the form of separate nuclei, or nodes. These nodes are located in the thickness of the white matter, closer to the base of the brain. Accumulations of gray matter in connection with their position are called basal (subcortical, central) nuclei or nodes. The basal nuclei of the hemispheres include the striatum, consisting of the caudate and lenticular nuclei, the fence and the amygdala. The striatum got its name due to the fact that on horizontal and frontal sections of the brain it looks like alternating bands of gray and white matter. Most medially and in front is the caudate nucleus. It is located anterior to the thalamus, from which (on a horizontal section) it is separated by a strip of white matter - the anterior leg of the internal capsule. The anterior part of the caudate nucleus is thickened and forms a head, which forms the lateral wall of the anterior horn of the lateral ventricle. Located in the frontal lobe of the hemisphere, the head of the caudate nucleus adjoins the anterior perforated substance. At this point, the head of the caudate nucleus connects to the lenticular nucleus. Tapering posteriorly, the head continues into a thinner body, which lies in the region of the bottom of the central part of the lateral ventricle and is separated from the thalamus by a terminal strip of white matter. The posterior part of the caudate nucleus - the tail gradually becomes thinner, bends downward, participates in the formation of the upper wall of the lower horn of the lateral ventricle. The tail reaches the amygdala, which lies in the anteromedial temporal lobe (behind the anterior perforated substance). Lateral to the head of the caudate nucleus is a layer of white matter - the anterior leg (femur) of the internal capsule, which separates this nucleus from the lenticular nucleus. The lenticular nucleus, which received its name for its resemblance to the lentil grain, is located lateral to the thalamus and caudate nucleus. The lenticular nucleus separates the posterior leg (thigh) of the internal capsule from the thalamus. The lower surface of the anterior part of the lenticular nucleus is adjacent to the anterior perforated substance and is connected to the caudate nucleus. The medial part of the lentiform nucleus on a horizontal section of the brain narrows and faces the knee of the internal capsule, located on the border of the thalamus and the head of the caudate nucleus. The lateral surface of the lentiform nucleus is convex and faces the base of the insular lobe of the cerebral hemisphere. On the frontal section of the brain, the lentiform nucleus has the shape of a triangle, the apex of which faces the medial side, and the base - the lateral side. Two parallel vertical layers of white matter, located almost in the sagittal plane, divide the lenticular. core into three parts. The most lateral is the shell, which has a darker color. Medial to the shell are two light cerebral plates - medial and lateral, which unite common name"Pale shore". The medial plate is called the medial pale ball, the lateral plate is called the lateral pale ball. The caudate nucleus and putamen are phylogenetically newer formations. The pale ball is an older formation. The fence is located in the white matter of the hemisphere, on the side of the shell, between the latter and the cortex of the insular lobe. The fence looks like a thin vertical plate of gray matter. It is separated from the shell by a layer of white matter - the outer capsule, from the cortex of the islet - the same layer, called the "outermost capsule." The amygdala is located in the white matter of the temporal lobe of the hemisphere, about 1.5-2.0 cm posterior to the poles.
2. The first signal system of reality is the system of our direct sensations, perceptions, impressions from specific objects and phenomena of the surrounding world. The word (speech) is the second signal system (signal of signals). It arose and developed on the basis of the first signaling system and is significant only in close relationship with it. Thanks to the second signal system (the word), a person more quickly than animals forms temporary connections, because the word carries the socially developed meaning of the subject. Temporary human neural connections are more stable and persist without reinforcement for many years. The word is a means of cognition of the surrounding reality, a generalized and indirect reflection of its essential properties. With the word "a new principle of nervous activity is introduced - distraction and at the same time generalization of countless signals - a principle that determines an unlimited orientation in the surrounding world and creates the highest human adaptation - science." The action of a word as a conditioned stimulus can have the same force as the immediate first signal irritant Under the influence of the word are not only mental, but also physiological processes (this is the basis of suggestion and self-hypnosis). The second signal system has two functions - communicative (it provides communication between people) and the function of reflecting objective patterns. subject, but also contains a generalization.The second signal system includes the word audible, visible (written) and spoken.Typological features of higher nervous activity were considered above.Higher nervous activity of a person is divided into three types: 1) mental; 2) artistic; 3) medium (mixed). The mental type includes persons with a significant predominance of the second signal system over the first. They have more developed abstract thinking (mathematicians, philosophers); a direct reflection of reality occurs in them in insufficiently vivid images. The artistic type includes people with a lesser predominance of the second signaling system over the first. They are characterized by liveliness, the brightness of specific images (artists, writers, artists, designers, inventors, etc.). The average, or mixed, type of people occupies an intermediate position between the first two. The excessive predominance of the second signal system, bordering on its separation from the first signal system, is an undesirable quality of a person. "It must be remembered," said I. P, Pavlov, - that the second signal system matters through the first signal system and in connection with the latter, and if it breaks away from the first signal system, then you turn out to be an idle talker, a talker and will not find a place for yourself in life. The first signal system, as a rule, has a less developed tendency to abstract, theorize. Modern research higher nervous activity are characterized by the development of an integral approach to the study of the integral work of the brain.
