The use of parabiosis in zootechnical practice. Laws of stimulation Neuromuscular synapse

Causes of parabiosis

These are a variety of damaging effects on an excitable tissue or cell that do not lead to gross structural changes, but to some extent 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 reversible changes in protoplasmic proteins underlie parabiosis. Under the action of a damaging agent, the cell (tissue), without losing its structural integrity, completely stops functioning. This state develops in phase, 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 the biological death of the cell (tissue) occurs. If this agent is removed in time, then the tissue returns to its normal state in the same phase.

Experiments N.E. Vvedensky

Vvedensky conducted experiments on a neuromuscular preparation of a frog. On the sciatic nerve of the neuromuscular preparation, testing stimuli of different strengths were successively applied. One stimulus was weak (threshold strength), that is, it caused the smallest contraction of the gastrocnemius muscle. The other stimulus was strong (maximum), that is, the smallest of those that cause maximum contraction calf 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, and 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 amplitude of contraction 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 referred to as parabiosis.

Biological significance of parabiosis

Parabiosis is not only a laboratory phenomenon, but a phenomenon that, under certain conditions, can develop in a whole organism. For example, a parabiotic phenomenon develops in the brain during sleep. It should be noted that parabiosis, as a physiological phenomenon, obeys the general biological law of force, with the difference that with an increase in the stimulus, the response of the tissue does not increase, but decreases.

Medical significance of parabiosis

Parabiosis underlies the action of local anesthetics. They bind reversibly to specific sites located within voltage-gated sodium channels. For the first time, a similar effect was seen in cocaine, however, due to toxicity and addictiveness, safer analogues are currently used - lidocaine and tetracaine. One of the followers of Vvedensky, N.P. Rezvyakov proposed to consider pathological process as a stage of parabiosis, therefore, for its treatment, it is necessary to use antiparabiotic agents.


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    Parabiosis… Spelling Dictionary

    parabiosis- functional changes in the nerve after exposure to strong and prolonged stimuli, described by N. E. Vvedensky. If normal conditions are characterized by a direct and relatively proportional ratio of the force applied to the nerve ... ... Great Psychological Encyclopedia

    Splicing, crossing Dictionary of Russian synonyms. parabiosis noun, number of synonyms: 2 crossing (27) … Synonym dictionary

    PARABIOSIS- (from Greek para near and bios life), a term with a double meaning. 1. The connection of two organisms in order to study mutual influences through the circulatory and lymphatic systems. Parabiosis experiments were carried out on mammals, birds and ... ... Big Medical Encyclopedia

    - (from steam ... and Greek bios life) 1) the reaction of living tissue to the effects of stimuli (at a certain strength and duration of their action), accompanied by reversible changes in its basic properties of excitability and conductivity. Concept and theory ... ... Big Encyclopedic Dictionary

    - (from the Greek para near, near and bios life) functional changes in the nerve after exposure to strong and prolonged stimuli, described by N.E. Vvedensky. If, under normal conditions, direct and relative ... Psychological Dictionary

    - (from steam ... and ... biosis), 1) the reaction of excitable tissue to the effects of stimuli, characterized by the fact that the altered part of the nerve (muscle) acquires low lability and therefore is not capable of conducting a given rhythm of stimulation. Concept and... Biological encyclopedic dictionary

    parabiosis- The method of obtaining parabiotic twins by connecting the circulatory systems (anastomoses) or splicing their tissues. [Arefiev V.A., Lisovenko L.A. English Russian explanatory dictionary of genetic terms 1995 407s.] Topics genetics EN parabiosis ... Technical Translator's Handbook

    PARABIOSIS- English parabiosis German Parabiose French parabiose see > ... Phytopathological dictionary-reference book

    - (see pair ... + ... bios) 1) the method of artificial splicing of two animals, in which a common blood circulation is established between them; appl. in biological experiments to study the mutual influence of organs and tissues of fused organisms ... ... Dictionary of foreign words of the Russian language

The concept of parabiosis(para - about, bios - life) to physiology nervous system introduced by N. E. Vvedensky. In 1901, N. E. Vvedensky's monograph "Excitation, inhibition and anesthesia" was published, in which, based on his research, he suggested the unity of the processes of excitation and inhibition.

N. E. Vvedensky discovered that excitable tissues to the most various(ether, cocaine, direct current, etc.) extremely strong impact respond with a peculiar phase reaction, the same in all cases, which he called parabiosis.

