NOT. Vvedensky in 1902 showed that a section of a nerve that has undergone alteration - poisoning or damage - acquires low lability. This means that the state of excitement arising in this area disappears more slowly than in the normal area. Therefore, at a certain stage of poisoning, when exposed to the overlying normal area with a frequent rhythm of irritation, the poisoned area is not able to reproduce this rhythm, and excitation is not transmitted through it. This state of reduced lability N.E. Vvedensky called parabiosis(from the word "para" - about and "bios" - life), to emphasize that in the area of parabiosis, normal vital activity is disturbed.
Parabiosis- this is a reversible change, which, with the deepening and intensification of the action of the agent that caused it, turns into an irreversible disruption of life - death.
The classical experiments of N. Ye. Vvedensky were carried out on a neuromuscular preparation of a frog. The investigated nerve in a small area was subjected to alteration, that is, they caused a change in its state under the influence of the application of any chemical agent - cocaine, chloroform, phenol, potassium chloride, strong faradic current, mechanical damage, etc. a section of the nerve or above it, that is, in such a way that impulses arise in the parabiotic section or pass through it on their way to the muscle. N.E. Vvedensky judged the conduction of excitation along the nerve by muscle contraction.
In a normal nerve, an increase in the strength of the rhythmic stimulation of the nerve leads to an increase in the strength of the tetanic contraction ( rice. 160, A). With the development of parabiosis, these relations change naturally, and the following successive stages are observed.
- Provisional, or equalizing, phase... In this initial phase of alteration, the nerve's ability to conduct rhythmic impulses decreases with any strength of stimulation. However, as Vvedensky showed, this decrease has a sharper effect on the effects of stronger stimuli than more moderate ones: as a result of this, the effects of both are almost equalized ( rice. 160, B).
- Paradoxical phase follows the equalization and is the most characteristic phase of parabiosis. According to N.E. Vvedensky, it is characterized by the fact that strong excitations coming out of the normal points of the nerve are not transmitted at all to the muscle through the anesthetized area or cause only initial contractions, while very moderate excitations can cause rather significant tetanic contractions ( rice. 160, B).
- Braking phase- the last stage of parabiosis. During this period, the nerve completely loses its ability to conduct excitation of any intensity.
The dependence of the effects of nerve stimulation on the strength of the current is due to the fact that with an increase in the strength of stimuli, the number of excited nerve fibers increases and the frequency of impulses arising in each fiber increases, since a strong stimulus can cause a burst of impulses.
Thus, the nerve responds with a high frequency of excitation in response to severe stimulation. With the development of parabiosis, the ability to reproduce frequent rhythms, that is, lability, decreases. This leads to the development of the phenomena described above.
With low strength or a rare rhythm of stimulation, each impulse that arises in the intact part of the nerve is also conducted through the parabiotic site, since by the time it arrives in this area, the excitability, reduced after the previous impulse, has time to recover completely.
With strong irritation, when the impulses follow each other with a high frequency, each next impulse arriving at the parabiotic site enters the stage of relative refractoriness after the previous one. At this stage, the excitability of the fiber is sharply reduced, and the amplitude of the response is reduced. Therefore, spreading excitement does not arise, but only an even greater decrease in excitability occurs.
In the area of parabiosis, impulses that come quickly one after another, as they themselves, block the path. In the equalizing phase of parabiosis, all these phenomena are still weakly expressed, therefore, there is only a transformation of a frequent rhythm into a more rare one. As a result, the effects of frequent (strong) and relatively rare (moderate) stimuli are equalized in strength, while at the paradoxical stage, the cycles of recovery of excitability are so prolonged that frequent (strong) stimuli are generally ineffective.
With particular clarity, these phenomena can be traced on single nerve fibers when stimulated by stimuli of different frequencies. So, I. Tasaki influenced one of Ranvier's interceptions of the frog's myelinated nerve fiber with a urethane solution and investigated the conduction of nerve impulses through such an interception. He showed that while infrequent stimuli passed through the interception unhindered, frequent stimuli were delayed by it.
N. Ye. Vvedensky considered parabiosis as a special state of persistent, non-fluctuating excitement, as if frozen in one section of the nerve fiber. He believed that the waves of excitation arriving in this area from the normal parts of the nerve, as it were, are added to the “stationary” excitation present here and deepen it. Such a phenomenon was considered by N. Ye. Vvedensky as a prototype of the transition of excitation to inhibition in the nerve centers. Inhibition, according to N. Ye. Vvedensky, is the result of "overexcitation" of a nerve fiber or nerve cell.