In addition to the areas of the cerebral cortex that stimulate muscle contractions, two other brain structures are also important for normal motor function: the cerebellum and the basal ganglia. However, none of these structures can regulate movements independently; they always function in close connection with other motor control systems. The cerebellum mainly plays a role in synchronizing motor functions and ensuring a quick smooth transition from one muscle movement to the next. It also helps to regulate the intensity of muscle contractions with changes in muscle load, and also provides the necessary ongoing interaction between agonist and antagonist muscle groups. The basal ganglia help plan and execute complex motor programs by regulating the relative intensity and direction of individual movements, and by coordinating multiple sequential and parallel movements to perform specific complex motor tasks. Our next articles will outline the underlying mechanisms of cerebellar and basal ganglia function and review the general brain mechanisms underlying the complex coordination of gross motor activity. The cerebellum has long been called the silent area of the brain, largely because electrical stimulation of the cerebellum does not produce any conscious sensation and rarely causes any muscle activity. Removal of the cerebellum, however, leads to a sharp violation of the movements of the body. The cerebellum is especially important during fast movements, such as running, typing, playing the piano, and even talking. The loss of this area of the brain can cause almost complete incoordination of these movements, despite the fact that it does not cause muscle paralysis. Why is the cerebellum so important if it cannot directly cause muscle contractions? The answer is that the cerebellum provides a sequence of movements, and also controls and corrects the body's motor activity during its implementation so that this activity corresponds to the control signals. motor cortex and other parts of the brain. The cerebellum constantly receives updated information about the desired sequence of contractions from the areas of the brain that control movement. It also receives constant sensory information from the peripheral parts of the body, reporting successive changes in the state of each part of the body and its position, speed of movement, forces acting on it, and so on. Based on the sensory information received by the feedback mechanism from the periphery, the cerebellum has the ability to compare real movements with movements planned by the motor system. If there is no match between plan and reality, subconscious corrective signals are immediately sent back to the motor system in order to increase or decrease the levels of activation of certain muscles. In addition, the cerebellum helps the cerebral cortex to plan the next sequence of movement in advance, a fraction of a second before it begins, while the current movement is still in progress, which contributes to a smooth transition from one movement to the next. The cerebellum also knows how to “learn” from its mistakes, i.e. if the movement is not executed exactly as intended, the cerebellar circuit learns to increase or decrease this movement the next time. This possibility is associated with changes in the excitability of the corresponding cerebellar neurons, which allows subsequent muscle contractions to better match the planned movements.
The cerebellum, or small brain, is a suprasegmental structure located above the medulla oblongata and pons, behind the cerebral hemispheres. The cerebellum consists of several parts, different in origin in the evolution of vertebrates.
In humans, the cerebellum consists of two hemispheres located on the sides of the worm. The phylogenetically older part of the mammalian cerebellum includes the anterior lobe and the flocculonodular part of the posterior lobe. These structures of the cerebellum are predominantly associated with the spinal cord and vestibular apparatus, while the hemispheres mainly receive information from muscle and joint receptors, as well as from visual and auditory analyzers. On fig. 5.16 is a diagram of the mammalian cerebellum (see Appendix 6), reflecting the density of vestibular, proprioceptive (from muscles, tendons and joints) and cortical afferent projections to various zones of the cerebellum. According to this classification, the cerebellar cortex is divided into three regions:
1) archicerebellum (old cerebellum) - flocculonodular lobe (lobule X); in it predominantly vestibular afferents and fibers from the vestibular nuclei terminate; vestibular fibers are also partially projected into the uvula (lingula - lobule I) and the caudal part of the sleeve (uvula - lobule IX), which are usually also referred to as archicerebellum;
2) the paleocerebellum (ancient cerebellum) includes the anterior lobe (lobules II–V), the simple lobule (lobule VI), and the posterior part of the cerebellar corpus (lobules VIII–IX); paleocerebellum is closely connected with the spinal cord, and also has bilateral connections with the sensorimotor area of the cerebral cortex;
3) neocerebellum (new cerebellum) includes the middle part of the cerebellar corpus (lobule VII and partially lobules VI and VIII), which receives information from the cerebral cortex, as well as from auditory and visual receptors. Note that the main part of the cerebellar hemispheres belongs to the new cerebellum, which is best developed in humans.
In the thickness of the cerebellum there are three pairs of nuclei: dentate, located laterally; the core of the tent - medially; corky and rounded nuclei - between them.
Ticket 15
1 . Autonomic nervous system (definition). Functional value for the body. Differences between autonomic and somatic NS.
The autonomic nervous system (ANS) has its own centers, afferent and efferent conductors, different from the animal (somatic) nervous system, although many afferent parts are common.