N. E. Vvedensky studied the phenomenon of parabiosis on nerves, muscles, glands, spinal cord and came to the conclusion that parabiosis - it is a general, universal reaction excitable tissues for strong or prolonged exposure.

The essence of parabiosis lies in the fact that under the influence of an irritant in excitable tissues, their physiological properties change, first of all, lability decreases sharply.

The classical experiments of N. E. Vvedensky on the study of parabiosis were performed on a neuromuscular preparation of a frog. The nerve in a small area was subjected to damage (alteration) by chemicals (cocaine, chloroform, phenol, potassium chloride), strong faradic current, mechanical factor. Then an electric shock was applied to the altered area of ​​the nerve or above it. Thus, the impulses must either originate in the altered segment of the nerve or pass through it on their way to the muscle. Muscle contraction testified to the conduction of excitation along the nerve. The scheme of the experiment of N. E. Vvedensky is shown in fig. 62.

Rice. 62. Scheme of the experiment of N. E. Vvedensky on the study of parabiosis. A - electrodes for irritation of the normal (intact) section of the nerve; B - electrodes for stimulation of the "parabiotic part of the nerve"; B - discharge electrodes; G - phone; K 1, K 2, K 3 - telegraph keys; S 1 , S 2 and R 1 , R 2 - primary and secondary windings of induction coils; M - muscle

The development of parabiosis proceeds in three stages: provisional, paradoxical and inhibitory.

The first stage of parabiosis is the provisional, leveling, or transformation stage. This stage of parabiosis precedes the rest, hence its name - provisional. It is called equalizing because during this period of development of the parabiotic state, the muscle responds with contractions of the same amplitude to strong and weak stimuli applied to the section of the nerve located above the altered one. In the first stage of parabiosis, there is a transformation (alteration, translation) of frequent excitation rhythms into rarer ones. All the described changes in the response of the muscle and the nature of the occurrence of excitation waves in the nerve under the influence of irritation are the result of a weakening of the functional properties, especially lability, in the altered area of ​​the nerve.

The second stage of parabiosis is paradoxical. This stage occurs as a result of continuing and deepening changes in the functional properties of the parabiotic segment of the nerve. A feature of this stage is the paradoxical relationship of the altered part of the nerve to weak (rare) or strong (frequent) excitation waves coming here from normal parts of the nerve. Rare waves of excitation pass through the parabiotic segment of the nerve and cause muscle contraction. Frequent waves of excitation are either not carried out at all, as if they are damped here, which is observed when full development this stage, either cause the same contractile effect of the muscle as rare waves of excitation, or less pronounced (Fig. 63).

The third stage of parabiosis is inhibitory. characteristic feature This stage is that in the parabiotic section of the nerve, not only excitability and lability are sharply reduced, but it also loses the ability to conduct weak (rare) waves of excitation to the muscle.

Parabiosis is a reversible phenomenon. When the cause that caused parabiosis is eliminated, the physiological properties of the nerve fiber are restored. At the same time, the reverse development of the phases of parabiosis is observed - inhibitory, paradoxical, equalizing.

The presence of electronegativity in the altered section of the nerve allowed N. E. Vvedensky to consider parabiosis as a special type of excitation, localized at the site of its occurrence and unable to spread.

Parabiosis means "about life". It occurs when nerves are stimulated parabiotic stimuli(ammonia, acid, fat solvents, KCl, etc.), this irritant changes lability , reduces it. Moreover, it reduces it in phase, gradually.

^ Phases of parabiosis:

1. Observe first equalization phase parabiosis. Usually, a strong stimulus produces a strong response, and a smaller one produces a smaller one. Here, equally weak responses to stimuli of various strengths are observed (Demonstration of the graph).

2. Second phase - paradoxical phase parabiosis. A strong stimulus produces a weak response, a weak stimulus produces a strong response.

3. Third phase - braking phase parabiosis. There is no response to both weak and strong stimuli. This is due to the change in lability.

First and second phase - reversible , i.e. upon termination of the action of the parabiotic agent, the tissue is restored to its normal state, to its original level.

The third phase is not reversible, the inhibitory phase passes into tissue death after a short period of time.

^ Mechanisms of occurrence of parabiotic phases

1. The development of parabiosis is due to the fact that under the influence of a damaging factor, decreased lability, functional mobility . This underlies the answers that are called phases of parabiosis .

