A system of reflexes that are innate. Reflexes unconditioned and conditioned

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).

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.

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

A reflex is the body's response to irritation from the external or internal environment.

Types of reflexes - all reflex acts of the whole organism are divided into unconditioned and conditioned reflexes.

Unconditioned reflexes are inherited; they are inherent in every biological species; their arches are formed at the time of birth and normally remain throughout life. However, they can change under the influence of illness.

Classification of reflexes

The main mechanism of the central nervous system activity is the reflex as the body’s response to the action of a stimulus, carried out with the participation of the central nervous system. Translated from Latin, this word means “reflection.” This term was first used by the French philosopher R. Descartes to characterize the body's reactions in response to irritation of the senses. He was the first to express the idea that all manifestations of the effector activity of the body are caused by very real physical factors. In other words, Descartes theoretically showed that every action has a very real physical cause. After R. Descartes, the idea of reflex was developed by the Czech researcher J. Prochazka, who developed the doctrine of reflective actions.

The morphological substrate of the reflex is the reflex arc - a set of morphological structures that ensure the implementation of the reflex. In other words, the reflex arc is the path along which excitation passes during the implementation of the reflex. There are several classifications of reflexes. Thus, I.M. Sechenov identified the following types of reflexes: 1. involuntary movements, which contain pure reflexes and reflexes with a mental element; 2. voluntary movements containing reflexes with mental elements.

Classification by receptor link.

· Interoceptive: information that excites the receptor and triggers the reflex is received from the receptors of internal organs;

· Exteroceptive: information that excites the receptor and triggers the reflex is received from the external environment using sensory systems;

· Proprioceptive: reflexes triggered from receptors in muscles, tendons and joints.

· according to the central link, they are distinguished: central (true) - the main link is located in the central nervous system and peripheral - the central link is located outside the central nervous system.

The central ones, in turn, are divided into spinal and cerebral. Spinal reflexes are divided into cervical, thoracic, lumbar and sacral. Cerebral reflexes are divided into cerebellar, cerebral reflexes and brain stem reflexes. Brainstem reflexes are divided into bulbar, diencephalic and mesencephalic.

Reflex arc (nerve arc) is the path traversed by nerve impulses during the implementation of a reflex.

The reflex arc consists of:

receptor - a nerve link that perceives irritation;

afferent link - centripetal nerve fiber - processes of receptor neurons that transmit impulses from sensory nerve endings to the central nervous system;

central link - nerve center (optional element, for example for the axon reflex);

efferent link - carry out transmission from the nerve center to the effector.

effector - an executive organ whose activity changes as a result of a reflex.

executive organ - puts the body into action.

The simplest reflex arc in humans is formed by two neurons - sensory and motor (motoneuron). An example of a simple reflex is the knee reflex. In other cases, three (or more) neurons are included in the reflex arc - sensory, intercalary and motor. In a simplified form, this is the reflex that occurs when a finger is pricked with a pin. This is a spinal reflex; its arc passes not through the brain, but through the spinal cord. The processes of sensory neurons enter the spinal cord as part of the dorsal root, and the processes of motor neurons exit the spinal cord as part of the anterior root. The bodies of sensory neurons are located in the spinal ganglion of the dorsal root (in the dorsal ganglion), and intercalary and motor neurons are located in the gray matter of the spinal cord.

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 magnitude. 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 magnitude. 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
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 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
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

Swallowing, salivation, rapid breathing due to lack of oxygen - all these are reflexes. There are a huge variety of them. Moreover, they may differ for each individual person and animal. Read more about the concepts of reflex, reflex arc and types of reflexes further in the article.

What are reflexes

This may sound scary, but we do not have one hundred percent control over all our actions or the processes of our body. We are, of course, not talking about decisions to get married or go to university, but about smaller but very important actions. For example, about jerking our hand when accidentally touching a hot surface or trying to hold on to something when we slip. It is in such small reactions that reflexes appear, controlled by the nervous system.

