Brain structure, meaning and functions. Divisions of the brain. Their functions Functional significance of various parts of the brain

Today we will talk about the human brain, what parts it consists of, and how they work. To begin with, remember that the central nervous system consists of the spinal cord and the brain. Moreover, it can be divided into lower departments- This is the spinal cord itself. Its main task is to conduct signals. He does very little management, and where he does, these are very simple management functions, such as the simplest reflexes.

In contact with

Middle departments The central nervous system is part of the brain. They are mainly involved in regulating the activities of organs and systems and communicating between them. Higher department The central nervous system is the cerebral cortex and most of our brain. But this is typical only for a very small number of living creatures: humans, other great apes, many dolphins, whales, killer whales, dogs and wolves. In most other mammals, the cortex is thin and does not take up as much space as in humans.

The cortex is a department that creates a kind of holistic picture of the world, where consciousness arises, and it controls the body as a whole. The central nervous system is connected to the rest of the body peripheral nervous system, which is simply nerves that transmit various data. The peripheral nervous system connects the central nervous system to the organs and limbs.

Higher department - cerebral cortex - regulates the connection and relationship of the organism as a whole with the environment.

Brain structure

The cortex takes up most of the volume of our brain. But besides this, there are much more ancient, but no less important parts of the brain. All vertebrates have 5 parts of the brain:

Oblong.
Average.
Cerebellum.
Intermediate.
Front.

Medulla oblongata and midbrain: structure and functions

The medulla oblongata and midbrain are collectively called barrel. They contain several vital centers:

protective reflexes (coughing, sneezing);
regulation of breathing;
regulation of vascular tone;
regulation of the respiratory system;
orientation reflexes.

So, the medulla oblongata is a vital organ. Accordingly, if an injury to the medulla oblongata occurs, the person dies very quickly due to damage to the respiratory center.

Cerebellum

The cerebellum is a specialized department that coordinates movements. It receives a large amount of information from the balance organs, orders from the cerebral cortex and implements movement.

For example, when you haven't slept for a very long time and fall asleep while sitting, your head begins to tilt to one side - this means that the cortex stops telling the cerebellum to maintain balance.

The cerebellum also regulates muscle tone. In order to sit or simply hold your head up, you need some constantly tense muscles. The cerebellum does this too. And muscle memory: probably many people are familiar with the fact that some movement that you have not done before is difficult to do the first time. But then it becomes easier and easier, and over time it begins to happen automatically due to the fact that the cerebellum begins to do this.

Involuntary movements, that is, for example, withdrawing a hand from something hot, are made quick by the cerebellum due to the fact that it takes control of them.

Thanks to the cerebellum, you can do voluntary movements not quickly, but precisely, for example, take something specific from the table.

So, the cerebellum provides:

speed of involuntary movements and accuracy of voluntary ones;
coordination of movements;
regulation of balance;
regulation of muscle tone;
muscle memory.

Diencephalon

These are several departments:

Thalamus means hillock. The hypothalamus is under the hillock. It is always located under the thalamus. The diencephalon is already a fairly high level of control, and here are the centers of various emotions and instincts: the pain center, the pleasure center, the centers of thirst, hunger and satiety, the center of sleep and wakefulness, the center of thermoregulation.

The thalamus is a set of structures that do very important things. Try now to realize how much information you receive from your senses every split second. You feel the temperature at every point of your body. You feel the touch of all clothing at every point with which it comes into contact, the heat and cold emanating from objects. You hear an insane amount of sounds. You smell a lot of smells. You understand where your arms, legs and head are in space. You see many objects. You know the distance to each of them, their color, their shape.

And all this happens all the time. This is a huge amount of information. If you received information in the form of raw data, you would go crazy with the need to process it. Therefore, 90% of all this information does not reach your consciousness. And a small part of it arrives in the form of already processed data. The thalamus does just that. It’s like a funnel: it takes a huge amount of information and filters out everything that’s irrelevant.

The thalamus processes all types of information except smell. The sense of smell immediately enters the cerebral hemispheres. It doesn’t just filter the rest of the information, but processes and summarizes it. For example, you see a person’s face, but you perceive it not as a set of individual features, but as a whole. But it will be difficult for you to describe the face of another person: you will have to imagine it and only then describe it. That's why the police use identikit photos: they don't ask you to tell what shape your ears are. They ask you to choose the best of different options. It's easier - you compare images. The thalamus is the most important organ that allows us to work with information much more efficiently.

Forebrain

Specifically, the cerebral cortex is a large part of the volume of our brain, and it is divided into lobes. Each of the lobes is paired, because we have two hemispheres, and each has one of these lobes: the frontal lobes, the seminal lobes, the temporal lobes and the occipital lobes.

Here are the highest centers, which:

process sensations;
give orders for movements.

Let's look at which parts of the cortex receive signals from where.

The occipital lobe deals with visual images. It receives signals from the eyes after they are processed by the thalamus, and a picture is formed here.
The parietal lobe receives information about the sense of touch—that is, the sense of touch and pain.
The temporal lobe receives information about sounds, tastes, smells, and the sense of balance. The brain itself does not feel pain - there are no nerve endings in it.
The frontal lobe is actually the place where consciousness lives and a holistic picture of the world is formed.

If certain parts of the brain are damaged, certain body functions will also suffer. Thus, destruction of the occipital lobe will lead to loss of vision. The eyes will see something, but you will not be able to perceive the picture.

If one feeling is missing, then the others will be more developed. The part of the brain that was involved in vision begins to deal with something else - hearing or tactile sensations, and in a person who is blind from birth, the remaining senses will be much more developed than in the ordinary person.

But if an adult already loses vision, not part of the brain, but, for example, the eyes due to injury, you can put a mechanical implant there, roughly speaking, a camera whose outputs are connected to the nerves and the signal is decoded so that the nervous system can understand it. A person will be able to see because there is a part of the brain that analyzes vision. Only the organs of vision are missing. Eye implants already exist, they don't have very good resolution, but they work.

The brain of humans and other vertebrates is symmetrically divided into right and left parts. In this case, the left side mainly controls the right side of the body and vice versa. There is a common misconception that the left hemisphere is “logical” and the right hemisphere is “emotional.” This is just a popular myth. In fact, their functions are somewhat different, but this is not so important.

Pathways

These are groups of nerve fibers that connect different parts of the brain and spinal cord. All nerve fibers of the same path begin and end on neurons that perform the same function.

Nerve fibers that carry out one-way connections.
Fibers that provide two-way communications.
Fibers connecting the cortex with the underlying sections.

The brain is the main regulator of all functions of a living organism. It is one of the elements of the central nervous system. The structure and functions of the brain are still the subject of study by doctors.

general description

The human brain consists of 25 billion neurons. These cells are the gray matter. The brain is covered with membranes:

arachnoid (the so-called cerebrospinal fluid, which is cerebrospinal fluid, circulates through its channels).