Parabiosis should be considered as an active state, characterized by a local, immobile act of arousal. The parabiotic site has all the signs of arousal, it is only incapable of conducting traveling waves of excitation. When this state reaches full development, the tissue, as it were, loses its functional properties, since, being in a state of its own strong excitement, it becomes refractory in relation to new stimuli. Local excitement is therefore manifested as inhibition, excluding the possibility of tissue functioning.
Local parabiotic arousal, along with its persistence and continuity, is capable of deepening under the influence of incoming impulses of excitement. Moreover, the stronger and more often these impulses, the more they deepen the local excitation and the worse they are conducted through the altered area. Therefore, the effects of strong and weak irritations in the equalizing phase are leveled, and in the paradoxical phase, strong irritations do not pass at all, while weak ones can still pass. In the inhibitory phase, the impulse that came from the normal section does not pass on its own and prevents the development of propagating excitation, since, adding up with stationary excitation, makes it stable and non-fluctuating.
The observed patterns allowed N.E. Vvedensky to put forward a theory according to which a single nature of the process of excitation and inhibition is established. The emergence of this or that state depends, according to this theory, on the strength and frequency of irritation and the functional state of the tissue. The regularities of parabiotic inhibition, established by N. Ye. Vvedensky, according to IP Pavlov, are reproduced on the "nerve cells of the cerebral cortex and thus turn out to be valid for the integral activity of the organism.
BACKGROUND: Dissecting kit, universal stand with horizontal myograph, electrostimulator, irritating electrodes, Ringer's solution, one of the following: 1% potassium chloride solution (Panangin), ether, alcohol or novocaine. The work is carried out on the frog.
The content of the work. Prepare a neuromuscular preparation and fix it in the myograph. While stimulating the nerve in the single stimulation mode, select the suprathreshold and submaximal strength of stimuli that cause weak and strong muscle contraction. Write down their values (mV).
Dampen a small cotton swab with the solution you have. Place it on the nerve closer to where it enters the muscle. Every 30 seconds, apply single stimuli to the nerve above the altered area. With careful preparation of the drug, it is possible to trace the successive development of the phases of parabiosis (Fig. 10).
Rice. 10. Sequential development of the phases of parabiosis: A - initial state;
B - equalizing phase; B - paradoxical phase; Г - braking phase.
Registration of the protocol.
1. Write down the results of the experiment in a notebook.
2. Glue the kimograms in accordance with the phases of parabiosis, compare them with the standard (Fig. 10).
3. Explain the mechanism of parabiosis.
CONTROL OF THE TOPIC ASSEMBLY.
Test task for the lesson "Mechanisms of propagation and transmission of excitement"
1. By activation of Na + / K + -ATPase;
2. Reducing the intensity of the stimulus;
3. Inactivation of the Na + -channel system;
4. By activating the K + -channel system;
5. Cell fatigue;
2. The membrane of the nerve fiber that limits the nerve ending is called:
1.post-synaptic
2.subsynaptic
3.synaptic cleft
4. presynaptic
3. Electrotonic propagation of excitation along the membrane of the nerve cell:
1. Accompanied by membrane depolarization
2. Accompanied by membrane hyperpolarization;
3. It occurs without changing the membrane charge;
4. It occurs without changing the permeability of membrane ion channels;
5. Impossible
4. Inhibitory and excitatory synapses differ:
1. specific location on the cage;
2.the mechanism of mediator ejection
3.the chemical structure of the mediator
4. the receptor apparatus of the postsynaptic membrane;
5.size
5. When excitation (AP) occurs in the body of the neuron (soma), the mound:
1. It will spread in the direction from the body of the neuron;
2. It will spread towards the body of the neuron;
3.it will spread in both directions
4. The emergence of excitation in the body of the neuron (soma) is impossible;
6. The role of acetylcholine in the mechanism of synaptic transmission of excitation in the myoneural synapse is as follows:
1. Acetylcholine interacts with a specific receptor on the postsynaptic membrane
and thus facilitates the opening of sodium channels.
