The cerebral cortex is part of most creatures on earth, but it is in humans that this area has reached the greatest development. Experts say that this contributed to the age-old labor activity that accompanies us throughout our lives.
In this article, we will look at the structure, as well as what the cerebral cortex is responsible for.
The cortical part of the brain plays the main functioning role for the human body as a whole and consists of neurons, their processes and glial cells. The cortex consists of stellate, pyramidal and spindle-shaped nerve cells. Due to the presence of warehouses, the cortical area occupies a fairly large surface.
The structure of the cerebral cortex includes a layered classification, which is divided into the following layers:
- Molecular. It has distinctive differences, which is reflected in the low cellular level. A low number of these cells, consisting of fibers, are closely interconnected
- External granular. The cellular substances of this layer are sent to the molecular layer
- layer of pyramidal neurons. It is the widest layer. Reached the greatest development in the precentral gyrus. The number of pyramidal cells increases within 20-30 microns from the outer zone of this layer to the inner
- Internal granular. Directly the visual cortex of the brain is the area where the inner granular layer has reached its maximum development.
- Internal pyramidal. It consists of large pyramidal cells. These cells are carried down to the molecular layer
- Layer of multimorphic cells. This layer is formed by nerve cells of a different nature, but mostly of a spindle-shaped type. The outer zone is characterized by the presence of larger cells. The cells of the internal section are characterized by a small size
If we consider the layered level more carefully, we can see that the cerebral cortex of the cerebral hemispheres takes on the projections of each of the levels occurring in different parts of the CNS.
Areas of the cerebral cortex
Features of the cellular structure of the cortical part of the brain is divided into structural units, namely: zones, fields, regions and subregions.
The cerebral cortex is classified into the following projection zones:
- Primary
- Secondary
- Tertiary
In the primary zone, certain neuron cells are located, to which a receptor impulse (auditory, visual) is constantly supplied. The secondary department is characterized by the presence of peripheral analyzer departments. The tertiary receives processed data from the primary and secondary zones, and is itself responsible for conditioned reflexes.
Also, the cerebral cortex is divided into a number of departments or zones that allow you to regulate many human functions.
Allocates the following zones:
- Sensory - areas in which the zones of the cerebral cortex are located:
- visual
- Auditory
- Flavoring
- Olfactory
- Motor. These are cortical areas, the stimulation of which can lead to certain motor reactions. They are located in the anterior central gyrus. Its damage can lead to significant motor impairment.
- Associative. These cortical regions are located next to the sensory areas. Impulses of nerve cells that are sent to the sensory zone form an exciting process of associative divisions. Their defeat entails severe impairment of the learning process and memory functions.
Functions of the lobes of the cerebral cortex
The cerebral cortex and subcortex perform a number of human functions. The lobes of the cerebral cortex themselves contain such necessary centers as:
- Motor, speech center (Broca's center). It is located in the lower region of the frontal lobe. Its damage can completely disrupt speech articulation, that is, the patient can understand what is being said to him, but cannot answer
- Auditory, speech center (Wernicke's center). Located in the left temporal lobe. Damage to this area can result in the person being unable to understand what the other person is saying, while still remaining able to express themselves. Also in this case, written speech is seriously impaired.
Speech functions are performed by sensory and motor areas. Its functions are related to written speech, namely reading and writing. The visual cortex and the brain regulate this function.
Damage to the visual center of the cerebral hemispheres leads to a complete loss of reading and writing skills, as well as to a possible loss of vision.
In the temporal lobe there is a center that is responsible for the memorization process. A patient with a lesion in this area cannot remember the names of certain things. However, he understands the very meaning and functions of the object and can describe them.
For example, instead of the word "cup", a person says: "this is where liquid is poured in order to then drink."
Pathologies of the cerebral cortex
There are a huge number of diseases that affect the human brain, including its cortical structure. Damage to the cortex leads to disruption of its key processes, and also reduces its performance.
The most common diseases of the cortical part include:
- Pick's disease. It develops in people in old age and is characterized by the death of nerve cells. At the same time, the external manifestations of this disease are almost identical to Alzheimer's disease, which can be seen at the stage of diagnosis, when the brain looks like a dried walnut. It is also worth noting that the disease is incurable, the only thing that therapy is aimed at is the suppression or elimination of symptoms.
- Meningitis. This infectious disease indirectly affects the parts of the cerebral cortex. It occurs as a result of damage to the cortex by infection with pneumococcus and a number of others. It is characterized by headaches, fever, pain in the eyes, drowsiness, nausea
- Hypertonic disease. With this disease, foci of excitation begin to form in the cerebral cortex, and outgoing impulses from this focus begin to constrict blood vessels, which leads to sharp jumps in blood pressure
- Oxygen starvation of the cerebral cortex (hypoxia). This pathological condition most often develops in childhood. It occurs due to a lack of oxygen or a violation of blood flow in the brain. Can lead to irreversible changes in neuronal tissue or death
Most pathologies of the brain and cortex cannot be determined based on the symptoms and external signs that appear. To identify them, you need to go through special diagnostic methods that allow you to explore almost any, even the most inaccessible places and subsequently determine the state of a particular area, as well as analyze its work.
The cortical area is diagnosed using various techniques, which we will discuss in more detail in the next chapter.
Conducting a survey
For high-precision examination of the cerebral cortex, methods such as:
- Magnetic resonance and computed tomography
- Encephalography
- Positron emission tomography
- Radiography
An ultrasound examination of the brain is also used, but this method is the least effective in comparison with the above methods. Of the advantages of ultrasound, the price and speed of the examination are distinguished.
In most cases, patients are diagnosed with cerebral circulation. For this, an additional series of diagnostics can be used, namely;
- Doppler ultrasound. Allows you to identify the affected vessels and changes in the speed of blood flow in them. The method is highly informative and absolutely safe for health.
- Rheoencephalography. The work of this method is to register the electrical resistance of tissues, which allows you to form a line of pulsed blood flow. Allows you to determine the state of blood vessels, their tone and a number of other data. Less informative than the ultrasonic method
- X-ray angiography. This is a standard X-ray examination, which is additionally carried out using intravenous administration of a contrast agent. Then the X-ray is taken. As a result of the spread of the substance throughout the body, all blood flows in the brain are highlighted on the screen.
These methods provide accurate information about the state of the brain, cortex and blood flow parameters. There are also other methods that are used depending on the nature of the disease, the patient's condition and other factors.
The human brain is the most complex organ, and many resources are spent on studying it. However, even in the era of innovative methods of its research, it is not possible to study certain parts of it.
The processing power of processes in the brain is so significant that even a supercomputer is not even close to the corresponding indicators.
