Norms

Introduced the term reflex. Classification of reflexes

1.1The 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 physiology. Analytical and systematic approach to the study of body functions. Method of acute and chronic experiment.
3.3 Definition of physiology as a science. Physiology as the scientific basis for diagnosing health and predicting the functional state and performance of a person.
4.4 Determination 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 The concept of regulation of physiological functions. Mechanisms and methods of regulation. The concept of self-regulation.
6.6Basic principles of reflex activity of the nervous system (determinism, synthesis analysis, unity of structure and function, self-regulation)
7.7 Definition of reflex. Classification of reflexes. Modern structure of the reflex arc. Feedback, its meaning.
8.8 Humoral connections in the body. Characteristics and classification of physiologically and biologically active substances. The relationship between nervous and humoral regulatory mechanisms.
9.9 Teachings of P.K. Anokhin about functional systems and self-regulation of functions. Nodal mechanisms of functional systems, general diagram
10.10Self-regulation of the constancy of the internal environment of the body. The concept of homeostasis and homeokinesis.
11.11 Age-related 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 a stimulus, types of stimuli, characteristics. The concept of irritation threshold.
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 increase.
14.3 Modern ideas about the structure and function of membranes. Membrane ion channels. Cell ion gradients, 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 for its assessment. Changes in excitability under the influence of direct current (electroton, cathodic depression, accommodation).
18.7 Correlations between the phases of changes in excitability during excitation and 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 Definition of mediators and synoptic receptors, their classification and role in conducting signals in excitatory and inhibitory synapses.
21Definition of transmitters 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. Strength and muscle function. Law of force.
23.12 Single contraction and its phases. Tetanus, factors influencing 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 natural conditions.
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 through nerves. The mechanism of nerve impulse transmission along unmyelinated and myelinated nerve fibers.
28.17 Receptors of sensory organs, concept, classification, basic properties and features. Excitation mechanism. The concept of functional mobility.
29.1 Neuron as a structural and functional unit in the central nervous system. Classification of neurons according to structural and functional characteristics. The mechanism of excitation penetration in a neuron. Integrative function of a neuron.
Question 30.2 Definition of the nerve center (classical and modern). Properties of nerve centers determined by their structural links (irradiation, convergence, aftereffect of excitation)
Question 32.4 Inhibition in the central nervous system (I.M. Sechenov). Modern ideas about the main types of central inhibition, postsynaptic, presynaptic and their mechanisms.
Question 33.5 Definition of coordination in the central nervous system. Basic principles of the coordination activity of the central nervous system: reciprocity, common “final” path, dominant, temporary connection, feedback.
Question 35.7 The medulla oblongata and the pons, the participation of their centers in the processes of self-regulation of functions. 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. Decerebrate rigidity and the mechanism of its occurrence (gamma rigidity).
Question 38.10 Static and statokinetic reflexes. Self-regulatory mechanisms 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 inhibitory influences of the reticular formation of the brain stem on the cerebral cortex. The role of the Russian Federation in the formation of the integrity of the body.
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, motivation, stress.
Question 42.14 The limbic system of the brain, its role in the formation of motivation, emotions, self-regulation of autonomic functions.
Question 43.15 Thalamus, functional characteristics and features of nuclear groups of the thalamus.
44.16. The role of the basal ganglia in the formation of muscle tone and complex motor acts.
45.17 Structural and functional organization of the cerebral cortex, projection and association zones. Plasticity of cortex functions.
46.18 Functional asymmetry of the BP cortex, dominance of the hemispheres and its role in the implementation of higher mental functions (speech, thinking, etc.)
47.19 Structural and functional features of the autonomic nervous system. Autonomic neurotransmitters, main types of receptor substances.
48.20 Divisions of the autonomic nervous system, relative physiological antagonism and biological synergism of their effects on innervated organs.
49.21 Regulation of autonomic functions (kbp, limbic system, hypothalamus) of the body. Their role in the autonomic support of goal-directed behavior.
50.1 Determination of hormones, their formation and secretion. Effect on cells and tissues. Classification of hormones according to various criteria.
51.2 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 Pituitary hormones and their participation in the regulation of endocrine organs and body functions.
53.4 Physiology of the thyroid and parathyroid glands. Neurohumoral mechanisms regulating 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 regulation of reproductive processes.
57.1 Concept of the blood system (Lang), its properties, composition, functions. Composition of blood. Basic physiological blood constants and mechanisms of their maintenance.
58.2 Composition of blood plasma. Blood osmotic pressure fs, ensuring the constancy of blood osmotic pressure.
59.3 Blood 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 Red blood cells and 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 that accelerate and slow down blood clotting.
