What part of the bark is large. Zones and lobes of the cerebral cortex

The human is a surface layer that covers the cerebral hemisphere and is mainly formed by vertically oriented nerve cells (the so-called neurons), as well as their processes and efferent (centrifugal), afferent bundles (centripetal) and nerve fibers.

In addition, the basis of the composition of the cortex, in addition, includes cells, as well as neuroglia.

A very significant feature of the structure is the horizontal dense layering, which is primarily due to the whole ordered arrangement of each body of nerve cells and fibers. There are 6 main layers, which mainly differ in their own width, the overall density of its location, the size and shape of all the constituent external neurons.

Predominantly, precisely because of the vertical orientation of their processes, these bundles of all the various nerve fibers, as well as the bodies of neurons, which have a vertical striation. And for the full-fledged functional organization of the human cerebral cortex, the column-like, vertical location of absolutely all internal nerve cells on the surface of the cerebral cortex zone is of great importance here.

The main type of all the main nerve cells that are part of the cerebral cortex are special pyramidal cells. The body of these cells resembles an ordinary cone, from the height of which one long and thick, apical dendrite begins to depart. An axon and shorter basal dendrites also depart from the base of the body of this pyramidal cell, heading into a full-fledged white matter, which is located directly under the cerebral cortex, or branching in the cortex.

All the dendrites of the cells of the pyramid carry a fairly large number of spines, outgrowths, which take the most active part in the full formation of synaptic contacts at the end of afferent fibers that come to the cerebral cortex from other subcortical formations and sections of the cortex. The axons of these cells are able to form efferent main pathways that go directly from the C.G.M. The sizes of all pyramidal cells can vary from 5 to 150 microns (150 are giant cells named after Betz). In addition to pyramidal neurons, K.G.M. the composition includes some spindle-shaped and stellate types of interneurons that are involved in receiving incoming afferent signals, as well as the formation of interneuronal functional connections.

Features of the cerebral cortex

Based on various phylogenesis data, the cerebral cortex is divided into ancient (paleocortex), old (archicortex), and new (neocortex). In the phylogeny of K.G.M. there is a relative ubiquitous increase in the territory of the new surface of the crust, with a slight decrease in the area of the old and ancient.

Functionally, the areas of the cerebral cortex are divided into 3 types: associative, motor and sensory. In addition, the cerebral cortex is also responsible for the corresponding areas.

What is the cerebral cortex responsible for?

In addition, it is important to note that the entire cerebral cortex, in addition to all of the above, is responsible for everything. As part of the zones of the cerebral cortex, these are neurons that are diverse in structure, including stellate, small and large pyramidal, basket, fusiform and others. In a functional relationship, all main neurons are divided into the following types:

Intercalary neurons (fusiform, small pyramidal and others). Intercalary neurons also have subdivisions and can be both inhibitory and excitatory (small and large basket neurons, neurons with cystic neurons and candelabra-shaped axons)
Afferent (these are the so-called stellate cells) - which receive impulses from all specific pathways, as well as various specific sensations. It is these cells that transmit impulses directly to the efferent and intercalary neurons. Groups of polysensory neurons, respectively, receive different impulses from the optic tubercles of the associative nuclei
Efferent neurons (they are called large pyramidal cells) - impulses from these cells go to the so-called periphery, where they provide a certain type of activity

Neurons, as well as processes on the surface of the cerebral cortex, are also arranged in six layers. Neurons that perform the same reflex functions are located strictly one above the other. Thus, individual columns are considered to be the main structural unit of the surface of the cerebral cortex. And the most pronounced connection between the third, fourth and fifth stage of the layers of K.G.M.

Pads of the cerebral cortex

The following factors can also be considered proof of the presence of columns in the cerebral cortex:
With the introduction of various microelectrodes into the K.G.M. an impulse is recorded (recorded) strictly perpendicularly under the full impact of a similar reflex reaction. And when the electrodes are inserted in a strictly horizontal direction, characteristic impulses are recorded for various reflex reactions. Basically, the diameter of one column is 500 µm. All adjacent columns are tightly connected in all functional respects, and are also often located with each other in close reciprocal relationships (some inhibit, others excite).

When stimuli act on the response, many columns are also involved and a perfect synthesis and analysis of stimuli occurs - this is the screening principle.

Since the cerebral cortex grows in the periphery, then all the superficial layers of the cerebral cortex are fully related to all signal systems. These superficial layers consist of a very large number of nerve cells (about 15 billion) and, together with their processes, with the help of which the possibility of such unlimited closing functions, wide associations is created - this is the essence of all the activity of the signaling second system. But with all this, the second s.s. works with other systems.

