The concept of rudimentary reflexes. Reflex concept. Types of reflexes. Features of unconditioned (innate memory) and conditioned (acquired memory) reflexes

A living organism for a certain impact, taking place with the participation. According to the generally accepted classification, reflexes are divided into unconditioned and conditioned.

Unconditioned reflexes are innate, characteristic of this species, responses to environmental influences.

1. Vital (vital). The instincts of this group ensure the preservation of the life of the individual. They are characterized by the following signs:

a) dissatisfaction with the corresponding one leads to the death of the individual; and

b) to satisfy this or that need, no other individual of the given species is needed.

Vital instincts include:

- food,

- drinking,

- defensive,

- regulation of sleep-wakefulness,

- reflex to save energy.

2. Zoosocial (role). Reflexes of this group arise only when interacting with individuals of their own species. These include:

- sexual,

- parent,

- reflex of emotional resonance (empathy),

- territorial,

- hierarchical (reflexes of domination or submission).

3. Reflexes of self-development (satisfaction of ideal needs).

These reflexes are not associated with individual or species adaptation to the existing situation. They are directed towards the future. These reflexes cannot be deduced from other needs considered in the previous groups; these are independent reflexes. Self-development reflexes include:

- research

- imitation and game

- reflex of overcoming (resistance, freedom).

Conditioned reflexes are subdivided as follows.

Biologically:

- food;

- genital;

- defensive;

- motor;

- indicative - a reaction to a new stimulus.

Differences between the orienting reflex and other conditioned reflexes:

- congenital reaction of the body;

By the nature of the conditioned signal:

- natural - conditioned reflexes caused by acting in natural conditions: sight, conversation about food;

- artificial - caused by stimuli that are not associated with this reaction under normal conditions.

By the complexity of the conditional signal:

- simple - the conditioned signal consists of 1 stimulus (light causes the release of saliva);

- complex - the conditioned signal consists of a complex of stimuli:

- conditioned reflexes arising on a complex of simultaneously acting stimuli;

- conditioned reflexes arising on a complex of sequentially acting stimuli, each of them “layering” on the previous one;

- a conditioned reflex to a chain of stimuli that also act one after the other, but do not “overlap” each other.

The first two are easy, the last one is difficult.

By the type of irritant:

- exteroceptive - occur most easily;

The child is the first to develop proprioceptive reflexes (sucking reflex to posture).

By changing a particular function:

- positive - accompanied by increased function;

- negative - accompanied by a weakening of the function.

By the nature of the response:

- somatic;

- vegetative (vaso-motor).

By the combination of a conditioned signal and an unconditioned stimulus in time:

- cash - an unconditioned stimulus acts in the presence of a conditioned signal, the effect of these stimuli ends simultaneously.

Distinguish:

- coinciding available conditioned reflexes - the unconditioned stimulus acts 1-2 s after the conditioned signal;

- delayed - the unconditioned stimulus acts 3-30 s after the conditioned signal;

- belated - the unconditioned stimulus acts 1-2 minutes after the conditioned signal.

The first two come about easily, the last one is difficult.

- trace - the unconditioned stimulus acts after the termination of the conditioned signal. In this case, a conditioned reflex arises to trace changes in the brain region of the analyzer. The optimal interval is 1-2 minutes.

In various orders:

- conditioned reflex of the 1st order - is developed on the basis of an unconditioned reflex;

- conditioned reflex of the 2nd order - is developed on the basis of the conditioned reflex of the 1st order, etc.

In dogs, conditioned reflexes can be developed up to the 3rd order, in monkeys - up to the 4th order, in children - up to the 6th order, in adults - up to the 9th order.

So, unconditioned reflexes- constant innate responses of the body to certain actions of stimuli, carried out with the help of the nervous system. A distinctive feature of all unconditioned reflexes is their innateness, the ability to be inherited from generation to generation.

Among the characteristics of unconditioned reflexes, they are also distinguished, that they:

- are specific, that is, characteristic of all representatives of a given species;

- have a cortical representation, but can be carried out without the participation of the cerebral cortex;

- relatively constant, stable and highly stable;

- carried out in response to adequate stimuli applied to one specific receptive field.

Conditioned reflex is an acquired reflex characteristic of an individual (individual).

Conditioned reflexes:

- arise during the life of an individual and are not fixed genetically (not inherited);

- arise under certain conditions and disappear in their absence.

