Регуляция нервной деятельности представляет собой the processes of excitation and inhibition in the central nervous system. At first, it occurs as an elementary reaction to irritation. In the process of evolution, complication of neurohumoral functions occurred, leading to the formation of the main divisions of the nervous and endocrine systems. In this article we will study one of the main processes - inhibition in the central nervous system, types and mechanisms of its implementation.
Nervous tissue, its structure and function
One type of animal tissue callednervous, has a special structure that provides both the process of excitation and activating the function of inhibition in the central nervous system. Nerve cells consist of the body and processes: short (dendrites) and long (axon), which ensures the transmission of nerve impulses from one neurocyte to another. The end of the nerve cell axon is in contact with the dendrites of the next neurocyte in places called synapses. They provide the transmission of bioelectric pulses through the nervous tissue. Moreover, the excitation always moves in the same direction - from the axon to the body or the dendrites of another neurocyte.
Another property, besides excitement, flowsin nervous tissue, inhibition in the central nervous system. It is the response of the body to the action of the stimulus, leading to a decrease or complete cessation of motor or secretory activity, in which centrifugal neurons are involved. Inhibition in the nervous tissue can occur without prior excitation, but only under the influence of an inhibitory mediator, such as GABA. It is one of the main braking transmitters. Here you can call a substance such as glycine. This amino acid is involved in enhancing inhibitory processes and stimulates the production of gamma aminobutyric acid molecules in synapses.
I. M. Sechenov and his work in neurophysiology
Выдающийся российский ученый, создатель теории Reflex activity of the brain proved the presence in the central parts of the nervous system of special cell complexes capable of inactivating bioelectric processes. The discovery of braking centers in the central nervous system was made possible through the use of three types of experiments by I. Sechenov. These include: cutting cortex areas in different areas of the brain, stimulating individual gray matter loci with physical or chemical factors (electric current, sodium chloride solution), and also using the method of physiological stimulation of brain centers. IM Sechenov was an excellent experimenter, conducting ultra-precise cuts in the zone between the visual mounds and directly in the thalamus of the frog itself. He observed a decrease and complete cessation of the motor activity of the limbs of the animal.
Так, нейрофизиологом был открыт особый вид nervous process - inhibition in the central nervous system. The types and mechanisms of its formation will be discussed in more detail in the following sections, and now we once again pay attention to this fact: in such departments as the medulla oblongata and visual hillocks, there is a section called the braking or “Sechenov” center. The scientist also proved its presence not only in mammals, but also in humans. Moreover, I. M. Sechenov discovered the phenomenon of tonic excitation of inhibitory centers. He understood by this process a slight excitement in centrifugal neurons and muscles associated with them, as well as in the nerve centers of inhibition.
Do nerve processes interact?
Studies of prominent Russian physiologists I.P. Pavlova and I. M. Sechenov proved that the work of the central nervous system is characterized by the coordination of the body's reflex reactions. The interaction of the processes of excitation and inhibition in the central nervous system leads to a coordinated regulation of body functions: motor activity, respiration, digestion, excretion. Bioelectric processes simultaneously occur in the nerve centers and can consistently vary over time. This ensures the correlation and timely passage of response reflexes to signals from the internal and external environment. Numerous experiments conducted by neurophysiologists have confirmed the fact that excitation and inhibition in the central nervous system are key nervous phenomena, which are based on certain regularities. Let us dwell on them in more detail.
The nerve centers of the cerebral cortex are capabledistribute both kinds of processes throughout the nervous system. This property is called irradiation of excitation or inhibition. The opposite phenomenon is the reduction or limitation of the brain region that propagates bioimpulses. It is called concentration. Scientists observe both types of interaction during the formation of conditioned motor reflexes. During the initial stage of the formation of motor skills, due to the irradiation of arousal, several muscle groups are simultaneously reduced at once, not necessarily participating in the performance of the motor act being formed. Only after repeated repetitions of the formed complex of physical movements (skating, skiing, cycling), as a result of the concentration of excitation processes in specific nerve foci of the cortex, all human movements become highly coordinated.