64.8 Vascular-platelet hemostasis.
65.9 Coagulation, anticoagulation and fibrinolytic blood systems as the main components of the apparatus of a functional system for maintaining a fluid state of blood
66.10 Concept of blood groups. Avo and Rh factor systems. Determination of blood group. Rules for blood transfusion.
67.11 Lymph, its composition, functions. Non-vascular liquid 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 The importance of blood circulation for the body.
71.2 Heart, the significance of its chambers and valve apparatus. Cardiocycle and its structure.
73. PD of cardiomyocytes
74. The ratio of excitation, excitability and contraction of the cardiomyocyte in various phases of the cardiac cycle. Extrasystoles
75.6 Intracardiac and extracardiac factors involved in the regulation of cardiac activity, their physiological mechanisms.
Extracardiac
Intracardiac
76. Reflex regulation of heart activity. Reflexogenic zones of the heart and blood vessels. Intersystem cardiac reflexes.
77.8 Auscultation of the heart. Heart sounds, their origin, listening locations.
78. Basic laws of hemodynamics. Linear and volumetric velocity of blood flow 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 that determine its value. Types of blood pressure. The concept of mean arterial pressure.
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 blood pressure. The importance of vascular reflexogenic zones. 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 FCG.
92.1 Breathing, its essence and main stages. Mechanisms of external respiration. Biomechanics of inhalation and exhalation. Pressure in the pleural cavity, its origin and role in the ventilation mechanism.
93.2Gas exchange in the lungs. Partial pressure of gases (oxygen and carbon dioxide) in the alveolar air and gas tension in the blood. Methods for analyzing blood and air gases.
94. Transport of oxygen in the blood. Dissociation curve of oxyhemoglobin. The influence of various factors on the affinity of hemoglobin for oxygen. Oxygen capacity of the blood. Oxygemometry and oxygemography.
98.7 Methods for determining pulmonary volumes and capacities. Spirometry, spirography, pneumotachometry.
99Respiratory center. Modern representation of its structure and localization. Autonomy of the respiratory center.
101 Self-regulation of the respiratory cycle, mechanisms of change of respiratory phases. The role of peripheral and central mechanisms.
102 Humoral influences on respiration, the role of carbon dioxide and pH levels. The mechanism of the first breath of a newborn. The concept of respiratory analeptics.
103.12 Breathing under conditions of low and high barometric pressure and when the gas environment changes.
104. Fs ensures the constancy of the blood gas composition. Analysis of its central and peripheral components
105.1. Digestion, its meaning. Functions of the digestive tract. Research in the field of digestion by P. Pavlov. 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. Composition and physiological role of saliva. Regulation of salivation. The structure of the reflex arc of salivation.
109.5. Swallowing is the phase of 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. Phases of gastric juice separation.
111.7. Digestion in the duodenum. Exocrine activity of the pancreas. 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 duodenum.
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 large intestine, colon motility.
116 Fs, ensuring constant power supply. The thing is in the blood. Analysis of central and peripheral components.
117) The concept of metabolism in the body. Processes of assimilation and dissimilation. Plastic energetic role of nutrients.
118) Methods for determining energy consumption. Direct and indirect calorimetry. Determination of the respiratory coefficient, its significance for determining energy consumption.
119) Basic metabolism, its significance for the clinic. Conditions for measuring basal metabolism. Factors influencing the basal metabolic rate.
120) Energy balance of the body. Work exchange. Energy expenditure of the body during different types of labor.
121) Physiological nutritional standards depending on age, type of work and state of the body. Principles of compiling food rations.
122. 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. Temperature of various areas of the skin and internal organs. Nervous and humoral mechanisms of thermoregulation.
125) Heat dissipation. Methods of heat transfer from the surface of the body. Physiological mechanisms of heat transfer and their regulation
126) The excretory system, 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 tubules, mechanisms of its regulation. 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 amount of filtration, reabsorption and secretion of the kidneys. The concept of purification coefficient.
131.1 Pavlov's teaching on analyzers. Concept of sensory systems.
132.3 Conductor 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 influence of light. Perception of light.
136.7 Modern ideas about the perception of light. Methods for studying the function of the visual analyzer. The main forms of color vision impairment.
137.8 Hearing analyzer. Sound-collecting and sound-conducting apparatus. Receptor section of the auditory analyzer. Mechanism of the occurrence of receptor potential in the hair cells of the spinal organ.
138.9. Theory of sound perception. Methods for studying the auditory analyzer.
140.11 Physiology of the taste analyzer. Receptor, conduction and cortical sections. Classification of taste sensations. Methods for studying the taste analyzer.
141.12 Pain and its biological significance. The concept of nociception and central mechanisms of pain. Actinociceptive system. Neurochemical mechanisms of actinociception.
142. The concept of the antipain (antinociceptive) system. Neurochemical mechanisms of antinociception, rolendorphins and exorphins.
143. Conditioned reflex as a form of adaptation of animals and humans to changing living conditions….
Rules for developing conditioned reflexes
Classification of conditioned reflexes