The cerebral cortex and the brain itself are constantly being explored, as a result of which the discovery of various new facts about it becomes more and more. The most common discoveries:
- In 2017, an experiment was conducted in which a person and a supercomputer were involved. It turned out that even the most technically equipped equipment is able to simulate only 1 second of brain activity. It took 40 minutes to complete the task.
- The amount of human memory in an electronic unit of measurement of the amount of data is about 1000 terabytes.
- The human brain consists of more than 100 thousand vascular plexuses, 85 billion nerve cells. Also in the brain there are about 100 trillion. neural connections that process human memories. Thus, when learning something new, the structural part of the brain also changes.
- When a person wakes up, the brain accumulates an electric field with a power of 25 watts. This power is enough to light an incandescent lamp
- The mass of the brain is only 2% of the total mass of a person, however, the brain consumes about 16% of the energy in the body and more than 17% of oxygen
- The brain is 80% water and 60% fat. Therefore, to maintain normal brain function, a healthy diet is essential. Eat foods that contain omega-3 fatty acids (fish, olive oil, nuts) and drink the required amount of fluid daily
- Scientists have found that if a person "sits" on a diet, the brain begins to eat itself. And low levels of oxygen in the blood for several minutes can lead to undesirable consequences.
- Human forgetfulness is a natural process, and the destruction of unnecessary information in the brain allows it to remain flexible. Also, forgetfulness can occur artificially, for example, when drinking alcohol, which inhibits natural processes in the brain.
The activation of mental processes makes it possible to generate additional brain tissue that replaces the damaged one. Therefore, it is necessary to constantly develop mentally, which will significantly reduce the risk of dementia in old age.
The cerebral cortex , a layer of gray matter 1-5 mm thick, covering the cerebral hemispheres of mammals and humans. This part of the brain, which developed in the later stages of the evolution of the animal world, plays an extremely important role in the implementation of mental, or higher nervous activity, although this activity is the result of the work of the brain as a whole. Due to bilateral connections with the underlying parts of the nervous system, the cortex can participate in the regulation and coordination of all body functions. In humans, the cortex makes up an average of 44% of the volume of the entire hemisphere as a whole. Its surface reaches 1468-1670 cm2.
The structure of the bark . A characteristic feature of the structure of the cortex is the oriented, horizontal-vertical distribution of its constituent nerve cells in layers and columns; thus, the cortical structure is distinguished by a spatially ordered arrangement of functioning units and connections between them. The space between the bodies and processes of the nerve cells of the cortex is filled with neuroglia and the vascular network (capillaries). Cortical neurons are divided into 3 main types: pyramidal (80-90% of all cortical cells), stellate and fusiform. The main functional element of the cortex is the afferent-efferent (i.e., perceiving centripetal and sending centrifugal stimuli) long-axon pyramidal neuron. Stellar cells are distinguished by weak development of dendrites and powerful development of axons, which do not extend beyond the diameter of the cortex and cover groups of pyramidal cells with their branchings. Stellar cells play the role of perceiving and synchronizing elements capable of coordinating (simultaneously inhibiting or exciting) spatially close groups of pyramidal neurons. A cortical neuron is characterized by a complex submicroscopic structure. Topographically different areas of the cortex differ in the density of the cells, their size, and other characteristics of the layered and columnar structure. All these indicators determine the architecture of the cortex, or its cytoarchitectonics. The largest divisions of the territory of the cortex are the ancient (paleocortex), old (archicortex), new (neocortex) and interstitial cortex. The surface of the new cortex in humans occupies 95.6%, the old 2.2%, the ancient 0.6%, the intermediate 1.6%.
If we imagine the cerebral cortex as a single cover (cloak) covering the surface of the hemispheres, then the main central part of it will be the new cortex, while the ancient, old and intermediate will take place on the periphery, i.e. along the edges of this cloak. The ancient cortex in humans and higher mammals consists of a single cell layer, indistinctly separated from the underlying subcortical nuclei; the old bark is completely separated from the latter and is represented by 2-3 layers; the new cortex consists, as a rule, of 6-7 layers of cells; intermediate formations - transitional structures between the fields of the old and new crust, as well as the ancient and new crust - from 4-5 layers of cells. The neocortex is subdivided into the following regions: precentral, postcentral, temporal, inferior parietal, superior parietal, temporo-parietal-occipital, occipital, insular, and limbic. In turn, the areas are divided into sub-areas and fields. The main type of direct and feedback connections of the new cortex are vertical bundles of fibers that bring information from the subcortical structures to the cortex and send it from the cortex to the same subcortical formations. Along with vertical connections, there are intracortical - horizontal - bundles of associative fibers passing at various levels of the cortex and in the white matter under the cortex. Horizontal bundles are most characteristic of layers I and III of the cortex, and in some fields for layer V.
Horizontal bundles provide information exchange both between fields located on adjacent gyri and between distant areas of the cortex (for example, frontal and occipital).
Functional features of the cortex are determined by the distribution of nerve cells and their connections in layers and columns mentioned above. Convergence (convergence) of impulses from various sense organs is possible on cortical neurons. According to modern concepts, such a convergence of heterogeneous excitations is a neurophysiological mechanism of the integrative activity of the brain, i.e., analysis and synthesis of the body's response activity. It is also essential that the neurons are combined into complexes, apparently realizing the results of the convergence of excitations to individual neurons. One of the main morpho-functional units of the cortex is a complex called a column of cells, which passes through all the cortical layers and consists of cells located on one perpendicular to the surface of the cortex. The cells in the column are closely interconnected and receive a common afferent branch from the subcortex. Each column of cells is responsible for the perception of predominantly one type of sensitivity. For example, if at the cortical end of the skin analyzer one of the columns reacts to touching the skin, then the other - to the movement of the limb in the joint. In the visual analyzer, the functions of perception of visual images are also distributed in columns. For example, one of the columns perceives the movement of an object in a horizontal plane, the neighboring one - in a vertical one, etc.
The second complex of cells of the new cortex - the layer - is oriented in the horizontal plane. It is believed that the small cell layers II and IV consist mainly of receptive elements and are "entrances" to the cortex. The large cell layer V is the exit from the cortex to the subcortex, and the middle cell layer III is associative, connecting various cortical zones.