1.1 The role of physiology in the materialistic understanding of the essence of life. The significance of the works of I.M.Sechenov and I.P. Pavlov in the creation of the materialistic foundations of physiology.
2.2 Stages of development of development of physiology. Analytical and systematic approach to the study of body functions. Acute and chronic experiment method.
3.3 The definition of physiology as a science. Physiology as a scientific basis for diagnosing health and predicting the functional state and working capacity of a person.
4.4 Definition of physiological function. Examples of physiological functions of cells, tissues, organs and systems of the body. Adaptation as the main function of the body.
5.5 Concept of regulation of physiological functions. Mechanisms and methods of regulation. The concept of self-regulation.
6.6 Basic principles of reflex activity of the nervous system (determinism, analysis, synthesis, unity of structure and function, self-regulation)
7.7 Definition of reflex. Reflex classification. The modern structure of the reflex arc. Feedback, its meaning.
8.8 Humoral connections in the body. Characterization and classification of physiologically and biologically active substances. The relationship between the nervous and humoral mechanisms of regulation.
9.9 The doctrine of P.K. Anokhin about functional systems and self-regulation of functions. Nodal mechanisms of functional systems, general diagram
10.10 Self-regulation of the constancy of the internal environment of the body. The concept of homeostasis and homeokinesis.
11.11 Age features of the formation and regulation of physiological functions. Systemogenesis.
12.1 Irritability and excitability as the basis of tissue response to irritation. The concept of an irritant, types of irritants, characteristics. The concept of the threshold of irritation.
13.2 Laws of irritation of excitable tissues: the value of the strength of the stimulus, the frequency of the stimulus, its duration, the steepness of its growth.
14.3 Modern ideas about the structure and function of membranes. Ionic channels of membranes. Ionic gradients of the cell, mechanisms of origin.
15.4 Membrane potential, theory of its origin.
16.5. Action potential, its phases. Dynamics of membrane permeability in different phases of the action potential.
17.6 Excitability, methods of its assessment. Changes in excitability under the action of direct current (electroton, cathodic depression, accommodation).
18.7 Relationships between the phases of changes in excitability during excitation with the phases of the action potential.
19.8 Structure and classification of synapses. Mechanism of signal transmission in synapses (electrical and chemical) Ionic mechanisms of postsynaptic potentials, their types.
20.10 Determination of mediators and synoptic receptors, their classification and role in conducting signals in excitatory and inhibitory synapses.
21 Determination of mediators and synaptic receptors, their classification and role in the conduction of signals in excitatory and inhibitory synapses.
22.11 Physical and physiological properties of muscles. Types of muscle contractions. Muscle strength and work. The law of power.
23.12 Single contraction and its phases. Thetanus, factors affecting its size. The concept of optimum and pessimum.
24.13 Motor units, their classification. Role in the formation of dynamic and static contractions of skeletal muscles in vivo.
25.14 Modern theory of muscle contraction and relaxation.
26.16 Features of the structure and functioning of smooth muscles
27.17 Laws of conduction of excitation along the nerves. The mechanism of nerve impulse conduction through myelin-free and myelinated nerve fibers.
28.17 Receptors of the sense organs, concept, classification, basic properties and features. Excitation mechanism. Functional mobility concept.
29.1 Neuron as a structural and functional unit in the central nervous system. Classification of neurons by structural and functional characteristics. The mechanism of penetration of excitation in a neuron. Integrative function of a neuron.
Question 30.2 Definition of the nerve center (classical and modern). Properties of nerve centers due to their structural links (irradiation, convergence, aftereffect of excitation)
Question 32.4 Braking in CNS (I.M.Sechenov). Modern ideas about the main types of central inhibition of postsynaptic, presynaptic and their mechanisms.
Question 33.5 Determination of coordination in CNS. The basic principles of the coordination activity of the central nervous system: prescription, general "final" path, dominant, temporal connection, feedback.
Question 35.7 The medulla oblongata and the pons, the participation of their centers in the processes of self-regulation of functions. The reticular formation of the brainstem and its descending influence on the reflex activity of the spinal cord.
Question 36.8 Physiology of the midbrain, its reflex activity and participation in the processes of self-regulation of functions.
37.9 The role of the midbrain and medulla oblongata in the regulation of muscle tone. Decerebral stiffness and the mechanism of its occurrence (gamma-regidity).
Question 38.10 Static and statokinetic reflexes. Self-regulatory mechanisms for maintaining body balance.
Question 39.11 Physiology of the cerebellum, its influence on motor (alpha-regidity) and autonomic functions of the body.
40.12 Ascending activating and inhibiting influences of the reticular formation of the brainstem on the cerebral cortex. The role of the Russian Federation in the formation of the integral activity of the organism.
Question 41.13 Hypothalamus, characteristics of the main nuclear groups. The role of the hypothalamus in the integration of autonomic, somatic and endocrine functions, in the formation of emotions, motivations, stress.
Question 42.14 The limbic system of the brain, its role in the formation of motivations, emotions, self-regulation of autonomic functions.
Question 43.15 Thalamus, functional characteristics and features of the nuclear groups of the thalamus.
44.16. The role of the basal nuclei in the formation of muscle tone and complex motor acts.
45.17 Structural and functional organization of the cerebral cortex, projection and associative zones. Plasticity of the functions of the cortex.
46.18 Functional asymmetry of the bp cortex, dominance of the hemispheres and its role in the realization of higher mental functions (speech, thinking, etc.)
47.19 Structural and functional features of the autonomic nervous system. Mediators of vegetative NS, the main types of receptor substances.
48.20 Departments of autonomic ns, relative physiological antagonism and biological synergism of their effects on innervated organs.
49.21 Regulation of autonomic functions (kbp, libmic system, hypothalamus) of the body. Their role in the vegetative provision of purposeful behavior.
50.1 Determination of hormones, their formation and secretion. Action on cells and tissues. Classification of hormones according to different characteristics.