7.7 Definition of reflex. Classification of reflexes. Modern structure of the reflex arc. Feedback, its meaning.

Reflex- the main form of nervous activity. The body's response to stimulation from the external or internal environment, carried out with the participation of the central nervous system, is called reflex.

Based on a number of characteristics, reflexes can be divided into groups

By type of education: conditioned and unconditioned reflexes

By type of receptor: exteroceptive (skin, visual, auditory, olfactory), interoceptive (from receptors of internal organs) and proprioceptive (from receptors of muscles, tendons, joints)

By effector: somatic or motor (skeletal muscle reflexes), for example flexor, extensor, locomotor, statokinetic, etc.; vegetative internal organs - digestive, cardiovascular, excretory, secretory, etc.

According to biological significance: defensive, or protective, digestive, sexual, orientation.

According to the degree of complexity of the neural organization of reflex arcs, a distinction is made between monosynaptic, whose arcs consist of afferent and efferent neurons (for example, knee), and polysynaptic, whose arcs also contain 1 or more intermediate neurons and have 2 or several synaptic switches (for example, flexor).

According to the nature of the influences on the activity of the effector: excitatory - causing and enhancing (facilitating) its activity, inhibitory - weakening and suppressing it (for example, a reflex increase in heart rate by the sympathetic nerve and a decrease in it or cardiac arrest by the vagus).

Based on the anatomical location of the central part of the reflex arcs, spinal reflexes and cerebral reflexes are distinguished. Neurons located in the spinal cord are involved in the implementation of spinal reflexes. An example of the simplest spinal reflex is the withdrawal of a hand from a sharp pin. Brain reflexes are carried out with the participation of brain neurons. Among them there 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.

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, unchangeable reaction of the body to external and internal signals, regardless of the conditions for the occurrence and course of reactions. Unconditioned reflexes ensure the body's adaptation to constant environmental conditions. The main types of unconditioned reflexes: food, protective, orientation, sexual.

An example of a defensive reflex is the reflexive withdrawal of the hand from a hot object. Homeostasis is maintained, for example, by a reflex increase in breathing when there is 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), involved in unconditioned reflexes, are closed in the segmental apparatus of the spinal cord, but can also be closed higher (for example, in the subcortical ganglia or in the cortex). Other parts of the nervous system are also involved in reflexes: the brain stem, cerebellum, and cerebral cortex.

The arcs of unconditioned reflexes are formed at the time of birth and remain throughout life. However, they can change under the influence of illness. Many unconditioned reflexes appear only at a certain age; Thus, the grasping reflex characteristic of newborns fades away at the age of 3-4 months.