Attention!

The cerebral cortex is a layer gray matter on the surface of the cerebral hemispheres, 2-5 mm thick, forming numerous furrows, convolutions significantly increasing its area. The cortex is formed by the bodies of neurons and glial cells arranged in layers ("screen" type of organization). Beneath it lies white matter, represented by nerve fibers.

The cortex is the youngest phylogenetically and the most complex part of the brain in terms of morphological and functional organization. This is the place of higher analysis and synthesis of all information entering the brain. Here is the integration of all complex forms of behavior. The cerebral cortex is responsible for consciousness, thinking, memory, "heuristic activity" (the ability to generalize, discover). The cortex contains more than 10 billion neurons and 100 billion glial cells.

Cortical neurons in terms of the number of processes, they are only multipolar, and in terms of their place in the reflex arcs and the functions they perform, they are all intercalary, associative. According to function and structure, more than 60 types of neurons are distinguished in the cortex. There are two main groups according to their shape: pyramidal and non-pyramidal. pyramidal neurons are the main type of cortical neurons. The sizes of their perikaryas are from 10 to 140 microns; on the cut they have a pyramidal shape. From their upper angle, a long (apical) dendrite extends upward, which divides in a T-shape in the molecular layer. Lateral dendrites extend from the lateral surfaces of the body of the neuron. There are numerous synapses of other neurons on the dendrites and body of the neuron. An axon departs from the base of the cell, which either goes to other parts of the cortex, or to other parts of the brain and spinal cord. Among the neurons of the cerebral cortex, there are associative- connecting areas of the cortex within one hemisphere, commissural– their axons go to the other hemisphere, and projection- their axons go to the underlying parts of the brain.

Among non-pyramidal neurons, the most common are stellate and spindle-shaped cells. stellate Neurons are small cells with short, highly branching dendrites and axons that form intracortical connections. Some of them have an inhibitory, while others have an excitatory effect on pyramidal neurons. Fusiform neurons have a long axon that can run either vertically or horizontally. The bark is built on screen type, that is, neurons similar in structure and function are arranged in layers (Fig. 9-7). There are six such layers in the cortex:

1.Molecular layer - outermost. It contains a plexus of nerve fibers located parallel to the surface of the cortex. The bulk of these fibers are ramifications of the apical dendrites of the pyramidal neurons of the underlying layers of the cortex. Afferent fibers also come here from the visual tubercles, which regulate the excitability of cortical neurons. Neurons in the molecular layer are mostly small, spindle-shaped.

2. Outer granular layer. Consists of a large number of stellate cells. Their dendrites go into the molecular layer and form synapses with thalamo-cortical afferent nerve fibers. Lateral dendrites communicate with neighboring neurons of the same layer. Axons form associative fibers that go through the white matter to neighboring areas of the cortex and form synapses there.

3. Outer layer of pyramidal neurons(pyramid layer). It is formed by pyramidal neurons of medium size. Just like the neurons of the second layer, their dendrites go to the molecular layer, and the axons go to the white matter.

4. Inner granular layer. It contains many stellate neurons. These are associative, afferent neurons. They form numerous connections with other cortical neurons. Here is another layer of horizontal fibers.

5. Inner layer of pyramidal neurons(ganglionic layer). It is formed by large pyramidal neurons. The latter are especially large in the motor cortex (precentral gyrus), where they are up to 140 microns in size and are called Betz cells. Their apical dendrites rise into the molecular layer, their lateral dendrites form connections with neighboring Betz cells, and their axons are projection efferent fibers going to the medulla oblongata and spinal cord.

6. Layer of fusiform neurons(a layer of polymorphic cells) consists mainly of spindle-shaped neurons. Their dendrites go to the molecular layer, and their axons go to the visual tubercles.

The six-layer type of cortical structure is characteristic of the entire cortex, however, in its different parts, the severity of the layers, as well as the shape and location of neurons and nerve fibers, differ significantly. Based on these features, K. Brodman identified 50 cytoarchitectonic structures in the cortex. fields. These fields also differ in function and metabolism.

The specific organization of neurons is called cytoarchitectonics. So, in the sensory areas of the cortex, the pyramidal and ganglionic layers are weakly expressed, and the granular layers are well expressed. This type of bark is called granular. In the motor zones, on the contrary, the granular layers are poorly developed, while the pyramidal ones are well developed. This agranular type bark.

