reflexes) R. is the least complex motor reaction of C. n. With. to the sensory input signal, carried out with minimal delay. R.'s expression is an involuntary, stereotypical act, determined by the locus and nature of the stimulus that causes it. However, over many R. can be under conscious control. R. can be caused by stimulation of any sensory modality. There are a lot of R., and we will not give a complete list of them here. Instead, for several With specific examples we will illustrate those principles that apply to all R. The simplest reflex is the myotatic reflex, or muscle stretch reflex. This reflex can be induced in any skeletal muscle, although the most famous example is the knee reflex. Anat. The basis of the myotatic reflex is a monosynaptic (with one synapse) reflex arc. It includes a sensory end organ, a sensory nerve fiber with its cell body in the dorsal root ganglion, an α-motoneuron, on which the sensory axon forms a synapse, and an axon of this β-motoneuron returning to the muscle, from which the sensory fiber comes. The sensory end organ in the muscle stretch reflex is the muscle spindle. The muscle spindle has muscle endings called. intrafusal fibers, and a central, non-muscular region associated with the ending of the afferent nerve. Intrafusal fibers are innervated by α-motoneurons of the anterior roots of the spinal cord. Higher centers of the brain can influence the muscle stretch reflex by modulating the activity of α-motoneurons. This reflex is caused by stretching of the muscle, which leads to an increase in the length of the muscle spindle and, consequently, to an increase in the frequency of action potential generation in the sensory (afferent) nerve fiber. Increased activity in the afferent fiber increases the discharge of the target motor neuron, which causes contraction of the extrafusal fibers of the muscle, from which the afferent signal comes. When extrafusal fibers contract, the muscle shortens and activity in the afferent fibers decreases. There are also more complex reflex arcs, including one or several. intercalary neurons between the afferent and efferent parts of the reflex. An example of the simplest polysynaptic (with more than one synapse) reflex is the tendon reflex. The sensory end organ, the Golgi corpuscle, is located in the tendons. An increase in the load on the tendon, usually caused by contraction of the muscle attached to it, is an exciting stimulus, which leads to stretching of the Golgi bodies and the emergence of impulse activity in them, widespread. according to afferent fiber. The afferent coming from the tendon sensory end organ ends at an interneuron in the spinal cord. This interneuron has an inhibitory effect on the β-motoneuron, reducing activity in its efferent axon. As this axon returns to the muscle attached to the stretched tendon, the muscle relaxes and the stress on the tendon is reduced. The muscle stretch reflex and tendon reflex work in concert to provide the basic mechanism for quickly regulating the degree of muscle contraction. These R. are useful for quick adaptations to changes in the position of the leg when a person. you have to walk on uneven ground. Of course, other polysynaptic spinal R. also participate in locomotion. These R. include many more interneurons in the structure of the reflex arc. The neurological basis of these complex R. is formed by divergent (from one neuron to several) and convergent (from several neurons to one) connections of interneurons. An example of the action of these R. is given to us by a person stepping with his bare foot on a sharp object and reflexively withdrawing his wounded leg. The sensory input here is pain. Pain afferent fibers travel to the spinal cord and form synapses on interneurons. Some of these interneurons excite motor neurons, which cause the flexor muscles of the injured leg to contract, pulling the leg up, but other interneurons contribute to the inhibition of motor neurons serving the extensor muscles of the same leg. This allows the leg to rise quickly and smoothly. Dr. neurons receiving pain input send axons across the midline of the spinal cord, excite the extensor motor neurons of the opposite leg and inhibit the motor neurons innervating its flexors. This causes the uninjured leg to become rigid and provide support as the injured leg is pulled upward. On top of that, interneurons also relay information. into the upper and lower parts of the spinal cord, causing intersegmental R., which coordinate the contraction of the muscles of the trunk and upper extremities. Monosynaptic and polysynaptic spinal nerve fibers form the basic mechanism for maintaining and adapting posture. Motor systems of the brain influence spinal nerves through input circuits going to interneurons and β-motoneurons. Thus, changes in spinal R. may indicate pathology in the motor systems of the brain. An example of this is hyperreflexia associated with injury to the lateral spinal motor tract or damage to the motor areas of the frontal lobe. There are a number of visual R. As an example, we can name. pupillary reflex, manifested in the constriction of the pupil in response to the illumination of the eye with bright light. This reflex requires an intact retina, optic nerve, midbrain, and third pair of cranial nerves, but does not depend