Переключения в работе нервных центров могут also occur due to induction. It manifests itself when the following condition is fulfilled: first, a concentration of inhibition or excitation occurs, and these processes must be of sufficient strength. In science, there are two types of induction: S-phase (central inhibition in the central nervous system enhances excitation) and a negative form (excitation causes a process of inhibition). Sequential induction is also encountered. In this case, the nervous process changes to the opposite in the very nervous center. Studies of neurophysiologists have proved the fact that the behavior of higher mammals and humans is determined by the phenomena of induction, irradiation and concentration of the nervous processes of arousal and inhibition.
Unconditional braking
Let us consider in more detail the types of inhibition in the CNS andLet us dwell on its form, which is inherent in both animals and man. The term itself was proposed by I. Pavlov. The scientist considered this process to be one of the innate properties of the nervous system and singled out two types of it: extinguishing and permanent. Let us dwell on them in more detail.
Suppose there is a hot spot in the cortex,generating impulses to the working body (to the muscles, secretory cells of the glands). Due to changes in the conditions of the external or internal environment, another excited portion of the cerebral cortex arises. It produces bioelectrical signals of greater intensity, which inhibits the excitation in the previously active nerve center and its reflex arc. Extinguishing inhibition in the central nervous system leads to the fact that the intensity of the orienting reflex gradually decreases. The explanation for this is the following: the primary stimulus no longer causes the excitation process in the receptors of the afferent neuron.
Another type of inhibition observed as inman, and in animals, demonstrates the experience conducted by the Nobel Prize winner in 1904, I. P. Pavlov. During the feeding of the dog (with fistula removed from the cheek), the experimenters turned on a sharp beep - salivation from the fistula was stopped. This type of braking scientist called transcendent.
Being a congenital property, inhibition in the central nervous systemproceeds according to the unconditional-reflex mechanism. It is rather passive and does not cause the consumption of large amounts of energy, leading to the cessation of conditioned reflexes. Permanent unconditioned inhibition accompanies many psychosomatic diseases: dyskinesias, spastic and flaccid paralysis.
What is a damping brake
Continuing to study the mechanisms of inhibition in the CNS,Consider what constitutes one of its species, called a fading brake. It is well known that the orienting reflex is the body's response to the effects of a new extraneous signal. In this case, a nerve center is formed in the cerebral cortex, which is in a state of arousal. It forms the reflex arc, which is responsible for the reaction of the organism and is called the orientation reflex. This reflex act causes the inhibition of the conditioned reflex that is happening at the moment. After a multiple repetition of a foreign stimulus, the reflex, called the indicative one, gradually diminishes and finally disappears. This means that it does not cause more inhibition of the conditioned reflex. Such a signal and received the name of the extinguishing brake.
Таким образом, внешнее торможение условных reflexes associated with the influence on the body of an extraneous signal and is an innate property of the central and peripheral nervous system. A sudden or new stimulus, for example, a painful sensation, an extraneous sound, a change in illumination, not only causes an indicative reflex, but also contributes to the weakening or even complete cessation of the conditioned reflex arc active at the moment. If the extraneous signal (except for the painful) acts repeatedly, the inhibition of the conditioned reflex appears less. The biological role of the unconditioned form of the nervous process is to conduct the body’s response to the stimulus, which is the most important at the moment.
Internal braking
Its other name is used in physiology.higher nervous activity, conditional inhibition. The main prerequisite for the emergence of such a process is the lack of reinforcement of signals coming from the outside world with innate reflexes: digestive, salivary. The braking processes in the central nervous system that occur under these conditions require a certain time interval. Consider their types in more detail.
Например, дифференцировочное торможение возникает as a response to environmental signals that coincide in amplitude, intensity and strength to a conditioned stimulus. This form of interaction between the nervous system and the surrounding world allows the body to more subtly distinguish between stimuli and isolate from their totality the one that receives reinforcement by the innate reflex. For example, the sound of a bell with a force of 15 Hz, supported by a feeding trough with food, in a dog developed a conditional salivating response. If another beep, with a force of 25 Hz, is not applied to the animal, without supporting it with food, in the first series of experiments on a dog from a fistula, saliva will be allocated to both conditioned stimuli. After some time, the animal will differentiate these signals, and at the sound of 25 Hz, the saliva from the fistula will cease to stand out, that is, differentiating inhibition will develop.