A characteristic structural difference between the ANS and the somatic one is the presence of two peripheral neurons - preganglionic and postganglionic, which is an analogue of a motor neuron, placed on the periphery, outside the spinal cord. In the sympathetic ANS, this neuron is located in the ganglion, in the parasympathetic - intramurally, in the wall of the innervated organ. There are a number of characteristic differences in the structure and functions of the autonomic and sympathetic NS:
1. The presence of a preganglionic and postganglionic neuron in the reflex arc of the ANS.
2. Transection of the anterior roots of the spinal cord causes various changes in the efferent part of the somatic and vegetative arch. In somatic transection, the body of the motor neuron is disconnected from its axon, which leads to degeneration of the latter and the development of deep trophic disturbances and dysfunction in the tissues of the innervated organ.
3. The next significant difference between the ANS and the SNS is in the features of the output of fibers from the brain..
4. There are also differences in the distribution of autonomic and somatic nerves on the periphery.
5. ANS fibers differ from SNS fibers in their smaller diameter and speed of excitation.
2 . Classification of conditioned reflexes. Conditions for the development of conditioned reflexes.
Classification of reflexes. Reflexes are very diverse, and they can be classified according to a variety of criteria.
1. First of all, all reflexes are divided by origin into unconditional and conditional. unconditioned reflexes are inherited, they are fixed in genetic code, and conditioned reflexes are created in the process of individual life on the basis of unconditioned ones.
2. By biological significance, reflexes are divided into food, sexual, defensive, orientation, posture-tonic, locomotor, etc.
3. Depending on the location of the receptors from which this reflex act begins, reflexes are divided into interoceptive and exteroceptive, as well as proprioceptive.
4. Depending on the type of receptors - visual, auditory, gustatory, olfactory, pain, tactile.
5. Depending on the location of the central part of the reflex arc - spinal, bulbar, mesencephalic, diencephalic, cortical.
6. Depending on the duration
response - phasic and tonic.
7. Depending on the nature of the response - motor, secretory, vasomotor.
8. Depending on belonging to a particular organ system or functional system - respiratory, cardiac, digestive, etc.
9. Depending on the external manifestation of the reflex reaction - flexion, rubbing, scratching, blinking, vomiting, sucking, etc.
All these classifications are conditional, and are used only for the convenience of studying some aspect of the organism's activity, because sometimes they can arise simultaneously from the same receptor field and interact with each other in different ways.
Methods for studying each type of reflex can be different and depend on their specifics. You will get to know them in practice.
Ticket number 16
1. Inhibition in the central nervous system. Classification of central braking.
Braking - local nervous process leading to inhibition or elimination of excitation. Unlike excitation, it does not spread through the nervous structures, like PD
Inhibition in the CNS performs two main functions:
First, it coordinates the functions, i.e. it directs excitation along certain paths to certain nerve centers, while turning off those paths and neurons whose activity is not currently needed to obtain a specific adaptive result.
(An example of the importance of the inhibition process for the functioning of the organism can be observed in an experiment with the introduction of strychnine to an animal).
Strychnine (an analeptic) blocks inhibitory synapses in the central nervous system (mainly glycinergic) and, thereby, eliminates the basis for the formation of the inhibition process. Under these conditions, irritation of the animal causes an uncoordinated reaction, which is based on diffuse (generalized) irradiation of excitation.
Secondly, inhibition performs a protective or protective function, protecting nerve cells from overexcitation and exhaustion under the action of superstrong and prolonged stimuli.
In the course of evolution, simultaneously with the process of excitation, inhibitory mechanisms that limited and interrupted it were formed.
Central braking classification
On various grounds:
According to the electrical state of the membrane - depolarization and hyperpolarization;
In relation to the synapse, presynaptic and postsynaptic;
According to the neuronal organization - translational, lateral (lateral), recurrent and reciprocal.
The phenomenon of central inhibition was discovered by I.M. Sechenov in 1862.
The experience was as follows. The GM was cut in the frog at the level of the visual tubercles and the BP was removed. The time of the withdrawal reflex of the hind legs was measured when they were immersed in a weak solution of sulfuric acid. This time is an indicator of the excitability of the nerve centers, since the reflex is carried out by the spinal centers.
If a NaCl crystal is applied to the incision of the optic tubercles, then the reflex time will sharply lengthen. THEM. Sechenov came to the conclusion that there are NCs in the thalamic region of the frog's brain that have an inhibitory effect on the SM reflexes.
2. Physiology of sleep. Types and stages of sleep. Electrophysiological characteristics of sleep.
Sleep is a physiological state of immobility with weakened muscle tone and sharply limited sensory contact with external environment
Sleep is a specific state of the brain and the body as a whole, characterized by significant immobility, an almost complete lack of response to external stimuli, certain phases of the electrical activity of the brain, and specific somatovegetative reactions.
Sleep is a specially organized activity of the brain, aimed at processing the information received during wakefulness and restoring the working capacity of the nervous system.