Conditioned reflexes arise during individual development and accumulation of new skills. The development of new temporary connections between neurons depends on environmental conditions. Conditioned reflexes are formed on the basis of unconditioned ones with the participation of 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 initiate a reflex response if it is presented for some time together with an unconditioned stimulus. For example, if you let a dog smell meat, it will secrete gastric juice (this is an unconditioned reflex). If you ring a bell at the same time as the meat, the dog’s nervous system associates this sound with food, and gastric juice will be released in response to the bell, even if the meat is not presented. Conditioned reflexes underlie acquired behavior

Reflex arc(nerve arc) - the path traversed by nerve impulses during the implementation of a 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), there is 1 synapse between them;

2) complex – polysynaptic reflex arcs. They consist of 3 neurons (there may be more) - a receptor, one or more intercalary and an effector.

The feedback loop establishes a connection between the realized result of the reflex response and the nerve center that issues executive commands. With the help of this component, the open reflex arc is transformed into a closed one.

Rice. 5. Reflex arc of the knee reflex:

1 - receptor apparatus; 2 - sensory nerve fiber; 3 - intervertebral node; 4 - sensory neuron of the spinal cord; 5 - motor neuron of the spinal cord; 6 - motor fiber of the nerve

Higher nervous activity (HNA)

Higher nervous activity (HNA) is a complex and interconnected set of nervous processes that underlie human behavior. GND ensures maximum human adaptability to environmental conditions.

GND is based on complex electrical and chemical processes occurring in the cells of the cerebral cortex. By receiving information through the senses, the brain ensures the interaction of the body with the environment and maintains the constancy of the internal environment in the body.

The doctrine of higher nervous activity is based on the works of I.M. Sechenov - “Reflexes of the brain”, I.P. Pavlova (theory of conditioned and unconditioned reflexes), P.K. Anokhin (theory of functional systems) and numerous other works.

Features of human higher nervous activity:

developed mental activity;
speech;
ability for abstract logical thinking.

The creation of the doctrine of higher nervous activity began with the works of the great Russian scientists I.M. Sechenov and I.P. Pavlova.

Ivan Mikhailovich Sechenov in his book “Reflexes of the Brain” proved that a reflex is a universal form of interaction between the body and the environment, that is, not only involuntary, but also voluntary, conscious movements have a reflex character. They begin with irritation of any sensory organs and continue in the brain in the form of certain nervous phenomena that lead to the launch of behavioral reactions.

A reflex is the body's response to irritation, occurring with the participation of the nervous system.

THEM. Sechenov argued that brain reflexes include three parts:

The first, initial link is stimulation in the senses caused by external influences.
The second, central link is the processes of excitation and inhibition occurring in the brain. On their basis, mental phenomena arise (sensations, ideas, feelings, etc.).
The third, final link is the movements and actions of a person, i.e. his behavior. All these links are interconnected and condition each other.

Sechenov concluded that the brain is an area of continuous change of excitation and inhibition. These two processes constantly interact with each other, which leads to both strengthening and weakening (delay) of reflexes. He also drew attention to the existence of innate reflexes, which people inherit from their ancestors, and acquired ones, which arise throughout life as a result of learning. I.M. Sechenov’s assumptions and conclusions were ahead of their time.

The successor of the ideas of I.M. Sechenov became I.P. Pavlov.

Ivan Petrovich Pavlov divided all reflexes that arise in the body into unconditional and conditional.

Unconditioned reflexes

Unconditioned reflexes are inherited by offspring from their parents, persist throughout the life of the organism and are reproduced from generation to generation ( permanent). They are characteristic of all individuals of a certain species, i.e. group.

In unconditioned reflexes constant reflex arcs, which pass through the brain stem or through the spinal cord (for their implementation participation of the cortex is not necessarycerebral hemispheres).

There are food, defensive, sexual and indicative unconditioned reflexes.

Food: separation of digestive juices in response to irritation of oral receptors, swallowing, sucking movements in a newborn.
Defensive: withdrawal of a hand that has touched a hot object or when experiencing painful irritation, coughing, sneezing, blinking, etc.
Genital: The process of reproduction is associated with sexual reflexes.
Approximate(I.P. Pavlov called it the “what is this?” reflex) ensures the perception of an unfamiliar stimulus. An indicative reflex appears in response to a new stimulus: a person becomes alert, listens, turns his head, squints his eyes, and thinks.