Liquor is a shock absorber that protects the brain from shock.

Despite the fact that the brains of women and men are equally developed, they have different masses. So, among representatives of the stronger sex, its weight is on average 1375 g, and among women - 1245 g. The weight of the brain is about 2% of the weight of a person of normal build. It has been established that the level of a person’s mental development is in no way related to his weight. It depends on the number of connections created by the brain.

Brain cells are neurons that generate and transmit impulses and glia that perform additional functions. Inside the brain there are cavities called ventricles. Paired cranial nerves (12 pairs) depart from it to different parts of the body. The functions of the parts of the brain are very different. The vital functions of the body completely depend on them.

Structure of the brain: table indicating the main functions.

Structure

The structure of the brain, pictures of which are presented below, can be considered in several aspects.

So there are 5 main parts of the brain:

final (80% of the total mass);

intermediate;

posterior (cerebellum and pons);

oblong.

The brain is also divided into 3 parts:

cerebral hemispheres;

brain stem;

cerebellum.

Structure of the brain: drawing with the names of the departments.

Finite brain

The structure of the brain cannot be briefly described, since without studying its structure it is impossible to understand its functions.

The telencephalon extends from the occipital to the frontal bone.

It distinguishes 2 large hemispheres: left and right.

It differs from other parts of the brain by the presence of a large number of convolutions and grooves.

The structure and development of the brain are closely interrelated.

Experts distinguish 3 types of cerebral cortex:

ancient, which includes the olfactory tubercle;

perforated anterior substance;

semilunar, subcallosal and lateral subcallosal gyri;

old, which includes the hippocambus and dentate gyrus (fascia);

new, represented by the rest of the cortex.

Structure of the cerebral hemispheres:

they are separated by a longitudinal groove, in the depths of which the fornix and corpus callosum are located.

They connect the hemispheres of the brain.

The corpus callosum is a new cortex made up of nerve fibers.

There is a vault underneath it.

The structure of the cerebral hemispheres is presented as a multi-level system. So they distinguish between lobes (parietal, frontal, occipital, temporal), cortex and subcortex.

The cerebral hemispheres perform many functions. The right hemisphere controls the left half of the body, and the left hemisphere controls the right. They complement each other.

Bark

Cortex- This is a 3 mm thick surface layer covering the hemispheres. It consists of vertically oriented nerve cells with processes. It also contains afferent and efferent nerve fibers, neuroglia. What is the cerebral cortex? This is a complex structure with horizontal layering. The structure of the cerebral cortex: it has 6 layers (outer granular, molecular, outer pyramidal, inner granular, inner pyramidal, spindle cells), which have different density, width, size and shape of neurons. Due to the vertical bundles of nerve fibers, neurons and their processes present in the cortex, it has vertical striations. The human cerebral cortex, which contains more than 10 billion neurons, has an area of about 2200 sq.cm.

The cerebral cortex is responsible for several specific functions. Moreover, each of its parts is responsible for something of its own. Functions of the cerebral cortex:

temporal lobe - hearing and smell;

occipital - vision;

parietal - touch and taste;

frontal - speech, movement, complex thinking.

Each neuron (gray matter) has up to 10 thousand contacts with other neurons. The white matter of the brain is made up of nerve fibers. A certain part of them connects both hemispheres. The white matter of the cerebral hemispheres consists of 3 types of fibers:

association (connecting different cortical areas in one hemisphere);

commissural (connecting the hemispheres);

projection (conducting paths of analyzers that connect the cerebral cortex with the underlying formations). Inside the hemispheres of the brain there are clusters of gray matter (basal ganglia). Their function is to transmit information. The white matter of the human brain occupies the space between the basal ganglia and the cerebral cortex. There are 4 parts in it (depending on its location):

located in the convolutions between the furrows;

present in the outer parts of the hemispheres;

part of the internal capsule;

located in the corpus callosum.

The white matter of the brain is formed by nerve fibers that connect the gyral cortex of both hemispheres and the underlying formations. The subcortex of the brain consists of subcortical nuclei. The telencephalon controls all processes important for human life and our intellectual abilities.

Diencephalon

It consists of a ventral (hypothalamus) and dorsal (metathalamus, thalamus, epithalamus) part. The thalamus is a mediator in which all received stimuli are sent to the cerebral hemispheres. It is often called the optic thalamus. Thanks to it, the body quickly adequately adapts to a changing external environment. The thalamus is connected to the cerebellum limbic system.

The hypothalamus is a subcortical center in which the regulation of autonomic functions occurs. Its influence occurs through the endocrine glands and the nervous system. It is involved in the regulation of the functioning of some endocrine glands and metabolism. Below it is the pituitary gland. Thanks to it, body temperature, digestive and cardiovascular systems are regulated. The hypothalamus regulates wakefulness and sleep, shapes drinking and eating behavior.

hindbrain

This section consists of the pons located in front and the cerebellum located behind it. The structure of the cerebral pons: its dorsal surface is covered by the cerebellum, and its ventral surface has a fibrous structure. These fibers are directed transversely. On each side of the bridge they pass into the cerebellar middle peduncle. The bridge itself looks like a white thick roller. It is located above the medulla oblongata. The nerve roots emerge from the bulbar-pontine groove. Hindbrain: structure and functions - on the frontal section of the bridge, it is noticeable that it consists of a large ventral (anterior) and a small dorsal (posterior) part. The border between them is the trapezoidal body. Its thick transverse fibers belong to the auditory tract. The hindbrain provides the conductive function.

Cerebellum, often called the small brain, is located behind the pons. It covers the rhomboid fossa and occupies almost the entire posterior fossa of the skull. Its mass is 120-150 g. The cerebral hemispheres hang above the cerebellum, separated from it by a transverse fissure of the brain. The inferior surface of the cerebellum is adjacent to the medulla oblongata. It distinguishes 2 hemispheres, as well as the upper and lower surfaces and the worm. The boundary between them is called a deep horizontal gap. The surface of the cerebellum is cut by many slits, between which there are thin ridges (gyri) of the medulla. The groups of gyri located between the deep grooves are lobules, which, in turn, make up the lobes of the cerebellum (anterior, flocnonodular, posterior).

There are 2 types of substance in the cerebellum. Gray is on the periphery. It forms the cortex, which contains the molecular, pyriform neurons and granular layer. The white matter of the brain is always located under the cortex. Likewise, in the cerebellum it forms the brain body. It penetrates into all convolutions in the form of white stripes covered with gray matter. The white matter of the cerebellum itself contains interspersed gray matter (nuclei). In cross-section, their relationship resembles a tree. Our coordination of movement depends on the functioning of the cerebellum.

Midbrain

This section extends from the anterior edge of the pons to the papillary bodies and optic tracts. It contains a cluster of nuclei, which are called quadrigeminal tubercles. The midbrain is responsible for hidden vision. It also contains the center of the orienting reflex, which ensures the body turns in the direction of a sharp noise.