51.2 The hypothalamic-pituitary system, its functional connections. Trans and para pituitary regulation of the endocrine glands. The mechanism of self-regulation in the activity of the endocrine glands.
52.3 Hormones of the pituitary gland and their participation in the regulation of endocrine organs and body functions.
53.4 Physiology of the thyroid and parathyroid glands. Neurohumoral mechanisms of regulation of their functions.
55.6 Physiology of the adrenal glands. The role of hormones of the cortex and medulla in the regulation of body functions.
56.7 Sex glands. Male and female sex hormones and their physiological role in the formation of sex and the regulation of reproduction processes.
57.1 Concept of the blood system (Lang), its properties, composition, function. Composition of blood. Basic physiological blood constants and mechanisms of their maintenance.
58.2 Composition of blood plasma. Osmotic blood pressure fs, which ensures the constancy of the osmotic pressure of the blood.
59.3 Plasma proteins, their characteristics and functional significance. Oncotic pressure in blood plasma.
60.4 blood pH, physiological mechanisms that maintain the constancy of acid-base balance.
61.5 Erythrocytes, their functions. Counting methods. Types of hemoglobin, its compounds, their physiological significance. Hemolysis.
62.6 Regulation of erythro and leukopoiesis.
63.7 Concept of hemostasis. The process of blood coagulation and its phases. Factors accelerating and slowing down blood clotting.
64.8 Vascular-platelet hemostasis.
65.9 Coagulant, anticoagulant and fibrinolytic blood system, as the main components of the apparatus of the functional system for maintaining the fluid state of blood
66.10 Concept of blood groups. Avo and Rh factor systems. Determination of the blood group. Blood transfusion rules.
67.11 Lymph, its composition, functions. Non-vascular fluid media, their role in the body. Exchange of water between blood and tissues.
68.12 Leukocytes and their types. Counting methods. Leukocyte formula. Functions of leukocytes.
69.13 Platelets, quantity and functions in the body.
70.1 Significance of blood circulation for the body.
71.2 Heart, the importance of its chambers and valve apparatus. Cardiocycle and its structure.
73. PD of cardiomyocytes
74. Correlation of excitation, excitability and contraction of the cardiomyocyte in different phases of the cardiocycle. Extrasystoles
75.6 Intracardial and extracardiac factors involved in the regulation of the heart, their physiological mechanisms.
Extracardiac
Intracardiac
76. Reflex regulation of the heart. Reflexogenic zones of the heart and blood vessels. Intersystem cardiac reflexes.
77.8 Auscultation of the heart. Heart sounds, their origins, listening places.
78. Basic laws of hemodynamics. Linear and volumetric blood flow velocity in various parts of the circulatory system.
79.10 Functional classification of blood vessels.
80. Blood pressure in various parts of the circulatory system. Factors determining its value. Types of blood pressure. Mean arterial pressure concept.
81.12 Arterial and venous pulse, origin.
82.13 Physiological features of blood circulation in the myocardium, kidneys, lungs, brain.
83.14 The concept of basal vascular tone.
84. Reflex regulation of systemic arterial pressure. The importance of vascular reflexogenic zones. The vasomotor center, its characteristics.
85.16 Capillary blood flow and its features. Microcirculation.
89. Bloody and bloodless methods for determining blood pressure.
91. Comparison of ECG and FKG.
92.1 Breathing, its essence and main stages. External respiration mechanisms. Biomechanics of inhalation and exhalation. Pressure in the pleural cavity, its origin and role in the mechanism of ventilation of the lungs.
93.2 Gas exchange in the lungs. The partial pressure of gases (oxygen and carbon dioxide) in the alveolar air and the tension of gases in the blood. Methods for analyzing blood and air gases.
94. Transport of oxygen by blood. Dissociation curve of oxyhemoglobin. Influence of various factors on the affinity of hemoglobin for oxygen. Oxygen capacity of blood. Oxigemometry and oxyhemography.
98.7 Methods for determining lung volumes and capacities. Spirometry, spirography, pneumotachometry.
99 Respiratory center. Modern representation and its structure and localization. The autonomy of the respiratory center.
101 Self-regulation of the respiratory cycle, mechanisms of the change of respiratory phases. The role of peripheral and central mechanisms.
102 Humoral effects on respiration, the role of carbon dioxide and pH levels. The mechanism of the first inhalation of a newborn. The concept of respiratory analeptics.
103.12 Breathing under conditions of low and high barometric pressure and with a change in the gas environment.
104. FS providing constant blood gas composition. Analysis of its central and peripheral components
105.1. Digestion, its meaning. Digestive tract functions. Research in the field of digestion by I.P. Pavlova. Methods for studying the functions of the gastrointestinal tract in animals and humans.
106.2. Physiological bases of hunger and satiety.
107.3. Principles of regulation of the digestive system. The role of reflex, humoral and local regulatory mechanisms. Gastrointestinal hormones.
108.4. Digestion in the oral cavity. Self-regulation of the chewing act. The composition and physiological role of saliva. Regulation of salivation. The structure of the reflex arc of salivation.
109.5. Swallowing its phase is the self-regulation of this act. Functional features of the esophagus.
110.6. Digestion in the stomach. Composition and properties of gastric juice. Regulation of gastric secretion. The phases of the separation of gastric juice.
111.7. Digestion in the 12-persistent intestine. Exocrine pancreatic activity. Composition and properties of pancreatic juice. Regulation of pancreatic secretion.
112.8. The role of the liver in digestion: barrier and bile-forming functions. Regulation of the formation and secretion of bile into the 12-persistent intestine.
113.9. Motor activity of the small intestine and its regulation.
114.9. Cavity and parietal digestion in the small intestine.
115.10. Features of digestion in the colon, motility of the colon.
116 Fs, ensuring the consistency of the pit. The thing is in the blood. Analysis of central and peripheral components.
117) The concept of metabolism in the body. Assimilation and dissimilation processes. The plastic energy role of nutrients.
118) Methods for determining energy consumption. Direct and indirect calorimetry. Determination of the respiratory coefficient, its value for determining energy expenditure.
119) Basic metabolism, its importance for the clinic. Conditions for measuring basal metabolic rate. Factors affecting the basal metabolic rate.
120) Energy balance of the body. Working exchange. Energy costs of the body for different types of labor.