The localization of functions in the cortex is characterized by dynamism due to the fact that, on the one hand, there are strictly localized and spatially delimited cortical zones associated with the perception of information from a particular sense organ, and on the other hand, the cortex is a single apparatus in which individual structures are closely connected and if necessary, they can be interchanged (the so-called plasticity of cortical functions). In addition, at any given moment, cortical structures (neurons, fields, regions) can form coordinated complexes, the composition of which changes depending on specific and nonspecific stimuli that determine the distribution of inhibition and excitation in the cortex. Finally, there is a close interdependence between the functional state of the cortical zones and the activity of the subcortical structures. Territories of the crust differ sharply in their functions. Most of the ancient cortex is included in the olfactory analyzer system. The old and intermediate cortex, being closely related to the ancient cortex both by systems of connections and evolutionarily, are not directly related to the sense of smell. They are part of the system that controls the regulation of vegetative reactions and emotional states. New cortex - a set of final links of various perceiving (sensory) systems (cortical ends of analyzers).
It is customary to single out projection, or primary, and secondary, fields, as well as tertiary fields, or associative zones, in the zone of one or another analyzer. Primary fields receive information mediated through the smallest number of switches in the subcortex (in the optic tubercle, or thalamus, diencephalon). On these fields, the surface of peripheral receptors is, as it were, projected. In the light of modern data, projection zones cannot be considered as devices that perceive “point to point” irritations. In these zones, certain parameters of objects are perceived, i.e., images are created (integrated), since these parts of the brain respond to certain changes in objects, to their shape, orientation, speed of movement, etc.
Cortical structures play a primary role in the learning of animals and humans. However, the formation of some simple conditioned reflexes, mainly from the internal organs, can be provided by subcortical mechanisms. These reflexes can also form at lower levels of development, when there is no cortex yet. Complex conditioned reflexes underlying integral behavioral acts require the preservation of cortical structures and the participation of not only the primary zones of the cortical ends of the analyzers, but also the associative - tertiary zones. Cortical structures are directly related to the mechanisms of memory. Electrical stimulation of certain areas of the cortex (for example, the temporal one) evokes complex pictures of memories in people.
A characteristic feature of the activity of the cortex is its spontaneous electrical activity, recorded in the form of an electroencephalogram (EEG). In general, the cortex and its neurons have rhythmic activity, which reflects the biochemical and biophysical processes taking place in them. This activity has a varied amplitude and frequency (from 1 to 60 Hz) and changes under the influence of various factors.
The rhythmic activity of the cortex is irregular, but it is possible to distinguish several different types of it (alpha, beta, delta, and theta rhythms) by the frequency of potentials. The EEG undergoes characteristic changes in many physiological and pathological conditions (different phases of sleep, tumors, seizures, etc.). The rhythm, i.e. frequency, and amplitude of the bioelectric potentials of the cortex are set by subcortical structures that synchronize the work of groups of cortical neurons, which creates the conditions for their coordinated discharges. This rhythm is associated with the apical (apical) dendrites of the pyramidal cells. The rhythmic activity of the cortex is superimposed by influences coming from the sense organs. So, a flash of light, a click or a touch on the skin causes the so-called. the primary response, consisting of a series of positive waves (the downward deflection of the electron beam on the oscilloscope screen) and a negative wave (the upward deflection of the beam). These waves reflect the activity of the structures of a given area of the cortex and change in its various layers.
Phylogeny and ontogeny of the cortex . The bark is the product of a long evolutionary development, during which the ancient bark first appears, arising in connection with the development of the olfactory analyzer in fish. With the release of animals from the water to land, the so-called. a cloak-like part of the cortex, completely separated from the subcortex, which consists of old and new cortex. The formation of these structures in the process of adaptation to the complex and diverse conditions of terrestrial existence is connected (by the improvement and interaction of various perceiving and motor systems. In amphibians, the cortex is represented by the ancient and the rudiment of the old cortex, in reptiles the ancient and old cortex are well developed and the rudiment of the new cortex appears. The greatest development the new cortex reaches in mammals, and among them in primates (monkeys and humans), proboscis (elephants) and cetaceans (dolphins, whales).Due to the uneven growth of individual structures of the new cortex, its surface becomes folded, covered with furrows and convolutions. telencephalon in mammals is inextricably linked with the evolution of all parts of the central nervous system.This process is accompanied by an intensive growth of direct and feedback connections connecting cortical and subcortical structures.Thus, at higher stages of evolution, the functions of subcortical formations begin to be controlled by cortical structures. This phenomenon is called corticolization of functions. As a result of corticolization, the brain stem forms a single complex with the cortical structures, and damage to the cortex at the higher stages of evolution leads to a violation of the vital functions of the body. Associative zones undergo the greatest changes and increase during the evolution of the neocortex, while the primary, sensory fields decrease in relative magnitude. The growth of the new cortex leads to the displacement of the old and ancient on the lower and median surfaces of the brain.
Modern scientists know for certain that thanks to the functioning of the brain, such abilities as awareness of signals received from the external environment, mental activity, and memorization of thinking are possible.
The ability of a person to be aware of his own relationships with other people is directly related to the process of excitation of neural networks. And we are talking about those neural networks that are located in the cortex. It is the structural basis of consciousness and intellect.
In this article, we will consider how the cerebral cortex is arranged, the zones of the cerebral cortex will be described in detail.
neocortex
The cortex includes about fourteen billion neurons. It is thanks to them that the functioning of the main zones is carried out. The vast majority of neurons, up to ninety percent, form the neocortex. It is part of the somatic NS and its highest integrative department. The most important functions of the cerebral cortex are the perception, processing, interpretation of information that a person receives with the help of various sense organs.
In addition, the neocortex controls the complex movements of the human body's muscle system. It contains centers that take part in the process of speech, memory storage, abstract thinking. Most of the processes that take place in it form the neurophysical basis of human consciousness.
What parts of the cerebral cortex are made up of? The areas of the cerebral cortex will be discussed below.
paleocortex
It is another large and important section of the cortex. Compared to the neocortex, the paleocortex has a simpler structure. The processes that take place here are rarely reflected in consciousness. In this section of the cortex, the higher vegetative centers are localized.
Communication of the cortical layer with other parts of the brain
It is important to consider the connection that exists between the underlying parts of the brain and the cerebral cortex, for example, with the thalamus, bridge, middle bridge, basal ganglia. This connection is carried out with the help of large bundles of fibers that form the inner capsule. The fiber bundles are represented by wide layers, which are composed of white matter. They contain a huge number of nerve fibers. Some of these fibers provide transmission of nerve signals to the cortex. The rest of the bundles transmits nerve impulses to the nerve centers located below.
How is the cerebral cortex structured? The areas of the cerebral cortex will be presented below.
The structure of the bark
The largest part of the brain is its cortex. Moreover, cortical zones are only one type of parts distinguished in the cortex. In addition, the cortex is divided into two hemispheres - right and left. Between themselves, the hemispheres are connected by bundles of white matter, forming the corpus callosum. Its function is to ensure the coordination of the activities of both hemispheres.