2. In normal condition tissue obeys the law of stimulus force. The greater the force of irritation, the greater the response. There is a stimulus that causes 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 is reduced. This phenomenon is the pessimum of the frequency or strength of the stimulus.

3. The value of the optimum coincides with the value of lability. Because lability is the maximum ability of the tissue, the maximum response of the tissue. If the lability changes, then the values ​​at which the pessimum develops instead of the optimum shift. If tissue lability is changed, then the frequency that caused the optimum response will now cause the pessimum.

^ Biological significance of parabiosis

The discovery by Vvedensky of parabiosis on a neuromuscular preparation in laboratory conditions had enormous implications for medicine:

1. Showed that the phenomenon of death not instantly , there is a transitional period between life and death.

2. This transition is carried out phase by phase .

3. First and second phases reversible , and the third not reversible .

These discoveries led in medicine to the concepts - clinical death, biological death.

clinical death is a reversible state.

^ Biological death- an irreversible state.

As soon as the concept of "clinical death" was formed, a new science appeared - resuscitation("re" is a reflexive preposition, "anima" is life).

^ 9. DC action…

direct current on tissue two types of action:

1. Excitatory action

2. Electrotonic action.

The excitatory action is formulated in three Pfluger laws:

1. Under the action of direct current on the tissue, excitation occurs only at the moment of closing the circuit or at the moment of opening the circuit, or with a sharp change in current strength.

2. Excitation occurs when the circuit is under the cathode, and when it is opened, under the anode.

3. The cathode-closing threshold is less than the anode-break threshold.

Let's take a look at these laws:

1. Excitation occurs when closing and opening or with a strong current, because it is these processes that create the necessary conditions for the occurrence of depolarization of the membranes under the electrodes.

2. ^ Under the cathode, closing the circuit, we essentially introduce a powerful negative charge on the outer surface of the membrane. This leads to the development of the process of membrane depolarization under the cathode.

^ Therefore, it is under the cathode that the excitation process occurs when the circuit is closed.

Consider a cell under the anode. When the circuit is closed, a powerful positive charge is introduced to the surface of the membrane, which leads to membrane hyperpolarization. Therefore, there is no excitation under the anode. Under the influence of current develops accommodation. KUD is shifting following the membrane potential, but to a lesser extent. Excitability is reduced. No conditions for arousal

Let's open the circuit - the potential of the membrane will quickly return to its original level.

^ KUD cannot change quickly, it will return gradually and the rapidly changing membrane potential will reach KUD - there will be arousal . In that main reason that excitation arises at the moment of opening.

At the moment of opening under the cathode ^ KUD slowly returns to its original level, and the membrane potential does this quickly.

1. Under the cathode, with prolonged action of direct current on the tissue, a phenomenon will occur - cathodic depression.

2. An anode block will appear under the anode at the moment of closing.

The main sign of cathodic depression and the anode block is decrease in excitability and conductivity to zero level. However, the biological tissue remains alive.

^ Electrotonic action of direct current on tissue.

Under the electrotonic action is understood such an action of direct current on the tissue, which leads to a change in the physical and physiological properties of the tissue. In connection with these distinguish two types of electricity:


  1. Physical electrotone.

  2. Physiological electric tone.

Under the physical electric tone is understood a change in the physical properties of the membrane that occurs under the action of a direct current - a change permeability membranes, a critical level of depolarization.

Physiological electric tone is understood as a change in the physiological properties of the tissue. Namely - excitability, conduction under the influence of electric current.

In addition, the electrotone is divided into anelectroton and catelectroton.

Anelectroton - changes in the physical and physiological properties of tissues under the influence of the anode.

Kaelektroton - changes in the physical and physiological properties of tissues under the influence of a cathode.

The permeability of the membrane will change and this will be expressed in the hyperpolarization of the membrane and under the action of the anode the FAC will gradually decrease.

In addition, under the anode, under the action of a direct electric current, a physiological component of the electric tone. This means that excitability changes under the action of the anode. How does excitability change under the action of the anode? They turned on the electric current - the CUD shifted down, the membrane hyperpolarized, the level of the resting potential shifted sharply.

