Conditioned reflexes are reactions of the whole organism or any part thereof to external or internal stimuli. They are manifested through the disappearance, weakening or strengthening of certain activities.
Conditioned reflexes are assistants to the body, allowing it to quickly respond to any changes and adapt to them.
History
The idea of a conditioned reflex was first 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. His entire nervous system is involved in his work. This allows you to maintain a connection between the body and 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 proved that conditioned reflexes are body reactions that are acquired throughout life, based on unconditioned reflexes.
Instincts
Certain reflexes of an unconditional type are characteristic of each type of living organism. They are called instincts. Some of them are very complex. An example of this is the bees that sculpt honeycombs, or birds, winding 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, as they are characteristic of all representatives of a certain species. Instincts are permanent and persist throughout life. They manifest themselves on adequate stimuli, which are attached to a specific single receptive field. Physiologically unconditioned reflexes are closed in the stem section of the brain and at the level of the spinal cord. They manifest themselves through an anatomically expressed
reflex arc.As for the monkey and man, then the implementation of most of the complex unconditioned reflexes is impossible without the participation of the cerebral cortex. With violations of its integrity, 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, can they disappear. For example, a canary domesticated about three hundred years ago does not currently have instinct for nests. The following types of unconditioned reflexes are distinguished:
- The instinct of self-preservation, which is the reaction of the body to a variety of physical or chemical stimuli. Such reflexes, in turn, can occur locally (pulling the arm) or be complex (flight from danger).
- Nutritional instinct, which is caused by hunger and appetite. This unconditioned reflex includes a whole chain of sequential actions - from searching for prey to attacking it and further eating.
- Parental and sexual instincts related to the maintenance and reproduction of the species.
- A comfortable instinct that serves to keep the body clean (bathing, scratching, shaking, etc.).
- An indicative instinct when the eyes and head turn toward 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 water and food.
The occurrence of conditioned reflexes
Throughout life, acquired reactions of the body are added to 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 representatives of the species and absent in others. In addition, a conditioned reflex is a reaction that may not persist 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 conditioned reflex mechanism closes at the level of the
cerebral cortex. If you remove it, then only instincts remain.
The formation of conditioned reflexes occurs on the basis of the unconditioned. To implement this process, a certain condition must be met. At the same time, any change in the external environment should be combined with the internal state of the body over time and be perceived by the cerebral cortex with an unconditional reaction of the body. Only in this case does a conditioned stimulus or signal appear that contributes to the occurrence of a conditioned reflex.
Examples
For the appearance of such a reaction of the body as the release of saliva when the knives and forks ring, as well as when the cup for feeding the animal is knocked (in humans and dogs, respectively), an indispensable condition is the repeated coincidence of these sounds with the process of providing food.
In the same way, the sound of a bell or the inclusion of a light bulb will cause the dog's paws to bend if these phenomena repeatedly occur accompanied by electrical irritation of the animal’s legs, as a result of which an unconditioned flexion reflex appeared.
A conditioned reflex is the withdrawal of the child's arms from the fire and the subsequent crying. However, these phenomena will only occur if the type of fire, even once, coincides with a burn.
Reaction Components
The body's reaction to irritation is a change in breathing, secretion, movement, etc. As a rule, unconditioned reflexes are rather complex reactions. That is why several components are included in their composition at once. For example, a defensive reflex is accompanied not only by defensive movements, but also by rapid breathing, acceleration of the activity of the heart muscle, and a change in blood composition. In this case, vocal reactions may appear. As for the food reflex, there are also respiratory, secretory and cardiovascular components.
Conditional reactions usually reproduce the structure of unconditioned ones. This occurs in connection with the stimulation of the same nerve centers by stimuli.
Classification of conditioned reflexes
Responses acquired by the body to various stimuli are divided by type. Some of the existing classifications are of great importance in solving not only theoretical, but also practical problems. One area of application of this knowledge is sports.
Natural and artificial reactions of the body
There are conditioned reflexes that arise upon the action of signals characteristic of the constant properties of unconditioned stimuli. An example of this is the appearance and smell of food. Such conditioned reflexes are natural. They are characterized by the speed of development and great durability. Natural reflexes, even in the absence of subsequent reinforcement, can be maintained throughout life. The value of the conditioned reflex in this case 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 generated to a variety of indifferent signals, such as smell, sound, temperature, light, etc. Under natural conditions, they are not irritants. It is such reactions that are called artificial. They are produced slowly and, in the absence of reinforcements, quickly disappear. For example, artificial conditioned reflexes of a person are reactions to the sound of a call, touching the skin, weakening or enhancing lighting, etc.