Sleep types:
DAILY NATURAL:
1. Monophasic and polyphasic sleep
2. Slow-wave or orthodox sleep
3. REM or REM sleep
SEASONAL;
PATHOLOGICAL;
NARCOTIC;
HYPNOTIC
Sleep stages:
1. STAGE OF SLEEP - gradual replacement of the alpha rhythm with low-amplitude theta waves
2. STAGE OF SLEEPING SPINDLES - between two-three-phase slow oscillations, sleepy spindles of high amplitude and frequency (12-16 Hz) arise
3. STAGE OF DELTA WAVE APPEARANCE - up to 50% of the rhythm is periodically occupied by delta waves
4. STAGE OF DEEP DELTA SLEEP - more than 50% of the rhythm is occupied by delta waves
PARADOXICAL SLEEP - RHYTHM DESYNCHRONIZATION EVERY 90-100 MIN
Electrophysiological characteristics of sleep
Electric "whirlwinds" are constantly rushing through the brain. They can be registered by simultaneously recording electrical vibrations from many points of the head. For different physiological states, the resulting electroencephalograms (EEG) will have a peculiar pattern. In the process of transition from wakefulness to sleep, i.e., in the process of falling asleep, as well as during awakening, EEG changes have a fairly definite and consistent order. Although the information contained in the EEG is still far from being deciphered, nevertheless, shifts in the overall electrical activity are quite typical for sleep of different depths, so much so that even methods of automatically controlling the depth of anesthesia are used in surgery. They are based on the timely registration of EEG changes with the help of special devices that monitor its shifts. Features of the EEG during sleep and wakefulness have been known for a long time. However, relatively recently, interesting data have been obtained that have made it possible to re-evaluate their significance.
Animal observations have shown that falling asleep is accompanied by the appearance of slow waves in the electroencephalogram, similar to those observed during low-frequency stimulation of the thalamic nuclei. However, after about an hour, these slow waves characteristic of sleep are large. the amplitudes disappear and are replaced by fast, high-frequency, low-amplitude oscillations characteristic of the waking state of the animal. Nevertheless, there are no signs of awakening at this time, and tests with irritations showed that sleep becomes deeper during this period - stronger stimuli are needed to wake the animal. Such a dream lasts 10-20 minutes, after which slow waves again appear in the EEG of animals.
It is curious that "REM" sleep (i.e., with rapid high-frequency electrical activity) never sets in in animals immediately, but only after a previous period of "slow" sleep (i.e., sleep with slow waves in the EEG). But during a 6-8-hour sleep, attacks of REM sleep usually occur several times, quite regularly, with an interval of about an hour and a half.
American scientists Dement and Kleitman and Frenchman Jouvet called REM sleep "paradoxical" sleep, since the EEG of animals during this period of sleep completely resembles the EEG of waking animals. At the same time, it is precisely this stage that corresponds to the most pronounced shifts in the body characteristic of sleep: complete relaxation of muscles, slowing of heart contractions, lowering of blood pressure, etc. eye movements, twitching of limbs, tail, licking are observed.
During sleep, the subjects recorded electroencephalogram, respiration, electrocardiogram, and with the help of light sensors mounted on the eyelids, eye movements. It turned out that people also have slow rhythms during the night, in the EEG they are replaced by fast ones about 4-5 times (Fig. 3). In these short periods In REM sleep, they also experience rapid eye movements, fluctuating blood pressure, and irregular heart rhythms.
1 Fig. 3. Changes in the electrical activity of the brain in a cat, characteristic of "slow" and "rapid" sleep;
I - initial electrical activity of the brain;
II - stage of "slow" sleep;
III - the stage of "deep" (paradoxical sleep).
Interestingly, if a person is awakened during REM sleep, then in most cases the sleeper will say that he just had a dream. If a person is awakened during a "slow" sleep or 10-15 minutes after a period of "REM" sleep, then he will usually answer that he has not seen any dreams. On this basis, Jouvet and others suggested that people dream during REM sleep. The eye movements observed during this, fluctuations in the heart rate and breathing, apparently reflect the experiences experienced in a dream.
Scientists have tried waking people up during REM sleep to prevent them from dreaming. At the same time, despite the sufficient total duration of sleep, after 5-6 days they had mental disorders. And animals deprived of REM sleep for several days died, although in general they slept.
All this suggests that "fast" sleep is of some particular importance for the vital activity of the body.
Ticket number 17
1. Processes of inhibition in the cerebral cortex. Types of conditional inhibition.
Answer: Inhibition processes in the cerebral cortex.
The formation of a conditioned reflex is based on the processes of interaction of excitations in the cerebral cortex. However, for the successful completion of the process of closing the temporal connection, it is necessary not only to activate the neurons involved in this process, but also to suppress the activity of those cortical and subcortical formations that impede this process. Such inhibition is carried out due to the participation of the inhibition process.
