FUNCTIONS OF THE CROBAL HEMISPHERES

Functionally, the cerebral cortex is divided into three areas: sensory, motor (motor) and associative cortex. The sensory area includes those areas of the cerebral cortex in which sensory stimuli are projected. The sensory cortex is located predominantly in the parietal, temporal, and occipital lobes of the cerebrum. Afferent pathways to the sensory cortex come predominantly from specific sensory nuclei of the thalamus. Areas of the sensory cortex include primary and secondary areas bark. In the primary areas of the cortex, sensations of the same quality are formed. In secondary areas sensations are formed in the cortex that occur in response to the action of several stimuli.

The main sensory areas of the cortex are located in:

Postcentral gyrus: skin sensitivity from tactile, pain temperature receptors; sensitivity of the musculoskeletal system - muscles, joints, tendons; tactile and gustatory sensitivity of the tongue.

- middle temporal gyrus (and. Geschl), sound sensations are formed here, -

Superior and middle temporal gyrus, here the center of the vestibular analyzer is localized, sensations of the “body scheme” are formed

- the area of ​​the sphenoid gyrus is the primary visual area located in the occipital cortex.

The associative area of ​​the cortex includes areas located near the sensory and motor areas, but not directly performing sensory or motor functions. The boundaries of these areas are not clearly marked. In the associative cortex, zones can be distinguished:

Thalamolobic system;

thalamotenic system;

The thalamotemporal system.

The thalamofrontal system is involved in the formation of dominant motivation: this function is due to the two-way connection between the frontal cortex and the limbic system, provides the probability of predicting and self-control of actions by constantly comparing the result of the action with the original intentions.

The thalamotheme system performs the functions of gnosis, the formation of a "body schema" - stereognosis, and praxis. Gnosis is a function of various types of recognition: shapes, sizes, meanings of objects, understanding of speech, knowledge of processes and patterns. Stereognosis is a function that provides the ability to recognize objects by touch. In the center of the stereognosis, sensations are formed that are responsible for the creation of a three-dimensional model of the body - the “body scheme”. Praxis is a function aimed at performing some activity, its center is located in the supramarginal gyrus, provides storage and implementation of the program of motor acts (handshake, combing, etc.).

The thalamotemporal system is located in the superior gyrus of the temporal cortex, where the auditory center of Wernicke's speech is located. It provides speech gnosis - recognition and storage of oral speech. In the middle part of the superior temporal gyrus, there is a center for recognizing musical sounds. Within the boundaries of the temporal, parietal and occipital lobes there is a center for reading written speech, which provides recognition and storage of images of written speech.

The motor cortex occupies the areas of the frontal lobe of the cerebral cortex. AT primary motor cortex(precentral gyrus) are neurons that innervate the motor neurons of the muscles of the face, trunk and limbs. secondary motor cortex located on the lateral surface of the hemispheres, in front of the precentral gyrus (premotor cortex). It performs higher motor functions associated with the planning and coordination of voluntary movements. This cortex receives the bulk of efferent impulses from the basal ganglia and the cerebellum and is involved in recoding information from programs of complex movements. In the premotor cortex there are centers associated with human social functions:

In the posterior part of the middle frontal gyrus - the center of written speech,

In the posterior part of the inferior frontal gyrus, Broca's motor speech center, which provides speech praxis, as well as the musical motor center, which determines the tonality of speech.

Motor cortex neurons receive afferent inputs through the thalamus from muscle, joint, and skin receptors, as well as from the basal ganglia and cerebellum. The main efferent outputs of the motor cortex to the stem and spinal motor centers form pyramidal cells of the cortex. Pyramidal neurons of the motor cortex excite or inhibit motor neurons of the stem and spinal centers.

One of the basic principles of the functioning of the cerebral cortex is the principle of interhemispheric asymmetry. Interhemispheric asymmetry is due to the asymmetric localization of the nervous apparatus of the second signaling system and the dominance of the right hand as a means of adaptive behavior. According to modern neurophysiology (V.L. Bianchi), the left hemisphere of the large brain in humans specializes in performing verbal symbolic functions, and the right hemisphere in the implementation of spatial figurative functions. The result of such a functional division is the asymmetry of mental activity, which is manifested by differences in the types of mental operations. The dominance of the left hemisphere determines the thinking type, and the right hemisphere determines the artistic type of thinking.