Medulla

It is a continuation of the spinal cord. The structure of the brain and spinal cord have much in common. This becomes clear upon a detailed examination of the white matter of the medulla oblongata. The white matter of the brain is represented by long and short nerve fibers. Gray matter is presented in the form of nuclei. This brain is responsible for coordination of movement, balance, regulation of metabolism, blood circulation and breathing. It is also responsible for coughing and sneezing.

The structure of the brainstem: it is a continuation of the spinal cord, divided into the midbrain and hindbrain. The trunk is called the medulla oblongata, midbrain, diencephalon and pons. The structure of the brain stem consists of ascending and descending pathways that connect it with the brain and spinal cord. It controls articulate speech, breathing and heartbeat.

The medulla oblongata is a direct continuation of the spinal cord; in an adult, its length is about 25 mm. It is somewhat flattened in the anteroposterior direction and has the shape of a truncated cone, tapering towards the spinal cord and widening towards the pons. On both sides of the anterior median fissure of the medulla oblongata there are convex white cords - pyramids, which consist of fibers of the descending corticospinal (pyramidal) tract that is still common here. The pyramids taper downwards, about 2/3 of their fibers gradually move to the opposite side, forming a cross of the pyramids; going down below, they form the lateral corticospinal tract. A minority of the fibers remain on the same side, passing into the anterior funiculi of the spinal cord in the form of the anterior corticosninal tract (Fig. 11.5).

Along the entire medulla oblongata there is reticular formation, which is represented by the interweaving of nerve fibers and the nerve cells lying between them. The reticular formation is connected by ascending and descending fibers to the cerebral cortex, cerebellum and spinal cord, exerting an activating effect on the cerebral cortex and motor nuclei of the spinal cord.

The hypoglossal nerve emerges from the side of the pyramids, the roots of which are located corresponding to the anterior roots of the spinal cord (see.

The lateral funiculi occupy the lateral surfaces of the medulla oblongata. Their ventral (anteroinferior) part consists of olives, dorsal (posterior superior) - inferior cerebellar peduncles. The olives are oval in shape and are composed of neuronal cell bodies (olive nuclei). They are functionally closely connected with the cerebellum and are responsible for maintaining the body in an upright position. The lower cerebellar peduncles are massive fibrous cords. Diverging upward to the sides, they laterally limit the lower corner of the bottom of the fourth ventricle of the brain - rhomboid fossa. All formations located between the rhomboid fossa and the pyramids belong to tire

From the lateral cords of the medulla oblongata, the roots of the accessory, vagus and glossopharyngeal cranial nerves, located corresponding to the dorsal roots of the spinal cord, sequentially emerge. Peripheral nervous system).

In the lower part, on the dorsal (posterior) surface of the medulla oblongata, there is a posterior median groove, on the sides of which the thin and wedge-shaped bundles of the posterior cords of the spinal cord end in thickenings. In the thickenings are located the nuclei of these bundles, extending

Rice. 11.4.

Rice. 11.5.

1 - fourth ventricle; 2 - dorsal nucleus of the vagus nerve; 3 - nucleus of the vestibular nerve; 4 - nucleus of the solitary tract; 5 - posterior (dorsal) spinocerebellar tract; 6 - spinal nucleus of the trigeminal nerve; 7 - spinal tract of the trigeminal nerve; 8 - nucleus of the hypoglossal nerve; 9 - olive kernel;
10 - olive; 11 - corticospinal tract (pyramidal); 12 - medial loop; 13 - hypoglossal nerve; 14 - anterior outer arc fibers;
15 - double core; 16 - spinothalamic and spino-tegmental tracts;
17 - vagus nerve; 18 - central (anterior) spinocerebellar tract

from them, the nerve fibers pass to the opposite side in the form of a medial loop, then heading to the bridge, some of the fibers enter the lower cerebellar peduncles. The proprioceptive pathways of the cerebellar direction - the anterior and posterior spinocerebellar - pass through the medulla oblongata and the inferior cerebellar peduncles.

Functions of the medulla oblongata. The medulla oblongata, like the spinal cord, performs two functions - reflex And conductor. The medulla oblongata contains the nuclei of the following cranial nerves:

- pair IX - glossopharyngeal nerve; its core is formed by three parts - motor, sensitive and vegetative. The motor part is involved in the innervation of the muscles of the pharynx and oral cavity, the sensitive part receives information from the taste receptors of the posterior third of the tongue; autonomic innervates the salivary glands;
- pair X - vagus nerve, has three nuclei: the autonomic one innervates the larynx, esophagus, heart, stomach, intestines, digestive glands; the sensitive receives information from the receptors of the alveoli of the lungs and other internal organs, and the motor (the so-called mutual) ensures the sequence of contractions of the muscles of the pharynx and larynx during swallowing;

pair XI - accessory nerve; its nucleus is partially located in the medulla oblongata; innervates the sternocleidomastoid and trapezius muscles;

Pair XII - hypoglossal nerve - motor nerve of the tongue, its core is mostly located in the medulla oblongata.

The medulla oblongata, like the spinal cord, has a sensitive and motor connection with the periphery. Through sensory fibers it receives impulses from receptors in the scalp, mucous membranes of the eyes, nose, mouth, from the organ of hearing, the vestibular apparatus (organ of balance), from receptors in the larynx, trachea, lungs, as well as from interoreceptors of the cardiovascular system and the digestive system.

Through the medulla oblongata, many simple and complex reflexes are carried out, covering many life-supporting organ systems:

- protective reflexes: coughing, sneezing, blinking, tearing, vomiting;
- food reflexes: sucking, swallowing, secretion of digestive glands;
- cardiovascular reflexes that regulate the activity of the heart and blood vessels;
- reflex breathing centers: inhalation center - inspiratory and exhalation center - expiratory, providing automatic ventilation of the lungs;
- vestibular centers that ensure maintaining body posture despite gravity.

The special importance of this part of the central nervous system is determined by the fact that the most important life support centers (respiratory, cardiovascular, etc.) are located in the medulla oblongata, therefore not only removal, but even damage to the medulla oblongata ends in death.

In addition to the reflex function, the medulla oblongata performs a conductive function. Conducting pathways pass through the medulla oblongata, connecting the cortex, diencephalon, midbrain, cerebellum and spinal cord with a bilateral connection.

The pons has the form of a transverse ridge located between the midbrain above and the medulla oblongata below. The dorsal surface of the bridge participates in the formation of the rhomboid fossa - the bottom of the fourth cerebral ventricle. At the top, the pons is sharply demarcated from the cerebral peduncles. On the sides it narrows and passes into the middle cerebellar peduncles, which extend into the cerebellar hemispheres. The border between the middle cerebellar peduncles and the pons is the site of exit of the trigeminal nerve roots.