In its outward manifestation, inhibition is the opposite of excitation. With it, a weakening or cessation of the activity of neurons is observed, or a possible excitation is prevented.
Cortical inhibition is usually divided into unconditioned and conditional, acquired. The unconditional forms of inhibition include external, arising in the center as a result of its interaction with other active centers of the cortex or subcortex, and transcendental, which occurs in cortical cells with excessively strong irritations. These types (forms) of inhibition are congenital and appear already in newborns.
External unconditional inhibition is manifested in the weakening or termination of conditioned reflex reactions under the action of any extraneous stimuli. If a dog calls UR to a bell, and then acts on a strong extraneous irritant (pain, smell), then the salivation that has begun will stop. Unconditioned reflexes are also inhibited (the Turk reflex in a frog when pinching the second paw).
Cases of external inhibition of conditioned reflex activity are encountered at every step and in the conditions of the natural life of animals and humans. This includes a constantly observed decrease in activity and indecision in actions in a new, unusual environment, a decrease in the effect or even the complete impossibility of activity in the presence of extraneous stimuli (noise, pain, hunger, etc.).
External inhibition of conditioned reflex activity is associated with the appearance of a reaction to an extraneous stimulus. It comes the easier, and is the stronger, the stronger the extraneous stimulus and the less strong the conditioned reflex. External inhibition of the conditioned reflex occurs immediately upon the first application of an extraneous stimulus. Consequently, the ability of cortical cells to fall into a state of external inhibition is an innate property of the nervous system. This is one of the manifestations of the so-called. negative induction.
Translimiting inhibition develops in cortical cells under the action of a conditioned stimulus, when its intensity begins to exceed a certain limit. Transmarginal inhibition also develops under the simultaneous action of several individually weak stimuli, when the total effect of the stimuli begins to exceed the working capacity limit of the cortical cells. An increase in the frequency of the conditioned stimulus also leads to the development of inhibition. The development of translimiting inhibition depends not only on the strength and nature of the action of the conditioned stimulus, but also on the state of the cortical cells, on their performance. With a low level of efficiency of cortical cells, for example, in animals with a weak nervous system, in old and sick animals, a rapid development of translimiting inhibition is observed even with relatively weak stimuli. The same is observed in animals brought to considerable nervous exhaustion by prolonged action of stimuli of moderate strength.
Transmarginal inhibition has a protective value for the cells of the cortex. This is a parabiotic type of phenomenon. During its development, similar phases are noted: equalizing, when both strong and moderate in strength conditioned stimuli cause a response of the same intensity; paradoxical, when weak stimuli cause a stronger effect than strong stimuli; ultraparadoxical phase, when inhibitory conditioned stimuli cause an effect, but positive ones do not; and, finally, the inhibitory phase, when no stimuli cause a conditioned response.
Types of conditional inhibition.
Conditioned (internal) inhibition develops in cortical cells under certain conditions under the influence of the same stimuli that previously evoked conditioned reflex reactions. In this case, braking does not occur immediately, but after a more or less long-term development. Internal inhibition, like a conditioned reflex, occurs after a series of combinations of a conditioned stimulus with the action of a certain inhibitory factor. Such a factor is the cancellation of unconditional reinforcement, a change in its nature, etc. Depending on the condition of occurrence, the following types of conditioned inhibition are distinguished: extinction, retardation, differentiation, and signal ("conditional brake").
Fading inhibition develops when the conditioned stimulus is not reinforced. It is not associated with fatigue of the cortical cells, since an equally long repetition of the conditioned reflex with reinforcement does not lead to a weakening of the conditioned reaction. Fading inhibition develops the easier and faster, the less strong the conditioned reflex and the weaker the unconditioned reflex, on the basis of which it was developed. Fading inhibition develops the faster, the shorter the interval between conditioned stimuli repeated without reinforcement. Extraneous stimuli cause a temporary weakening and even complete cessation of extinctive inhibition, i.e. temporary restoration of the extinguished reflex (disinhibition). The developed extinction inhibition also causes suppression of other conditioned reflexes, weak and those whose centers are located close to the center of the primary extinction reflexes (this phenomenon is called secondary extinction).
The quenched conditioned reflex after some time is restored by itself, i.e. fading inhibition disappears. This proves that the extinction is associated with temporal inhibition, not with a break in the temporal connection. The extinguished conditioned reflex is restored the faster, the stronger it is and the weaker it was inhibited. Repeated extinction of the conditioned reflex occurs faster.
The development of extinction inhibition is of great biological importance, since it helps animals and humans to free themselves from previously acquired conditioned reflexes that have become useless in the new, changed conditions.
Delayed inhibition develops in cortical cells when reinforcement is delayed in time from the onset of action of the conditioned stimulus. Externally, this inhibition is expressed in the absence of a conditioned reflex reaction at the beginning of the action of the conditioned stimulus and its appearance after a certain delay (delay), and the time of this delay corresponds to the duration of the isolated action of the conditioned stimulus. Delayed inhibition develops the faster, the smaller the lag of the reinforcement from the beginning of the action of the conditioned signal. With a continuous action of a conditioned stimulus, it develops faster than with an intermittent one.