PRACTICAL WORK

To determine the coefficient of functional asymmetry, forms are used, which are sheets of paper (A4), on which there are 8 equal rectangles, 4 in a row. Each rectangle is filled sequentially from left to right from No. 1 to No. 4 and in the opposite direction from No. 5 to No. 8. The form of the form is shown in Figure 1.

Figure 1 - Task form

Instructions: “At my signal, you must begin to put dots in each rectangle of the form. For the time allotted for each rectangle (5 s), you must put as many points in it as possible. You need to move from one rectangle to another on command, without interrupting work. Always work at your maximum pace. Now take a pencil in your right (or left hand) and place it in front of the first rectangle of the form.

Using the stopwatch, the experimenter gives a signal: “Start!”, Then every 5 seconds he gives the command: “Next!”. After 5 seconds of work in rectangle No. 8, the experimenter gives the command: "Stop". Count the number of dots in each square and complete Table 1 in your workbook.

Table 1 - Study Protocol

Using the results of Table 1, plot the relationship between the time to complete a task step (x-axis) and the number of points for each hand (y-axis). Make a conclusion, guided by the following pattern: for right-handers, the performance of the right hand is higher than that of left-handers, and for left-handers, the opposite is true.

Calculate the coefficient of functional asymmetry for the performance of the left and right hands, obtaining the total values ​​of the performance of the hands by adding all the data for each of the eight rectangles. To calculate, use the formula for estimating the coefficient of functional asymmetry (1):

KF A = ​​[(SR - SL) / (SR + SL)] (1)

where KF A is the coefficient of functional asymmetry, f.u.;

SR is the total amount of points set by the right hand, pcs;

SL is the total sum of points set by the right left, pcs.

The sign of the coefficient of functional asymmetry is interpreted as follows: if the value of the coefficient takes a positive value "+", this indicates a shift in the balance towards the activity of the left hemisphere; if the obtained coefficient takes a negative value, the “–” sign, this indicates the activity of the right hemisphere.

Analyze the result and draw a conclusion.

Synonyms: projection cortex or cortical section of analyzers

Tertiary cortex

There are two curves on one graph - for the right (blue) and left hand (red);

The cerebral cortex is the highest part of the central nervous system, which appears last in the process of phylogenetic development and is formed later than other parts of the brain in the course of individual (ontogenetic) development. The cortex is a layer of gray matter 2-3 mm thick, containing an average of about 14 billion (from 10 to 18 billion) nerve cells, nerve fibers and interstitial tissue (neuroglia). On its transverse section, according to the location of neurons and their connections, 6 horizontal layers are distinguished. Due to numerous convolutions and furrows, the surface area of ​​the bark reaches 0.2 m2. Directly below the cortex is white matter, consisting of nerve fibers that transmit excitation to and from the cortex, as well as from one part of the cortex to another.
Cortical neurons and their connections. Despite the huge number of neurons in the cortex, very few of their varieties are known. Their main types are pyramidal and stellate neurons.
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In the afferent function of the cortex and in the processes of excitation switching to neighboring neurons, the main role belongs to stellate neurons. They make up more than half of all cortical cells in humans. These cells have short branching axons, not extending beyond the gray matter of the cortex, and short branching dendrites. Star-shaped neurons are involved in the processes of perception of irritation and the unification of the activities of various pyramidal neurons.

Pyramidal neurons carry out the efferent function of the cortex and intracortical processes of interaction between neurons distant from each other. They are divided into large pyramids, from which projection, or efferent, paths to subcortical formations begin, and small pyramids, which form associative paths to other sections of the cortex. The largest pyramidal cells - Betz's giant pyramids - are located in the anterior central gyrus, in the so-called motor cortex. A characteristic feature of large pyramids is their vertical orientation in the thickness of the crust. From the cell body, the thickest (apical) dendrite is directed vertically upwards to the surface of the cortex, through which various afferent influences from other neurons enter the cell, and an efferent process - axon - departs vertically downwards.