In addition, there is the concept myeloarchitectonics. This is a certain organization of nerve fibers. So, in the cerebral cortex, vertical and three horizontal bundles of myelinated nerve fibers are distinguished. Among the nerve fibers of the cerebral cortex, there are associative- connecting areas of the cortex of one hemisphere, commissural- connecting the cortex of different hemispheres and projection fibers - connecting the cortex with the nuclei of the brain stem.

Rice. 9-7. The cerebral cortex of the human brain.

A, B. Location of cells (cytoarchitectonics).

B. Location of myelin fibers (myeloarchitectonics).

The cerebral cortex is present in the structure of the body of many creatures, but in humans it has reached its perfection. Scientists say that this became possible thanks to the age-old labor activity that accompanies us all the time. Unlike animals, birds or fish, a person is constantly developing his abilities and this improves his brain activity, including the functions of the cerebral cortex.

But, let's approach this gradually, first considering the structure of the crust, which is undoubtedly very exciting.

The internal structure of the cerebral cortex

The cerebral cortex has over 15 billion nerve cells and fibers. Each of them has a different shape, and form several unique layers responsible for certain functions. For example, the functionality of the cells of the second and third layers lies in the transformation of excitation and the correct redirection to certain parts of the brain. And, for example, centrifugal impulses represent the performance of the fifth layer. Let's take a closer look at each layer.

The numbering of the layers of the brain starts from the surface and goes deeper:

The molecular layer has a fundamental difference in its low level of cells. Their very limited number, consisting of nerve fibers are closely interconnected with each other.
The granular layer is otherwise called the outer layer. This is due to the presence of an inner layer.
The pyramidal level is named after its structure, because it has a pyramidal structure of neurons of various sizes.
The granular layer No. 2 is called the inner layer.
Pyramidal level No. 2 is similar to the third level. Its composition is the neurons of the pyramidal image having a medium and large size. They penetrate to the molecular level because it contains apical dendrites.
The sixth layer is fusiform cells, which have the second name "fusiform", which systematically pass into the white matter of the brain.

If we consider these levels in more depth, it turns out that the cerebral cortex takes on the projections of each level of excitation that occur in different parts of the central nervous system and are called "underlying". They, in turn, are transported to the brain through the nervous pathways of the human body.

Presentation: "Localization of higher mental functions in the cerebral cortex"

Thus, the cerebral cortex is an organ of higher nervous activity of a person, and regulates absolutely all nervous processes occurring in the body.

And this happens due to the peculiarities of its structure, and it is divided into three zones: associative, motor and sensory.

Modern understanding of the structure of the cerebral cortex

It is worth noting that there is a somewhat different idea of its structure. According to him, there are three zones that distinguish from each other not only the structure, but also its functional purpose.

The primary zone (motor), in which its specialized and highly differentiated nerve cells are located, receives impulses from auditory, visual and other receptors. This is a very important area, the defeat of which can lead to serious disorders of motor and sensory function.
The secondary (sensory) zone is responsible for the information processing functions. In addition, its structure consists of the peripheral sections of the analyzer nuclei, which establish the correct connections between stimuli. Her defeat threatens a person with a serious disorder of perception.
The associative, or tertiary zone, its structure allows it to be excited by impulses coming from the receptors of the skin, hearing, etc. It forms conditioned human reflexes, helping to cognize the surrounding reality.

Presentation: "Cerebral cortex"

Main functions

What is the difference between human and animal cerebral cortex? The fact that its purpose is to generalize all departments and control work. These functions provide billions of neurons with a diverse structure. These include such types as intercalary, afferent and efferent. Therefore, it will be relevant to consider each of these types in more detail.

The intercalated view of neurons has, at first glance, mutually exclusive functions, namely, inhibition and excitation.

The afferent type of neurons is responsible for impulses, or rather for their transmission. Efferent, in turn, provide a specific area of human activity and refer to the periphery.

Of course, this is medical terminology and it is worth digressing from it, concretizing the functionality of the human cerebral cortex in a simple folk language. So, the cerebral cortex is responsible for the following functions:

The ability to correctly establish a connection between internal organs and tissues. And what's more, it makes it perfect. This possibility is based on conditioned and unconditioned reflexes of the human body.
Organization of the relationship between the human body and the environment. In addition, it controls the functionality of organs, corrects their work and is responsible for the metabolism in the human body.
100% responsible for ensuring that the thinking processes are correct.
And the final, but no less important function is the highest level of nervous activity.

Having become acquainted with these functions, we come to understand that, which allowed each person and the whole family as a whole, to learn to control the processes that occur in the body.

