Conditioned reflexes are the reactions of the whole organism or any part of it to external or internal stimuli. They manifest themselves through the disappearance, weakening or strengthening of certain activities.
Conditioned reflexes are helpers of the body, allowing it to quickly respond to any changes and adapt to them.
History
For the first time the idea of a conditioned reflex was put forward by the French philosopher and scientist R. Descartes. Somewhat later, the Russian physiologist I. Sechenov created and experimentally proved a new theory regarding the reactions of the body. For the first time in the history of physiology, it was concluded that conditioned reflexes are a mechanism that is activated not only by segments of the spinal cord. The entire nervous system is involved in its work. This allows the body to maintain contact with the environment.
Studied the conditioned reflex Pavlov. This outstanding Russian scientist was able to explain the mechanism of action of the cerebral cortex and cerebral hemispheres. At the beginning of the 20th century, he created the theory of conditioned reflexes. This scientific work has become a real revolution in physiology. Scientists have proven that conditioned reflexes are reactions of the body thatare acquired throughout life, based on unconditioned reflexes.
Instincts
Certain reflexes of the unconditioned type are characteristic of each kind of living organisms. They are called instincts. Some of them are quite complex. Examples of this are bees that make honeycombs, or birds that build nests. Due to the presence of instincts, the body is able to optimally adapt to environmental conditions.
Unconditioned reflexes are innate. They are inherited. In addition, they are classified as species, since they are characteristic of all representatives of a particular species. Instincts are permanent and persist throughout life. They manifest themselves to adequate stimuli that are attached to a specific single receptive field. Physiologically, unconditioned reflexes are closed in the brainstem and at the level of the spinal cord. They appear through an anatomically pronounced reflex arc.
As for monkeys and humans, the implementation of most of their complex unconditioned reflexes is impossible without the participation of the cerebral cortex. When its integrity is violated, pathological changes in unconditioned reflexes occur, and some of them simply disappear.
Classification of instincts
Unconditioned reflexes are very strong. Only under certain conditions, when their manifestation becomes optional, they can disappear. For example, the canary, domesticated about three hundred years ago, is currently nothas the instinct to nest. There are the following types of unconditioned reflexes:
- Self-preservation instinct, which is the body's response to a variety of physical or chemical stimuli. These reflexes, in turn, can be local (withdrawal of the hand) or complex (flight from danger).
- Food instinct, which is caused by hunger and appetite. This unconditioned reflex includes a whole chain of successive actions - from searching for prey to attacking it and further eating.
- Parental and sexual instincts associated with the maintenance and reproduction of the species.
- A comfort instinct that serves to keep the body clean (bathing, scratching, shaking, etc.).
- An orienting instinct when the eyes and head turn towards the stimulus. This reflex is needed to save life.
- The instinct of freedom, which is especially pronounced in the behavior of animals in captivity. They constantly want to break free and often die, refusing food and water.
The emergence of conditioned reflexes
In the course of life, acquired reactions of the body are added to the inherited instincts. They are called conditioned reflexes. They are acquired by the body as a result of individual development. The basis for obtaining conditioned reflexes is life experience. Unlike instincts, these reactions are individual. They may be present in some members of the species and absent in others. In addition, a conditioned reflex is a reaction,which may not last throughout life. Under certain conditions, it is produced, fixed, disappears. Conditioned reflexes are reactions that can occur to various stimuli applied to different receptor fields. This is their difference from instincts.
The mechanism of the conditioned reflex closes at the level of the cerebral cortex. If it is removed, only instincts remain.
The formation of conditioned reflexes occurs on the basis of unconditioned ones. For the implementation of this process, a certain condition must be met. At the same time, any change in the external environment must be combined in time with the internal state of the organism and perceived by the cerebral cortex with a simultaneous unconditional reaction of the organism. Only in this case does a conditioned stimulus or signal appear that contributes to the emergence of a conditioned reflex.
Examples
For the appearance of such a reaction of the body as salivation when knives and forks ring, as well as when a cup for feeding an animal (in a person and in a dog, respectively), an indispensable condition is the repeated coincidence of these sounds with the process of providing food.
Similarly, the sound of a bell or the turning on of a light bulb will cause a dog's paw to flex if these phenomena are repeatedly accompanied by electrical stimulation of the animal's leg, resulting in an unconditioned flexion reflex.
The conditioned reflex is withdrawalhandles the child from the fire and the subsequent crying. However, these phenomena will take place only if the type of fire, even once, coincided with the receipt of a burn.
Reaction components
The body's response to irritation is a change in breathing, secretion, movement, etc. As a rule, unconditioned reflexes are quite complex reactions. That is why they include several components at once. For example, a defensive reflex is accompanied not only by defensive movements, but also by an increase in breathing, an acceleration of the activity of the heart muscle, and a change in the composition of the blood. In this case, voice reactions may also appear. As for the food reflex, there are also respiratory, secretory and cardiovascular components.
Conditional reactions usually reproduce the structure of unconditional ones. This occurs due to the excitation of stimuli of the same nerve centers.
Classification of conditioned reflexes
Acquired body responses to various stimuli are divided into types. Some of the existing classifications are of great importance in solving not only theoretical but also practical problems. One of the areas of application of this knowledge is sports activities.