Numerous contacts (for example, only on the dendrites of a large pyramid they number from 2 to 5 thousand) provides the possibility of a wide regulation of the activity of pyramidal cells from many other neurons. This makes it possible to coordinate the responses of the cortex (primarily its motor function) with a variety of influences from the external environment and the internal environment of the body.

The cerebral cortex is characterized by an abundance of interneuronal connections. As the human brain develops after birth, the number of intercentral interconnections increases, especially intensively up to 18 years.

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Primary, secondary and tertiary fields of the cortex. Features of the structure and functional significance of individual sections of the cortex make it possible to distinguish individual cortical fields.

There are three main groups of fields in the cortex: primary, secondary and tertiary fields.

Primary fields are associated with the sense organs and organs of movement on the periphery, they mature earlier than others in ontogeny, and have the largest cells. These are the so-called nuclear zones of the analyzers, according to I.P. Pavlov (for example, the field of pain, temperature, tactile and muscular-articular sensitivity in the posterior central gyrus of the cortex, the visual field in the occipital region, the auditory field in the temporal region and the motor field in the anterior central gyrus of the cortex) (Fig. 54). These fields carry out the analysis of individual stimuli entering the cortex from the corresponding receptors. When primary fields are destroyed, so-called cortical blindness, cortical deafness, etc. occur. Secondary fields, or peripheral zones of analyzers, are located nearby, which are connected with individual organs only through primary fields. They serve to summarize and further process the incoming information. Separate sensations are synthesized in them into complexes that determine the processes of perception. When the secondary fields are affected, the ability to see objects, hear sounds is preserved, but the person does not recognize them, does not remember their meaning. Both humans and animals have primary and secondary fields.

Tertiary fields, or analyzer overlap zones, are the furthest from direct connections with the periphery. These fields are only available to humans. They occupy almost half of the territory of the cortex and have extensive connections with other parts of the cortex and with nonspecific brain systems. The smallest and most diverse cells predominate in these fields. The main cellular element here are stellate neurons. Tertiary fields are located in the posterior half of the cortex - on the borders of the parietal, temporal and occipital regions and in the anterior half - in the anterior parts of the frontal regions. In these zones, the largest number of nerve fibers connecting the left and right hemispheres ends, therefore their role is especially great in organizing the coordinated work of both hemispheres. Tertiary fields mature in humans later than other cortical fields; they carry out the most complex functions of the cortex. Here the processes of higher analysis and synthesis take place. In tertiary fields, on the basis of the synthesis of all afferent stimuli and taking into account the traces of previous stimuli, the goals and objectives of behavior are developed. According to them, the programming of motor activity takes place. The development of tertiary fields in humans is associated with the function of speech. Thinking (inner speech) is possible only with the joint activity of analyzers, the unification of information from which occurs in tertiary fields.

With congenital underdevelopment of tertiary fields, a person is not able to master speech (pronounces only meaningless sounds) and even the simplest motor skills (cannot dress, use tools, etc.).

Perceiving and evaluating all signals from the internal and external environment, the cerebral cortex carries out the highest regulation of all motor and emotional-vegetative reactions.

Functions of the cerebral cortex. The cerebral cortex performs the most complex functions of organizing the adaptive behavior of the organism in the external environment. This is primarily a function of higher analysis and synthesis of all afferent stimuli.

Afferent signals enter the cortex through different channels, into different nuclear zones of the analyzers (primary fields), and then are synthesized in secondary and tertiary fields, thanks to the activity of which a holistic perception of the external world is created. This synthesis underlies the complex mental processes of perception, representation, and thought. The cerebral cortex is an organ closely associated with the emergence of consciousness in a person and the regulation of his social behavior. An important aspect of the activity of the cerebral cortex is the closing function - the formation of new reflexes and their systems (conditioned reflexes, dynamic stereotypes, see Chapter XV).