121) Physiological norms of nutrition, depending on age, type of work and state of the body. Principles of drawing up food rations.
122. The constancy of the temperature of the internal environment of the body as a condition for the normal course of metabolic processes….
123) Human body temperature and its daily fluctuations. The temperature of various areas of the skin and internal organs. Nervous and humoral mechanisms of thermoregulation.
125) Heat transfer. Methods for transferring heat from the surface of the body. Physiological mechanisms of heat transfer and their regulation
126) The system of excretion, its main organs and their participation in maintaining the most important constants of the internal environment of the body.
127) Nephron as a structural and functional unit of the kidney, structure, blood supply. The mechanism of formation of primary urine, its quantity and composition.
128) Formation of final urine, its composition. Reabsorption in the tubules, the mechanisms of its regulation. The processes of secretion and excretion in the renal tubules.
129) Regulation of kidney activity. The role of nervous and humoral factors.
130. Methods for assessing the magnitude of filtration, reabsorption and secretion of the kidneys. The concept of the coefficient of purification.
131.1 Pavlov's doctrine about analyzers. The concept of sensory systems.
132.3 Wiring department of analyzers. The role and participation of switching nuclei and reticular formation in the conduction and processing of afferent excitations
133.4 Cortical section of analyzers. Processes of higher cortical analysis of afferent excitations. Interaction of analyzers.
134.5 Adaptation of the analyzer, its peripheral and central mechanisms.
135.6 Characteristics of the visual analyzer. Receptor apparatus. Photochemical processes in the retina under the action of light. Perception of light.
136.7 Modern ideas about the perception of light. Methods for studying the function of the visual anatizer. The main forms of color vision impairment.
137.8 Auditory analyzer. Sound-collecting and sound-conducting apparatus. The receptor section of the auditory analyzer. The mechanism of the appearance of the receptor potential in the hair cells of the spinal organ.
138.9. Theory of sound perception. Methods of learning the auditory analyzer.
140.11 Physiology of the taste analyzer. Receptor, conduction and cortical divisions. Classification of taste sensations. Methods for the study of the taste analyzer.
141.12 Pain and its biological significance. Concept of nociception and central mechanisms of pain. Actinociceptive system. Neurochemical mechanisms of actinociception.
142. Concept of anti-pain (antinociceptive) system. Neurochemical mechanisms of antinociception, role of endorphins and exorphins.
143. Conditioned reflex as a form of adaptation of animals and humans to changing living conditions….
Rules for the development of conditioned reflexes
Classification of conditioned reflexes
144.2 Physiological mechanisms of the formation of conditioned reflexes. Classical and modern ideas about the formation of temporary connections.
Reflex- the main form of nervous activity. The body's response to irritation from the external or internal environment, which is carried out with the participation of the central nervous system, is called reflex.
According to a number of signs, reflexes can be divided into groups.
Unconditioned reflexes- hereditarily transmitted (congenital) reactions of the body, inherent in the entire species. They perform a protective function, as well as the function of maintaining homeostasis (adaptation to environmental conditions).
Unconditioned reflexes are an inherited, invariable reaction of the body to external and internal signals, regardless of the conditions for the occurrence and course of reactions. Unconditioned reflexes ensure the adaptation of the body to constant environmental conditions. The main types of unconditioned reflexes: food, protective, orienting, sexual.
An example of a protective reflex is the reflexive withdrawal of the hand from a hot object. Homeostasis is maintained, for example, by a reflex increase in breathing rate with an excess of carbon dioxide in the blood. Almost every part of the body and every organ is involved in reflex reactions.
The simplest neural networks, or arcs (according to Sherrington's expression), involved in unconditioned reflexes, are closed in the segmental apparatus of the spinal cord, but they can also close higher (for example, in the subcortical ganglia or in the cortex). Other parts of the nervous system are also involved in reflexes: brain stem, cerebellum, cerebral cortex.
Arcs of unconditioned reflexes are formed by the time of birth and persist throughout life. However, they can change under the influence of the disease. Many unconditioned reflexes appear only at a certain age; thus, the grasping reflex inherent in newborns fades away at the age of 3-4 months.
Conditioned reflexes arise in the course of individual development and the accumulation of new skills. The development of new temporary connections between neurons depends on the conditions of the external environment. Conditioned reflexes are formed on the basis of unconditioned ones with the participation of the higher parts of the brain.
The development of the doctrine of conditioned reflexes is associated primarily with the name of I.P. Pavlov. He showed that a new stimulus can start a reflex response if it is presented for some time together with an unconditioned stimulus. For example, if a dog is allowed to sniff meat, then gastric juice is secreted from it (this is an unconditioned reflex). If, at the same time as the meat, the bell rings, then the dog's nervous system associates this sound with food, and gastric juice will be secreted in response to the bell, even if the meat is not presented. Conditioned Reflexes Underlie Acquired Behavior
Reflex arc(nerve arch) - the path traversed by nerve impulses during the implementation of the reflex
The reflex arc consists of six components: receptors, afferent pathway, reflex center, efferent pathway, effector (working organ), feedback.
Reflex arcs can be of two types:
1) simple - monosynaptic reflex arcs (reflex arc of the tendon reflex), consisting of 2 neurons (receptor (afferent) and effector), between them there is 1 synapse;
2) complex - polysynaptic reflex arcs. They include 3 neurons (there may be more) - receptor, one or more intercalated and effector.
The feedback loop establishes a connection between the realized result of a reflex reaction and the nerve center, which issues executive commands. With the help of this component, an open reflex arc is transformed into a closed one.
Rice. 5. Reflex arc of the knee reflex:
1 - receptor apparatus; 2 - sensitive nerve fiber; 3 - intervertebral node; 4 - sensitive neuron of the spinal cord; 5 - motor neuron of the spinal cord; 6 - motor fiber of the nerve