Natural and artificial reactions of the body
There are conditioned reflexes that arise under the action of signals characteristic of the constant properties of unconditioned stimuli. An example of this is the sight and smell of food. Such conditioned reflexes arenatural. They are characterized by the speed of production and great durability. Natural reflexes, even in the absence of subsequent reinforcement, can be maintained throughout life. The value of the conditioned reflex is especially great at the very first stages of the life of the organism, when it adapts to the environment.
However, reactions can also be developed to a variety of indifferent signals, such as smell, sound, temperature change, light, etc. e. Under natural conditions, they are not irritants. It is these reactions that are called artificial. They are developed slowly and in the absence of reinforcement quickly disappear. For example, artificial conditioned human reflexes are reactions to the sound of a bell, touching the skin, weakening or strengthening lighting, etc.
First and highest order
There are such types of conditioned reflexes that are formed on the basis of unconditional ones. These are first order reactions. There are also higher categories. So, reactions that are developed on the basis of already existing conditioned reflexes are referred to as reactions of a higher order. How do they arise? When such conditioned reflexes are developed, the indifferent signal is reinforced with well-learned conditioned stimuli.
For example, an irritation in the form of a call is constantly reinforced by food. In this case, a first-order conditioned reflex is developed. On its basis, a reaction to another stimulus, for example, to light, can be fixed. This will become a second order conditioned reflex.
Positive and negative reactions
Conditionalreflexes can affect the activity of the body. Such reactions are considered positive. The manifestation of these conditioned reflexes can be secretory or motor functions. If there is no activity of the organism, then the reactions are classified as negative. For the process of adaptation to the constantly changing conditions of the environment of existence, both one and the second type are of great importance.
At the same time, there is a close relationship between them, since when one kind of activity is manifested, another is certainly oppressed. For example, when the command “Attention!” Sounds, the muscles are in a certain position. At the same time, motor reactions (running, walking, etc.) are inhibited.
Educational mechanism
Conditioned reflexes occur with the simultaneous action of a conditioned stimulus and an unconditioned reflex. In this case, certain conditions must be met:
- the unconditioned reflex is biologically stronger;
- the manifestation of the conditioned stimulus is somewhat ahead of the action of the instinct;
- the conditioned stimulus is necessarily reinforced by the influence of the unconditioned one;
- the body must be awake condition and be he althy;
- the condition of the absence of extraneous stimuli producing a distracting effect is observed.
The centers of conditioned reflexes located in the cerebral cortex establish a temporary connection (short circuit) between themselves. In this case, stimulation is perceived by cortical neurons, which are part of the arc of the unconditioned reflex.
Inhibition of conditioned responses
Forin order to ensure adequate behavior of the organism and for better adaptation to environmental conditions, the development of conditioned reflexes alone will not be enough. It will take the opposite direction of action. It is the inhibition of conditioned reflexes. This is the process of eliminating those reactions of the body that are not necessary. According to the theory developed by Pavlov, certain types of cortical inhibition are distinguished. The first of these is the unconditional. It appears as a response to the action of some extraneous stimulus. There is also internal inhibition. They call it conditional.
External braking
This reaction received such a name due to the fact that its development is facilitated by the processes taking place in those parts of the cortex that do not take part in the implementation of reflex activity. For example, a foreign smell, sound, or change in lighting before the food reflex begins can reduce it or contribute to its complete disappearance. The new stimulus is a brake on the conditioned response.
Food reflexes can also be eliminated by painful stimuli. Overflow of the bladder, vomiting, internal inflammatory processes, etc. contribute to the inhibition of the body's reaction. All of them inhibit food reflexes.
Internal braking
It occurs when the received signal is not reinforced by an unconditioned stimulus. Internal inhibition of conditioned reflexes occurs if, for example, the animal is periodically switched on during the day.an electric light bulb in front of the eyes, without bringing food. It has been experimentally proven that saliva production will decrease each time. As a result, the reaction will die out completely. However, the reflex will not disappear without a trace. He just slows down. This has also been experimentally proven.
Conditioned inhibition of conditioned reflexes can be eliminated the very next day. However, if this is not done, then the body's reaction to this stimulus will subsequently disappear forever.
Varieties of internal inhibition
Classify several types of elimination of the body's response to stimuli. Thus, at the basis of the disappearance of conditioned reflexes, which are simply not needed under given specific conditions, is extinction inhibition. There is another variation of this phenomenon. This is a distinctive, or differentiated inhibition. So, the animal can distinguish the number of beats of the metronome at which food is brought to it. This happens when the given conditioned reflex has been previously worked out. The animal distinguishes stimuli. This reaction is based on internal inhibition.
Meaning of eliminating reactions
Conditioned inhibition plays a significant role in the life of the organism. Thanks to him, the process of adaptation to the environment is much better. The ability to navigate in a variety of complex situations gives a combination of excitation and inhibition, which are two forms of a single nervous process.
Conclusion
There are an infinite number of conditioned reflexes. They are the factor thatdetermines the behavior of a living organism. With the help of conditioned reflexes, animals and humans adapt to their environment.
There are many indirect signs of body reactions that have a signal value. For example, an animal, knowing in advance about the approach of danger, builds its behavior in a certain way.
The process of developing conditioned reflexes, which belong to the highest order, is a synthesis of temporary connections.
The basic principles and regularities that are manifested in the formation of not only complex, but also elementary reactions are the same for all living organisms. From this follows an important conclusion for philosophy and the natural sciences that the human brain cannot but obey the general laws of biology. In this regard, it can be studied objectively. However, it should be borne in mind that the activity of the human brain has a qualitative specificity and a fundamental difference from the work of the animal brain.