Due to the unusually long duration of preservation of traces of previous irritations (memory) in the cortex, a huge amount of information is accumulated in it. This goes a long way in preserving the individual experience, which is used as needed.
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It has been experimentally shown that in the higher representatives of the animal world, after complete surgical removal of the cortex, the higher nervous activity deteriorates sharply. They lose the ability to subtly adapt to the external environment and exist independently in it.

The cerebral cortex is the youngest formation of the central nervous system. The activity of the cerebral cortex is based on the principle of a conditioned reflex, therefore it is called a conditioned reflex. It provides a quick connection with the external environment and adaptation of the body to changing environmental conditions.

Deep grooves divide each cerebral hemisphere into frontal, temporal, parietal, occipital lobes and insula. The islet is located deep in the Sylvian furrow and is closed from above by parts of the frontal and parietal lobes of the brain.

The cerebral cortex is divided into the ancient ( archiocortex), old (paleocortex) and new (neocortex). The ancient cortex, along with other functions, is related to the sense of smell and ensuring the interaction of brain systems. The old cortex includes the cingulate gyrus, the hippocampus. In the new cortex, the greatest development of size, differentiation of functions is noted in humans. The thickness of the new bark is 3-4 mm. The total area of ​​the cortex of an adult is 1700-2000 cm 2, and the number of neurons - 14 billion (if they are arranged in a row, a chain 1000 km long is formed) - is gradually depleted and by old age is 10 billion (more than 700 km). The cortex contains pyramidal, stellate, and fusiform neurons.

Pyramidal neurons have different sizes, their dendrites carry a large number of spines: the axon of the pyramidal neuron goes through the white matter to other areas of the cortex or structures of the central nervous system.

stellate neurons have short, well-branched dendrites and a short axon that provides neuronal connections within the cerebral cortex itself.

spindle neurons provide vertical or horizontal interconnections of neurons of different layers of the cortex.

The structure of the cerebral cortex

The cortex contains a large number of glial cells that perform supporting, metabolic, secretory, and trophic functions.

The outer surface of the cortex is divided into four lobes: frontal, parietal, occipital, and temporal. Each lobe has its own projection and associative areas.

The cerebral cortex has a six-layer structure (Fig. 1-1):

• molecular layer(1) light, composed of nerve fibers and has a small number of nerve cells;
• outer granular layer(2) consists of stellate cells, which determine the duration of the circulation of excitation in the cerebral cortex, i.e. related to memory
• pyramid mark layer(3) is formed from small pyramidal cells and, together with layer 2, provides cortical-cortical connections of various convolutions of the brain;
• inner granular layer(4) consists of stellate cells, specific thalamocortical pathways end here, i.e. pathways starting from receptor-analyzers.
• inner pyramidal layer(5) consists of giant pyramidal cells, which are the output neurons, their axons go to the brainstem and spinal cord;
• layer of polymorphic cells(6) consists of heterogeneous triangular and spindle-shaped cells that form corticothalamic pathways.

I - afferent pathways from the thalamus: STA - specific thalamic afferents; NTA - nonspecific thalamic afferents; EMF - efferent motor fibers. The numbers indicate the layers of the cortex; II - pyramidal neuron and the distribution of endings on it: A - non-specific afferent fibers from the reticular formation and; B — recurrent collaterals from axons of pyramidal neurons; B — commissural fibers from mirror cells of the opposite hemisphere; D - specific afferent fibers from the sensory nuclei of the thalamus

Rice. 1-1. Connections of the cerebral cortex.

The cellular composition of the cortex in terms of the diversity of morphology, functions, and forms of communication is unparalleled in other parts of the CNS. The neuronal composition, the distribution over the layers in different areas of the cortex are different. This made it possible to isolate 53 cytoarchitectonic fields in the human brain. The division of the cerebral cortex into cytoarchitectonic fields is more clearly formed as its function improves in phylogenesis.

The functional unit of the cortex is a vertical column about 500 µm in diameter. Speaker - zone of distribution of branches of one ascending (afferent) thalamocortical fiber. Each column contains up to 1000 neural ensembles. The excitation of one column inhibits neighboring columns.