Thanks to unconditioned reflexes, the integrity of the body is preserved, the constancy of its internal environment is maintained, and reproduction occurs.

A complex chain of unconditioned reflexes is called instinct.

Example:

A mother feeds and protects her child, birds build nests - these are examples of instincts.

Conditioned reflexes

Along with hereditary (unconditioned) reflexes, there are reflexes that are acquired by every person throughout life. Such reflexes individual, and certain conditions are necessary for their formation, which is why they were called conditional.

A reflex is the body's response to internal or external stimulation, carried out and controlled by the central nervous system. The first scientists who developed ideas about what was previously a mystery were our compatriots I.P. Pavlov and I.M. Sechenov.

What are unconditioned reflexes?

An unconditioned reflex is an innate, stereotypical reaction of the body to the influence of the internal or environmental environment, inherited by the offspring from the parents. It remains in a person throughout his life. Reflex arcs pass through the brain and the cerebral cortex does not take part in their formation. The significance of the unconditioned reflex is that it ensures the adaptation of the human body directly to those environmental changes that often accompanied many generations of his ancestors.

What reflexes are unconditioned?

An unconditioned reflex is the main form of activity of the nervous system, an automatic reaction to a stimulus. And since a person is influenced by various factors, the reflexes are different: food, defensive, orientation, sexual... Food include salivation, swallowing and sucking. Defensive actions include coughing, blinking, sneezing, and jerking limbs away from hot objects. Approximate reactions include turning the head and squinting the eyes. Sexual instincts include those associated with reproduction, as well as caring for offspring. The significance of the unconditioned reflex is that it ensures the preservation of the integrity of the body and maintains the constancy of the internal environment. Thanks to him, reproduction occurs. Even in newborn children, one can observe an elementary unconditioned reflex - this is sucking. By the way, it is the most important. The irritant in this case is touching the lips of any object (pacifier, mother's breast, toy or finger). Another important unconditioned reflex is blinking, which occurs when a foreign body approaches the eye or touches the cornea. This reaction belongs to the protective or defensive group. Also observed in children, for example, when exposed to strong light. However, the signs of unconditioned reflexes are most clearly manifested in various animals.

What are conditioned reflexes?

Conditioned reflexes are those acquired by the body during life. They are formed on the basis of inherited ones, subject to exposure to an external stimulus (time, knocking, light, and so on). A striking example is the experiments conducted on dogs by academician I.P. Pavlov. He studied the formation of this type of reflexes in animals and was the developer of a unique method for obtaining them. So, to develop such reactions, the presence of a regular stimulus - a signal - is necessary. It triggers the mechanism, and repeated repetition of the stimulus allows it to develop. In this case, a so-called temporary connection arises between the arcs of the unconditioned reflex and the centers of the analyzers. Now the basic instinct awakens under the influence of fundamentally new external signals. These stimuli from the surrounding world, to which the body was previously indifferent, begin to acquire exceptional, vital importance. Each living creature can develop many different conditioned reflexes during its life, which form the basis of its experience. However, this applies only to this particular individual; this life experience will not be inherited.

An independent category of conditioned reflexes

It is customary to classify into a separate category conditioned reflexes of a motor nature developed throughout life, that is, skills or automated actions. Their meaning is to master new skills, as well as develop new motor forms. For example, over the entire period of his life a person masters many special motor skills that are associated with his profession. They are the basis of our behavior. Thinking, attention, and consciousness are freed up when performing operations that have reached automaticity and become a reality of everyday life. The most successful way to master skills is to systematically perform the exercise, timely correction of noticed errors, and knowledge of the ultimate goal of any task. If the conditioned stimulus is not reinforced by the unconditioned stimulus for some time, it is inhibited. However, it does not disappear completely. If you repeat the action after some time, the reflex will be restored fairly quickly. Inhibition can also occur when a stimulus of even greater strength appears.