Reflex- This is a stereotyped (monotonous, repeating the same), response of the body to the action of stimuli with the obligatory participation of the central nervous system.

Reflexes are divided into unconditional and conditional.

TO unconditioned reflexes relate:

1. Reflexes aimed at preserving the species. They are the most biologically significant, prevail over other reflexes, are dominant in a competitive situation, namely: sexual reflex, parental reflex, territorial reflex (this is the protection of one's territory; this reflex manifests itself in both animals and humans), hierarchical reflex (the principle of subordination is reflexively embedded in a person, i.e. we are ready to obey, but we definitely want to command too - relations in society are built on this, but there is also a biological basis).

2 self-preservation reflexes They are aimed at preserving the individual, personality, individual: drinking reflex, food reflex, defensive reflex, aggressive reflex (attack is the best defense).

3. Reflexes of self-development: research reflex, play reflex (pronounced in children; adults - business games), imitation reflex (imitation of certain personalities, events), overcoming reflex (freedom).

Instinct- a set of innate aspirations, expressed in the form of complex automatic behavior.

In a narrow sense, it is a set of complex hereditary acts of behavior characteristic of individuals of a given species under certain conditions. Instincts form the basis of animal behavior. In humans, instincts undergo modification under the influence of individual experience.

Differing from reflexes in complexity. Those. it is BEHAVIOR caused by certain INTERNAL influences (hormones, pain, sex drive). In fact, instinct lies in an inherited group of reflexes that act on the animal IN GENERAL, and not just cause a reaction, for example, of a small group of muscles.

Conditioned reflexes- these are reflexes acquired during life, they are individual and are not inherited, they are formed only on the basis of unconditioned ones. Conditioned reflexes provide a more subtle adaptation to environmental conditions, because it is they that allow a person to carry out an anticipatory reflection of reality (due to conditioned reflexes, we are prepared for the effects of real stimuli). The conditioned stimuli to which the conditioned reflex is formed are always of a signal nature, i.e. they signal that an unconditioned stimulus is about to act. The conditioned stimulus, after the elaboration of the conditioned reflex, upon presentation, evokes a reaction that was previously elicited by the unconditioned stimulus.

6. The variety of synapses in the central nervous system ...

The contact of a neuron with other cells is called synapse.

Synapses share by the method of transmission of excitation on

1.synapses with electrical transmission of excitation

2.synapses with chemical transmission of excitation

The first group of synapses is few in number, up to 1-3% of the total. The ways of influencing the process of conducting are not known.

The second group is synapses with chemical transmission.

Mediator molecules go to the postsynaptic membrane, to the region of the subsynaptic membrane, which has many chemoreceptors of the same type and form a complex "Mediator - receptor"... This triggers the activation of the corresponding receptor-guided ion channels.

Mediators are

1 .derivative amino acids.

The most widely distributed mediators in the central nervous system are amines:

acetylcholine- a choline derivative,

catecholamines: adrenaline, norepinephrine, dopamine - derivatives of tyrosine,

serotonin- a derivative of tryptophan,

histamine - histidine derivative ,

Other amino acid derivatives - GABA, glycine, glutamine and etc.

1. Neuropeptides- endorphins, enkephalins

Subsynaptic membrane receptors

The name of the receptor is determined by the mediator with which it interacts:

cholinergic receptors, adrenergic receptors, dopamine receptors, serotonin / tryptamine / receptors, histamine receptors, GABA receptors, endorphin receptors, etc.

Mediators have 2 types of action

1.ionotropic - change the permeability of the channels for ions

2.metabotropic - through secondary mediators, they start and inhibit the corresponding processes in the cells.

Mediators are biologically active substances, they are also synthesized in nerve cells. However, they do not stand out everywhere. They are concentrated and released only at the point of contact of the neuron with other cells.

All picks can be divided on excitatory mediators and inhibitory mediators. Consequently and synapses are divided into exciting and inhibitory.

Exciting mediators interacting with the receptor of the subsynaptic membrane cause the activation of sodium channels and form the incoming sodium current, which causes the appearance of partial depolarization, i.e. the receptor potential, which at the level of the synapse is denoted as excitatory postsynaptic potential (EPSP).

Brake pick causes an increase in the incoming potassium current or the incoming chlorine current, i.e. causes local hyperpolarization... This forms inhibitory postsynaptic potential (TPSP). End effect(action potential or inhibitory potential) is formed due to summation EPSP or TPSP.

Under normal, vivo conditions, the mediator is disconnected from the receptors and destroyed by enzymes (cholinesterase, etc.) that are present in the synapse. Approximately 20-30% of the neurotransmitter is removed in this way from the synaptic cleft - the first method of inactivation.

Another way to inactivate the mediator - pharmacy - reuptake by the presynaptic membrane... Due to this, the synapse sparingly consumes the mediator.

7. Inhibition in the central nervous system ...

The central part of the reflex arc performs its functions due to the constant interaction of processes of inhibition and excitation.

Central braking- This is inhibition that develops within the central nervous system. It is innate, genetically determined, it is a stereotyped reaction.

Braking- This is the suppression of the function of neurons in the central nervous system. Distinguish between primary and secondary central inhibition.