The pons is separated from the pyramids of the medulla oblongata by a deep transverse groove, from the middle part of which the roots of the right and left abducens nerves (VI pair) emerge, and from the lateral (side) - the roots of the facial (VII pair) and vestibulocochlear (VIII pair) nerves. Most of the mass of the pons is white matter, i.e. accumulations of nerve fibers that form pathways and cranial nerves.

Functions of the pons. The pons performs motor, sensory, integrative and conductive functions. Important functions of the bridge are associated with the presence of cranial nerve nuclei in it.

V pair - trigeminal nerve (mixed). The motor nucleus of the nerve innervates the muscles of mastication, the muscles of the velum palatine, and the tensor tympani muscles. The sensitive nucleus receives afferent axons from receptors on the skin of the face, nasal mucosa, teeth, 2/3 of the tongue, periosteum of the skull bones, and conjunctiva of the eyeball.

VI pair - abducens nerve (motor), innervates the rectus externus muscle, which abducts the eyeball outward.

VII pair - facial nerve (mixed), innervates the facial muscles, sublingual and submandibular salivary glands, transmits information from the taste buds of the anterior part of the tongue.

VIII pair - vestibulocochlear (sensitive) nerve. The cochlear part of this nerve ends in the brain in the cochlear nuclei; vestibular - in the triangular nucleus, Deiters nucleus, Bekhterev nucleus. Here the primary analysis of vestibular irritations, their strength and direction takes place.

All ascending and descending pathways pass through the bridge, connecting the bridge with the cerebellum, spinal cord, cerebral cortex and other structures of the central nervous system. The pontocerebellar pathways through the pons carry out the controlling influence of the cerebral cortex on the cerebellum. In addition, the pons contains centers that regulate the activity of the inhalation and exhalation centers located in the medulla oblongata.

The cerebellum, or “small brain,” is located posterior to the pons and medulla oblongata. It consists of a middle, unpaired, phylogenetically old part - the worm - and paired hemispheres, characteristic only of mammals. The cerebellar hemispheres develop in parallel with the cerebral cortex and reach significant sizes in humans. The worm on the underside is located deep between the hemispheres; its upper surface gradually passes into the hemispheres (Fig. 11.6).

Rice. 11.6. Structure of the cerebellum(A - view from the side, B - vertical section):

A: 1 - cerebral peduncle; 2 - superior surface of the hemisphere

cerebellum; 3 - pituitary gland; 4 - white plates; 5 - bridge; 6 - dentate nucleus; 7 - white matter; 8 - medulla; 9 - olive kernel; 10 - inferior surface of the cerebellar hemisphere; 11 - spinal cord.

B: 1 - superior surface of the cerebellar hemisphere; 2 - white plates;

3 - worm; 4 - white matter; 5 - tent; 6 - horizontal slot;
7 - lower surface of the cerebellar hemisphere

In general, the cerebellum has extensive efferent connections with all motor systems of the brainstem: corticospinal, rubrosiinal, reticulospinal and vestibulospinal. The afferent inputs of the cerebellum are no less diverse.

The entire surface of the cerebellum is divided into lobes by deep grooves. In turn, each lobe is divided into convolutions by parallel grooves; groups of convolutions form the cerebellar lobules. The hemispheres and vermis of the cerebellum consist of gray matter lying on the periphery - the cortex - and white matter located deeper, which contains clusters of nerve cells that form the cerebellar nuclei - tent nuclei, spherical, cork-shaped and jagged.

The cerebellar cortex has a specific structure that is not repeated anywhere in the central nervous system. All cells of the cerebellar cortex are inhibitory, with the exception of the granular cells of the deepest layer, which have an excitatory effect.

The activity of the neuronal system of the cerebellar cortex is reduced to inhibition of the underlying nuclei, which prevents long-term circulation of excitation along neural circuits. Any excitatory impulse arriving at the cerebellar cortex turns into inhibition within a time of about 100 ms. This is how an automatic erasure of previous information occurs, which allows the cerebellar cortex to participate in the regulation of rapid movements.

Functionally, the cerebellum can be divided into three parts: archiocerebellum (ancient cerebellum), paleocerebellum (old cerebellum) and neocerebellum (new cerebellum). Archiocerebellum is a vestibular regulator, its damage leads to imbalance. Function paleocerebellum - mutual coordination of posture and targeted movement, as well as correction of relatively slow movements using a feedback mechanism. If the structures of this part of the cerebellum are damaged, it is difficult for a person to stand and walk, especially in the dark, in the absence of visual correction. Neocerebellum participates in programming complex movements, the execution of which occurs without the use of a feedback mechanism. The result is a purposeful movement performed at high speed, such as playing the piano. When the structures of the neocerebellum are disrupted, complex sequences of movements are disrupted, they become arrhythmic and slowed down.

The cerebellum is involved in the regulation of movements, making them smooth, precise, proportionate, ensuring correspondence between the intensity of muscle contraction and the task of the movement being performed. The cerebellum also influences a number of autonomic functions, for example, the gastrointestinal tract, blood pressure levels, and blood composition.

For a long time, the cerebellum was considered a structure responsible solely for the coordination of movements. Today, its participation in the processes of perception, cognitive and speech activity is recognized.

Midbrain located above the pons and represented by the cerebral peduncles and quadrigeminal. The cerebral peduncles consist of a base and a tegmentum, between which there is a substantia nigra containing highly pigmented cells. The tectum of the brain contains the nuclei of the trochlear (IV pair) and oculomotor (III pair) nerves. The cavity of the midbrain is represented by a narrow canal - the Sylvian aqueduct, which connects the III and IV cerebral ventricles. The length of the midbrain in an adult is about

2 cm, weight - 26 g. During embryonic development, the midbrain is formed from the midbrain bladder, the lateral protrusions of which move forward and form the retina, which structurally and functionally represents the nerve center of the midbrain located on the periphery.

The largest nuclei of the midbrain are the red nuclei, the substantia nigra, the nuclei of the cranial (oculomotor and trochlear) nerves and the nuclei of the reticular formation. Through the midbrain there are ascending pathways to the thalamus, cerebral hemispheres and cerebellum and descending pathways to the medulla oblongata and spinal cord.

The midbrain performs conductive, motor and reflex functions.

Conductive function of the midbrain is that all ascending pathways to the overlying sections pass through it: the thalamus (medial lemniscus, spinothalamic tract), the cerebrum and the cerebellum. Descending tracts pass through the midbrain to the medulla oblongata and spinal cord. This pyramidal tract, corticopontine fibers, ruboreticulospinal tract.