Compare unconditioned and conditioned reflexes

As mentioned above, these reactions differ in the nature of their occurrence and have different formation mechanisms. In order to understand what the difference is, just compare unconditioned and conditioned reflexes. Thus, the first ones are present in a living creature from birth; throughout life they do not change or disappear. In addition, unconditioned reflexes are the same in all organisms of a particular species. Their significance lies in preparing a living being for constant conditions. The reflex arc of this reaction passes through the brain stem or spinal cord. As an example, here are some (congenital): active secretion of saliva when a lemon enters the mouth; sucking movement of the newborn; coughing, sneezing, withdrawing hands from a hot object. Now let's look at the characteristics of conditioned reactions. They are acquired throughout life, can change or disappear, and, no less important, each organism has its own individual (its own). Their main function is to adapt a living creature to changing conditions. Their temporary connection (reflex centers) is created in the cerebral cortex. An example of a conditioned reflex is the reaction of an animal to a nickname or the reaction of a six-month-old child to a bottle of milk.

Unconditioned reflex diagram

According to the research of academician I.P. Pavlova, the general scheme of unconditioned reflexes is as follows. Certain receptor nerve devices are affected by certain stimuli from the internal or external world of the body. As a result, the resulting irritation transforms the entire process into the so-called phenomenon of nervous excitation. It is transmitted along nerve fibers (as if through wires) to the central nervous system, and from there it goes to a specific working organ, already turning into a specific process at the cellular level of a given part of the body. It turns out that certain stimuli are naturally connected with this or that activity in the same way as cause and effect.

Features of unconditioned reflexes

The characteristics of unconditioned reflexes presented below systematize the material presented above; it will help to finally understand the phenomenon we are considering. So, what are the features of inherited reactions?

Unconditioned instinct and reflex of animals

The exceptional constancy of the nervous connection underlying unconditional instinct is explained by the fact that all animals are born with a nervous system. She is already able to respond appropriately to specific environmental stimuli. For example, a creature may flinch at a sharp sound; he will secrete digestive juice and saliva when food enters his mouth or stomach; it will blink when visually stimulated, and so on. Innate in animals and humans are not only individual unconditioned reflexes, but also much more complex forms of reactions. They are called instincts.

An unconditioned reflex, in fact, is not a completely monotonous, template, transfer reaction of an animal to an external stimulus. It is characterized, although elementary, primitive, but still by variability, variability, depending on external conditions (strength, peculiarities of the situation, position of the stimulus). In addition, it is influenced by the internal states of the animal (decreased or increased activity, posture, etc.). So, also I.M. Sechenov, in his experiments with decapitated (spinal) frogs, showed that when the toes of the hind legs of this amphibian are exposed, the opposite motor reaction occurs. From this we can conclude that the unconditioned reflex still has adaptive variability, but within insignificant limits. As a result, we find that the balancing of the organism and the external environment achieved with the help of these reactions can be relatively perfect only in relation to slightly changing factors of the surrounding world. The unconditioned reflex is not able to ensure the animal’s adaptation to new or sharply changing conditions.

As for instincts, sometimes they are expressed in the form of simple actions. For example, the rider, thanks to his sense of smell, finds the larvae of another insect under the bark. It pierces the bark and lays its egg in the found victim. This ends all of its actions that ensure continuation of the family. There are also complex unconditioned reflexes. Instincts of this kind consist of a chain of actions, the totality of which ensures procreation. Examples include birds, ants, bees and other animals.

Species specificity

Unconditioned reflexes (specific) are present in both humans and animals. It should be understood that such reactions will be the same in all representatives of the same species. An example is a turtle. All species of these amphibians retract their heads and limbs into their shell when danger arises. And all the hedgehogs jump and make a hissing sound. In addition, you should know that not all unconditioned reflexes occur at the same time. These reactions vary with age and season. For example, the breeding season or the motor and sucking actions that appear in an 18-week fetus. Thus, unconditioned reactions are a kind of development for conditioned reflexes in humans and animals. For example, as cubs grow older, they transition to the category of synthetic complexes. They increase the body's adaptability to external environmental conditions.