Most of them are inherent in us at birth, others are acquired later. In a sense, we can be compared to a computer, into which, even during assembly, programs are installed in accordance with which it operates. Later, the user will be able to download new programs, add new action algorithms, but the basic settings will remain.

Reflexes are not limited to humans. They are characteristic of all multicellular organisms that have a CNS (central nervous system). Various types of reflexes are carried out constantly. They contribute to the proper functioning of the body, its orientation in space, and help us quickly respond to danger. The absence of any basic reflexes is considered a disorder and can make life much more difficult.

Reflex arc

Reflex reactions occur instantly, sometimes you don’t have time to think about them. But despite all their apparent simplicity, they are extremely complex processes. Even the most basic action in the body involves several parts of the central nervous system.

The irritant acts on the receptors, the signal from them travels along the nerve fibers and goes directly to the brain. There, the impulse is processed and sent to the muscles and organs in the form of a direct instruction to action, for example, “raise your hand,” “blink,” etc. The entire path that the nerve impulse travels is called a reflex arc. In its full version it looks something like this:

Receptors are nerve endings that perceive a stimulus.
Afferent neuron - transmits a signal from receptors to the center of the central nervous system.
The interneuron is a nerve center that is not involved in all types of reflexes.
Efferent neuron - transmits a signal from the center to the effector.
An effector is an organ that carries out a reaction.

The number of arc neurons may vary, depending on the complexity of the action. The information processing center can pass through either the brain or the spinal cord. The simplest involuntary reflexes are carried out by the spinal cord. These include changes in the size of the pupil when the lighting changes or withdrawal when pricked with a needle.

What types of reflexes are there?

The most common classification is the division of reflexes into conditioned and unconditioned, depending on how they were formed. But there are other groups, let’s look at them in the table:

Classification sign	Types of reflexes
By nature of education	Conditional Unconditional
According to biological significance	Defensive Approximate Digestive
By type of executive body	Motor (locomotor, flexor, etc.) Vegetative (excretory, cardiovascular, etc.)
By influence on the executive body	Exciting Brake
By type of receptor	Exteroceptive (olfactory, cutaneous, visual, auditory) Proprioceptive (joints, muscles) Interoceptive (endings of internal organs).

Unconditioned reflexes

Congenital reflexes are called unconditioned. They are transmitted genetically and do not change throughout life. Within them, simple and complex types of reflexes are distinguished. They are most often processed in the spinal cord, but in some cases the cerebral cortex, cerebellum, brainstem, or subcortical ganglia may be involved.

A striking example of unconditioned reactions is homeostasis - the process of maintaining the internal environment. It manifests itself in the form of regulation of body temperature, blood clotting during cuts, and increased breathing with increased amounts of carbon dioxide.

Unconditioned reflexes are inherited and are always tied to a specific species. For example, all cats land strictly on their paws; this reaction manifests itself in them already in the first month of life.

Digestive, orientation, sexual, protective - these are simple reflexes. They manifest themselves in the form of swallowing, blinking, sneezing, salivation, etc. Complex unconditioned reflexes manifest themselves in the form of individual forms of behavior, they are called instincts.

Conditioned reflexes

Unconditioned reflexes alone are not enough in the course of life. In the course of our development and acquisition of life experience, conditioned reflexes often arise. They are acquired by each individual individually, are not hereditary and can be lost.

They are formed with the help of the higher parts of the brain on the basis of unconditioned reflexes and arise under certain conditions. For example, if you show an animal food, it will produce saliva. If you show him a signal (lamp light, sound) and repeat it every time food is served, the animal will get used to it. Next time, saliva will begin to be produced when the signal appears, even if the dog does not see the food. Such experiments were first carried out by the scientist Pavlov.

All types of conditioned reflexes are developed in response to certain stimuli and are necessarily reinforced by negative or positive experience. They underlie all our skills and habits. On the basis of conditioned reflexes, we learn to walk, ride a bicycle, and can acquire harmful addictions.