Secondary central braking- this is such inhibition that occurs after the primary excitation and is initiated by it.

The main mechanism of nervous activity in both the lowest and the most complex living organisms is a reflex. A reflex is the body's response to stimuli from the external or internal environment. Reflexes are distinguished by the following features:

They always begin with nervous excitement caused by some stimulus in one or another receptor;

They always end with a certain reaction of the body (for example, movement or secretion).

In general, reflex activity is a complex analyzing and synthesizing work of the cerebral cortex, the essence of which is the differentiation of numerous stimuli and the establishment of various connections between them. The analysis of stimuli is performed by complex nervous organs - analyzers. Each analyzer consists of three parts:

1) a peripheral perceiving organ (receptor);

2) the conducting afferent, i.e. centripetal, path through which nervous excitement is transmitted from the periphery to the center;

3) the cortical part of the analyzer.

The transmission of nervous excitation from the receptors first to the central parts of the nervous system, and then from them along the effective, ie, centrifugal, paths back to the receptors for the response, which takes place during the reflex, is carried out along the reflex arc. The reflex arc (reflex ring) consists of a receptor, an afferent nerve, a central link, an efferent nerve and an efferent \ ra (muscles or glands).

The initial analysis of stimuli is carried out at the receptors and in the lower parts of the brain. It is of an elementary nature and is due to the degree of perfection of one or another receptor. The highest and most subtle analysis of stimuli is carried out by the cerebral cortex, which is a set of cerebral endings of all analyzers.

In the course of reflex activity, the process of differential inhibition is also carried out, during which the excitations caused by unreinforced conditioned stimuli gradually fade away, while the excitations that strictly correspond to the main, reinforced conditioned stimulus remain. Due to the differential \ By precise inhibition, a very fine differentiation of stimuli is achieved. Because of this, the formation of conditioned reflexes to complex stimuli becomes possible. In this case, the conditioned reflex is caused by the action of only the complex of stimuli in its whole form and is not caused by the action of any one of the stimuli included in the complex.

In addition, a distinction is made between external unconditioned inhibition, which can occur in all parts of the nervous system, and internal conditioned inhibition, which develops only in the cerebral cortex. External unconditioned inhibition arises under the action of a constant stimulus, under the influence of which the conditioned reaction developed earlier is terminated. Under the action of a sudden external stimulus of sufficient strength, the developed conditioned reflex may appear weakly or even disappear altogether (for example, drivers who talk on a cell phone while driving often get into accidents).

Internal, or active, inhibition occurs when a conditioned reflex is extinguished when it is repeatedly evoked by a conditioned stimulus without reinforcement by a conditioned one (for example, this effect is used when treating a patient with alcoholism using coding or conditioned reflex therapy).

Unconditioned reflex is an innate, hereditarily fixed form of response to a biologically significant effect of the external world or to changes in the internal environment of the body. The term was introduced by I.P. Pavlov to designate a qualitatively unique class of reflexes - the basis of lifelong formation of conditioned reflex connections.

Unlike conditioned reflexes, which serve to adapt the organism to changing circumstances, unconditioned reflexes have their own characteristics and determine adaptation to relatively constant factors and do not depend on the presence of reinforcement. Reinforcement is an unconditioned stimulus that causes a significant reaction of the body, when combined with the preceding action of an indifferent stimulus, a classic conditioned reflex is developed. Reinforcement that is harmful to the body (for example, electric shock) is called negative (punishment); food reinforcement - positive (reward).

The tops of the arcs of unconditioned reflexes lie in the brain stem and partly in the spinal cord, so they can be carried out without the participation of the cerebral cortex, that is, involuntarily. But, since the work of the underlying departments is controlled by the cortex, and the processes in it affect the processes in other departments, there is also the possibility of an arbitrary influence on the action of unconditioned reflexes.

An unconditioned reflex takes place if:

Vital irritant at work;

The reflex center is in an excited state.

Unconditioned reflexes stop if:

Signals of achieving the required result have been received;

The innate program of actions has been fulfilled

The irritant has ceased to act;

A stronger (significant) stimulus began to act.

Usually, the following types of unconditioned reflexes are distinguished:

a) vegetative (salivary, changes in skin color, sweating, pain, reactions of the body to energy expenditures during activity, pupillary,

Bots of the heart and respiratory organs, etc.); b) behavioral (orientation-research, food, defensive, hygienic, procreation, migration, herd (group behavior).

Unconditioned reflexes are stable, they change little in the process of life. For example, it is very difficult for a person not to react when one or another unconditioned stimulus acts on him (that is, an irritant that necessarily causes the propagation of excitation along a certain, innately organized chain or network of neurons).

With the growth and development of humans and animals, the system of unconditional reflex connections turns out to be insufficient (poor, inert, too simple) to provide all the necessary variety of reactions in a constantly changing and infinitely diverse environment. Conditioned reflexes, temporary connections between some stimuli and certain responses to them, begin to form and acquire more and more importance in behavior.

Conditioned reflex is an innate or acquired (learned) reaction that automatically (involuntarily) follows in response to a biologically neutral stimulus, which has turned into a signal warning the body of an impending biologically important effect.

Any neutral external stimulus, if it coincides several times in time with the action on the body of an unconditioned stimulus, begins to cause a response characteristic of this unconditioned stimulus. For example, a type of food that, when first presented, did not cause salivation, begins to cause it after

then, as the appearance of food several times coincides with its ingress into the mouth, that is, with unconditioned irritation.