2. Acetylcholine, promotes the accumulation of mediator in the presynaptic apparatus
3. Acetylcholine promotes the release of the transmitter from the presynaptic apparatus.
4. Acetylcholine penetrates the postsynaptic membrane and depolarizes it (forms EPSP);
5. Acetylcholine penetrates the postsynaptic membrane and hyperpolarizes it (forms TPSP);
7. The mediator provides the transmission of excitement
1. Only in interneuronal synapses;
2. Only in the neuromuscular synapses;
3. At all chemical synapses;
4. In any synapses
5. In all electrical synapses;
8. On the presynaptic membrane of the neuromuscular synapse of human skeletal muscles are formed:
1.only exciting potentials
2.only braking potentials
3.and exciting and inhibitory potentials
4.for contraction, excitatory muscles, for relaxation - inhibitory
5.on the presynaptic membrane potential is not formed
9. TPSP of the neuromuscular synapse is formed:
1. On the presynaptic membrane;
2. In the axonal mound
3. On the postsynaptic membrane
4. EPSPs are not formed in neuromuscular synapses;
10. The release of acetylcholine into the synaptic cleft in the myoneural synapse leads to:
1.depolarization of the postsynaptic membrane;
2. hyperpolarization of the postsynaptic membrane;
3. depolarization of the presynatic membrane;
4. blocking the conduction of excitation;
5. hyperpolarization of the presynaptic membrane;
11. The diffusion mechanism of propagation of the mediator in the synaptic cleft is the cause of:
1. Synaptic depression;
2. Synaptic delay;
3. Inactivation of the mediator;
4. Saltatory spread of excitement;
12. Saltatory conduction of a nerve impulse is carried out:
1. On the membrane of the neuron body;
2. On the membrane of myelinated nerve fibers;
3. On the membrane of unmyelinated nerve fibers;
4. On the nerves;
13. At the moment of the passage of the excitation wave along the nerve fiber, the excitability of the fiber at the place of its passage:
1. Increases to maximum;
2. Decreases to the minimum;
3. Decreases to the threshold;
4. Does not change;
14. Directions of the propagation of excitation along the nerve fiber and its membrane current on its membrane:
1. Parallel and coincident;
2. Parallel and opposite;
3. Perpendicular;
4. Sinusoidal;
15. Excitation in non-myelinated nerve fibers spreads:
1. Jumping, (jumping) over the fiber sections covered with the myelin sheath;
3. Continuously along the entire membrane from the excited area to the adjacent
unexcited site
4. Electrotonically and in both directions from the place of origin
Experimental facts that form the basis of the doctrine of parabiosis, N.V. Vvedensky (1901) described in his classic work "Excitation, Inhibition and Anesthesia."
In the study of parabiosis, as well as in the study of lability, the experiments were carried out on a neuromuscular preparation.
N. Ye. Vvedensky found that if a section of a nerve is subjected to alteration (i.e., to the action of a damaging agent) through, for example, poisoning or injury, then the lability of such a section is sharply reduced. The restoration of the initial state of the nerve fiber after each action potential in the damaged area occurs slowly. When this site is exposed to frequent stimuli, it is not able to reproduce the given rhythm of stimulation, and therefore the conduction of impulses is blocked.
The neuromuscular preparation was placed in a humid chamber, and three pairs of electrodes were placed on its nerve to apply stimuli and biopotentials. In addition, the experiments recorded contraction of the muscle and the potential of the nerve between the intact and altered areas. If the area between the irritating electrodes and the muscle is exposed to drugs and continues to irritate the nerve, then the response to irritation suddenly disappears after a while. NOT. Vvedensky, investigating the effect of drugs in such conditions and listening with a telephone to the biocurrents of the nerve below the anesthetized area, noticed that the rhythm of irritation begins to transform some time before the response of the muscle to irritation completely disappears. This state of reduced lability was named by N. Ye. Vvedensky parabiosis. In the development of the state of parabiosis, three successive phases can be noted:
Equalizing,
Paradoxical and
Brake,
which are characterized by varying degrees of excitability and conductivity when weak (rare), moderate and strong (frequent) irritations are applied to the nerve.
If the narcotic substance continues to act after the development of the inhibitory phase, then irreversible changes can occur in the nerve, and it dies.
If the action of the drug is stopped, then the nerve slowly restores its original excitability and conductivity, and the recovery process goes through the development of a paradoxical phase
In a state of parabiosis, there is a decrease in excitability and lability.