Excitation and inhibition

Each reflex is accompanied by excitation and inhibition. It would seem that these are absolutely opposite actions. The first stimulates the functioning of organs, the other is designed to inhibit it. However, they both simultaneously participate in the implementation of any types of reflexes.

Inhibition does not in any way interfere with the manifestation of the reaction. This nervous process does not affect the main nerve center, but dulls the others. This happens so that the excited impulse reaches strictly for its intended purpose and does not spread to organs that perform the opposite action.

When bending the arm, inhibition controls the extensor muscles; when turning the head to the left, it inhibits the centers responsible for turning to the right. Lack of inhibition would lead to involuntary and ineffective actions that would only get in the way.

Animal reflexes

The unconditioned reflexes of many species are very similar to each other. All animals have a feeling of hunger or the ability to secrete digestive juice at the sight of food; when hearing suspicious sounds, many listen or begin to look around.

But some reactions to stimuli are the same only within a species. For example, hares run away when they see an enemy, while other animals try to hide. Porcupines, equipped with spines, always attack a suspicious creature, a bee stings, and opossums pretend to be dead and even imitate the smell of a corpse.

Animals can also acquire conditioned reflexes. Thanks to this, dogs are trained to guard the house and listen to the owner. Birds and rodents easily get used to people feeding them and do not run away at the sight of them. Cows are very dependent on their daily routine. If you disrupt their routine, they produce less milk.

Human reflexes

Like other species, many of our reflexes appear in the first months of life. One of the most important is sucking. With the smell of milk and the touch of the mother's breast or a bottle that imitates it, the baby begins to drink milk from it.

There is also a proboscis reflex - if you touch the baby’s lips with your hand, he sticks them out with a tube. If the baby is placed on his stomach, his head will necessarily turn to the side, and he himself will try to rise. With the Babinski reflex, stroking the baby's feet causes the toes to fan out.

Most of the very first reactions accompany us only for a few months or years. Then they disappear. Among the types of human reflexes that remain with him for life: swallowing, blinking, sneezing, olfactory and other reactions.

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

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

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

a) failure to satisfy the corresponding requirement leads to the death of the individual; And

b) no other individual of a given species is needed to satisfy a particular need.

Vital instincts include:

– food,

– drinking,

– defensive,

– sleep-wake regulation,

- energy saving reflex.

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

– sexual,

– parental,

– reflex of emotional resonance (empathy),

– territorial,

– hierarchical (reflexes of dominance or submission).

3. Self-development reflexes (satisfying ideal needs).

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

– research

– imitation and game

– reflex of overcoming (resistance, freedom).

Conditioned reflexes are divided as follows.

According to biological characteristics:

– food;

– sexual;

– defensive;

– motor;

– indicative – reaction to a new stimulus.

Differences between the orienting reflex and other conditioned reflexes:

– innate reaction of the body;

According to the nature of the conditional signal:

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

– artificial – caused by stimuli not associated with a given reaction under normal conditions.

According to the complexity of the conditional signal:

– simple – the conditioned signal consists of 1 stimulus (light causes salivation);

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

– conditioned reflexes that arise in response to a complex of simultaneously acting stimuli;

– conditioned reflexes that arise in response to a complex of sequentially acting stimuli, each of them “layers” on the previous one;

– a conditioned reflex to a chain of stimuli that also act one after another, but do not “layer” on top of each other.

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

By type of stimulus:

– exteroceptive – arise most easily;

The child’s first to appear are proprioceptive reflexes (sucking reflex to posture).

By changing a particular function:

– positive – accompanied by increased function;

– negative – accompanied by weakening of function.

By the nature of the response:

– somatic;

– vegetative (vascular-motor).

Based on the combination of a conditioned signal and an unconditioned stimulus over time:

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

There are:

– coinciding existing 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;

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

The first two arise easily, the last one is difficult.

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

In different 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 it is possible to develop conditioned reflexes 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 also highlight the fact that they:

– are specific, i.e. characteristic of all representatives of a given species;

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

– relatively constant, characterized by stability and great stability;

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

Conditioned reflex- this 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.