The difference between the KUD and the resting potential increases at the beginning of the electric current under the anode. Means excitability under the anode at the beginning will decrease. The membrane potential will slowly shift down, and the CUD will shift quite strongly. This will lead to the restoration of excitability to its original level, and with prolonged action of direct current excitability will increase under the anode, since the difference between the new KUDa level and the membrane potential will be less than at rest.

^ 10. Structure of biomembranes…

The organization of all membranes has much in common, they are built according to the same principle. The basis of the membrane is a lipid bilayer (double layer of amphiphilic lipids), which have a hydrophilic "head" and two hydrophobic "tails". In the lipid layer, lipid molecules are spatially oriented, facing each other with hydrophobic "tails", the heads of the molecules are facing the outer and inner surfaces of the membrane.

^ Membrane lipids: phospholipids, sphingolipids, glycolipids, cholesterol.

Perform, in addition to the formation of the bilipid layer, other functions:


  • form an environment for membrane proteins (allosteric activators of a number of membrane enzymes);

  • are the forerunners of some second intermediaries;

  • perform an "anchor" function for some peripheral proteins.

Among membrane proteins allocate:

peripheral - located on the outer or inner surfaces of the bilipid layer; on the outer surface, these include receptor proteins, adhesion proteins; on the inner surface - proteins of systems of secondary messengers, enzymes;

integral - partially immersed in the lipid layer. These include receptor proteins, adhesion proteins;

transmembrane - penetrate the entire thickness of the membrane, with some proteins passing through the membrane once, while others - many times. This type of membrane proteins forms pores, ion channels and pumps, carrier proteins, receptor proteins. Transmembrane proteins play a leading role in the interaction of the cell with the environment, providing signal reception, its passage into the cell, amplification at all stages of propagation.

In the membrane, this type of protein forms domains (subunits), which provide transmembrane proteins with the most important functions.

The domains are based on transmembrane segments formed by non-polar amino acid residues twisted in the form of an os-helix and extra-membrane loops representing the polar regions of proteins that can protrude far enough beyond the bilipid layer of the membrane (denoted as intracellular, extracellular segments), COOH- and NH 2 -terminal parts of the domain.

Often, the transmembrane, extra- and intracellular parts of the domain - subunits - are simply isolated. Membrane proteins also divided into:


  • structural proteins: give the membrane a shape, a number of mechanical properties (elasticity, etc.);

  • transport proteins:

  • form transport streams (ion channels and pumps, carrier proteins);

  • contribute to the creation of transmembrane potential.

  • proteins that provide intercellular interactions:

Adhesive proteins bind cells to each other or to extracellular structures;


  • protein structures involved in the formation of specialized intercellular contacts (desmosomes, nexuses, etc.);

  • proteins directly involved in the transmission of signals from one cell to another.

The membrane contains carbohydrates in the form glycolipids and glycoproteins. They form oligosaccharide chains, which are located on the outer surface of the membrane.

^ Membrane properties:

1. Self-assembly in aqueous solution.

2. Closure (self-linking, closure). The lipid layer always closes on itself with the formation of completely delimited compartments. This provides self-crosslinking when the membrane is damaged.

3. Asymmetry (transverse) - the outer and inner layers of the membrane differ in composition.

4. Fluidity (mobility) of the membrane. Lipids and proteins can, under certain conditions, move in their layer:


  • lateral mobility;

    • rotation;

    • bending,

And also go to another layer:


  • vertical movements (flip flops)

5. Semi-permeability (selective permeability, selectivity) for specific substances.

^ Functions of membranes

Each of the membranes in the cell plays a biological role.

Cytoplasmic membrane:

Separates the cell from the environment;

Carries out the regulation of metabolism between the cell and the microenvironment (transmembrane exchange);

Produces recognition and reception of stimuli;

Takes part in the formation of intercellular contacts;

Provides attachment of cells to the extracellular matrix;

Forms electrogenesis.

Date added: 2015-02-02 | Views: 3624 |

4. Lability- functional mobility, the rate of elementary cycles of excitation in the nervous and muscle tissues. The concept of "L." introduced by the Russian physiologist N. E. Vvedensky (1886), who considered the measure of L. to be the highest frequency of tissue stimulation reproduced by it without rhythm transformation. L. reflects the time during which the tissue restores performance after the next cycle of excitation. The greatest L. are distinguished by the processes of nerve cells - axons, capable of reproducing up to 500-1000 impulses per 1 sec; less labile central and peripheral points of contact - synapses (for example, a motor nerve ending can transmit no more than 100-150 excitations per 1 second to a skeletal muscle). Inhibition of the vital activity of tissues and cells (for example, by cold, drugs) reduces L., since at the same time the recovery processes slow down and the refractory period lengthens.