Unconditional inhibition

In the process of life, each organism is regularly exposed - both from the outside and from the inside - to various stimuli. Each of them is capable of causing a corresponding reaction - a reflex. If all of them could be realized, then the life activity of such an organism would become chaotic. However, this does not happen. On the contrary, reactionary activity is characterized by consistency and orderliness. This is explained by the fact that unconditioned reflexes are inhibited in the body. This means that the most important reflex at a particular moment in time delays the secondary ones. Typically, external inhibition can occur at the moment of starting another activity. The new pathogen, being stronger, leads to the attenuation of the old one. And as a result, the previous activity will automatically stop. For example, a dog is eating, and at that moment the doorbell rings. The animal immediately stops eating and runs to meet the newcomer. There is a sharp change in activity, and the dog’s salivation stops at this moment. Unconditional inhibition of reflexes also includes some innate reactions. In them, certain pathogens cause the complete cessation of certain actions. For example, the anxious clucking of a hen makes the chicks freeze and hug the ground, and the onset of darkness forces the canary to stop singing.

In addition, there is also a protective It arises as a response to a very strong stimulus that requires the body to take actions that exceed its capabilities. The level of such influence is determined by the frequency of impulses of the nervous system. The more excited a neuron is, the higher the frequency of the stream of nerve impulses it generates. However, if this flow exceeds certain limits, then a process will arise that will begin to interfere with the passage of excitation through the neural circuit. The flow of impulses along the reflex arc of the spinal cord and brain is interrupted, resulting in inhibition that preserves the executive organs from complete exhaustion. What conclusion follows from this? Thanks to the inhibition of unconditioned reflexes, the body selects from all possible options the most adequate one, capable of protecting against excessive activity. This process also contributes to the exercise of so-called biological precautions.

It is based on the inextricable unity of congenital and acquired forms of adaptation, i.e. unconditioned and conditioned reflexes.

Unconditioned reflexes are innate, relatively constant species-specific reactions of the body, carried out through the nervous system in response to the action of certain stimuli. They ensure the coordinated activity of various functional systems of the body, aimed at maintaining its homeostasis and interaction with the environment. Examples of simple unconditioned reflexes include knee, blink, swallow and others.

There is a large group of complex unconditioned reflexes: self-preservation, food, sexual, parental (caring for offspring), migration, aggressive, locomotor (walking, running, flying, swimming), etc. Such reflexes are called instincts. They underlie the innate behavior of animals and represent complexes of stereotypical species-specific motor acts and complex forms of behavior.

A conditioned reflex is a reaction of the body acquired during an individual’s life, carried out due to the formation in the higher parts of the central nervous system of temporary variable reflex pathways in response to the action of any signal stimulus, for the perception of which there is a responsible receptor apparatus. An example is the classical conditioned reflex of I.P. Pavlov - the release of saliva by a dog to the sound of a bell, which had previously been connected several times with feeding animals. A conditioned reflex is formed as a result of a combination of the action of two stimuli - conditioned and unconditioned.

An unconditioned stimulus is a stimulus that causes an unconditioned reflex to occur. For example, turning on a bright light causes the pupil to constrict; the action of an electric current causes the dog to withdraw its paw.

A conditioned stimulus is any neutral stimulus that, after repeated combination with an unconditioned stimulus, acquires a signal value. Yes, the sound of the bell, which is repeated, leaves the animal indifferent to it. However, when the sound of the bell is combined with feeding the animal (an unconditioned stimulus), then after several repetitions of both stimuli the bell becomes a conditioned stimulus, alerting the animal to the presentation of food and causing it to salivate.

Conditioned reflexes can be classified according to receptor characteristics, the nature of the conditioned stimulus, the time of action of the conditioned and unconditioned stimuli, and the effector characteristic.

Based on receptor characteristics, conditioned reflexes are divided into external and interoceptive.

Exteroceptive reflexes are produced in response to visual, auditory, olfactory, gustatory, skin-mechanical stimuli, etc. They play a major role in the interaction of the organism with the environment, and therefore are formed and specialized relatively easily.
Interoceptive conditioned reflexes are formed by combining stimulation of the receptors of internal organs with any unconditioned reflex. They form much more slowly and are diffuse in nature.