N.E. Vvedensky's doctrine of parabiosis is universal in nature, since the patterns of response revealed in the study of a neuromuscular preparation are inherent in the whole organism. Parabiosis is a form of adaptive reactions of living entities to various influences, and the doctrine of parabiosis is widely used to explain the various response mechanisms of not only cells, tissues, organs, but also the whole organism.
Additionally: Parabiosis - means "near life". It occurs when parabiotic stimuli (ammonia, acid, fat solvents, KCl, etc.) act on the nerves, this stimulus changes lability, reduces it. Moreover, it reduces it in phases, gradually.
Phases of parabiosis:
1. First, an equalizing phase of parabiosis is observed. Usually, a strong stimulus gives a strong response, and a smaller one gives a smaller one. Here, equally weak responses to stimuli of varying strength are observed (Demonstration of the graph).
2. The second phase is the paradoxical phase of parabiosis. A strong stimulus gives a weak response, a weak stimulus gives a strong response.
3. The third phase is the inhibitory phase of parabiosis. There is no response to both weak and strong stimuli. This is due to a change in lability.
The first and second phases are reversible, i.e. upon termination of the action of the parabiotic agent, the tissue is restored to its normal state, to the initial level.
The third phase is not reversible, the inhibitory phase after a short period of time turns into tissue death.
Mechanisms of the occurrence of parabiotic phases
1. The development of parabiosis is due to the fact that under the influence of the damaging factor there is a decrease in lability, functional mobility. This is the basis of the responses, which are called the phases of parabiosis.
2. In a normal state, the tissue obeys the law of the force of irritation. The greater the strength of the irritation, the greater the response. There is an irritant that elicits the maximum response. And this value is designated as the optimum frequency and strength of stimulation.
If this frequency or strength of the stimulus is exceeded, then the response decreases. This phenomenon is a pessimum of the frequency or strength of stimulation.
3. The value of the optimum coincides with the value of lability. Because lability is the maximum tissue capacity, the maximum tissue response. If the lability changes, then the values at which the pessimum develops instead of the optimum are shifted. If we change the lability of the tissue, then the frequency that caused the optimum response will now cause a pessimum.
The biological significance of parabiosis
Vvedensky's discovery of parabiosis on a neuromuscular preparation in laboratory conditions had colossal consequences for medicine:
1. Showed that the phenomenon of death is not instantaneous, there is a transitional period between life and death.
2. This transition is carried out in phases.
3. The first and second phases are reversible, and the third is not reversible.
These discoveries have led in medicine to the concepts - clinical death, biological death.
Clinical death is a reversible condition.
Biological death is an irreversible condition.
As soon as the concept of "clinical death" was formed, a new science appeared - resuscitation ("re" - a recurrent preposition, "anima" - life).
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Physiology
General physiology. Physiological foundations of behavior. Higher nervous activity. Physiological foundations of human mental functions. Physiology of purposeful activity. Adaptation of the body to various conditions of existence. Physiological cybernetics. Private physiology. Blood, lymph, tissue fluid. Circulation. Breath. Digestion. Metabolism and energy. Nutrition. Central nervous system. Methods for the study of physiological functions. Physiology and biophysics of excitable tissues.