The ascending path passes through all cortical layers (specific path). The non-specific pathway also passes through all cortical layers. The white matter of the hemispheres is located between the cortex and the basal ganglia. It consists of a large number of fibers running in different directions. These are the pathways of the telencephalon. There are three types of paths.

• projection- connects the cortex with the diencephalon and other parts of the central nervous system. These are ascending and descending paths;
• commissural - its fibers are part of the cerebral commissures that connect the corresponding parts of the left and right hemispheres. They are part of the corpus callosum;
• associative - connects areas of the cortex of the same hemisphere.

Areas of the cerebral cortex

According to the characteristics of the cellular composition, the surface of the cortex is divided into structural units following order: zones, regions, sub-regions, fields.

The zones of the cerebral cortex are divided into primary, secondary and tertiary projection zones. They contain specialized nerve cells, which receive impulses from certain receptors (auditory, visual, etc.). Secondary zones are peripheral sections of the analyzer cores. The tertiary zones receive processed information from the primary and secondary zones of the cerebral cortex and play an important role in the regulation of conditioned reflexes.

In the gray matter of the cerebral cortex, sensory, motor and associative zones are distinguished:

• sensory areas of the cerebral cortex - areas of the cortex in which the central sections of the analyzers are located:
  visual zone - occipital lobe of the cerebral cortex;
  auditory zone - temporal lobe of the cerebral cortex;
  zone of taste sensations - the parietal lobe of the cerebral cortex;
  zone of olfactory sensations - the hippocampus and the temporal lobe of the cerebral cortex.

Somatosensory zone located in the posterior central gyrus, nerve impulses from the proprioreceptors of muscles, tendons, joints and impulses from temperature, tactile and other skin receptors come here;

• motor areas of the cerebral cortex areas of the cortex, upon stimulation of which motor reactions appear. They are located in the anterior central gyrus. When it is damaged, significant movement disorders are observed. The paths along which the impulses go from the cerebral hemispheres to the muscles form a cross, therefore, when the motor zone of the right side of the cortex is stimulated, the muscles of the left side of the body contract;
• associative zones - areas of the cortex adjacent to the sensory areas. Nerve impulses entering the sensory zones lead to the excitation of the associative zones. Their peculiarity is that excitation can occur when impulses are received from various receptors. The destruction of associative zones leads to serious learning and memory impairments.

Speech function is associated with sensory and motor areas. Motor center of speech (Broca's center) located in the lower part of the left frontal lobe, when it is destroyed, speech articulation is disturbed; while the patient understands speech, but he can not speak.

Auditory Speech Center (Wernicke Center) located in the left temporal lobe of the cerebral cortex, when it is destroyed, verbal deafness occurs: the patient can speak, express his thoughts orally, but does not understand someone else's speech; hearing is preserved, but the patient does not recognize the words, written speech is disturbed.

Speech functions associated with written speech - reading, writing - are regulated visual center of speech located on the border of the parietal, temporal and occipital lobes of the cerebral cortex. His defeat leads to the impossibility of reading and writing.

The temporal lobe contains the center responsible for memorization layer. A patient with a lesion in this area does not remember the names of objects, he needs to prompt the right words. Forgetting the name of the object, the patient remembers its purpose, properties, therefore, describes their qualities for a long time, tells what is done with this object, but cannot name it. For example, instead of the word "tie", the patient says: "this is what is put on the neck and tied with a special knot so that it is beautiful when they go to visit."

Functions of the frontal lobe:

• management of innate behavioral responses with the help of accumulated experience;
• coordination of external and internal motivations of behavior;
• development of a strategy of behavior and a program of action;
• mental characteristics of the individual.

Composition of the cerebral cortex

The cerebral cortex is the highest structure of the central nervous system and consists of nerve cells, their processes and neuroglia. The cortex contains stellate, fusiform and pyramidal neurons. Due to the presence of folds, the bark has a large surface area. The ancient cortex (archicortex) and the new cortex (neocortex) are distinguished. The bark consists of six layers (Fig. 2).