Parabiosis- a state bordering between life and death of the cell.

Causes of parabiosis- a variety of damaging effects on an excitable tissue or cell that do not lead to gross structural changes, but to some extent violate its functional state. Such reasons can be mechanical, thermal, chemical and other irritants.

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 reversible changes in protoplasmic proteins underlie parabiosis. Under the action of a damaging agent, the cell (tissue), without losing its structural integrity, completely stops functioning. This state develops in phase, 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 the biological death of the cell (tissue) occurs. If this agent is removed in time, then the tissue returns to its normal state in the same phase.

Experiments N.E. Vvedensky.

Vvedensky conducted experiments on a neuromuscular preparation of a frog. Testing stimuli of different strengths were successively applied to the sciatic nerve of the neuromuscular preparation. One stimulus was weak (threshold strength), that is, it caused the smallest contraction of the gastrocnemius muscle. Another stimulus was strong (maximum), that is, the smallest of those that cause the maximum contraction of the calf 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, and 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 amplitude of contraction 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 CNS. its physiological properties. Structure and classification of neurons.

Neurons- This is the main structural and functional unit of the nervous system, which has specific manifestations of excitability. The neuron is able to receive signals, process them into nerve impulses and conduct them to nerve endings that are in contact with another neuron or reflex organs (muscle or gland).

Types of neurons:

1. Unipolar (they have one process - an axon; characteristic of invertebrate ganglia);

2. Pseudo-unipolar (one process, dividing into two branches; characteristic of the ganglia of higher vertebrates).

3. Bipolar (there is an axon and a dendrite, typical for peripheral and sensory nerves);

4. Multipolar (axon and several dendrites - typical for the brain of vertebrates);

5. Isopolar (it is difficult to differentiate the processes of bi- and multipolar neurons);

6. Heteropolar (it is easy to differentiate the processes of bi- and multipolar neurons)



Functional classification:

1. Afferent (sensitive, sensory - they perceive signals from the external or internal environment);

2. Insertion connecting neurons with each other (ensure 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 - axon hillock;

4 - axon;

5 -Schwan cage;

6 - interception of Ranvier;

7 - efferent nerve endings.

Sequential synoptic union of all 3 neurons forms reflex arc.

Excitation, which arose in the form of a nerve impulse in any part of the neuron membrane, runs through its entire membrane and through all its processes: both along the axon and along the dendrites. transmitted excitation from one nerve cell to another only in one direction- from the axon transmitting neuron on perceiving neuron through synapses located on its dendrites, body or axon.

Synapses provide one-way transmission of excitation. Nerve fiber (outgrowth of a neuron) can transmit nerve impulses in both directions, and one-way excitation transfer appears only in nerve circuits consisting of several neurons connected by synapses. It is synapses that provide one-way transmission of excitation.

Nerve cells receive and process the information that comes to them. This information comes to them in the form of control chemicals: neurotransmitters . It may 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 operation of the neuron, but do not transmit excitation to it.

The nervous system plays an exceptional integrating role in the life of the organism, as it unites (integrates) it into a single whole and integrates it into environment. It ensures consistent performance separate parts organism ( coordination), maintaining an equilibrium state in the body ( homeostasis) and adaptation of the organism 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: shell, protoplasm, nucleus, mitochondria, ribosomes and other organelles.

Three parts are distinguished in a neuron: the cell body - the soma, a long process - the axon, and many short branched processes - dendrites. The soma performs metabolic functions, the 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 dendritic zone. The axon terminates in a group of terminal branches for signaling to other neurons or executing organs. Along with the general similarity in the structure of neurons, there is a great diversity due to their functional differences (Fig. 1).

Assimilation of the rhythm of stimulation by excitable structures

Lability can change during prolonged exposure to stimuli. This, in particular, is confirmed by the ability of the tissue to increase its functional mobility in the course of its life. At the same time, new properties appear in the tissue, and it acquires the ability to reproduce a higher rhythm of stimulation. This phenomenon, observed in tissues, was studied by a student and follower of Vvedensky, academician A.A. Ukhtomsky, and called the process mastering the rhythm .