Presentation: "Structural and functional characteristics of the sensory cortex"

Academician Pavlov, in his multiple studies, has repeatedly pointed out that it is the cortex that is both the manager and the distributor of human and animal activity.

But, it is also worth noting that the cerebral cortex has ambiguous functions. This is mainly manifested in the work of the central gyrus and the frontal lobes, which are responsible for muscle contraction on the side completely opposite to this irritation.

In addition, its different parts are responsible for different functions. For example, the occipital lobes are for visual, and the temporal lobes are for auditory functions:

To be more specific, the occipital lobe of the cortex is actually a projection of the retina, which is responsible for its visual functions. If any violations occur in it, a person may lose orientation in an unfamiliar environment and even complete, irreversible blindness.
The temporal lobe is an area of auditory reception that receives impulses from the cochlea of the inner ear, that is, is responsible for its auditory functions. Damage to this part of the cortex threatens a person with complete or partial deafness, which is accompanied by a complete misunderstanding of words.
The lower lobe of the central gyrus is responsible for brain analyzers or, in other words, taste reception. She receives impulses from the oral mucosa and her defeat threatens to lose all taste sensations.
And finally, the anterior part of the cerebral cortex, in which the piriform lobe is located, is responsible for olfactory reception, that is, the function of the nose. Impulses come into it from the nasal mucosa, if it is affected, then the person will lose his sense of smell.

It is not worth reminding once again that a person is at the highest stage of development.

This confirms the structure of a particularly developed frontal region, which is responsible for labor activity and speech. It is also important in the process of formation of human behavioral reactions and its adaptive functions.

There are many studies, including the work of the famous academician Pavlov, who worked with dogs, studying the structure and functioning of the cerebral cortex. All of them prove the advantages of man over animals, precisely due to its special structure.

True, one should not forget that all parts are in close contact with each other and depend on the work of each of its components, so that the perfection of a person is the key to the work of the brain as a whole.

From this article, the reader has already understood that the human brain is complex and still poorly understood. However, it is the perfect device. By the way, few people know that the power of processing processes in the brain is so high that next to it the most powerful computer in the world is powerless.

Here are some more interesting facts that scientists have published after a series of tests and studies:

2017 was marked by an experiment in which a hyper-powerful PC tried to simulate only 1 second of brain activity. The test took about 40 minutes. The result of the experiment - the computer did not cope with the task.
The memory capacity of the human brain can accommodate the n-number bt, which is expressed by 8432 zeros. Approximately it is 1000 Tb. If on an example, then the historical information for the last 9 centuries is stored in the national British archive and its volume is only 70 Tb. Feel how significant the difference between these numbers is.
The human brain contains 100 thousand kilometers of blood vessels, 100 billion neurons (a figure equal to the number of stars in our entire galaxy). In addition, there are one hundred trillion neural connections in the brain that are responsible for the formation of memories. Thus, when you learn something new, the structure of the brain changes.
During awakening, the brain accumulates an electric field with a power of 23 W - this is enough to light Ilyich's lamp.
By weight, the brain consists of 2% of the total mass, but it uses approximately 16% of the energy in the body and more than 17% of the oxygen in the blood.
Another interesting fact is that the brain consists of 75% water, and the structure is somewhat similar to Tofu cheese. And 60% of the brain is fat. In view of this, healthy and proper nutrition is necessary for the correct functioning of the brain. Eat fish, olive oil, seeds or nuts every day and your brain will work long and clear.
Some scientists, after conducting a series of studies, noticed that when dieting, the brain begins to “eat” itself. And low oxygen levels for five minutes can lead to irreversible consequences.
Surprisingly, a human being is not able to tickle himself, because. the brain tunes in to external stimuli and in order not to miss these signals, the actions of the person himself are slightly ignored.
Forgetfulness is a natural process. That is, the elimination of unnecessary data allows the CNS to be flexible. And the effect of alcoholic beverages on memory is explained by the fact that alcohol slows down the processes.
The brain's response to alcoholic beverages is six minutes.

The activation of the intellect allows the production of additional brain tissue that compensates for those that are sick. In view of this, it is recommended to engage in development, which in the future will save you from a weak mind and various mental disorders.

Engage in new activities - this is best for brain development. For example, communication with people who are superior to you in one or another intellectual field is a powerful tool for developing your intellect.

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 act as receptive 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 sections 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, inferoparietal, superior parietal, temporoparietal-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 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.Improvement of the cortex The 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.

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.