Motor function of the midbrain is realized through the nuclei of the trochlear nerve, the nuclei of the oculomotor nerve, the red nucleus, and the substantia nigra.

red kernels, receiving information from the motor zone of the cerebral cortex, subcortical nuclei and cerebellum about the upcoming movement and the state of the musculoskeletal system, they regulate muscle tone, preparing its level for the upcoming voluntary movement. Black substance is connected with the basal ganglia lying at the base of the forebrain hemispheres - the striatum and the globus pallidus - and regulates the acts of chewing, swallowing (their sequence), provides fine regulation of plastic muscle tone and precise movements of the fingers, for example, when writing. Neurons of the nuclei oculomotor and trochlear nerves regulate the movement of the eye up, down, out, towards the nose and down to the corner of the nose. Neurons of the accessory nucleus of the oculomotor nerve (Yakubovich's nucleus) regulate the lumen of the pupil and the curvature of the lens. Also associated with the midbrain implementation of rectifying and statokinetic reflexes. Rectifying reflexes consist of two phases: raising the head and subsequent raising the body. The first phase is carried out due to the reflex influences of the receptors of the vestibular apparatus and skin, the second is associated with the proprioceptors of the muscles of the neck and torso. Statokinetic reflexes are aimed at returning the body to its original position when moving the body in space, during rotation.

Functionally independent structures of the midbrain are quadrigeminal tubercles. The upper ones participate in the activity of the primary subcortical centers of the visual analyzer, the lower ones - the auditory one. They are where the primary switching of visual and auditory information occurs. The main function of the quadrigeminal tuberosities is organization alarm reactions and the so-called start reflexes to sudden, not yet recognized, visual (superior colliculus) or auditory

(inferior colliculus) signals. Activation of the midbrain under the influence of alarming factors through the hypothalamus leads to increased muscle tone and increased heart contractions; preparation for avoidance or a defensive reaction occurs. In addition, if the quadrigeminal reflex is impaired, a person cannot quickly switch from one type of movement to another.

The diencephalon is located under the corpus callosum and fornix, fused on the sides with the cerebral hemispheres. It includes: the thalamus (visual thalamus), hypothalamus (sub-tubercular region), epithalamus (supra-tubercular region) and metathalamus (sub-tubercular region) (Fig. 11.7). The cavity of the diencephalon is the third ventricle of the brain.

Rice. 11.7.

1 - medulla oblongata; 2 - bridge; 3 - cerebral peduncles; 4 - thalamus; 5 - pituitary gland;
6" - projection of the nuclei of the subtubercular region; 7 - corpus callosum; 8 - pineal gland;
9 - tubercles of the quadrigeminal; 10 - cerebellum

Epithalamus includes the endocrine gland - pineal gland(pineal body). In the dark, it produces the hormone melatonin, which is involved in organizing the body’s circadian rhythm and affects the regulation of many processes, in particular skeletal growth and the rate of puberty (see. Endocrine system).

Metathalamus represented by the external and median geniculate bodies. External geniculate body is the subcortical center of vision, its neurons react differently to color stimulation, turning on and off the light, i.e. can perform a detector function.

Median geniculate body- subcortical, thalamic hearing center. Efferent pathways from the medial geniculate body go to the temporal lobe of the cerebral cortex, reaching the primary auditory zone there.

Thalamus, or visual tubercle, is a paired ovoid-shaped organ, the anterior part of which is pointed (anterior tubercle), and the posterior expanded part (cushion) hangs over the geniculate bodies. The median surface of the thalamus faces the cavity of the third ventricle of the brain.

The thalamus is called the “collector of sensitivity”, since afferent (sensitive) pathways from all receptors except the olfactory ones converge to it. In the nuclei of the thalamus, information coming from various types of receptors is switched to the thalamocortical pathways that begin here, facing the cerebral cortex.

The main function of the thalamus is the integration (unification) of all types of sensitivity. To analyze the external environment, there are not enough signals from individual receptors. In the thalamus, information received through various channels is compared and its biological significance is assessed. There are about 40 pairs of nuclei in the optic thalamus, which are divided into specific(the ascending afferent pathways end on the neurons of these nuclei), nonspecific(nuclei of the reticular formation) and associative.

Individual neurons of specific thalamic nuclei are excited by receptors only of their own type. From specific nuclei, information about the nature of sensory stimuli enters strictly defined areas of the III-IV layers of the cerebral cortex ( somatotopic localization). Dysfunction of specific nuclei leads to loss of specific types of sensitivity, since the nuclei of the thalamus, like the cerebral cortex, have a somatotopic localization. Signals from receptors in the skin, eyes, ear, and muscular system go to specific nuclei of the thalamus. Signals from the interoceptors of the projection zones of the vagus and celiac nerves and the hypothalamus also come here.

Neurons of nonspecific nuclei form their connections according to a mesh type. Their axons rise into the cerebral cortex and contact all its layers, forming not local, but diffuse connections. Nonspecific nuclei receive connections from the reticular formation of the brainstem, hypothalamus, limbic system, basal ganglia, and specific nuclei of the thalamus. Increased activity of nonspecific nuclei causes a decrease in the activity of the cerebral cortex (development of a sleepy state).

The complex structure of the thalamus, the presence of interconnected specific, nonspecific and associative nuclei in it allows it to organize such motor reactions as sucking, chewing, swallowing, laughter, and ensure the connection of vegetative and motor acts.

Through the associative nuclei, the thalamus is connected with all the motor nuclei of the subcortex - the striatum, globus pallidus, hypothalamus and with the nuclei of the midbrain and medulla oblongata. The thalamus is the center of organization and implementation of instincts, drives, and emotions. The ability to receive information about the state of many body systems allows the thalamus to participate in the regulation and determination of the functional state of the body as a whole.

Hypothalamus(subthalamus) - a structure of the diencephalon, part of the limbic system and organizing emotional, behavioral, homeostatic reactions of the body. The hypothalamus has a large number of nerve connections with the cerebral cortex, subcortical ganglia, thalamus optic, midbrain, pons, medulla oblongata and spinal cord. The nuclei of the hypothalamus have a powerful blood supply, its capillaries are easily permeable to high-molecular protein compounds, which explains the high sensitivity of the hypothalamus to humoral changes.

In humans, the hypothalamus finally matures by the age of 13-14, when the formation of hypothalamic-pituitary neurosecretory connections ends. Due to powerful afferent connections with the olfactory brain, basal ganglia, thalamus, hippocampus, and cerebral cortex, the hypothalamus receives information about the state of almost all brain structures. At the same time, the hypothalamus sends information to the thalamus, reticular formation, autonomic centers of the brain stem and spinal cord.

Neurons of the hypothalamus have features that determine the specific functions of the hypothalamus itself. These include the absence of a blood-brain barrier between neurons and blood, the high sensitivity of hypothalamic neurons to the composition of the blood washing them and the ability to secrete hormones and neurotransmitters. This allows the hypothalamus to influence the autonomic functions of the body through humoral and neural pathways.

In general, the hypothalamus regulates the functions of the nervous and endocrine systems; it houses the centers of homeostasis, heat regulation, hunger and satiety, thirst and its satisfaction, sexual behavior, fear, and rage. A special place in the functions of the hypothalamus is occupied by the regulation of the activity of the pituitary gland. The hypothalamus and pituitary gland produce neuroregulatory substances - enkephalins and endorphins, which have a morphine-like effect and help reduce stress.