First and highest order
There are types of conditioned reflexes that are formed on the basis of the unconditioned. These are first order reactions. There are higher categories. Thus, reactions that are developed on the basis of existing conditioned reflexes are classified as higher order reactions. How do they arise? When such conditioned reflexes are developed, the indifferent signal is reinforced by well-assimilated conditioned stimuli.
For example, annoyance in the form of a bell is constantly reinforced by food. In this case, the development of a conditioned reflex of the first order occurs. On its basis, a reaction to another stimulus, for example, to light, can also be fixed. This will become a second-order conditioned reflex.
Positive and negative reactions
Conditioned reflexes can affect the activity of the body. Such reactions are positive. The manifestation of these conditioned reflexes can be secretory or motor functions. If there is no activity of the body, then the reactions are classified as negative. For the process of adaptation to constantly changing conditions of the environment of existence, both one and the second species are of great importance.
At the same time, there is a close relationship between them, since the manifestation of one kind of activity will inevitably inhibit another. 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.
Education 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 a conditioned stimulus is somewhat ahead of instinct;
- a conditioned stimulus is necessarily reinforced by the influence of the unconditioned;
- the body must be awake and healthy;
- the condition of the absence of extraneous stimuli producing a distracting effect is met.
The centers of conditioned reflexes located in the cerebral cortex establish a temporary connection (closure) between themselves. In this case, irritation is perceived by cortical neurons, which are located in the arc of the unconditioned reflex.
Inhibition of conditioned reactions
In order to ensure adequate behavior of the body and for better adaptation to environmental conditions, the development of conditioned reflexes alone will not be enough. An opposite action will be required. It is the inhibition of conditioned reflexes. This is the process of eliminating those reactions of the body in which there is no need. According to the theory developed by Pavlov, certain types of cortical inhibition are distinguished. The first of them is unconditional. It appears as a response to the action of any extraneous stimulus. There is also internal inhibition. It is called conditional.
External braking
This reaction received its name in connection with the fact that processes that take place in those parts of the cortex that do not participate in the implementation of reflex activity contribute to its development. For example, an extraneous smell, sound, or a change in lighting prior to the onset of a food reflex can reduce it or contribute to complete disappearance. A new stimulus is a brake on the conditioned reaction.
Food reflexes can also be eliminated by painful stimuli. Inhibition of the body's reaction is facilitated by overflow of the bladder, vomiting, internal inflammatory processes, etc. All of them inhibit food reflexes.
Internal braking
It occurs when the received signal is not supported by an unconditioned stimulus. Internal inhibition of conditioned reflexes occurs if, for example, an animal is periodically turned on by an electric bulb in front of his eyes during the day without bringing food. It has been experimentally proven that each time the production of saliva will decrease. As a result, the reaction will completely fade. However, the reflex will not disappear without a trace. It will simply slow down. It is also proven experimentally.
The conditioned inhibition of conditioned reflexes can be eliminated the very next day. However, if this is not done, then the reaction of the body to this stimulus subsequently disappears forever.
Varieties of internal braking
Classify several types of elimination of the body's response to stimuli. So, the basis for the disappearance of conditioned reflexes, which in these specific conditions are simply not needed, is extinction inhibition. There is another variation of this phenomenon. This is distinctive, or differentiated inhibition. So, the animal can distinguish the number of strokes of the metronome at which food will be brought to it. This occurs when a given conditioned reflex is previously developed. The animal distinguishes irritants. At the heart of this reaction is internal inhibition.
The meaning of eliminating reactions
Conditional inhibition plays a significant role in the life of the body. Thanks to him, the process of adaptation to the environment is much better. The possibility of orientation in a variety of complex situations gives a combination of excitement and inhibition, which are two forms of a single nervous process.
Conclusion
There are an infinite number of conditioned reflexes. They are the factor that determines 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, in a certain way builds its behavior.
The process of developing conditioned reflexes, which belong to the highest order, is a synthesis of temporary connections.
The basic principles and patterns that are manifested in the formation of not only complex, but also elementary reactions, are the same for all living organisms. An important conclusion follows from this for philosophy and the natural sciences that the human brain cannot but obey the general laws of biology. In this regard, it can be objectively studied. However, it should be borne in mind that the activity of the human brain has qualitative specificity and a fundamental difference from the work of the animal’s brain.