Classification of areas of the cerebral cortex according to their location
Despite the fact that the bark has a huge number of folds, in general, the location of its individual convolutions and furrows is constant. The main ones are a guideline in the selection of areas of the cortex. These zones (lobes) include - occipital, temporal, frontal, parietal. Although they are classified by location, each of them has its own specific functions.
auditory area of the cerebral cortex
For example, the temporal zone is the center in which the cortical section of the hearing analyzer is located. If there is damage to this section of the cortex, deafness may occur. In addition, Wernicke's speech center is located in the auditory zone. If it is damaged, then the person loses the ability to perceive oral speech. The person perceives it as simple noise. Also in the temporal lobe there are neuronal centers that belong to the vestibular apparatus. If they are damaged, the sense of balance is disturbed.
Speech areas of the cerebral cortex
The speech zones are concentrated in the frontal lobe of the cortex. The speech motor center is also located here. If it is damaged in the right hemisphere, then the person loses the ability to change the timbre and intonation of his own speech, which becomes monotonous. If the damage to the speech center occurred in the left hemisphere, then articulation, the ability to articulate speech and singing disappear. What else is the cerebral cortex made of? The areas of the cerebral cortex have different functions.
visual zones
In the occipital lobe is the visual zone, in which there is a center that responds to our vision as such. The perception of the surrounding world occurs precisely with this part of the brain, and not with the eyes. It is the occipital cortex that is responsible for vision, and damage to it can lead to partial or complete loss of vision. The visual area of the cerebral cortex is considered. What's next?
The parietal lobe also has its own specific functions. It is this zone that is responsible for the ability to analyze information that relates to tactile, temperature and pain sensitivity. If there is damage to the parietal region, the reflexes of the brain are disturbed. A person cannot recognize objects by touch.
Motor zone
Let's talk about the motor zone separately. It should be noted that this area of the cortex does not correlate in any way with the lobes discussed above. It is part of the cortex containing direct connections to motor neurons in the spinal cord. This name is given to neurons that directly control the activity of the muscles of the body.
The main motor area of the cerebral cortex is located in the gyrus, which is called the precentral. This gyrus is a mirror image of the sensory area in many ways. Between them there is a contralateral innervation. In other words, the innervation is directed to the muscles that are located on the other side of the body. An exception is the facial area, which is characterized by bilateral muscle control located on the jaw, lower face.
Slightly below the main motor zone is an additional zone. Scientists believe that it has independent functions that are associated with the process of outputting motor impulses. The additional motor zone has also been studied by specialists. Experiments that were performed on animals show that stimulation of this zone provokes the occurrence of motor reactions. A feature is that such reactions occur even if the main motor zone was isolated or completely destroyed. It is also involved in planning movements and motivating speech in the dominant hemisphere. Scientists believe that if the additional motor is damaged, dynamic aphasia can occur. The reflexes of the brain suffer.
Classification according to the structure and functions of the cerebral cortex
Physiological experiments and clinical trials, which were carried out at the end of the nineteenth century, made it possible to establish the boundaries between areas on which different receptor surfaces are projected. Among them, there are sense organs that are directed to the outside world (skin sensitivity, hearing, vision), receptors embedded directly in the organs of movement (motor or kinetic analyzers).
The areas of the cortex, in which various analyzers are located, can be classified according to their structure and functions. So, there are three of them. These include: primary, secondary, tertiary areas of the cerebral cortex. The development of the embryo involves the laying of only primary zones, characterized by simple cytoarchitectonics. Next comes the development of secondary, tertiary develop in the very last turn. Tertiary zones are characterized by the most complex structure. Let's consider each of them in a little more detail.
Center fields
Over the years of clinical research, scientists have managed to accumulate significant experience. Observations made it possible to establish, for example, that damage to various fields, as part of the cortical sections of different analyzers, can be reflected far from being equivalent in the overall clinical picture. If we consider all these fields, then among them one can be distinguished, which occupies a central position in the nuclear zone. Such a field is called the central or primary. It is located simultaneously in the visual zone, in the kinesthetic zone, in the auditory zone. Damage to the primary field entails very serious consequences. A person cannot perceive and carry out the most subtle differentiation of stimuli that affect the corresponding analyzers. How else are areas of the cerebral cortex classified?
Primary Zones
In the primary zones, there is a complex of neurons that is most predisposed to providing bilateral connections between the cortical and subcortical zones. It is this complex that connects the cerebral cortex with a variety of sensory organs in the most direct and shortest way. In this regard, these zones have the ability to very detailed identification of stimuli.
An important common feature of the functional and structural organization of the primary areas is that they all have a clear somatic projection. This means that individual peripheral points, for example, skin surfaces, retina, skeletal muscles, cochlea of the inner ear, have their own projection into strictly limited, corresponding points that are located in the primary zones of the cortex of the corresponding analyzers. In this regard, they were given the name of the projection zones of the cerebral cortex.
Secondary zones
In another way, these zones are called peripheral. This name was not given to them by chance. They are located in the peripheral sections of the cortex. Secondary zones differ from the central (primary) zones in their neuronal organization, physiological manifestations, and architectonic features.
Let's try to figure out what effects occur if the secondary zones are affected by an electrical stimulus or if they are damaged. The effects that arise mainly concern the most complex types of processes in the psyche. In the event that secondary zones are damaged, elementary sensations remain relatively intact. Basically, there are violations in the ability to correctly reflect the mutual relationships and entire complexes of elements that make up the various objects that we perceive. For example, if the secondary zones of the visual and auditory cortex were damaged, then one can observe the occurrence of auditory and visual hallucinations that unfold in a certain temporal and spatial sequence.
Secondary areas are of significant importance in the implementation of the mutual connections of stimuli that are distinguished using the primary areas of the cortex. In addition, they play a significant role in the integration of functions that are carried out by the nuclear fields of different analyzers as a result of combining into complex complexes of receptions.
Thus, secondary zones are of particular importance for the implementation of mental processes in more complex forms that require coordination and are associated with a detailed analysis of the relationships between objective stimuli. During this process, specific connections are established, which are called associative. Afferent impulses entering the cortex from the receptors of various external sense organs reach the secondary fields through many additional switches in the associative nucleus of the thalamus, which is also called the thalamic thalamus. Afferent impulses following in the primary zones, in contrast to impulses, follow in the secondary zones, reach them in a way that is shorter. It is implemented by means of a relay-core, in the thalamus.
We figured out what the cerebral cortex is responsible for.
What is the thalamus?