Extraneous stimuli cause temporary disinhibition of delayed inhibition. Thanks to its development, the conditioned reflex becomes more accurate, timing to the right moment with a distant conditioned signal. This is its great biological significance.
Differential inhibition develops in cortical cells under the intermittent action of a constantly reinforced conditioned stimulus and unreinforced stimuli similar to it.
The newly formed SD usually has a generalized, generalized character, i.e. evoked not only by a specific conditioned stimulus
(for example, a tone of 50 Hz), but numerous stimuli similar to it, addressed to the same analyzer (tones of 10-100 Hz). However, if in the future only sounds with a frequency of 50 Hz are reinforced, while others are left without reinforcement, then after a while the reaction to similar stimuli will disappear. In other words, out of the mass of similar stimuli, the nervous system will respond only to the reinforced one, i.e. biologically significant stimulus, and the reaction to other stimuli is inhibited. This inhibition ensures the specialization of the conditioned reflex, vital distinction, differentiation of stimuli according to their signal value.
Differentiation is developed the easier, the greater the difference between the conditioned stimuli. With the help of this inhibition, it is possible to study the ability of animals to distinguish sounds, figures, colors, etc. So, according to Gubergrits, a dog can distinguish a circle from an ellipse with a ratio of semiaxes of 8:9.
Extraneous stimuli cause disinhibition of differential inhibition. Starvation, pregnancy, neurotic conditions, fatigue, etc. can also lead to disinhibition and perversion of previously developed differentiations.
Signal braking ("conditional brake"). Inhibition of the "conditioned brake" type develops in the cortex when the conditioned stimulus is not reinforced in combination with some additional stimulus, and the conditioned stimulus is reinforced only when it is applied in isolation.
Under these conditions, the conditioned stimulus in combination with an extraneous stimulus becomes inhibitory (as a result of the development of differentiation), and the extraneous stimulus itself acquires the property of an inhibitory signal (conditioned brake). It becomes capable of inhibiting any other conditioned reflex if it is attached to the conditioned signal.
The conditioned brake easily develops when the conditioned and surplus stimulus act simultaneously. In a dog, it is not produced if this interval is more than 10 seconds. Extraneous stimuli cause disinhibition of signal inhibition. Its biological significance lies in the fact that it clarifies the conditioned reflex
Internal braking mechanism. Internal conditioned inhibition arises and is localized in the cortical elements of the temporal connection, i.e. where this connection is formed. There are many hypotheses that explain the physiological mechanisms of the development and strengthening of conditioned inhibition. However, with all this, the intimate mechanism of inhibition is associated with the processes of changes in ion transport, which lead to an increase in the difference between the membrane potential and the critical level of depolarization.
2. Theory of occurrence and purpose of sleep. The state of the vegetative sphere during sleep.
Answer: Purpose of sleep.
There are several theories explaining the purpose and biological significance of sleep. First of all, it should be said about the theory of restoring the efficiency of nerve cells. It was considered long time that night sleep is extremely protective, it is needed for the rest of nerve cells that work intensively during wakefulness. This point of view was held by I.P. Pavlov and many other scientists. However, with the development of physiological science and the discovery of sleep phases, it became clear that during sleep, nerve cells do not rest, but work differently.
Therefore, at present, the so-called most accepted all over the world. information theory of sleep. Now it has become clear that sleep is a specially organized activity of the brain, aimed at processing the information received during wakefulness.
The main difference in the mechanisms of organizing the activity of the NS during sleep is the greater synchronization of the work of individual nerve cells, especially during FMS. It is shown that in the phase of REM sleep, the information processing activity of the nervous system is enhanced, and certain manifestations of this activity reach the sphere of consciousness and can be included in the fabric of dreams.
What does it mean to process the information accumulated during wakefulness? First, some of the information that the human brain stored before this moment, you just need to forget, exclude from memory (for example, the fact that you had to come to a lecture today). Another part of the information is stored in the mechanisms of long-term memory, while corrections and additions are made to the memory matrices in accordance with the new information. The third part of the information is embedded in the structure of the personality and influences the formation of a person's character and the characteristics of his behavior in specific conditions. The fourth part of the information is involved in the construction of functional systems of purposeful human behavior after awakening, and so on.
As you can see, there are a lot of information processing channels. In a dream, an emotional restructuring of a person also takes place, which is well noted even in folk wisdom, summarized in sayings and proverbs ("to sleep with grief - not to see grief", "morning is wiser than evening", etc.)