Neurons of the nuclei of the anterior group of the hypothalamus produce vasopressin, or antidiuretic hormone (ADH), oxytocin and other hormones, which travel along axons to the posterior lobe of the pituitary gland - the neurohypophysis. Neurons of the nuclei of the median group of the hypothalamus produce so-called releasing factors that stimulate (liberins) and inhibit (statins) the activity of the anterior pituitary gland - the adenohypophysis, in which somatotropic, thyroid hormones and other hormones are formed (see. Endocrine system). Neurons of the hypothalamus also have the function of a homeostasis detector: they respond to changes in blood temperature, electrolyte composition and osmotic pressure of plasma, the amount and composition of blood hormones. The hypothalamus takes part in sexual function and puberty, in the regulation of the “wakefulness-sleep” cycle: the posterior parts of the hypothalamus activate wakefulness, stimulation of the anterior ones causes sleep, damage to the hypothalamus can cause so-called lethargic sleep.

The telencephalon is the youngest phylogenetically. It consists of two hemispheres, each of which is represented by the mantle, the olfactory brain and the basal or subcortical ganglia (nuclei). The average length of the hemispheres is 17 cm, height - 12 cm. The cavities of the telencephalon are the lateral ventricles, located in each of the hemispheres. The hemispheres of the brain are separated from each other by the longitudinal fissure of the brain and are connected by the corpus callosum, the anterior and posterior commissures and the commissure of the fornix. The corpus callosum consists of transverse fibers that extend laterally into the hemispheres, forming the radiance of the corpus callosum.

Olfactory brain represented by the olfactory bulbs, olfactory tubercle, septum pellucidum and adjacent areas of the cortex (preperiform, periamygdala and diagonal). This is a smaller part of the telencephalon, it provides the function of the first sense organ that appeared in living beings - the function of smell and, in addition, is part of the limbic system. Damage to the structure of the limbic system causes profound impairment of emotions and memory.

(nuclei of gray matter) are located deep in the cerebral hemispheres. They make up approximately 3% of their volume. The basal ganglia form numerous connections both between the structures that make up them and other parts of the brain (cerebral cortex, thalamus, substantia nigra, red nucleus, cerebellum, motor neurons of the spinal cord). The basal ganglia include the strongly elongated and curved caudate nucleus and the lentiform nucleus embedded in the thickness of the white matter. It is divided into the shell and the globus pallidus by two white plates. Together, the caudate nucleus and putamen are called the striatum, are connected anatomically and are characterized by alternating white and gray matter (Fig. 11.8).

Rice. 11.8.

Striatum takes part in the organization and regulation of movements and ensuring the transition of one type of movement to another. Stimulation caudate nucleus inhibits the perception of visual, auditory and other types of sensory information, inhibits the activity of the cortex, subcortex, unconditioned reflexes (food, defensive, etc.) and the development of conditioned reflexes, leading to the onset of sleep. When the striatum is damaged, memory loss for events preceding the injury is observed. Bilateral damage to the striatum encourages forward movement, while unilateral damage leads to manege movements (walking in a circle). A disorder of the functions of the striatum is associated with a disease of the nervous system - chorea (involuntary movements of the facial muscles, muscles of the arms and torso). Shell ensures the organization of eating behavior. When it is damaged, trophic disorders of the skin are observed, and its irritation causes salivation and changes in breathing. Functions globus pallidus consist in provoking an indicative reaction, movement of limbs, eating behavior (chewing, swallowing).

The cloak, or cerebral cortex, is a plate of gray matter separated from the cavity of the ventricles by white matter, which contains a huge number of nerve fibers, divided into three groups:

1. Pathways connecting different parts of the cerebral cortex within one hemisphere - associative paths. There are short, or arcuate, associative fibers that connect two adjacent gyri, and long ones that stretch from one lobe to another, remaining within the same hemisphere.
2. Commissural, or commissural, fibers connect the cortex of both hemispheres. The largest commissure of the brain is the corpus callosum.
3. Projection paths connect the cerebral cortex with the periphery. There are centrifugal (efferent, motor) fibers that carry nerve impulses from the cortex to the periphery, and centripetal (afferent, sensory) fibers that carry impulses from the periphery to the cerebral cortex.

The cerebral cortex is the highest division of the central nervous system. It ensures the perfect organization of animal behavior based on innate and acquired functions during ontogenesis. It is divided into ancient ( archicortex), old (paleocortex) and new ( neocortex). Ancient bark participates in ensuring the sense of smell and the interaction of various brain systems. old bark includes the cingulate gyrus, hippocampus and is involved in the implementation of innate reflexes and the emotional and motivational sphere. New crust is represented by the main part of the cerebral cortex and carries out the highest level of coordination of brain function and the formation of complex forms of behavior. The greatest development of the functions of the new cortex is observed in humans; its thickness in adulthood ranges from 1.5 to 4.5 mm and is maximum in the anterior central gyrus.

Morphological structure of the cerebral cortex. The cortex consists of numerous furrows And convolutions due to which the surface of the cortex increases significantly. They have individual differences not only between different people, but also in two hemispheres of the same person. Deep, permanent grooves divide the hemisphere into large areas - shares) consisting of lobules and convolutions. There are only six shares: frontal, parietal, temporal, occipital, marginal and island(see Fig. 11.4).

The deepest primary grooves are distinguished, which divide the hemispheres into lobes. Lateral groove (Silvieva) separates the frontal lobe from the temporal lobe, central sulcus (Rolandova) - frontal from parietal. Parieto-occipital sulcus is located on the medial surface of the hemisphere and separates the parietal and occipital lobes; on the superolateral surface there is no clear boundary between these lobes. On the medial surface of the hemisphere there are the cingulate, collateral and olfactory grooves. cingulate groove runs parallel to the corpus callosum, separating the frontal and parietal lobes from the cingulate gyrus. Collateral groove demarcates the temporal, marginal and occipital lobes on the lower surface of the hemisphere. In the anterior part of the lower surface of the hemisphere is located olfactory sulcus with the olfactory bulb, which continues into the olfactory tract.

The insular lobe is located deep in the lateral sulcus. It is surrounded on three sides by a circular groove, its surface is indented with grooves and convolutions. Functionally, this lobe is connected to the olfactory brain.

Secondary grooves are less deep; they divide the lobes into convolutions and are located outside the convolutions of the same name. Tertiary (innominate) grooves give the gyri an individual shape and increase the area of their cortex.