on the integrity of the nuclei of the lateral geniculate body or the visual cortex. R. tj can be caused by stimulation of sensory input from internal organs. The baroreceptor reflex is an example of such an autonomic reflex. Increased blood pressure stretches receptors in large vessels near the heart. This enhances the flow of afferent impulses to the nuclei of the solitary tract of the medulla oblongata. Neurons in the nuclei of the solitary tract switch impulses to the motor nuclei of the vagus nerve and transmit them to the spinal cord, causing a decrease in heart rate and blood pressure. It is very difficult to gain conscious control over this reflex, but it is possible to develop a conditioned reflex on its basis using the technique of classical conditioning. See also Acetylcholinesterase, Electrical stimulation of the nervous system, Endorphins/enkephalins, Neural network models, Neurotransmitters, Sensorimotor processes M. L. Woodruff
REFLEX
reaction to receptor stimulation is a natural response of the body to a stimulus mediated by the nervous system. It is caused by the influence of a certain external or internal environmental factor on the analyzer. Manifests itself in muscle contraction and secretion. The principle of reflex in the activity of the brain was formulated by the French philosopher R. Descartes, although the term itself entered science later.
The manifestation of reflexes is unclear in protozoa, maximum in coelenterates, average in worms and insects, and gradually disappears in animals of a higher degree of development, but even in humans it does not disappear completely.
There are differences between unconditioned and conditioned reflexes.
Reflex
In psychology, the term has several meanings, ranging from a technical definition (innate behavior exhibited without conscious effort and not changing depending on the situation) to non-specific (an act carried out under the influence of an “impulse”). In the theory of classical conditioning, it is defined as “an unlearned association between stimuli and corresponding responses.” Thus, salivation at the sight of food is an unconditioned reflex.
REFLEX
jerk) is the body's response to a particular influence, carried out through the nervous system. For example, the knee jerk reflex (see Patellar reflex) consists of a sharp “throwing” movement of the leg, resulting from contraction of the quadriceps femoris muscle in response to stretching when tapping its tendon. Determining this, as well as some other reflexes, such as the Achilles and ulnar extensor reflex, allows you to monitor the state of the spinal nerves that are involved in these reflexes.
REFLEX
reflex) - the body's response to certain influences carried out through the nervous system. Thus, a painful stimulus (for example, a pin prick) will lead to the emergence of a reflex of withdrawing the finger even before the brain sends a message about the need for the muscles to participate in this process. See Conditioned reflex, Patellar reflex. Plantar reflex.
Reflex
Word formation. Comes from Lat. reflexus - reflected.
Specificity. Manifests itself in muscle contraction, secretion, etc.
Conditioned reflexes,
Unconditioned reflexes.
REFLEX
1. In general - any relatively simple, “mechanical” reaction. Reflexes are generally considered to be species-specific, innate patterns of behavior that are largely beyond the control of will and choice and show little variability from individual to individual. This value is preferred in specialized literature. 2. Not acquired connection between the response and the stimulus. This meaning simply expands the first by including in the definition the presence of a stimulus that causes a reflex. 3. More metaphorical meaning - any unconscious, impulsive action. This value is significantly broader than the previous ones, although it is not generally recommended. Many authors use the terms reflex and reaction interchangeably, despite the fact that the term reaction does not carry any connotations of species-specific, innate qualities that the concept of reflex has (at least in its basic meaning). Consequently, many compound terms are used in the literature with either of these two general names; for example, the so-called startle response is often called the startle reflex. See reaction.
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.
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 have the following features:
They always begin with nervous excitation 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 a variety of connections between them. Analysis of stimuli is performed by complex nervous organs - analyzers. Each analyzer consists of three parts:
1) peripheral perceptive organ (receptor);
2) the conducting afferent, i.e., centripetal, path along which nervous excitation is transmitted from the periphery to the center;
3) the cortical part of the analyzer.
The transfer of nervous excitation from receptors first to the central parts of the nervous system, and then from them along efferent, i.e., centrifugal, pathways back to the receptors for a response, which takes place during the reflex, is carried out along a reflex arc. The reflex arc (reflex ring) consists of a receptor, an afferent nerve, a central link, an efferent nerve and an effector. \ ra (muscles or glands).