The transformation of one or another indifferent stimulus into a signal, that is, into a significant, conditioned stimulus, means that a connection has been developed between the centers of the brain that perceive this stimulus and other centers containing information about its important vital significance. This is how a conditioned reflex is formed. Thanks to such a transformation, an indifferent stimulus itself acquires meaning, becoming a signal of the onset of an important event, therefore a person begins to react to facts, events, signs that were previously indifferent to him. He begins to anticipate the course of future events, to react in advance to signs of upcoming important phenomena, which also increases the success of his behavior in the world around him.

Conditioned reflexes have their own characteristics that distinguish them from unconditioned:

All conditioned reflexes presuppose the formation in the cerebral cortex of temporary neural connections that need periodic reinforcement (individual conditioned reflexes in humans, developed on the basis of the multilateral connection of several stimuli and constantly reinforced in the process of life practice, often practically do not fade away - eating, dressing, communication with people, speaking in their native language, etc. - and, conversely, conditioned reflexes that are developed in activities that are not everyday (playing a musical instrument, reading and writing in a foreign language, sports, etc.) systematic reinforcements by repeating these activities);

Unconditioned reflexes may be different in individual representatives of the same animal species (for example, a trained animal has conditioned reflexes that an untrained animal of the same species does not possess);

The coincidence in time of the unconditioned and neutral stimuli is a necessary condition for a neutral stimulus to be able to evoke a reaction previously characteristic only of an unconditioned stimulus (thanks to this coincidence, a neutral stimulus seems to "signal" the body about the imminent impact of an unconditioned stimulus, as a result of which it is called a signal );

On the basis of the already fixed conditioned reflexes, new ones are formed, called conditioned reflexes of the first, second order, etc. education and training, conditioned reflexes up to the ninth order, layering on numerous reflexes developed in previous life experience).

There are different conditions for the formation of a conditioned reflex, which include:

Its implementation by the higher departments of the central nervous system;

The presence of a biologically neutral signal perceived by the sense organs (biological neutrality of the signal means that it does not in itself cause a strong unconditioned reaction);

The conditioned signal must precede in time the unconditioned stimulus (reinforcement);

The excitability of the unconditioned reflex center should be high enough;

No interference from other signals;

Repeated presentation of conditioned and unconditioned signals before the formation of an internal connection.

Conditioned reflexes are classified for various reasons. They may be:

Olfactory, tactile, etc., depending on the organ in which the reaction to irritation occurs;

Salivary, pupillary, etc., depending on the unconditioned reflex, on the basis of which they were formed;

Active and inhibitory. The former cause vigorous human activity, the latter stop, inhibit, restrain, interfere with it. Both can have both positive and negative significance for a person's solution to problems. Thus, an overly active reaction to danger - affective fear, panic - are harmful, and an inhibitory reaction to the command "stop!" - useful;

Reflexes to verbal signals and unconditioned stimuli. The former are well stable and often more significant. The latter can quickly disappear if they are not reinforced by frequently repeated exposure situations.

Reflex is the main form of activity of the nervous system.

The hypothesis of a fully reflexive nature of the activity of the higher parts of the brain was first developed by the scientist-physiologist I.M.Sechenov. Before him, physiologists and neurologists did not dare to raise the question of the possibility of physiological analysis of mental processes, which were left to be solved by psychology.

Further, the ideas of I.M.Sechenov were developed in the works of I.P. Pavlov, who opened the way for an objective experimental study of the functions of the cortex, developed a method for developing conditioned reflexes and created the doctrine of higher nervous activity. Pavlov, in his writings, introduced the division of reflexes into unconditioned, which are carried out by innate, hereditarily fixed nervous pathways, and conditioned, which, according to Pavlov's views, are carried out through nervous connections formed in the process of the individual life of a person or animal.

Charles S. Sherrington (Nobel Prize in Physiology or Medicine, 1932) made a great contribution to the formation of the doctrine of reflexes. He discovered coordination, mutual inhibition and facilitation of reflexes.

The meaning of the doctrine of reflexes

The study of reflexes provided a lot for understanding the very essence of nervous activity. However, the reflex principle itself could not explain many forms of purposeful behavior. At present, the concept of reflex mechanisms is supplemented by the concept of the role of needs in the organization of behavior, it has become a generally accepted idea that the behavior of animals, including humans, is active in nature and is determined not only by certain stimuli, but also by plans and intentions that arise under the influence of certain needs. These new ideas were expressed in the physiological concepts of PK Anokhin's "functional system" or NA Bernstein's "physiological activity". The essence of these concepts boils down to the fact that the brain can not only adequately respond to stimuli, but also foresee the future, actively make plans of behavior and implement them in action. The idea of an "action acceptor" or "model of the required future" allows us to speak of "outstripping reality."

General mechanism of reflex formation

Neurons and pathways of nerve impulses during a reflex act form a so-called reflex arc:

Stimulus - receptor - neuron - effector - reaction.

In humans, most reflexes are carried out with the participation of at least two neurons - sensory and motor (motor neuron, executive neuron). In the reflex arcs of most reflexes, interneurons (interneurons) are also involved - one or more. Any of these neurons in humans can be located both inside the central nervous system (for example, reflexes with the participation of central chemo- and thermoreceptors) and outside it (for example, reflexes of the metasympathetic division of the ANS).

Classification

On a number of grounds, reflexes can be divided into groups.