IN frontal lobe The precentral sulcus is located parallel to the central sulcus. The upper and lower frontal grooves extend from it in the longitudinal direction, which divide the lobe into one vertical and three horizontal gyri. The vertical gyrus is located between the central and precentral sulci and is called the precentral gyrus, it contains motor analyzer core. From the fifth layer of the cortex of this gyrus, the cortical descending path begins. The horizontal gyri are called the superior, middle and inferior frontal gyri. Located in the middle gyrus writing center - motor analyzer of written speech, the core of which is finally formed by the age of 7, as well as the center of combined rotation of the head and eyes in one direction. Localized in the inferior gyrus motor speech center(articulation) - Brocca's center, which has a bilateral anlage in embryogenesis and develops on the left in right-handers, and on the right in left-handers. The core of the motor analyzer of oral speech differentiates by 3 years.

Parietal lobe between the central and postcentral sulci contains the postcentral gyrus, which is center of touch, pain and temperature sensitivity. The interparietal groove runs perpendicular to the postcentral gyrus, dividing the posterior part of the parietal lobe into the superior and inferior parietal lobules. At the top is center of stereognosis(recognizing objects by touch). In the inferior parietal lobule the supramarginal gyrus is visible, into which the lateral gyrus abuts. The supramarginal gyrus is praxis center(purposeful actions underlying the formation of skills in various types of activities). Below the supramarginal gyrus lies the angular gyrus, where the visual analyzer of written speech(reading center), the core of which is formed by the age of 7. The last two centers have a bilateral anlage in embryogenesis; they subsequently develop on the left in right-handed people, and on the right in left-handed people.

Temporal lobe has two longitudinal - superior and inferior temporal - grooves, which divide it into three longitudinal gyri - superior, middle and inferior. All of them are parallel to the lateral groove. In the posterior part of the superior temporal gyrus there are sensory speech center - Wernicke Center. In its middle section there is core of the auditory analyzer. In a newborn, it is prepared to perceive various sound stimulation, but most selectively - to perceive the sounds of human speech. As speech develops, the cortical hearing center quickly becomes more complex. In the most medial part is the hippocampal gyrus. Its anterior section is represented by a hook, and is located here center of smell and taste.

Occipital lobe has variable and inconsistent furrows. On its medial surface there is a deep constant calcarine groove, located horizontally and running from the occipital pole to the parieto-occipital groove. Between the calcarine and occipito-parietal sulcus there is a triangular gyrus (wedge) and a lingual gyrus - visual analyzer center, the nucleus of which in a newborn is similar in its cellular composition to the nucleus of adults. Under the influence of external factors, its further complication occurs.

Island has the shape of a triangle, the top of which faces forward and downward. It is located in the lateral sulcus and is bounded on all sides by a deep circular sulcus, its surface is covered with short convolutions.

Marginal lobe located on the medial surface of the hemispheres and includes the cingulate and parahippocampal gyri. The cingulate gyrus begins below with the groove of the corpus callosum, and above with the cingulate groove, which separates it from the frontal and parietal lobes. It actively participates in the formation of interhemispheric connections and integrative processing of information by transmitting it from one hemisphere to another. The parahippocampal gyrus is bounded above by the hippocampal sulcus, and below by the collateral sulcus, separating it from the temporal lobe. The anterior end of the parahippocampal gyrus forms a hook, enclosing the anterior end of the hippocampal sulcus.

On the inner surface of the cortex there are a number of formations that belong to limbic system. This system regulates the functioning of internal organs, endocrine glands and provides emotional reactions.

Limbic system (from lat. limbus- edge, border) - an area located between the cerebral cortex and the medulla oblongata and, as it were, bordering it (Fig. 11.9). It consists of various anatomically and functionally related formations of the brain: nerve cell nuclei located in the anterior region of the thalamus, hypothalamus, amygdala nucleus and hippocampus, located adjacent to the amygdala nucleus. It also includes the olfactory bulb and the cingulate, hippocampal and dentate gyri. They form a ring over the corpus callosum.

Rice. 11.9

The main function of the limbic system is the ability to quickly adapt to changes in the external environment, quickly and adequately respond to danger. The main place in this adaptive activity belongs to emotions, the biological meaning of which is precisely to quickly assess the current needs of the body and stimulate an appropriate response to the action of a particular stimulus. In addition, the limbic system (mainly the hippocampus) takes an active part in the complex processes underlying memory, mainly short-term.

Features of the structure of the cerebral cortex in ontogenesis. The relationship of the grooves and gyri with the bones and sutures of the skull in a newborn child is different than in an adult. The main sulci (central, lateral) are well defined, but the branches of the main sulci and small gyri are poorly defined. Later, during the development of the cortex, the furrows become deeper, and the convolutions between them become more prominent. The relationship between the grooves, convolutions and sutures of the skull, characteristic of an adult, is established in children at 6-8 years of age.

During the first months of life, the development of the cortex occurs at a very rapid pace. Most neurons acquire a mature form, the processes of myelination of nerve fibers occur intensively, allowing them to respond to external stimuli in a more differentiated manner.

In the process of human evolution as a biological species, as well as in the process of ontogenesis - the individual development of each person - occurs corticalization of functions, i.e. inclusion of the cerebral cortex in the regulation of the functions of underlying brain structures. This makes it possible to organize more advanced regulation of body functions, taking into account individual experience stored in memory. Subsequently, as a particular reaction is automated, its execution is again transferred to the subcortical structures with the formation of an automatic response.

Different cortical zones mature unevenly. The somatosensory and motor cortex matures the earliest, and the visual and auditory cortex matures somewhat later. The development of the visual cortex is especially intense during the first half of life, which entails the development of other areas of the brain and their integration. Maturation of sensory and motor areas is generally completed by the age of 3 years. The associative cortex matures much later: by the age of 7, its main connections are formed, and final differentiation, the formation of neural ensembles and connections with other parts of the brain occur by adolescence). "The frontal areas of the cortex mature the latest (closer to 9 years). Gradual maturation of structures The cerebral cortex determines the age-related characteristics of higher nervous functions and behavioral reactions of children of various age groups.

Cytoarchitecture of the cerebral cortex. The total area of the human cerebral cortex is about 2200 cm 2, the number of cortical neurons exceeds 10 billion. The cortex contains pyramidal, stellate, and spindle-shaped neurons.

Pyramid neurons have different sizes, the axon of a pyramidal neuron, as a rule, passes through the white matter to other areas of the cortex or to other brain structures.

Star-shaped the cells have short, well-branched dendrites and a short axon that provides connections between neurons within the cerebral cortex itself.

Fusiform neurons provide vertical or horizontal connections between neurons of different layers of the cortex.

The cerebral cortex has a predominantly six-layer structure (Fig. 11.10).

Rice. 11.10.

Layer I is the upper molecular layer, represented mainly by the branches of the ascending dendrites of pyramidal neurons, among which rare horizontal cells and granule cells are located; fibers of the nonspecific nuclei of the thalamus also come here, regulating the level of excitability of the cerebral cortex through the dendrites of this layer.