From the thalamic nuclei, fibers approach each lobe of the cerebral hemispheres. The thalamus is a visual mound located in the central part of the anterior part of the brain, consists of a large number of nuclei, each of which transmits an impulse to certain areas of the cortex.
All signals that enter the cortex (the only exception is olfactory ones) pass through the relay and integrative nuclei of the thalamus opticus. From the nuclei of the thalamus, the fibers are sent to the sensory zones. Taste and somatosensory zones are located in the parietal lobe, auditory sensory zone - in the temporal lobe, visual - in the occipital lobe.
Impulses come to them, respectively, from the ventrobasal complexes, medial and lateral nuclei. Motor zones are associated with the ventral and ventrolateral nuclei of the thalamus.
EEG desynchronization
What happens if a very strong stimulus acts on a person who is in a state of complete rest? Naturally, a person will completely concentrate on this stimulus. The transition of mental activity, which is carried out from a state of rest to a state of activity, is reflected on the EEG by a beta rhythm, which replaces the alpha rhythm. The fluctuations become more frequent. This transition is called EEG desynchronization; it appears as a result of sensory excitation entering the cortex from nonspecific nuclei located in the thalamus.
activating reticular system
Diffuse nervous system is made up of non-specific nuclei. This system is located in the medial parts of the thalamus. It is the anterior part of the activating reticular system that regulates the excitability of the cortex. A variety of sensory signals can activate this system. Sensory signals can be both visual and olfactory, somatosensory, vestibular, auditory. The reticular activating system is a channel that transmits signal data to the surface layer of the cortex through non-specific nuclei located in the thalamus. The arousal of ARS is necessary for a person to be able to maintain a state of wakefulness. If disturbances occur in this system, then coma-like sleep-like states can be observed.
Tertiary zones
There are functional relationships between the analyzers of the cerebral cortex, which have an even more complex structure than the one described above. In the process of growth, the fields of the analyzers overlap. Such overlap zones, which are formed at the ends of the analyzers, are called tertiary zones. They are the most complex types of combining the activities of the auditory, visual, skin-kinesthetic analyzers. The tertiary zones are located outside the boundaries of the analyzers' own zones. In this regard, damage to them does not have a pronounced effect.
Tertiary zones are special cortical areas in which scattered elements of different analyzers are collected. They occupy a very vast territory, which is divided into regions.
The upper parietal region integrates the movements of the whole body with the visual analyzer, and forms a scheme of bodies. The lower parietal region combines generalized forms of signaling, which are associated with differentiated subject and speech actions.
No less important is the temporo-parieto-occipital region. She is responsible for the complicated integration of auditory and visual analyzers with oral and written speech.
It should be noted that in comparison with the first two zones, the tertiary ones are characterized by the most complex chains of interaction.
Based on all the above material, we can conclude that the primary, secondary, tertiary zones of the human cortex are highly specialized. Separately, it is worth emphasizing the fact that all three cortical zones that we considered, in a normally functioning brain, together with the connection systems and formations of the subcortical location, function as a single differentiated whole.
We examined in detail the zones and sections of the cerebral cortex.
The cortex works in conjunction with other structures. This part of the body has certain features associated with its specific activity. The main basic function of the cortex is the analysis of information coming from the organs and the storage of the received data, as well as their transmission to other parts of the body. The cerebral cortex performs communication with information receptors, which act as receivers of signals entering the brain.
Among the receptors, there are sense organs, as well as organs and tissues that carry out commands, which, in turn, are transmitted from the cortex.
For example, visual information coming from is sent along the nerves through the cortex to the occipital region, which is responsible for vision. If the image is not static, it is analyzed in the parietal zone, in which the direction of movement of the observed objects is determined. The parietal lobes are also involved in the formation of articulate speech and a person's perception of his location in space. The frontal lobes of the cerebral cortex are for the higher psyches involved in the formation of personality, character, abilities, behavioral skills, creative inclinations, etc.
Cortical lesions
With lesions of one or another part of the cerebral cortex, disturbances occur in the perception and functioning of certain sensory organs.
With damage to the frontal lobe of the brain, mental disorders occur, which most often manifest themselves in a serious violation of attention, apathy, memory loss, sloppiness and a feeling of constant euphoria. A person loses some personal qualities and serious deviations in behavior are noticed. Often there is frontal ataxia, which is in standing or walking, difficulty in movement, problems with accuracy, and the occurrence of hit and miss phenomena. There may also be a phenomenon of grasping, which consists in obsessive grasping of objects surrounding a person. Some scientists attribute the appearance of epileptic seizures after trauma to the frontal lobe.
When the frontal lobe is damaged, the abilities of the human psyche are significantly impaired.
With lesions of the parietal lobe, memory disorders are observed. For example, the appearance of astereognosis is possible, which manifests itself in the inability to recognize an object by touch when closing the eyes. Often there is apraxia, which manifests itself in a violation of the formation of a sequence of events and building a logical chain for performing a motor task. Alexia is characterized by an inability to read. Acalculia - a violation of the ability to conduct over numbers. The perception of one's own body in space and the inability to understand logical structures may also be impaired.
The affected temporal lobes are responsible for hearing and perception disorders. With lesions of the temporal lobe, the perception of oral speech is disturbed, bouts of dizziness, hallucinations and seizures, mental disorders and excessive irritation (irritation) begin. With injuries of the occipital lobe, visual hallucinations and disorders occur, the inability to recognize objects when looking at them, and a distortion in the perception of the shape of an object. Sometimes there are photomas - flashes of light that occur when the inner part of the occipital lobe is irritated.
The reticular formation of the brain stem occupies a central position in the medulla oblongata, pons varolii, midbrain and diencephalon.
The neurons of the reticular formation do not have direct contacts with the body's receptors. When the receptors are excited, nerve impulses arrive at the reticular formation along the collaterals of the fibers of the autonomic and somatic nervous system.
Physiological role. The reticular formation of the brain stem has an ascending effect on the cells of the cerebral cortex and a descending effect on the motor neurons of the spinal cord. Both of these influences of the reticular formation can be activating or inhibitory.
Afferent impulses to the cerebral cortex come in two ways: specific and nonspecific. specific neural pathway necessarily passes through the visual tubercles and carries nerve impulses to certain areas of the cerebral cortex, as a result, any specific activity is carried out. For example, when the photoreceptors of the eyes are stimulated, impulses through the visual tubercles enter the occipital region of the cerebral cortex and visual sensations arise in a person.
Nonspecific neural pathway necessarily passes through the neurons of the reticular formation of the brain stem. Impulses to the reticular formation come through the collaterals of a specific nerve pathway. Due to numerous synapses on the same neuron of the reticular formation, impulses of different values (light, sound, etc.) can converge (converge), while they lose their specificity. From the neurons of the reticular formation, these impulses do not arrive at any particular area of the cerebral cortex, but spread like a fan through its cells, increasing their excitability and thereby facilitating the performance of a specific function.