The evidence that sleep is associated with creative activity in processing information is also the well-known facts of solving a problem that tormented a person in a dream. It is known that Mendeleev's final version of his Periodic Table chemical elements saw in a dream, many mathematicians received a solution in a dream challenging tasks, many poets, waking up, wrote down the beautiful poems they dreamed of, Kekule discovered the benzene nucleus; Toscanini - fragments of musical works, etc.).
It is important that this information, which is the result of a nightly creative work, was recorded immediately after waking up, as it usually completely disappears from memory within 5-10 minutes after sleep. That is why many people believe that they never dream. They just don't remember them.
Theories of the origin of sleep and its neural mechanisms.
Since ancient times, scientists have tried to explain the mechanisms of sleep. There were so-called humoral theories, which attributed the main role in the development of sleep to one or another humoral factor (lactic acid, cholesterol, neurotoxins, hypnotoxins, etc.). However, after fundamental works P, K. Anokhin on Siamese twins who had common system blood circulation, but fell asleep at different times, interest in humoral theories has weakened, although it is recognized that a change in the concentration of various humoral agents can change the excitability of nerve cells and promote (or prevent) the onset of sleep.
In the laboratory of I.P. Pavlov, approximately from 1909, an intensive development of questions about the mechanisms of sleep began. The dream stopped Pavlov's attention because it prevented him from working with conditioned reflexes. As soon as the experimenter began to develop different kinds cortical inhibition, the dog naturally went to sleep. This prompted us to make sleep the subject of a special study, the results of which were presented in the article "Internal inhibition and sleep are one and the same process in their physical and chemical basis."
According to Pavlov's theory, sleep is a diffuse generalized inhibition, covering the entire cortex. The starting point from which the irradiation of inhibition occurs is necessarily located in the cortex. According to Pavlov, sleep is a cortical phenomenon in its very essence.
However, soon there was evidence that decortication does not change the nature of the alternation of sleep and wakefulness. These data forced Pavlov to suggest that the subcortical regions were also involved in oppression only in the absence of the cortex. Sleep, evoked from the subcortex, was not given the importance of a normal mechanism, and not a single experimental study was devoted to it in Pavlov's laboratory.
The first data on the participation of the hypothalamus in the mechanisms of sleep are found in the Viennese psychiatrist and neuropathologist Mutter, who in 1890 noted the symptom of drowsiness when the area of the bottom of the third ventricle was affected. After the epidemic of the so-called. "lethargic encephalitis" 1917-1921 in Europe, Economo suggested that the center of sleep (Economo's center) is located in the region of the bottom of the third ventricle.
Table 9
Theories of sleep
1. Theory of Z. Freud - deepening into inner world, the biological goal is rest
2. Cortical theory I.P. Pavlova - sleep is a protective inhibition of the cortex
3. Theory of sleep centers - Hess, Economo
4. Chemical - sleep is a consequence of the action of humoral regulators - Papenheimer's "delta sleep" peptide
5. Immune - the immune system forms microbial muramyl peptides (interleukin-1 and prostaglandin D-2) - Kruger
6. Energy - sleep is necessary for energy recovery
7. Information: a) lack of information
b) the need to process information
Progress in the study of the neural mechanisms of sleep is associated with the development of a microelectrode study technique. The experiments investigated the activity of neurons during REM and non-REM sleep, as well as in the wakeful state. It was possible to detect an increase in spike discharges in brain neurons in vast areas of the visual and parietal cortex, thalamus, reticular formation, and other structures. These data emphasized the active nature of the processes occurring in the nervous system during sleep.
In 1928, Hess showed the possibility of obtaining sleep with electrical stimulation of the diencephalic region - a rather extensive region lying between the Vic d'Azira bundle and the Meyer tract, as well as from the middle and partly ventromedial hypothalamus.
Currently, there are three groups of experimentally obtained facts that are important for building a unified neural theory of sleep:
1) irritation of certain diencephalic structures gives sleep;
2) the cessation of the activating action from the reticular formation - the ascending RF activating system - causes a decrease in cortical activity and promotes the development of sleep;
3) the occurrence in the cortex of prolonged or especially strong processes of internal inhibition leads to the development of sleep.
Modern theory The development of sleep considers sleep as the result of certain cyclic changes in the relationship between the cortex and the most important subcortical formations, and, in particular, the hypothalamus and the RF region of the brain stem. According to this theory, in the state of wakefulness, the cortex, and in particular its frontal regions, inhibits the activity of the so-called "Hess center", which is responsible for the development of sleep. The Hess center is able to inhibit the activity of the reticular activating system either at the level of the medulla oblongata or at the level of the thalamus, but since it itself is inhibited by impulses from the cortex during wakefulness, this does not happen, and under these conditions the RF activates the cortex, which further contributes to the suppression of activity center of Hess.
The state of the vegetative sphere during sleep.
