Unconditioned and conditioned reflexes
Higher nervous activity- a system that allows the human body and animals to adapt to variable environmental conditions. Evolutionarily, vertebrates have developed a number of innate reflexes, but their existence is not enough for successful development.
In the process of individual development, new adaptive reactions are formed - these are conditioned reflexes. An outstanding domestic scientist I.P. Pavlov is the founder of the doctrine of unconditioned and conditioned reflexes. He formed a conditioned reflex theory, which states that the acquisition of a conditioned reflex is possible when a physiologically indifferent stimulus acts on the body. As a result, a more complex system of reflex activity is formed.
I.P. Pavlov - the founder of the doctrine of unconditioned and conditioned reflexes
An example of this is Pavlov's study of dogs that salivated in response to a sound stimulus. Pavlov also showed that innate reflexes are formed at the level of subcortical structures, and new connections are formed in the cerebral cortex throughout the life of an individual under the influence of constant stimuli.
Conditioned reflexes
Conditioned reflexes are formed on the basis of unconditional, in the process of individual development of the organism, against the background of a changing external environment.
reflex arc The conditioned reflex consists of three components: afferent, intermediate (intercalary) and efferent. These links carry out the perception of irritation, the transmission of an impulse to the cortical structures and the formation of a response.
The reflex arc of the somatic reflex performs motor functions (for example, flexion movement) and has the following reflex arc:
The sensitive receptor perceives the stimulus, then the impulse goes to the posterior horns of the spinal cord, where the intercalary neuron is located. Through it, the impulse is transmitted to the motor fibers and the process ends with the formation of movement - flexion.
A necessary condition for the development of conditioned reflexes is:
- The presence of a signal that precedes the unconditional;
- the stimulus that will cause the catching reflex must be inferior in strength to the biologically significant effect;
- the normal functioning of the cerebral cortex and the absence of distractions are mandatory.
Conditioned reflexes are not formed instantly. They are formed for a long time under the constant observance of the above conditions. In the process of formation, the reaction either fades away, then resumes again, until a stable reflex activity sets in.
An example of the development of a conditioned reflex Classification of conditioned reflexes:
- A conditioned reflex formed on the basis of the interaction of unconditioned and conditioned stimuli is called reflex of the first order.
- Based on the classical acquired reflex of the first order, a second order reflex.
Thus, a defensive reflex of the third order was formed in dogs, the fourth could not be developed, and the digestive one reached the second. In children, conditioned reflexes of the sixth order are formed, in an adult up to the twentieth.
The variability of the external environment leads to the constant formation of many new behaviors necessary for survival. Depending on the structure of the receptor that perceives the stimulus, conditioned reflexes are divided into:
- Exteroceptive- irritation is perceived by body receptors, dominated by reflex reactions (gustatory, tactile);
- intraceptive- are caused by action on internal organs (changes in homeostasis, blood acidity, temperature);
- proprioceptive- are formed by stimulating the striated muscles of humans and animals, providing motor activity.
There are artificial and natural acquired reflexes:
artificial arise under the action of a stimulus that has no connection with an unconditioned stimulus (sound signals, light stimulation).
Natural are formed in the presence of a stimulus similar to the unconditioned (smell and taste of food).
Unconditioned reflexes
These are innate mechanisms that ensure the preservation of the integrity of the body, homeostasis of the internal environment and, most importantly, reproduction. Congenital reflex activity is formed in the spinal cord and cerebellum, controlled by the cerebral cortex. Characteristically, they persist for life.
reflex arcs hereditary reactions are laid down before the birth of a person. Some reactions are characteristic of a certain age, and then disappear (for example, in small children - sucking, grasping, searching). Others do not manifest themselves at first, but with the onset of a certain period they appear (sexual).
Unconditioned reflexes are characterized by the following features:
- Occur independently of the consciousness and will of a person;
- species - appear in all representatives (for example, coughing, salivation at the smell or sight of food);
- endowed with specificity - they appear when exposed to the receptor (pupil reaction occurs when a beam of light is directed to photosensitive areas). This also includes salivation, secretion of mucous secretions and enzymes of the digestive system when food enters the mouth;
- flexibility - for example, different foods lead to the secretion of a certain amount and various chemical composition of saliva;
- on the basis of unconditioned reflexes, conditioned ones are formed.