The initial analysis of stimuli takes place in the receptors and in the lower parts of the brain. It is elementary in nature and is determined by 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 combination of the brain endings of all analyzers.
During reflex activity, a process of differential inhibition is also carried out, during which excitations caused by non-reinforced conditioned stimuli gradually fade away, leaving excitations that strictly correspond to the main, reinforced conditioned stimulus. Thanks to the differentiation \ regulating inhibition achieves a very fine differentiation of stimuli. Because of this, it becomes possible to form conditioned reflexes to complex stimuli. In this case, the conditioned reflex is caused by the influence of only a complex of stimuli in its entire 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 occurs under the action of a constant stimulus, under the influence of which the previously developed conditioned reaction ceases. When exposed to a sudden external stimulus of sufficient strength, the developed conditioned reflex may manifest itself weakly or even disappear completely (for example, drivers talking on a cell phone while driving often get into accidents).
Internal, or active, inhibition occurs when a conditioned reflex fades when it is repeatedly evoked by a conditioned stimulus without reinforcement by a conditioned one (for example, this effect is used in the treatment of a patient with alcoholism using coding or conditioned reflex therapy).
Unconditioned reflex is an innate, hereditarily fixed form of response to the biologically significant influence 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 for the lifelong formation of conditioned reflex connections.
Unlike conditioned reflexes, which serve to adapt the body 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 action of an indifferent stimulus preceding it, a classical conditioned reflex is developed. Reinforcement that causes harm to the body (for example, electric shock) is called negative (punishment); reinforcement in the form of food is positive (reward).
The apexes 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 sections is controlled by the cortex, and the processes in it influence the processes in other sections, there is also the possibility of voluntary influence on the action of unconditioned reflexes.
An unconditioned reflex occurs if:
A vital stimulus is present;
The reflex center is in an excited state.
Unconditioned reflexes stop if:
Signals of achieving the required result are received;
The innate action program has been fulfilled
The stimulus has ceased its effect;
A stronger (significant) stimulus began to act.
Usually the following types of unconditioned reflexes are distinguished:
a) vegetative (salivation, changes in skin color, sweating, pain, body reactions to energy expenditure during activity, pupillary,
Bots of the heart and respiratory organs, etc.); b) behavioral (orientative-exploratory, food, defensive, hygienic, procreation, migration, herd (group behavior).
Unconditioned reflexes are stable and change little during life. For example, it is very difficult for a person not to react when he is exposed to one or another unconditioned stimulus (i.e., a stimulus that necessarily causes the spread of excitation along a certain, innately organized chain or network of neurons).
During the growth and development of man and animal, the system of unconditional reflex connections turns out to be insufficient (poor, inert, too simple) to provide all the necessary variety of reactions in the conditions of a constantly changing and infinitely diverse environment. Conditioned reflexes, temporary connections between certain stimuli and certain responses to them, begin to form and become increasingly important 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 about an upcoming biologically important effect.
Any neutral external stimulus, if it coincides several times in time with the action of an unconditioned stimulus on the body, begins to evoke a response characteristic of this unconditioned stimulus. For example, a type of food that did not cause salivation when first presented begins to cause it after
how the appearance of food several times coincides with its entry into the mouth, i.e., with unconditional irritation.
The transformation of one or another indifferent stimulus into a signal, i.e., 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 life significance. This is how a conditioned reflex is formed. Thanks to this transformation, the indifferent stimulus itself acquires meaning, becoming a signal of the onset of an important event, so 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 respond in advance to signs of upcoming important phenomena, which increases the success of his behavior in the world around him.