Rice. 2. The cerebral cortex

The upper molecular layer is formed mainly by the dendrites of the pyramidal cells of the underlying layers and the axons of the nonspecific nuclei of the thalamus. On these dendrites, synapses are formed by afferent fibers coming from the associative and nonspecific nuclei of the thalamus.

The outer granular layer is formed by small stellate cells and partly by small pyramidal cells. The fibers of the cells of this layer are located mainly along the surface of the cortex, forming cortico-cortical connections.

A layer of pyramidal cells of small size.

Inner granular layer formed by stellate cells. It ends with afferent thalamocortical fibers, starting from the receptors of the analyzers.

The inner pyramidal layer consists of large pyramidal cells involved in the regulation of complex forms of movement.

The multiform layer consists of verstenoid cells that form the corticothalamic pathways.

According to their functional significance, the neurons of the cortex are divided into sensory, perceiving afferent impulses from the nuclei of the thalamus and receptors of sensory systems; motor, sending impulses to the subcortical nuclei, intermediate, middle, medulla oblongata, cerebellum, reticular formation and spinal cord; and intermediate, which carry out the connection between the neurons of the cerebral cortex. The neurons of the cerebral cortex are in a state of constant excitation, which does not disappear even during sleep.

In the cerebral cortex, sensory neurons receive impulses from all receptors of the body through the nuclei of the thalamus. And each organ has its own projection or cortical representation, located in certain areas of the cerebral hemispheres.

There are four sensory and four motor areas in the cerebral cortex.

Motor cortex neurons receive afferent impulses through the thalamus from muscle, joint, and skin receptors. The main efferent connections of the motor cortex are carried out through the pyramidal and extrapyramidal pathways.

Animals have the most developed frontal area of ​​the cortex and its neurons are involved in providing goal-directed behavior. If this portion of the bark is removed, the animal becomes lethargic, drowsy. In the temporal region, the site of auditory reception is localized, and nerve impulses from the receptors of the cochlea of ​​the inner ear arrive here. The area of ​​visual reception is located in the occipital lobes of the cerebral cortex.

The parietal region, the extranuclear zone, plays an important role in the organization of complex forms of higher nervous activity. Here are scattered elements of the visual and skin analyzers, inter-analyzer synthesis is carried out.

Associative zones are located next to the projection zones, which carry out the connection between the sensory and motor zones. The associative cortex takes part in the convergence of various sensory excitations, which allows complex processing of information about the external and internal environment.

The brain is the main organ of a person that controls all his life functions, determines his personality, behavior and consciousness. Its structure is extremely complex and is a combination of billions of neurons grouped into departments, each of which performs its own function. Many years of research have made it possible to learn a lot about this organ.

What parts does the brain consist of?

The human brain is made up of several sections. Each of them performs its function, ensuring the vital activity of the body.

According to the structure, the brain is divided into 5 main sections.

Among them:

• Oblong. This part is a continuation of the spinal cord. It consists of nuclei of gray matter and paths from white. It is this part that determines the connection between the brain and the body.
• Average. It consists of 4 tubercles, two of which are responsible for vision and two for hearing.
• Rear. The hindbrain includes the pons and cerebellum. This is a small department in the back of the head, which weighs within 140 grams. Consists of two hemispheres fastened together.
• Intermediate. Consists of thalamus, hypothalamus.
• Finite. This section forms both hemispheres of the brain, connected by the corpus callosum. The surface is full of convolutions and furrows covered by the cerebral cortex. The hemispheres are divided into lobes: frontal, parietal, temporal and occipital.

The last section occupies more than 80% of the total mass of the organ. Also, the brain can be divided into 3 parts: the cerebellum, the trunk and the cerebral hemispheres.

In this case, the entire brain has a coating in the form of a shell, divided into three components:

• Cobweb (cerebrospinal fluid circulates through it)
• Soft (adjacent to the brain and full of blood vessels)
• Hard (contacts the skull and protects the brain from damage)

All components of the brain are important in the regulation of life and have a specific function. But the activity regulation centers are located in the cerebral cortex.