This material includes sections:
The role of physiology in the dialectical-materialistic understanding of the essence of life. The relationship of physiology with other sciences
The main stages in the development of physiology
Analytical and systematic approach to the study of body functions
The role of I.M.Sechenov and I.P. Pavlov in the creation of the materialistic foundations of physiology
The body's defense systems that ensure the integrity of its cells and tissues
General properties of excitable tissues
Modern ideas about the structure and function of membranes. Active and passive transport of substances across membranes
Electrical phenomena in excitable tissues. The history of their discovery
Action potential and its phases. Changes in the permeability of potassium, sodium and calcium channels during the formation of the action potential
Membrane potential, its origin
The ratio of the phases of excitability with the phases of the action potential and single contraction
The laws of irritation of excitable tissues
The action of direct current on living tissue
Physiological properties of skeletal muscle
Types and modes of skeletal muscle contraction. Single muscle contraction and its phases
Thetanus and its types. Optimum and pessimum of irritation
Lability, parabiosis and its phases (N.E. Vvedensky)
Muscle strength and work. Dynamometry. Ergography. Average load law
The spread of excitement along the non-fleshy nerve fibers
The structure, classification and functional properties of synapses. Features of the transfer of excitement in them
Functional properties of glandular cells
The main forms of integration and regulation of physiological functions (mechanical, humoral, nervous)
Systematic organization of functions. I.P. Pavlov - the founder of a systematic approach to understanding the functions of the body
The doctrine of P.K. Anokhin about functional systems and self-regulation of functions. Nodal mechanisms of a functional system
The concept of homeostasis and homeokinesis. Self-regulatory principles of maintaining the constancy of the internal environment of the body
The reflex principle of regulation (R. Descartes, G. Prokhazka), its development in the works of I.M.Sechenov, I.P. Pavlov, P.K. Anokhin
Basic principles and features of the propagation of excitation in the central nervous system
Inhibition in the central nervous system (IM Sechenov), its types and role. Modern understanding of central braking mechanisms
Principles of coordination activity of the central nervous system. General principles of coordination activity of the central nervous system
Autonomous and somatic nervous systems, their anatomical and functional differences
Comparative characteristics of the sympathetic and parasympathetic divisions of the autonomic nervous system
Congenital form of behavior (unconditioned reflexes and instincts), their importance for adaptive activity
Conditioned reflex as a form of adaptation of animals and humans to changing conditions of existence. Regularities of the formation and manifestation of conditioned reflexes; conditioned reflex classification
Physiological mechanisms of the formation of reflexes. Their structural and functional basis. Development of I.P. Pavlov's ideas about the mechanisms of formation of temporary connections
The phenomenon of inhibition in VND. Braking types. Modern understanding of braking mechanisms
Analytical and synthetic activity of the cerebral cortex
The architecture of a holistic behavioral act from the point of view of the theory of the functional system of P.K. Anokhin
Motivation. Classification of motivations, the mechanism of their occurrence
Memory, its significance in the formation of integral adaptive reactions
I.P. Pavlov's doctrine of the types of GNI, their classification and characteristics
The biological role of emotions. Theories of emotions. Vegetative and somatic components of emotions
Physiological mechanisms of sleep. Sleep phases. Sleep theories
I.P. Pavlov's doctrine about I and II signaling systems
The role of emotions in purposeful human activity. Emotional stress (emotional stress) and its role in the formation of psychosomatic diseases of the body
The role of social and biological motivations in the formation of purposeful human activity
Features of changes in autonomic and somatic functions in the body associated with physical labor and sports activities. Physical training, its impact on human performance
Features of human labor activity in the conditions of modern production. Physiological characteristics of labor with neuro-emotional and mental stress
Adaptation of the body to physical, biological and social factors. Types of adaptation. Features of human adaptation to the action of extreme factors
Physiological cybernetics. The main tasks of modeling physiological functions. Cybernetic study of physiological functions
The concept of blood, its properties and functions
Electrolyte composition of blood plasma. Osmotic blood pressure. A functional system that ensures the consistency of the osmotic pressure of the blood
A functional system that maintains a constant acid-base balance
Characteristics of blood corpuscles (erythrocytes, leukocytes, platelets), their role in the body
Humoral and nervous regulation of erythro- and leukopoiesis
The concept of hemostasis. The process of blood coagulation and its phases. Factors that accelerate and slow down blood clotting
Blood groups. Rh factor. Blood transfusion
Tissue fluid, cerebrospinal fluid, lymph, their composition, quantity. Functional value
The importance of blood circulation to the body. Blood circulation as a component of various functional systems that determine homeostasis
Heart, its hemodynamic function. Change in pressure and blood volume in the cavities of the heart in different phases of the cardiocycle. Systolic and minute blood volume
Physiological properties and features of cardiac muscle tissue. Modern understanding of the substrate, nature and the gradient of the heart's automation
Heart sounds and their origins