By type of education: conditioned and unconditioned reflexes.
By types of receptors: exteroceptive (skin, visual, auditory, olfactory), interoceptive (from receptors of internal organs) and proprioceptive (from receptors of muscles, tendons, joints)
By effectors: somatic, or motor (skeletal muscle reflexes), for example, flexor, extensor, locomotor, statokinetic, etc.; vegetative - digestive, cardiovascular, sweating, pupillary, etc.
By biological significance: defensive, or protective, digestive, sexual, indicative.
According to the degree of complexity of the neural organization of reflex arcs, monosynaptic arcs are distinguished, the arcs of which consist of afferent and efferent neurons (for example, the knee), and polysynaptic, the arches of which also contain one or more intercalary neurons and have two or more synaptic switches (for example, flexor painful).
By the nature of the influences on the activity of the effector: excitatory - causing and intensifying (facilitating) its activity, inhibitory - weakening and suppressing it (for example, a reflex increase in the heart rate of the sympathetic nerve and its reduction or cardiac arrest - by a wandering one).
According to the anatomical location of the central part of the reflex arcs, spinal reflexes and reflexes of the brain are distinguished. In the implementation of spinal reflexes, neurons located in the spinal cord are involved. An example of the simplest spinal reflex is pulling the hand away from a sharp pin. Reflexes of the brain are carried out with the participation of neurons in the brain. Among them are bulbar, carried out with the participation of neurons of the medulla oblongata; mesencephalic - with the participation of midbrain neurons; cortical - with the participation of neurons in the cerebral cortex. There are also peripheral reflexes carried out by the metasympathetic division of the ANS without the involvement of the brain and spinal cord.

Unconditional

Unconditioned reflexes are hereditarily transmitted (congenital) reactions of the body inherent in the entire species. They perform a protective function, as well as the function of maintaining homeostasis (constancy of the internal environment of the body).

Unconditioned reflexes are inherited, unchanging reactions of the body to certain influences of the external or internal environment, regardless of the conditions for the occurrence and course of reactions. Unconditioned reflexes ensure the adaptation of the body to constant environmental conditions. The main types of unconditioned reflexes: food, protective, orienting, sexual.

An example of a protective reflex is the reflexive withdrawal of the hand from a hot object. Homeostasis is maintained, for example, by a reflex increase in breathing rate with an excess of carbon dioxide in the blood. Almost every part of the body and every organ is involved in reflex reactions.

Neural organization of the simplest reflex

The simplest vertebrate reflex is considered to be monosynaptic. If the arc of the spinal reflex is formed by two neurons, then the first of them is represented by a cell of the spinal ganglion, and the second is a motor cell (motoneuron) of the anterior horn of the spinal cord. A long dendrite of the spinal ganglion goes to the periphery, forming a sensitive fiber of a nerve trunk, and ends with a receptor. The axon of the neuron of the spinal ganglion is part of the posterior root of the spinal cord, reaches the motor neuron of the anterior horn and through the synapse connects to the body of the neuron or one of its dendrites. The axon of the motor neuron of the anterior horn is part of the anterior root, then the corresponding motor nerve and ends with a motor plaque in the muscle.

There are no pure monosynaptic reflexes. Even the knee reflex, which is a classic example of a monosynaptic reflex, is polysynaptic, since the sensory neuron not only switches to the extensor motor neuron, but also gives off the axonal collateral, which switches to the insertion inhibitory neuron of the antagonist muscle, the flexor.

Conditional

Conditioned reflexes arise in the course of individual development and the accumulation of new skills. The development of new temporary connections between neurons depends on the conditions of the external environment. Conditioned reflexes are formed on the basis of unconditioned ones with the participation of the higher parts of the brain.

The development of the doctrine of conditioned reflexes is associated primarily with the name of I.P. Pavlov. He showed that a new stimulus can start a reflex response if it is presented for some time together with an unconditioned stimulus. For example, if a dog is allowed to sniff meat, then gastric juice is secreted from it (this is an unconditioned reflex). If, at the same time as the meat, the bell rings, then the dog's nervous system associates this sound with food, and gastric juice will be secreted in response to the bell, even if the meat is not presented. Conditioned reflexes are at the core of acquired behavior... These are the simplest programs. The world around us is constantly changing, so only those who quickly and expediently respond to these changes can successfully live in it. With the acquisition of life experience in the cerebral cortex, a system of conditioned reflex connections develops. This system is called dynamic stereotype... It underlies many habits and skills. For example, having learned to skate, bike, we subsequently no longer think about how we should move so as not to fall.

Axon reflex

The axon reflex is carried out along the branches of the axon without the participation of the neuron body. The reflex arc of the axon reflex does not contain synapses and neuronal bodies. With the help of axon reflexes, the regulation of the activity of internal organs and blood vessels can be carried out (relatively) independently of the central nervous system.

Pathological reflexes

Pathological reflexes is a neurological term for reflex reactions that are unusual for a healthy adult. In some cases, they are characteristic of earlier stages of phylo- or ontogenesis.

There is an opinion that mental dependence on something is caused by the formation of a conditioned reflex. For example, mental dependence on drugs is associated with the fact that the intake of a certain substance is associated with a pleasant state (a conditioned reflex is formed, which persists for almost the entire life).

Harlampy Tiras, Ph.D. in Biology, believes that "the idea of conditioned reflexes that Pavlov worked with is entirely based on forced behavior, and this gives an incorrect registration [of experimental results]." “We insist: the object should be studied when it is ready for it. Then we act as observers without raping the animal, and, accordingly, we get more objective results. " What exactly the author means by “violence” of an animal and what are the “more objective” results, the author does not specify.

Notes (edit)

, with. 320.
Pavlov I. Reflex of Freedom P. 163.