In experiments on cats with electrodes implanted in the region of the reticular formation of the brainstem, it was shown that stimulation of its neurons causes the awakening of a sleeping animal. With the destruction of the reticular formation, the animal falls into a long sleepy state. These data indicate the important role of the reticular formation in the regulation of sleep and wakefulness. The reticular formation not only affects the cerebral cortex, but also sends inhibitory and excitatory impulses to the spinal cord to its motor neurons. Due to this, it is involved in the regulation of skeletal muscle tone.
In the spinal cord, as already mentioned, there are also neurons of the reticular formation. It is believed that they maintain a high level of activity of neurons in the spinal cord. The functional state of the reticular formation itself is regulated by the cerebral cortex.
Cerebellum
Features of the structure of the cerebellum. Connections of the cerebellum with other parts of the central nervous system. The cerebellum is an unpaired formation; it is located behind the medulla oblongata and the pons, borders on the quadrigemina, is covered from above by the occipital lobes of the cerebral hemispheres, In the cerebellum, the middle part is distinguished - worm and located on the sides of it two hemisphere. The surface of the cerebellum consists of gray matter called the cortex, which includes the bodies of nerve cells. Inside the cerebellum is white matter, representing the processes of these neurons.
The cerebellum has extensive connections with various parts of the central nervous system due to three pairs of legs. lower legs connect the cerebellum to the spinal cord and medulla oblongata medium- with the pons and through it with the motor area of the cerebral cortex, upper with midbrain and hypothalamus.
The functions of the cerebellum were studied in animals in which the cerebellum was removed partially or completely, as well as by recording its bioelectrical activity at rest and during stimulation.
When half of the cerebellum is removed, an increase in the tone of the extensor muscles is noted, therefore, the limbs of the animal are extended, a bend of the body and a deviation of the head to the operated side are observed, sometimes rocking movements of the head. Often the movements are made in a circle in the operated direction (“manege movements”). Gradually, the marked violations are smoothed out, but some awkwardness of movements remains.
When the entire cerebellum is removed, more pronounced movement disorders occur. In the first days after the operation, the animal lies motionless with its head thrown back and elongated limbs. Gradually, the tone of the extensor muscles weakens, trembling of the muscles appears, especially the cervical ones. In the future, motor functions are partially restored. However, until the end of life, the animal remains a motor invalid: when walking, such animals spread their limbs wide, raise their paws high, i.e., they have impaired coordination of movements.
Movement disorders during the removal of the cerebellum were described by the famous Italian physiologist Luciani. The main ones are: aton and I - the disappearance or weakening of muscle tone; asthen and I - a decrease in the strength of muscle contractions. Such an animal is characterized by rapidly onset muscle fatigue; a stasis - loss of the ability to continuous tetanic contractions. In animals, trembling movements of the limbs and head are observed. The dog after removal of the cerebellum cannot immediately raise its paws, the animal makes a series of oscillatory movements with its paw before lifting it. If you put such a dog, then its body and head sway all the time from side to side.
As a result of atony, asthenia and astasia, the animal's coordination of movements is disturbed: a shaky gait, sweeping, awkward, inaccurate movements are noted. The whole complex of motor disorders in the lesion of the cerebellum is called cerebellar ataxia.
Similar disorders are observed in humans with damage to the cerebellum.
Some time after the removal of the cerebellum, as already indicated, all movement disorders are gradually smoothed out. If the motor area of the cerebral cortex is removed from such animals, then the motor disturbances increase again. Consequently, the compensation (restoration) of movement disorders in case of damage to the cerebellum is carried out with the participation of the cerebral cortex, its motor area.
The studies of L. A. Orbeli showed that when the cerebellum is removed, not only a drop in muscle tone (atony), but also its incorrect distribution (dystonia) is observed. L. L. Orbeli found that the cerebellum also affects the state of the receptor apparatus, as well as autonomic processes. The cerebellum has an adaptive-trophic effect on all parts of the brain through the sympathetic nervous system, it regulates the metabolism in the brain and thereby contributes to the adaptation of the nervous system to changing conditions of existence.
Thus, the main functions of the cerebellum are the coordination of movements, the normal distribution of muscle tone, and the regulation of autonomic functions. The cerebellum realizes its influence through the nuclear formations of the middle and medulla oblongata, through the motor neurons of the spinal cord. A large role in this influence belongs to the bilateral connection of the cerebellum with the motor area of the cerebral cortex and the reticular formation of the brain stem.
Structural features of the cerebral cortex.
The cerebral cortex is phylogenetically the highest and youngest part of the central nervous system.
The cerebral cortex consists of nerve cells, their processes and neuroglia. In an adult, the thickness of the cortex in most areas is about 3 mm. The area of the cerebral cortex due to numerous folds and furrows is 2500 cm 2. Most areas of the cerebral cortex are characterized by a six-layer arrangement of neurons. The cerebral cortex consists of 14-17 billion cells. The cellular structures of the cerebral cortex are represented pyramidal,spindle and stellate neurons.
stellate cells perform mainly an afferent function. Pyramidal and fusiformcells are predominantly efferent neurons.
In the cerebral cortex there are highly specialized nerve cells that receive afferent impulses from certain receptors (for example, from visual, auditory, tactile, etc.). There are also neurons that are excited by nerve impulses coming from different receptors in the body. These are the so-called polysensory neurons.
The processes of the nerve cells of the cerebral cortex connect its various sections to each other or establish contacts between the cerebral cortex and the underlying sections of the central nervous system. The processes of nerve cells that connect different parts of the same hemisphere are called associative, connecting most often the same parts of the two hemispheres - commissural and providing contacts of the cerebral cortex with other parts of the central nervous system and through them with all organs and tissues of the body - conductive(centrifugal). A diagram of these paths is shown in the figure.
Scheme of the course of nerve fibers in the cerebral hemispheres.
1 - short associative fibers; 2 - long associative fibers; 3 - commissural fibers; 4 - centrifugal fibers.
Neuroglia cells perform a number of important functions: they are a supporting tissue, participate in the metabolism of the brain, regulate blood flow inside the brain, secrete a neurosecretion that regulates the excitability of neurons in the cerebral cortex.
Functions of the cerebral cortex.
1) The cerebral cortex carries out the interaction of the organism with the environment due to unconditioned and conditioned reflexes;
2) it is the basis of the higher nervous activity (behavior) of the body;
3) due to the activity of the cerebral cortex, higher mental functions are carried out: thinking and consciousness;
4) the cerebral cortex regulates and integrates the work of all internal organs and regulates such intimate processes as metabolism.