Self-regulation of heart activity. The Law of the Heart (E.H. Starling) and Modern Additions to It
Humoral regulation of the heart
Reflex regulation of the heart. Characterization of the influence of parasympathetic and sympathetic nerve fibers and their mediators on the activity of the heart. Reflexogenic fields and their significance in the regulation of heart activity
Blood pressure, factors that determine the magnitude of arterial and venous blood pressure
Arterial and venous pulse, their origin. Analysis of the sphygmogram and phlebogram
Capillary blood flow and its features. Microcirculation and its role in the mechanism of exchange of fluid and various substances between blood and tissues
The lymphatic system. Lymphatic formation, its mechanisms. Lymph function and features of regulation of lymph formation and lymph flow
Functional features of the structure, function and regulation of the vessels of the lungs, heart and other organs
Reflex regulation of vascular tone. The vasomotor center, its efferent influences. Afferent influences on the vasomotor center
Humoral effects on vascular tone
Blood pressure - as one of the physiological constants of the body. Analysis of the peripheral and central components of the functional blood pressure self-regulation system
Breathing, its main stages. External respiration mechanism. Biomechanism of inhalation and exhalation
Gas exchange in the lungs. Partial pressure of gases (O2, CO2) in alveolar air and tension of gases in blood
Oxygen transport by blood. Oxyhemoglobin dissociation curve, its characteristics. Blood oxygen capacity
Respiratory center (N.A. Mislavsky). Modern understanding of its structure and localization. Respiratory center automation
Reflex self-regulation of breathing. Respiratory phase change mechanism
Humoral regulation of respiration. The role of carbon dioxide. Mechanism of the first inhalation of a newborn baby
Breathing in conditions of high and low barometric pressure and when the gas environment changes
A functional system that ensures the constancy of the blood gas constant. Analysis of its central and peripheral components
Food motivation. Physiological bases of hunger and satiety
Digestion, its meaning. Digestive tract functions. Types of digestion depending on the origin and location of hydrolysis
Principles of regulation of the digestive system. The role of reflex, humoral and local regulatory mechanisms. Hormones of the gastrointestinal tract, their classification
Digestion in the oral cavity. Self-regulation of the chewing act. The composition and physiological role of saliva. Salivation, its regulation
Digestion in the stomach. Composition and properties of gastric juice. Regulation of gastric secretion. Gastric acid separation phases
Types of stomach contractions. Neurohumoral regulation of stomach movements
Digestion in the duodenum. Exocrine pancreatic activity. Composition and properties of pancreatic juice. Regulation and adaptive nature of pancreatic secretion to types of food and food rations
The role of the liver in digestion. Regulation of the formation of bile, its secretion into the duodenum
Composition and properties of intestinal juice. Regulation of intestinal juice secretion
Cavity and membrane hydrolysis of nutrients in various parts of the small intestine. Motor activity of the small intestine and its regulation
Features of digestion in the colon
Absorption of substances in various parts of the digestive tract. Types and mechanism of absorption of substances through biological membranes
Plastic and energetic role of carbohydrates, fats and proteins ...
Basal metabolism, the meaning of its definition for the clinic
Energy balance of the body. Working exchange. Energy costs of the body for various types of labor
Physiological nutritional standards depending on age, type of work and state of the body
The constancy of the temperature of the internal environment of the body as a necessary condition for the normal course of metabolic processes. A functional system that maintains a constant temperature of the internal environment of the body
Human body temperature and its daily fluctuations. The temperature of various areas of the skin and internal organs
Heat transfer. Heat transfer methods and their regulation
Isolation as one of the components of complex functional systems that ensure the constancy of the internal environment of the body. Excretory organs, their participation in maintaining the most important parameters of the internal environment
Bud. Primary urine formation. Filter, quantity and composition
The formation of the final urine, its composition and properties. Characterization of the process of reabsorption of various substances in the tubules and the loop. Secretion and excretion processes in the renal tubules
Regulation of kidney activity. The role of nerve and humoral factors
The process of urination, its regulation. Excretion of urine
Excretory function of the skin, lungs and gastrointestinal tract
Formation and secretion of hormones, their transport by blood, action on cells and tissues, metabolism and excretion. Self-regulatory mechanisms of neurohumoral relationships and hormone-forming functions in the body
Pituitary hormones, its functional connections with the hypothalamus and participation in the regulation of the activity of endocrine organs
Physiology of the thyroid and parathyroid glands
Endocrine function of the pancreas and its role in the regulation of metabolism
Physiology of the adrenal glands. The role of hormones of the cortex and medulla in the regulation of body functions
Sex glands. Male and female sex hormones and their physiological role in sex formation and regulation of reproductive processes. Endocrine function of the placenta
The role of the spinal cord in the processes of regulation of the musculoskeletal system and autonomic functions of the body. Characteristics of spinal animals. How the spinal cord works. Clinically important spinal reflexes
Excitable tissues professor N. Ye. Vvedensky, studying the work of a neuromuscular drug when exposed to various stimuli.