Unconditioned reflexes are needed to fulfill the needs of the body, they are permanent, but as a result of illness or bad habits they can disappear. So, with a disease of the iris of the eye, when scars form on it, the reaction of the pupil to light exposure disappears.
Classification of unconditioned reflexes
Congenital reactions are classified into:
- Simple(quickly remove your hand from a hot object);
- complex(maintaining homeostasis in situations of increased CO 2 concentration in the blood by increasing the frequency of respiratory movements);
- the most difficult(instinctive behavior).
Classification of unconditioned reflexes according to Pavlov
Pavlov divided innate reactions into food, sexual, protective, orienting, statokinetic, homeostatic.
To food salivation at the sight of food and its entry into the digestive tract, the secretion of hydrochloric acid, gastrointestinal motility, sucking, swallowing, chewing.
Protective are accompanied by contraction of muscle fibers in response to an irritating factor. Everyone knows the situation when the hand reflexively withdraws from a hot iron or a sharp knife, sneezing, coughing, lacrimation.
indicative occur when sudden changes occur in nature or in the organism itself. For example, turning the head and body towards sounds, turning the head and eyes to light stimuli.
Sexual associated with reproduction, preservation of the species, this includes parental (feeding and caring for offspring).
Statokinetic provide bipedalism, balance, movement of the body.
homeostatic- independent regulation of blood pressure, vascular tone, respiratory rate, heart rate.
Classification of unconditioned reflexes according to Simonov
vital to maintain life (sleep, nutrition, economy of strength), depend only on the individual.
role-playing arise upon contact with other individuals (procreation, parental instinct).
The need for self-development(the desire for individual growth, for the discovery of something new).
Congenital reflexes are activated when necessary due to a short-term violation of internal constancy or variability of the external environment.
Table comparing conditioned and unconditioned reflexes
| Comparison of the characteristics of conditioned (acquired) and unconditioned (innate) reflexes | |
|---|---|
| Unconditional | Conditional |
| Congenital | Acquired in the course of life |
| Present in all members of the species | Individual for each organism |
| Relatively constant | Arise and fade with changes in the external environment |
| Formed at the level of the spinal cord and medulla oblongata | Carried out by the brain |
| Are laid in utero | Developed against the background of congenital reflexes |
| Occurs when an irritant acts on certain receptor zones | Manifested under the influence of any stimulus that is perceived by the individual |
Higher nervous activity carries out work in the presence of two interrelated phenomena: excitation and inhibition (congenital or acquired).
Braking
External unconditional braking(congenital) is carried out by the action on the body of a very strong stimulus. The termination of the action of the conditioned reflex occurs due to the activation of nerve centers under the influence of a new stimulus (this is transcendental inhibition).
When several stimuli (light, sound, smell) are simultaneously exposed to the studied organism, the conditioned reflex fades, but over time, the orienting reflex is activated and inhibition disappears. This type of inhibition is called temporary.
Conditional inhibition(acquired) does not arise by itself, it must be worked out. There are 4 types of conditional inhibition:
- Fading (disappearance of a persistent conditioned reflex without constant reinforcement by an unconditioned one);
- differentiation;
- conditional brake;
- delayed braking.
Braking is a necessary process in our life. In its absence, many unnecessary reactions would occur in the body that are not beneficial.
An example of external inhibition (the reaction of a dog to a cat and the SIT command) The meaning of conditioned and unconditioned reflexes
Unconditioned reflex activity is necessary for the survival and preservation of the species. A good example is the birth of a child. In the new world for him, many dangers await him. Due to the presence of innate reactions, the cub can survive in these conditions. Immediately after birth, the respiratory system is activated, the sucking reflex provides nutrients, touching sharp and hot objects is accompanied by an instant withdrawal of the hand (manifestation of protective reactions).
For further development and existence, one has to adapt to the surrounding conditions, conditioned reflexes help in this. They provide rapid adaptation of the body and can be formed throughout life.
The presence of conditioned reflexes in animals enables them to quickly respond to the voice of a predator and save their lives. A person at the sight of food carries out conditioned reflex activity, salivation begins, the production of gastric juice for the rapid digestion of food. The sight and smell of some objects, on the contrary, signals danger: the red cap of fly agaric, the smell of spoiled food.
The importance of conditioned reflexes in the daily life of man and animals is enormous. Reflexes help to navigate the terrain, get food, get away from danger, saving one's life.