Thus, with the appearance of the cerebral cortex, it begins to control all the processes occurring in the body, as well as all human activities, i.e., corticolization of functions occurs. IP Pavlov, characterizing the importance of the cerebral cortex, pointed out that it is the manager and distributor of all the activities of the animal and human organism.
Functional significance of various areas of the cortex brain . Localization of functions in the cerebral cortex brain . The role of individual areas of the cerebral cortex was first studied in 1870 by the German researchers Fritsch and Gitzig. They showed that stimulation of various parts of the anterior central gyrus and the frontal lobes proper causes contraction of certain muscle groups on the side opposite to the stimulation. Subsequently, the functional ambiguity of various areas of the cortex was revealed. It was found that the temporal lobes of the cerebral cortex are associated with auditory functions, the occipital lobes with visual functions, and so on. These studies led to the conclusion that different parts of the cerebral cortex are in charge of certain functions. The doctrine of the localization of functions in the cerebral cortex was created.
According to modern concepts, there are three types of zones of the cerebral cortex: primary projection zones, secondary and tertiary (associative).
Primary projection zones- these are the central sections of the analyzer cores. They contain highly differentiated and specialized nerve cells, which receive impulses from certain receptors (visual, auditory, olfactory, etc.). In these zones, a subtle analysis of afferent impulses of various meanings takes place. The defeat of these areas leads to disorders of sensory or motor functions.
Secondary zones- peripheral parts of the analyzer nuclei. Here, further processing of information takes place, connections are established between stimuli of different nature. When the secondary zones are affected, complex perceptual disorders occur.
Tertiary zones (associative) . The neurons of these zones can be excited under the influence of impulses coming from receptors of various values (from hearing receptors, photoreceptors, skin receptors, etc.). These are the so-called polysensory neurons, due to which connections are established between various analyzers. Associative zones receive processed information from the primary and secondary zones of the cerebral cortex. Tertiary zones play an important role in the formation of conditioned reflexes; they provide complex forms of cognition of the surrounding reality.
Significance of different areas of the cerebral cortex . Sensory and motor areas in the cerebral cortex
Sensory areas of the cortex . (projective cortex, cortical sections of analyzers). These are zones into which sensory stimuli are projected. They are located mainly in the parietal, temporal and occipital lobes. Afferent pathways in the sensory cortex come mainly from the relay sensory nuclei of the thalamus - ventral posterior, lateral and medial. The sensory areas of the cortex are formed by the projection and associative zones of the main analyzers.
Area of skin reception(the cerebral end of the skin analyzer) is represented mainly by the posterior central gyrus. The cells of this area perceive impulses from tactile, pain and temperature receptors of the skin. The projection of skin sensitivity within the posterior central gyrus is similar to that for the motor zone. The upper portions of the posterior central gyrus are associated with the receptors of the skin of the lower extremities, the middle portions with the receptors of the trunk and hands, and the lower portions with the receptors of the skin of the head and face. Irritation of this area in a person during neurosurgical operations causes sensations of touch, tingling, numbness, while pronounced pain is never observed.
Area of visual reception(the cerebral end of the visual analyzer) is located in the occipital lobes of the cerebral cortex of both hemispheres. This area should be considered as a projection of the retina.
Area of auditory reception(the cerebral end of the auditory analyzer) is localized in the temporal lobes of the cerebral cortex. This is where nerve impulses come from receptors in the cochlea of the inner ear. If this zone is damaged, musical and verbal deafness may occur, when a person hears, but does not understand the meaning of words; Bilateral damage to the auditory region leads to complete deafness.
The area of taste reception(the cerebral end of the taste analyzer) is located in the lower lobes of the central gyrus. This area receives nerve impulses from the taste buds of the oral mucosa.
Olfactory reception area(the cerebral end of the olfactory analyzer) is located in the anterior part of the piriform lobe of the cerebral cortex. This is where nerve impulses come from the olfactory receptors of the nasal mucosa.
In the cerebral cortex, several zones in charge of the function of speech(brain end of the motor speech analyzer). In the frontal region of the left hemisphere (in right-handed people) is the motor center of speech (Broca's center). With his defeat, speech is difficult or even impossible. In the temporal region is the sensory center of speech (Wernicke's center). Damage to this area leads to speech perception disorders: the patient does not understand the meaning of words, although the ability to pronounce words is preserved. In the occipital lobe of the cerebral cortex there are zones that provide the perception of written (visual) speech. With the defeat of these areas, the patient does not understand what is written.
V parietal cortex brain ends of the analyzers were not found in the cerebral hemispheres, it is referred to the associative zones. Among the nerve cells of the parietal region, a large number of polysensory neurons were found, which contribute to the establishment of connections between various analyzers and play an important role in the formation of reflex arcs of conditioned reflexes.
motor areas of the cortex The idea of the role of the motor cortex is twofold. On the one hand, it was shown that electrical stimulation of certain cortical zones in animals causes the movement of the limbs of the opposite side of the body, which indicated that the cortex is directly involved in the implementation of motor functions. At the same time, it is recognized that the motor area is an analyzer, i.e. represents the cortical section of the motor analyzer.
The brain section of the motor analyzer is represented by the anterior central gyrus and the parts of the frontal region located near it. When it is irritated, various contractions of the skeletal muscles occur on the opposite side. Correspondence between certain zones of the anterior central gyrus and skeletal muscles has been established. In the upper parts of this zone, the muscles of the legs are projected, in the middle - the torso, in the lower - the head.
Of particular interest is the frontal region itself, which reaches its greatest development in humans. When the frontal areas are affected in a person, complex motor functions are disturbed that ensure labor activity and speech, as well as adaptive, behavioral reactions of the body.
Any functional area of the cerebral cortex is in both anatomical and functional contact with other areas of the cerebral cortex, with subcortical nuclei, with formations of the diencephalon and reticular formation, which ensures the perfection of their functions.
1. Structural and functional features of the CNS in the antenatal period.
In the fetus, the number of CNS neurons reaches a maximum by the 20-24th week and remains in the postnatal period without a sharp decrease until old age. Neurons are small in size and the total area of the synaptic membrane.
Axons develop before dendrites, processes of neurons intensively grow and branch. There is an increase in the length, diameter and myelination of axons towards the end of the antenatal period.
Phylogenetically old pathways are myelinated earlier than phylogenetically new ones; for example, vestibulospinal tracts from the 4th month of intrauterine development, rubrospinal tracts from the 5th-8th month, pyramidal tracts after birth.