Registration of vegetative functions is one of the simplest and at the same time quite informative methods for an objective study of sleep. Already only one observation of respiration or hemodynamic parameters allows us to judge with sufficient certainty the phase of the wakefulness-sleep cycle. Big number interesting observations The state of the vegetative sphere during sleep is given in one of the world's first monographs on the physiology of sleep by M. Manasseina (1892). The thesis put forward by Manasseina that “only consciousness in a person ceases during sleep, all other functions, if not enhanced, then at least continue,” with some clarifications, is also legitimate now, especially when applied to the vegetative sphere.
Respiratory system. . Significant changes in the external respiration system begin already in the drowsiness phase. Against the background of slow breathing, periods of respiratory arrhythmia appear. It varies according to the type of hypopnoe, polypnoe, apnea, and at times has the character of periodic respiration of Cheyne-Stokes or Biot. Such phasic changes in respiration are central and coincide with the periods of sleep spindles. Reflex influences emanating from the internal organs also play a role in changing breathing during sleep (apnea was noted at the time of the onset of an episode of nocturnal enuresis).
The respiratory rate in stage C decreases compared to drowsiness. Pulmonary ventilation does not change, which is achieved by increasing the amplitude of breathing. In stages D and E, breathing of healthy people is regular, slow compared to wakefulness, but it can be more frequent than in stage C.
Signs of REM or REM sleep
1. Desynchronization response on the EEG
2. Rapid eyeball movements
3. Decreased muscle tone
4. Increase in thresholds of cortical neurons - deep sleep
The cardiovascular system. . Decrease in heart rate, lowering blood pressure, slowing blood flow have long been considered permanent signs natural sleep. Modern research confirms that these shifts take place during the transition of an animal or person from wakefulness to FMS. At the same time, if in the shallow stages of FMS these indicators are constant, then in stages B and C, fluctuations in blood pressure and pulse rate are noted. Blood pressure changes during the transition from one stage of FMS to another. In the superficial stages of FMS, the dependence of the pulse rate on the phase of respiration is clearly revealed, while in the deep stages it disappears. The decrease in BP in the FMS is more dependent on a decrease in heart rate than on a decrease in stroke volume.
With the onset of FBS in a person in cardiovascular system pronounced changes occur: the pulse becomes more frequent, becoming arrhythmic, extrasystole appears, the average value of blood pressure increases, the IOC increases. During sleep, cerebral blood flow changes significantly - in the FMS it decreases, in the FBS it increases.
Temperature, sweating and other vegetative functions. The temperature of the brain, like other autonomic indicators, quite naturally follows the level of wakefulness and the nature of sleep. During the transition from wakefulness to FMS, it decreases, during FBS it rises, and often to higher numbers than during wakefulness. Researchers disagree on the explanation of this fact. Saton and Kamamura believe that the main reason for this phenomenon is the increased brain metabolism in the FBS. Abrams, on the other hand, showed that the increase in brain temperature in the FBS depends on its warming by the flowing blood. It is possible that both of these mechanisms are present.
Naturally, the temperature cannot change outside the brain either. During a night's sleep, the body temperature drops to an average of 35.7 ° C in women, and up to 34.9 ° C in men.
There is a certain dynamics of sweating during sleep. During the relaxation period before sleep, there is a short weakening of sweating on the non-volar surfaces, which after falling asleep increases in proportion to sleep in the PMS. This is consistent with the data that 90% of sweat is released before the minimum daily temperature is reached. Sweating on the palms changes in the opposite way. Here it stops after falling asleep and is absent throughout the entire sleep until the moment of awakening.
This difference is explained different meaning local sweating. It is believed that psychogenic sweating is manifested on the palms, which is regulated by cortical areas, and thermogenic (extra-palmar) sweating has a central representation in the hypothalamic region.
With the onset of FBS, sweating decreases sharply. Against the background of such a decrease, bursts of perspiration are sometimes observed, and upon awakening at this moment, the subjects reported on an exciting dream. If the subjects were awakened after the end of FBS, then the report of emotionally rich dreams occurred when the same phasic increase in sweating was recorded. In cases where this was not the case, subjects could not recall the dream or reported emotionally indifferent dreams. A tonic decrease in sweating is observed under conditions of increasing environmental temperature.
Another vegetative indicator of the nature of sleep is the width of the pupil and the state of the nictitating membrane of animals. Being constricted in the FMS, the pupil periodically dilates and the nictitating membrane contracts in the FBS.
Analysis of motor activity of the stomach and acidity of gastric juice revealed changes in these parameters during sleep. The research was carried out with the help of radio pills. Physical activity The GI tract decreases in FMS and rises in FBS. All subjects showed large movements of the stomach at the 4th hour of night sleep. They continued to intensify in the second half of the night. The pH values of gastric juice during sleep range from 0.5 to 3.0, thus demonstrating an increase in acidity compared to wakefulness. This explains the characteristic nocturnal pain in patients with gastric ulcer and duodenal ulcer.
Of the other vegetative manifestations, it should be noted the occurrence of an erection of the penis in the FBS, even in those men who consider themselves impotent. This phenomenon is often evidence of the functional nature of impotence.