Conditioned reflexes have their own characteristics that distinguish them from unconditioned ones:
All conditioned reflexes involve the formation in the cerebral cortex of temporary nerve connections that require 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 one’s 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, playing sports, etc.) need systematic reinforcement through repetition of these activities);
Unconditioned reflexes may be different in individual representatives of the same species of animal (for example, a trained animal has such conditioned reflexes that an untrained animal of the same species does not have);
The coincidence in time of the unconditional and neutral stimuli is a necessary condition for the neutral stimulus to be capable of causing a reaction previously characteristic only of the unconditioned stimulus (due to such coincidence, the neutral stimulus, as it were, “signals” the body about the upcoming impact of the unconditioned stimulus, as a result of which it is called a signal );
On the basis of already fixed conditioned reflexes, new ones are formed, called conditioned reflexes of the first, second order, etc. In dogs, for example, conditioned reflexes of the third order were developed, in apes - of the fourth order (a person has those developed during life, in the process education and training, conditioned reflexes up to the ninth order, layered 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 parts of the central nervous system;
The presence of a biologically neutral signal perceived by the senses (biological neutrality of the signal means that it itself does not 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 quite high;
No interference from other signals;
Repeated presentation of conditioned and unconditional signals until an internal connection is formed.
Conditioned reflexes are classified on various grounds. They can be:
Olfactory, tactile, etc., depending on in which organ 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 active human activity, the latter stop, slow down, restrain, and interfere with it. Both can have both positive and negative implications for a person’s problem solving. Thus, an overly active reaction to danger - affective fear, panic - is 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 situations of influence.
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Types of reflexes |
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Congenital reflexes |
Acquired reflexes |
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Unconditional |
Conditional |
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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 |
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At birth, the body has ready-made reflex arcs |
The body does not have ready-made nerve pathways |
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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 |
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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
The term “reflex” was introduced by the French scientist R. Descartes in the 17th century. But to explain mental activity it was used by the founder of Russian materialistic physiology I.M. Sechenov. Developing the teachings of I.M. Sechenov. I. P. Pavlov experimentally studied the peculiarities of the functioning of reflexes and used the conditioned reflex as a method for studying higher nervous activity.
He divided all reflexes into two groups:
- unconditional;
- conditional.
Unconditioned reflexes
Unconditioned reflexes- innate reactions of the body to vital stimuli (food, danger, etc.).
They do not require any conditions for their production (for example, the release of saliva at the sight of food). Unconditioned reflexes are a natural reserve of ready-made, stereotypical reactions of the body. They arose as a result of the long evolutionary development of this animal species. Unconditioned reflexes are the same in all individuals of the same species. They are carried out using the spinal and lower parts of the brain. Complex complexes of unconditioned reflexes manifest themselves in the form of instincts.
Rice. 14. The location of some functional zones in the human cerebral cortex: 1 - zone of speech production (Broca's center), 2 - area of the motor analyzer, 3 - area of analysis of oral verbal signals (Wernicke's center), 4 - area of the auditory analyzer, 5 - analysis of written verbal signals, 6 - visual analyzer area
Conditioned reflexes
But the behavior of higher animals is characterized not only by innate, i.e., unconditioned reactions, but also by such reactions that are acquired by a given organism in the process of individual life activity, i.e. conditioned reflexes. The biological meaning of the conditioned reflex is that numerous external stimuli that surround the animal in natural conditions and in themselves do not have vital significance, preceding in the animal’s experience food or danger, the satisfaction of other biological needs, begin to act as signals, by which the animal orients its behavior (Fig. 15).
So, the mechanism of hereditary adaptation is an unconditioned reflex, and the mechanism of individual variable adaptation is conditioned a reflex produced when vital phenomena are combined with accompanying signals.
Rice. 15. Scheme of formation of a conditioned reflex
- a - salivation is caused by an unconditioned stimulus - food;
- b - excitation from a food stimulus is associated with a previous indifferent stimulus (light bulb);
- c - the light of the light bulb became a signal of the possible appearance of food: a conditioned reflex was developed to it
A conditioned reflex is developed on the basis of any of the unconditioned reactions. Reflexes to unusual signals that do not occur in a natural environment are called artificial conditioned. In laboratory conditions, it is possible to develop many conditioned reflexes to any artificial stimulus.
I. P. Pavlov associated with the concept of a conditioned reflex principle of signaling of higher nervous activity, the principle of synthesis of external influences and internal states.
Pavlov's discovery of the basic mechanism of higher nervous activity - the conditioned reflex - became one of the revolutionary achievements of natural science, a historical turning point in the understanding of the connection between the physiological and the mental.
Understanding the dynamics of formation and changes in conditioned reflexes began the discovery of complex mechanisms of human brain activity and the identification of patterns of higher nervous activity.