According to the nature of the conditioned stimulus, conditional reflexes are divided into natural and artificial. Natural reflexes are formed under the influence of natural unconditioned stimuli, for example, salivation to the smell or sight of food. Conditioned reflexes are called artificial. Artificial reflexes are often used in scientific experiments, since their parameters (strength, duration, etc.) can be arbitrarily adjusted.

Based on the time of action of conditioned and unconditioned stimuli, they are distinguished existing and trace conditioned reflexes. Existing conditioned reflexes are formed when reinforcement is given within the duration of the conditioned stimulus. Trace reflexes are conditioned reflexes that are formed in the event of the action of a reinforcing stimulus after the end of the conditioned signal. A special type of trace conditioned reflexes are timed reflexes, which are formed under the condition of regular repetition of an unconditioned stimulus at certain intervals.

According to the effector sign, conditional reflexes are divided into vegetative and somatomovement. Autonomic ones include food, cardiovascular, excretory, sexual and similar conditioned reflexes. An example of an autonomic conditioned reflex is the classic salivary reflex. Somatomotive include protective, food-producing conditioned reflexes, as well as complex behavioral reactions.

In real life, conditioned reflexes are usually formed not to one, but to several stimuli, so they can be divided into simple and complex(complex). Complex conditioned reflexes can be simultaneous or sequential, depending on the combination and sequence of action of a set of stimuli.

Unconditioned reflexes constitute the lower nervous activity, ensuring the implementation of various motor acts of life support, as well as the regulation of the functions of internal organs.

The elements of higher nervous and mental activity in the human animal are instincts and conditioned reflexes (learning reactions), which manifest themselves in the form of behavioral reactions.

Types of reflexes
Congenital reflexes	Acquired reflexes
Unconditional	Conditional
Inherited by offspring from parents and maintained throughout the life of the organism	Easily acquired when the necessary conditions arise for this, and are lost by the body during life
At birth, the body has ready-made reflex arcs	The body does not have ready-made nerve pathways
Provide adaptation of the organism only to changes in the environment, which have often been encountered by many generations of this species	Formed as a result of a combination of an indifferent stimulus with an unconditioned or previously developed conditioned reflex
Reflex arcs pass through the spinal cord or brain stem, the cerebral cortex is not involved in them	Reflex arcs pass through the cerebral cortex

Unconditional

Unconditioned reflexes are hereditarily transmitted (innate) reactions of the body, inherent to the entire species. They perform a protective function, as well as the function of maintaining homeostasis (adaptation to environmental conditions).

There are monosynaptic (involving the transmission of impulses to the command neuron through one synaptic transmission) and polysynaptic (involving the transmission of impulses through chains of neurons) reflexes.

Neural organization of the simplest reflex

The simplest reflex of vertebrates is considered monosynoptic. 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 by a motor cell (motoneuron) of the anterior horn of the spinal cord. The 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 a neuron of the spinal ganglion is part of the dorsal root of the spinal cord, reaches the motor neuron of the anterior horn and, through a synapse, connects with the body of the neuron or one of its dendrites. The axon of the anterior horn motor neuron is part of the anterior root, then the corresponding motor nerve and ends in a motor plaque in the muscle.

Pure monosynaptic reflexes do not exist. Even the knee reflex, which is a classic example of a monosynaptic reflex, is polysynaptic, since the sensory neuron not only switches to the motor neuron of the extensor muscle, but also sends an axonal collateral that switches to the inhibitory interneuron of the antagonist muscle, the flexor muscle.

Conditional

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

The development of the doctrine of conditioned reflexes is associated primarily with the name of I.P. Pavlova. He showed that a new stimulus can initiate a reflex response if it is presented for some time together with an unconditioned stimulus. For example, if you let a dog smell meat, it will secrete gastric juice (this is an unconditioned reflex). If you ring a bell at the same time as the meat, the dog’s nervous system associates this sound with food, and gastric juice will be released in response to the bell, even if the meat is not presented. Conditioned reflexes underlie 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 live successfully in it. As we gain life experience, a system of conditioned reflex connections develops in the cerebral cortex. Such a system is called a dynamic stereotype. It underlies many habits and skills. For example, having learned to skate or bicycle, we subsequently no longer think about how we should move so as not to fall.

reflex arc nerve impulse