Na- and K-channels are evenly distributed in the membrane of myelin and non-myelin fibers.
Excitability, conductivity, lability of nerve fibers is much lower than in adults.
The synthesis of most mediators begins during fetal development. Gamma-aminobutyric acid in the antenatal period is an excitatory mediator and, through the Ca2 mechanism, has morphogenic effects - it accelerates the growth of axons and dendrites, synaptogenesis, and the expression of pithoreceptors.
By the time of birth, the process of differentiation of neurons in the nuclei of the medulla oblongata and midbrain, the bridge, ends.
There is structural and functional immaturity of glial cells.
2. Features of the CNS in the neonatal period.
> The degree of myelination of nerve fibers increases, their number is 1/3 of the level of an adult organism (for example, the rubrospinal path is fully myelinated).
> The permeability of cell membranes for ions decreases. Neurons have a lower MP amplitude - about 50 mV (in adults, about 70 mV).
> There are fewer synapses on neurons than in adults, the neuron membrane has receptors for synthesized mediators (acetylcholine, GAM K, serotonin, norepinephrine to dopamine). The content of mediators in the neurons of the brain of newborns is low and amounts to 10-50% of mediators in adults.
> The development of the spiny apparatus of neurons and axospinous synapses is noted; EPSP and IPSP have a longer duration and lower amplitude than in adults. The number of inhibitory synapses on neurons is less than in adults.
> Increased excitability of cortical neurons.
> Disappears (more precisely, sharply decreases) mitotic activity and the possibility of regeneration of neurons. Proliferation and functional maturation of gliocytes continues.
Z. Features of the central nervous system in infancy.
CNS maturation progresses rapidly. The most intense myelination of CNS neurons occurs at the end of the first year after birth (for example, myelination of the nerve fibers of the cerebellar hemispheres is completed by 6 months).
The rate of conduction of excitation along axons increases.
There is a decrease in the duration of AP of neurons, the absolute and relative refractory phases are shortened (the duration of absolute refractoriness is 5-8 ms, relative 40-60 ms in early postnatal ontogenesis, in adults, respectively, 0.5-2.0 and 2-10 ms).
The blood supply to the brain in children is relatively greater than in adults.
4. Features of the development of the central nervous system in other age periods.
1) Structural and functional changes in nerve fibers:
An increase in the diameters of axial cylinders (by 4-9 years). Myelination in all peripheral nerve fibers is close to completion by 9 years, and pyramidal tracts are completed by 4 years;
The ion channels are concentrated in the region of nodes of Ranvier, the distance between the nodes increases. Continuous conduction of excitation is replaced by saltatory, the speed of its conduction after 5-9 years is almost the same as the speed in adults (50-70 m/s);
There is a low lability of nerve fibers in children of the first years of life; with age, it increases (in children 5-9 years old it approaches the norm for adults - 300-1,000 impulses).
2) Structural and functional changes in synapses:
Significant maturation of nerve endings (neuromuscular synapses) occurs by 7-8 years;
The terminal ramifications of the axon and the total area of its endings increase.
Profile material for students of the pediatric faculty
1. Development of the brain in the postnatal period.
In the postnatal period, the leading role in the development of the brain is played by the flows of afferent impulses through various sensory systems (the role of an information-enriched external environment). The absence of these external signals, especially during critical periods, can lead to slow maturation, underdevelopment of function, or even its absence.
The critical period in postnatal development is characterized by intense morphological and functional maturation of the brain and the peak of the formation of NEW connections between neurons.
The general regularity of the development of the human brain is the heterochrony of maturation: fvlogetically older sections develop earlier than younger ones.
The medulla oblongata of a newborn is functionally more developed than other departments: ALMOST all of its centers are active - respiration, regulation of the heart and blood vessels, sucking, swallowing, coughing, sneezing, the chewing center begins to function somewhat later In the regulation of muscle tone, the activity of the vestibular nuclei is reduced (reduced extensor tone) By the age of 6, these Centers complete the differentiation of neurons, myelination of fibers, and the coordination activity of the Centers improves.
The midbrain in newborns is functionally less mature. For example, the orienting reflex and the activity of the centers that control the movement of the eyes and THEM are carried out in infancy. The function of the Substance Black as part of the striopallidary system reaches perfection by the age of 7.
The cerebellum in a newborn is structurally and functionally underdeveloped during infancy, its increased growth and differentiation of neurons occurs, and the connections of the cerebellum with other motor centers increase. Functional maturation of the cerebellum generally begins at age 7 and is completed by age 16.
Maturation of the diencephalon includes the development of sensory nuclei of the thalamus and centers of the hypothalamus
The function of the sensory nuclei of the thalamus is already carried out in the Newborn, which allows the Child to distinguish between taste, temperature, tactile and pain sensations. The functions of the nonspecific nuclei of the thalamus and the ascending activating reticular formation of the brain stem in the first months of life are poorly developed, which leads to a short time of his wakefulness during the day. The nuclei of the thalamus finally develop functionally by the age of 14.
The centers of the hypothalamus in a newborn are poorly developed, which leads to imperfection in the processes of thermoregulation, regulation of water-electrolyte and other types of metabolism, and the need-motivational sphere. Most of the hypothalamic centers are functionally mature by 4 years. The most late (by the age of 16) the sexual hypothalamic centers begin to function.
By the time of birth, the basal nuclei have a different degree of functional activity. The phylogenetically older structure, the globus pallidus, is functionally well developed, while the function of the striatum manifests itself by the end of 1 year. In this regard, the movements of newborns and infants are generalized, poorly coordinated. As the striopalidar system develops, the child performs more and more precise and coordinated movements, creates motor programs of voluntary movements. Structural and functional maturation of the basal nuclei is completed by the age of 7.
The cerebral cortex in early ontogenesis matures later in structural and functional terms. The motor and sensory cortex develops the earliest, the maturation of which ends at the 3rd year of life (auditory and visual cortex somewhat later). The critical period in the development of the associative cortex begins at the age of 7 years and continues until the pubertal period. At the same time, cortical-subcortical interconnections are intensively formed. The cerebral cortex provides the corticalization of body functions, the regulation of voluntary movements, the creation of motor stereotypes for the implementation, and higher psychophysiological processes. The maturation and implementation of the functions of the cerebral cortex are described in detail in specialized materials for students of the pediatric faculty in topic 11, v. 3, topics 1-8.
The hematoliquor and blood-brain barriers in the postnatal period have a number of features.
In the early postnatal period, large veins are formed in the choroid plexuses of the ventricles of the brain, which can deposit a significant amount of blood 14, thereby participating in the regulation of intracranial pressure.
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