The human brain consists of many departments, each of which has a complex structure and performs a specific role. The largest of them is the final one, which consists of the cerebral hemispheres. All this is covered with three shells that provide protective and nourishing functions.

Learn about the structure and functions of the brain from the proposed video.

What functions does it perform?

The brain and its cortex perform a number of important functions.

Brain

It is difficult to list all the functions of the brain, because it is an extremely complex organ. This includes all aspects of the life of the human body. However, it is possible to single out the main functions performed by the brain.

The functions of the brain include all the feelings of a person. These are sight, hearing, taste, smell and touch. All of them are performed in the cerebral cortex. It is also responsible for many other aspects of life, including motor function.

In addition, diseases can occur against the background of external infections. The same meningitis that occurs due to infections of pneumococcus, meningococcus and the like. The development of the disease is characterized by pain in the head, fever, pain in the eyes and many other symptoms such as weakness, nausea and drowsiness.

Many diseases that develop in the brain and its cortex have not yet been studied. Therefore, their treatment is hampered by a lack of information. So it is recommended to consult a doctor at the first non-standard symptoms, which will prevent the disease by diagnosing it at an early stage.

Brain

Reflex function of the spinal cord

n Motoneurons of the spinal cord innervate all skeletal muscles (with the exception of the muscles of the face)

n The spinal cord carries out elementary motor reflexes - flexion and extension, rhythmic (stepping, scratching) reflexes that occur when the skin or proprioreceptors of muscles and tendons are irritated, and also sends constant impulses to the muscles, maintaining tone

n Special motor neurons innervate the respiratory muscles (intercostal muscles and diaphragm) and provide respiratory movements

n Autonomic neurons innervate all internal organs (heart, blood vessels, sweat glands, endocrine glands, digestive tract, genitourinary system).

The conduction function of the spinal cord is associated with:

n Transfer to the overlying parts of the nervous system received from the periphery of the flow of information;

n Conducting impulses from the brain to the spinal cord.

Brain located in the cranial cavity. It develops from the head of the neural tube and initially consists of three brain vesicles called in front of him, medium and rear.

The cerebral hemispheres, basal ganglia, hypothalamus and thalamus develop from the anterior cerebral bladder.

From the midbrain - the midbrain.

From the posterior cerebral bladder - the bridge, the medulla oblongata and the cerebellum.

The midbrain, pons, medulla oblongata are part of the brain stem.

big brain fills the anterior upper part of the cavity skulls, and also the anterior and middle cranial fossae. He is represented two hemispheres consisting of nerve cells (gray matter) and fibers (white matter). They are separated from each other by a deep longitudinal slit. At the bottom of this gap is corpus callosum - a wide arcuate curved plate of white matter, connecting the hemispheres to each other and consisting of transversely oriented nerve fibers (Fig. 11).

Areas of the big brain. With the help of deep lateral and central furrows each hemisphere is divided into: frontal, temporal, parietal and occipital lobes (Fig. 12).

The thin layer of gray matter covering each hemisphere is called bark.

The cortex is a thin layer (1.3-4.5 mm) of gray matter on the surface of the hemispheres. The surface of the cortex in the process of evolution increased due to the appearance of furrows and convolutions. The area of ​​the cortex in an adult is 2200-2600 cm 2. On the lower and inner surface of the cortex are the old and ancient cortex (archi - and paleocortex). They are functionally related to hypothalamus, amygdala, some midbrain nuclei and all together form limbic system, which plays an important role in the formation of emotions and attention, memory and learning. The limbic system is involved in the regulation of eating and drinking behavior, the wakefulness-sleep cycle, aggressive-defensive reactions, and it contains centers of pleasure and displeasure, unrequited joy, melancholy, fear.

On the outer surface of the cortex is a new bark - the neocortex. The entire cortex has 6-7 layers, differing in shape, size and location of neurons (Fig. 13). Permanent and temporary connections arise between the nerve cells of all layers of the cortex in the course of their activity.