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Subtitles
The causes of parabiosis
These are a variety of damaging effects on an excitable tissue or cell, which do not lead to gross structural changes, but in one way or another violate its functional state. Such reasons can be mechanical, thermal, chemical and other irritants.
The essence of the phenomenon of parabiosis
As Vvedensky himself believed, parabiosis is based on a decrease in excitability and conductivity associated with sodium inactivation. Soviet cytophysiologist N.A. Petroshin believed that parabiosis was based on reversible changes in protoplasmic proteins. Under the influence of a damaging agent, the cell (tissue), without losing its structural integrity, completely ceases to function. This state develops in phases, as the damaging factor acts (that is, it depends on the duration and strength of the acting stimulus). If the damaging agent is not removed in time, then biological death of the cell (tissue) occurs. If this agent is removed on time, then the tissue also phasically returns to its normal state.
The experiments of N.E. Vvedensky
Vvedensky conducted experiments on a frog neuromuscular preparation. Testing stimuli of varying strength were sequentially applied to the sciatic nerve of the neuromuscular preparation. One stimulus was weak (threshold strength), that is, it caused the minimal contraction of the gastrocnemius muscle. Another stimulus was strong (maximum), that is, the smallest of those that cause the maximum contraction of the gastrocnemius muscle. Then, at some point, a damaging agent was applied to the nerve and every few minutes the neuromuscular preparation was tested: alternately with weak and strong stimuli. At the same time, the following stages developed sequentially:
- Equalizing when, in response to a weak stimulus, the magnitude of muscle contraction did not change, but in response to a strong amplitude of muscle contraction it sharply decreased and became the same as in response to a weak stimulus;
- Paradoxical when, in response to a weak stimulus, the magnitude of muscle contraction remained the same, and in response to a strong stimulus, the magnitude of the contraction amplitude became less than in response to a weak stimulus, or the muscle did not contract at all;
- Brake when the muscle did not respond to both strong and weak stimuli by contraction. It is this state of the tissue that is designated as parabiosis.
Biological significance of parabiosis
... For the first time, a similar effect was noticed in cocaine, however, due to its toxicity and the ability to cause addiction, safer analogs, lidocaine and tetracaine, are currently used. One of the followers of Vvedensky, N.P. Rezvyakov proposed to consider the pathological process as a stage of parabiosis, therefore, antiparabiotic agents must be used for its treatment.4. Lability- functional mobility, the rate of flow of elementary cycles of excitation in the nervous and muscular tissues. The concept of "L." introduced by the Russian physiologist N.E. Vvedensky (1886), who considered the measure of L. the greatest frequency of tissue irritation, reproduced by it without changing the rhythm. L. reflects the time during which the tissue restores efficiency after the next cycle of excitation. The processes of nerve cells — axons — capable of reproducing up to 500-1000 impulses per second are distinguished by the greatest L. less labile are the central and peripheral places of contact - synapses (for example, the motor nerve ending can transmit no more than 100-150 excitations per second to the skeletal muscle). The suppression of the vital activity of tissues and cells (for example, by cold, drugs) reduces L., since this slows down the recovery processes and lengthens the refractory period.
Parabiosis- a state bordering between life and death of a cell.
The causes of parabiosis- a variety of damaging effects on an excitable tissue or cell, which do not lead to gross structural changes, but in one way or another violate its functional state. Such reasons can be mechanical, thermal, chemical and other irritants.
The essence of parabiosis... As Vvedensky himself believed, parabiosis is based on a decrease in excitability and conductivity associated with sodium inactivation. Soviet cytophysiologist N.A. Petroshin believed that parabiosis was based on reversible changes in protoplasmic proteins. Under the influence of a damaging agent, the cell (tissue), without losing its structural integrity, completely ceases to function. This state develops in phases, as the damaging factor acts (that is, it depends on the duration and strength of the acting stimulus). If the damaging agent is not removed in time, then biological death of the cell (tissue) occurs. If this agent is removed on time, then the tissue also phasically returns to its normal state.
The experiments of N.E. Vvedensky.