Vvedensky explained the occurrence of pessimal contraction in the muscle as the result of the transition of the excitatory process into the inhibitory process, which occurs due to excessive depolarization of the tissue and proceeds as a cathodic depression.

The experimental facts that form the basis of the doctrine of parabiosis, N.E. Vvedensky (1901) outlined in his classic work "Excitation, inhibition and anesthesia."

The experiments were carried out on a neuromuscular preparation. The scheme of experience is shown in fig. 2092313240 and 209231324.

The neuromuscular preparation was placed in a humid chamber, and three pairs of electrodes were placed on its nerve:

1. for causing irritation (stimulation)

2. for the diversion of biocurrents to the site, which was supposed to be affected by the chemical.

3. for the diversion of biocurrents after the area, which was supposed to be affected by a chemical substance.

In addition, in the experiments, muscle contraction and nerve potential between the intact and altered areas were recorded.

The pulse repetition frequency after the altered area could be judged by the presence, nature and amplitude of tetanic contraction of the gastrocnemius muscle. But we will return to this after studying the physiology of muscle contraction (lecture 5).

If the area between the irritating electrodes and the muscle is subjected to the action of narcotic substances and continues to irritate the nerve, then the response to irritation disappears after a while.

Rice. 209231324. Scheme of experience

N.E. Vvedensky, studying the effect of drugs under such conditions and listening to the biocurrents of the nerve below the anesthetized area with a telephone, noticed that the rhythm of irritation begins to transform some time before the response of the muscle to irritation completely disappears.

Noting this phenomenon, N.E. Vvedensky subjected it to a thorough study and showed that in the reaction of the nerve to the effects of narcotic substances, three successively alternating phases can be distinguished:

1. leveling

2. paradoxical

3. brake



The isolated phases were characterized by varying degrees of excitability and conductivity when weak (rare), moderate, and strong (frequent) stimulations were applied to the nerve (Fig.).

Rice. 050601100. Parabiosis and its phases. A - stimuli of different strength and responses to them; B - to parabiosis; C - to equalization; D - paradoxical; E - inhibitory phase of parabiosis

AT equalization phase there is an equalization of the response to stimuli of different strengths and there comes a moment when responses of equal magnitude are recorded to stimuli of different strengths. This is because in the leveling phase, the decrease in excitability is more pronounced for strong and moderate stimuli than for stimulation of weak strength. A more rapid decrease in excitability and conductivity for greater force (frequency) predetermines the development of the next paradoxical phase.

AT paradoxical phase the reaction is greater, the smaller the force of irritation. At the same time, it can be observed when a response is recorded to weak and moderate irritations, but not to strong ones.

The paradoxical phase is changing braking phase when all stimuli become ineffective and unable to elicit a response.

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.

Galvanometric studies made it possible to reveal that the section of the nerve, on which the substance acts, has a negative charge in relation to the intact one, since it depolarizes.

Later Vvedensky used various methods effects on the nerve: chemicals (ammonia, etc.), heating and cooling, direct electric current, etc., and in all cases observed similar changes in excitability in the studied preparation. Taking into account that the discovered phenomena can occur not only under the influence of drugs, but also under the influence of various other influences, Vvedensky chose the term parabiosis , since during the inhibitory phase the nerve loses its physiological properties and is similar to the dead nerve, and, in addition, true death can follow the inhibitory phase.

Summarizing the results of studies on the study of parabiosis, N.E. Vvedensky concluded that parabiosis is a peculiar, local, long-term state of excitation that occurs in response to various external influences that can interact with propagating excitation, and develops against the background of excessive, excessive depolarization.

Living formations in a state of parabiosis are characterized by a decrease in excitability and lability. Microelectrode studies of parabiosis confirm its legitimacy. Registration of changes in the membrane potential, in particular, showed that the development of parabiosis phases actually proceeds against the background of progressive depolarization. It is believed that the mechanism of depolarization inhibition is due to the inactivation of the flow of sodium ions into the cell or fiber.

The doctrine of N.E. Vvedensky about parabiosis is universal, since the patterns of response identified in the study of a neuromuscular preparation are inherent in the whole organism. Parabiosis is a form of adaptive response of living entities to various influences, and the doctrine of parabiosis is widely used to explain the various mechanisms of response not only of cells, tissues, organs, but of the whole organism.