Освободить мозг от информации, потерявшей vital role for the body - this function just performs inhibition in the central nervous system. Physiology has empirically proven that conditioned motor reactions that are well established by the skills developed can persist throughout a person’s life, for example, skating, cycling.
Summarizing, we can say that the processesbraking in the central nervous system is the weakening or cessation of certain body reactions. They are very important, since all reflexes of the body are corrected in accordance with the changed conditions, and if the conditional signal has lost its meaning, it can even completely disappear. Different types of inhibition in the central nervous system are basic for such abilities of the human psyche as preservation of self-control, discrimination of stimuli, expectation.
Delayed view of the nervous process
Experimentally, you can create a situation in whichthe body's response to the conditioned signal from the external environment is manifested even before exposure to an unconditioned stimulus, for example, food. With an increase in the time interval between the onset of a conditioned signal (light, sound, for example, metronome beats) and the moment of reinforcement for up to three minutes, the salivation of the above conditional stimuli becomes more and more late and manifests itself only when the animal has a feeding trough. The lag of the response to the conditioned signal characterizes the processes of inhibition in the central nervous system, called the retarded view, in which its flow time corresponds to the delay interval of the unconditioned stimulus, for example, food.
The value of inhibition in the central nervous system
The human body, figuratively speaking, is"Under the gun" a huge number of factors of external and internal environment, to which he is forced to respond and form a set of reflexes. Their nerve centers and arcs form in the brain and spinal cord. Congestion of the nervous system with a huge number of excited centers in the cerebral cortex negatively affects the mental health of a person, and also reduces his working capacity.
Biological basis of human behavior
Both types of nervous tissue activity likeexcitation and inhibition in the central nervous system are the basis of higher nervous activity. It determines the physiological mechanisms of human mental activity. The doctrine of higher nervous activity was formulated by I.P. Pavlov. His modern interpretation is as follows:
- Excitation and inhibition in the central nervous system, occurring in the interaction, provide complex mental processes: memory, thinking, speech, consciousness, and also form complex behavioral reactions of the person.
To compose a scientifically based mode of study, work, rest, scientists apply knowledge of the laws of higher nervous activity.
The biological significance of such an active nervousprocess as inhibition, can be defined as follows. Changes in the conditions of the external and internal environment (lack of reinforcement of the conditioned signal by the innate reflex) entail adequate changes in the adaptive mechanisms in the human body. Therefore, the acquired reflex act is oppressed (goes out) or disappears altogether, since it becomes inappropriate for the organism.
What is a dream?
I.P.Pavlov experimentally proved in his works the fact that the processes of inhibition in the central nervous system and sleep are of a single nature. In the period of wakefulness of the organism against the background of the general activity of the cerebral cortex, its individual parts are still diagnosed, covered by internal inhibition. During sleep, it radiates over the entire surface of the big hemispheres, reaching subcortical formations: the visual cusps (thalamus), hypothalamus, reticular formation and limbic system. As noted by the outstanding neurophysiologist PK Anokhin, all of the above-mentioned parts of the central nervous system, which are responsible for the behavioral sphere, emotions and instincts, decrease their activity during sleep. This entails a reduction in the generation of nerve impulses coming from under the cortex. Thus, the activation of the cortex is reduced. This provides the possibility of rest and restoration of metabolism both in the neurocytes of the large brain, and in the whole organism.
The experiences of other scientists (Hess, Economo) wereestablished special complexes of nerve cells that are included in the nonspecific nuclei of the visual hillocks. The excitation processes diagnosed in them cause a decrease in the frequency of biorhythms of the cortex, which can be regarded as a transition from active state (wakefulness) to sleep. Studies of such areas of the brain as Sylvius aqueduct and III ventricle pushed scientists to the idea of having a sleep regulation center. It is anatomically connected to the brain site responsible for waking. The defeat of this locus of the cortex due to injury or as a result of hereditary disorders in humans leads to pathological conditions of insomnia. We also note the fact that the regulation of such a process of inhibition, as vital for the organism, as sleep, is carried out by the nerve centers of the diencephalon and subcortical nuclei: caudate, amygdala, fencing and lenticular.