Vvedensky conducted experiments on a frog neuromuscular preparation. Testing stimuli of varying strength were sequentially applied to the sciatic nerve of the neuromuscular preparation. One stimulus was weak (threshold strength), that is, it caused the minimal contraction of the gastrocnemius muscle. Another stimulus was strong (maximum), that is, the smallest of those that cause the maximum contraction of the gastrocnemius muscle. Then, at some point, a damaging agent was applied to the nerve and every few minutes the neuromuscular preparation was tested: alternately with weak and strong stimuli. At the same time, the following stages developed sequentially:
1. Equalizing when, in response to a weak stimulus, the magnitude of muscle contraction did not change, but in response to a strong amplitude of muscle contraction it sharply decreased and became the same as in response to a weak stimulus;
2. Paradoxical when, in response to a weak stimulus, the magnitude of muscle contraction remained the same, and in response to a strong stimulus, the magnitude of the contraction amplitude became less than in response to a weak stimulus, or the muscle did not contract at all;
3. Brake when the muscle did not respond to both strong and weak stimuli by contraction. It is this state of the tissue that is designated as parabiosis.
PHYSIOLOGY OF THE CENTRAL NERVOUS SYSTEM
1. Neuron as a structural and functional unit of the central nervous system. Its physiological properties. The structure and classification of neurons.
Neurons- This is the main structural and functional unit of the nervous system, which has specific manifestations of excitability. A neuron is able to receive signals, process them into nerve impulses and conduct them to nerve endings in contact with another neuron or reflex organs (muscle or gland).
Types of neurons:
1. Unipolar (have one process - an axon; characteristic of the ganglia of invertebrates);
2. Pseudo-unipolar (one process dividing into two branches; typical of the ganglia of higher vertebrates).
3. Bipolar (there is an axon and dendrite, typical for peripheral and sensory nerves);
4. Multipolar (axon and several dendrites - typical for the vertebrate brain);
5. Isopolar (it is difficult to differentiate the processes of bi- and multipolar neurons);
6. Heteropolar (it is easy to differentiate processes of bi- and multipolar neurons)
Functional classification:
1. Afferent (sensitive, sensory - perceive signals from the external or internal environment);
2.Inserted connecting neurons with each other (provide the transfer of information within the central nervous system: from afferent neurons to efferent ones).
3. Efferent (motor, motor neurons - transmit the first impulses from the neuron to the executive organs).
home structural feature neuron - the presence of processes (dendrites and axons).
1 - dendrites;
2 - cell body;
3 - axonal mound;
4 - axon;
5 - Shvanovskaya cage;
6 - interception of Ranvier;
7 - efferent nerve endings.
Consecutive synoptic union of all 3 neurons forms reflex arc.
Excitation, which has arisen in the form of a nerve impulse in any part of the membrane of a neuron, runs through its entire membrane and along all its processes: both along the axon and along the dendrites. Transmitted excitement from one nerve cell to another in one direction only- from an axon transmitting neuron on perceiving neuron through synapses located on its dendrites, body or axon.
Synapses provide unilateral transmission of excitation... Nerve fiber (neuron outgrowth) can transmit nerve impulses in both directions, and one-way transmission of excitation appears only in nerve circuits consisting of several neurons connected by synapses. It is synapses that provide one-way transmission of excitation.
Nerve cells perceive and process information coming to them. This information comes to them in the form of control chemicals: neurotransmitters ... It can be in the form exciting or brake chemical signals, as well as in the form modulating signals, i.e. those that change the state or work of the neuron, but do not transmit excitation to it.
The nervous system plays an exceptional integrating role in the life of the organism, since it unites (integrates) it into a single whole and integrates it into the environment. It ensures the coordinated work of individual parts of the body ( coordination), maintaining an equilibrium state in the body ( homeostasis) and adaptation of the body to changes in the external or internal environment ( adaptive state and / or adaptive behavior).
A neuron is a nerve cell with processes, which is the main structural and functional unit of the nervous system. It has a structure similar to other cells: envelope, protoplasm, nucleus, mitochondria, ribosomes and other organelles.
In a neuron, three parts are distinguished: the cell body - the soma, the long process - the axon and many short branched processes - the dendrites. Soma performs metabolic functions, dendrites specialize in receiving signals from the external environment or from other nerve cells, the axon in conducting and transmitting excitation to an area remote from the dendrite zone. The axon ends in a group of terminal branches for transmitting signals to other neurons or executing organs. Along with the general similarity in the structure of neurons, there is a great variety due to their functional differences (Fig. 1).
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