Fig.11. Midsagittal section of a human head

Rice. 12. Areas of the large brain

The main types of cortical cells are pyramidal and stellate neurons.

stellate - perceive irritations and combine the activity of various pyramidal neurons.

pyramidal – carry out the efferent function of the cortex and the interaction between different areas of the cortex.

Rice. 13. List of layers of the cortex (starting from the surface): molecular layer (I), outer granular layer (II), pyramidal layer (III), or layer of middle pyramids, inner granular layer (IV), ganglionic layer (V), or layer large pyramids, layer of polymorphic cells (VI).

Under the cortex is the white matter of the cerebral hemispheres, which consists of associative, commissural and projection fibers. Associative fibers connect separate sections of the same hemisphere, and short associative fibers - separate gyrus and close fields. Commissural fibers - connect the symmetrical parts of both hemispheres, most of them pass through the corpus callosum. Projection fibers go beyond the hemispheres, are part of the descending and ascending paths. Through which two-way communication of the cortex with the underlying parts of the central nervous system is carried out.

There are known cases of the birth of children without the cerebral cortex (anencephaly). They live for several days (maximum 3-4 years). One such child slept almost all the time, he had some innate reactions (sucking, swallowing). Therefore, they concluded that in the process of phylogenesis, corticolization of functions occurs (everything that is acquired by the body during an individual life is associated with the cerebral cortex - all higher nervous activity).

There are 3 types of areas in the cortex - sensory, motor and associative (Fig. 14).

· Touch ( located behind the central sulcus). Each receptor apparatus in the cortex corresponds to a certain area, which Pavlov called the cortical nucleus of the analyzer. It is to the cortical nucleus of the analyzer that signals from the receptors of the sense organs come through the afferent fibers. In sensory areas, they secrete primary and secondary projection fields. The neurons of the projection primary fields highlight individual features of the signal (for example, contour, color, contrast). Secondary - form them into a holistic image. Sensory zones are localized in certain parts of the cortex: visual - in the occipital region, auditory - in the temporal region, gustatory - in the lower part of the parietal regions, the somatosensory zone (analyzing impulses from the receptors of muscles, joints, tendons and skin) is located in the region of the posterior central gyrus.

· Motor - zones, the irritation of which causes a motor reaction, are located in front of the central sulcus. In the motor cortex, the human body is projected as if upside down, that is, closer to the lateral groove there are areas that ensure the functioning of the muscles of the head, and at the opposite end of the precentral gyrus - the muscles of the lower limb (Fig. 15).

· Associative - do not have direct afferent and efferent connections with the periphery. They are associated with motor and sensory areas. There are centers associated with speech activity. Functions of association zones -

BUT) processing and storage of incoming information

B) transition from visual perception to abstract symbolic processes.

AT) Thinking (inner speech) is possible only with the joint activity of various sensory systems, the combination of information from which occurs in associative fields.

G) Purposeful human behavior, the formation of intentions and plans, programs of arbitrary movements

D) Responsible for the coordinated work of both hemispheres of the brain. As a rule, one of the hemispheres is leading - dominant. For the majority, if the leading hand is the right, the dominant hemisphere is the left. The left is better supplied with blood, it has more interconnections of neurons, it contains the motor center of speech, which is responsible for pronouncing words and the sensory center of speech, which is responsible for understanding words. A person has three forms of interhemispheric functional asymmetry, i.e. unequal contribution of the hemispheres: motor, sensory and mental. Motor and sensory - this is when a person with a leading right hand, the main thing is the left eye or left ear. Moreover, in each hemisphere there are centers that control both ears, both eyes, etc. This makes it possible to combine the functions of the two hemispheres in one, in case of damage. Mental asymmetry manifests itself in the form of specialization of the hemispheres. The left is more responsible for analytical processes, abstract thinking, logical thinking, anticipation of events. The right one processes the information as a whole, without dividing it into details, objective thinking, artistic thinking prevails, and functions are connected with the past, i.e. processing information based on past experience.

Higher centers of conscious behavior, morality, will and intellect are also distinguished in the cerebral cortex of the cerebral hemispheres.