Layer II - external granular, consists of stellate cells that determine the duration of circulation of excitation in the cerebral cortex, i.e. related to memory.

Layer III is the outer pyramidal layer, formed from small pyramidal cells and, together with layer II, provides cortico-cortical connections of various convolutions of the brain.

Layer IV is internal granular and contains predominantly stellate cells. Specific thalamocortical pathways end here, i.e. pathways starting from analyzer receptors.

Layer V is the internal pyramidal (ganglionic), a layer of large pyramids that are output neurons, their axons go to the brain stem and spinal cord. In the motor zone, this layer contains giant pyramidal cells discovered by Betz (Betz cells).

Layer VI is a layer of polymorphic cells; most of the neurons in this layer form corticothalamic tracts.

The distribution of neurons into layers in different areas of the cortex made it possible to identify 53 cytoarchitectonic fields (Brodmann fields) in the human brain, which improve as the cerebral cortex develops. In humans and higher mammals, along with primary ones, secondary and tertiary cortical fields are distinguished, ensuring the association of the functions of a given analyzer with the functions of other analyzers.

A feature of cortical fields is the screen principle of their functioning, which consists in the fact that the receptor projects its signal not onto one cortical neuron, but onto a field of neurons, which is formed by their connections. As a result, the signal is not focused point to point, but on many different neurons, which ensures its complete analysis and the possibility of transmission to other interested structures. Thus, one fiber entering the visual cortex can activate a zone measuring 0.1 mm. This means that one axon distributes its action over more than 5,000 neurons.

The functions of individual zones of the neocortex are determined by the characteristics of its structural organization, connections with other brain structures, participation in the perception, storage and reproduction of information in the organization and implementation of behavior, regulation of the functions of sensory systems and internal organs.

The structural differences in areas of the cerebral cortex are associated with differences in their functions. The cerebral cortex is divided into sensory, motor and associative areas (Fig. 11.11).

The cortical ends of the analyzers have their own topography - local location in certain areas of the cerebral cortex. They're called sensory areas of the cerebral cortex. The cortical ends of the analyzers of different sensory systems overlap. In addition, in each sensory system of the cortex there are polysensory neurons that respond not only to “their” adequate stimulus, but also to signals from other sensory systems. These mechanisms underlie the formation of multimodal connections that provide a combined response to various stimuli.

Rice. 11.11.

The cutaneous receptive system, thalamocortical pathways, project to the posterior central gyrus. There is a strict somatotopic division here. The receptive fields of the skin of the lower extremities are projected onto the upper sections of this gyrus, the torso onto the middle sections, and the arms and head onto the lower sections.

Pain and temperature sensitivity are mainly projected onto the posterior central gyrus. In the cortex of the parietal lobe (fields 5 and 7, see Fig. 11.11), where the sensitivity pathways also end, a more complex analysis is carried out: localization of irritation, discrimination, stereognosis. When the cortex is damaged, the functions of the distal parts of the extremities, especially the hands, are especially severely impaired.

The visual system is located in the occipital lobe of the brain: fields 17, 18, 19. The central visual pathway ends in field 17; it informs about the presence and intensity of the visual signal. In fields 18 and 19, the color, shape, size, and quality of objects are analyzed. Damage to field 19 of the cerebral cortex leads to the fact that the patient sees, but does not recognize the object (visual agnosia, and color memory is also lost).

The auditory system is projected in the transverse temporal gyri (Heschl's gyrus), in the depths of the posterior sections of the lateral (Sylvian) fissure (fields 41, 42, 52). It is here that the axons of the posterior colliculi and lateral geniculate bodies end.

The olfactory system projects to the region of the anterior end of the hippocampal gyrus (field 34). The bark of this area has not a six-layer, but a three-layer structure. When irritated, olfactory hallucinations are observed, damage to which leads to anosmia (loss of smell).

The taste system is projected in the hippocampal gyrus adjacent to the olfactory area of the cortex (field 43).

In the anterior central gyrus there are zones, the irritation of which causes movement, they are represented according to the somatotopic type, but in a completely different way: in the upper parts of the gyrus - the lower limbs, in the lower - the upper. This motor areas of the cerebral cortex.

In front of the anterior central gyrus lie premotor fields 6 and 8. They organize not isolated, but complex, coordinated, stereotypical movements. These fields also provide regulation of smooth muscle tone and plastic muscle tone through subcortical structures.

The second frontal gyrus, occipital, and superior parietal regions also take part in the implementation of motor functions.

The motor area of the cortex, like no other, has a large number of connections with other analyzers, which apparently determines the presence of a significant number of polysensory neurons in it.

All sensory projection areas and motor areas of the cortex occupy less than 20% of the surface of the cerebral cortex. The rest is associative areas. Each associative area of the cortex is connected by powerful connections with several projection areas. In associative areas, multimodal information is integrated, allowing for awareness of incoming information and complex behavioral acts. Association areas of the human brain are most pronounced in the frontal, parietal and temporal lobes.

Each projection area of the cortex is surrounded by association areas. Neurons in these areas are capable of perceiving multimodal information and have great learning abilities. The polysensory nature of neurons in the associative area of the cortex ensures their participation in combining incoming information and ensuring the interaction of sensory and motor areas of the cortex.

Thus, in the parietal associative area of the cortex, subjective ideas about the surrounding space and our body are formed. This becomes possible due to the comparison of somatosensory, proprioceptive and visual information. Frontal associative fields have connections with the limbic part of the brain and are involved in organizing action programs during the implementation of complex behavioral acts, taking into account their emotional coloring.

The first and most characteristic feature of the associative areas of the cortex is the ability of their neurons to perceive multimodal information, and not primary, but already processed information is received here, highlighting the biological significance of the signal. This allows you to formulate a program of targeted behavioral act.

The second feature of the associative area of the cortex is the ability to undergo plastic rearrangements depending on the significance of incoming information.

The third feature of the associative area of the cortex is manifested in the long-term storage of traces of sensory influences. Destruction of the associative area leads to pronounced impairments in learning and memory.

The distribution of functions across brain regions is not absolute. It has been established that almost all areas of the brain have polysensory neurons, which to a certain extent can take on the function of damaged modality-specific neurons. This makes it possible to compensate for damage to brain structures during those periods of childhood when the damaged function is not yet firmly fixed in the structure of the nervous tissue.

An important feature of the cerebral cortex is its ability to retain traces of excitation for a long time. This property gives the cortex exceptional importance in the mechanisms of associative processing and storage of information and accumulation of knowledge.

Interhemivarial asymmetry. There are anatomical and functional differences between the right and left hemispheres of the brain. As a result of neuropsychological studies, it was found that the cerebral hemispheres differ in functional specialization. Currently, it is considered proven that two types of thinking are associated with the functions of the left and right hemispheres in humans - abstract-logical and spatial-figurative, and they are designated by different terms:

- verbal and non-verbal (since abstract-logical thinking, unlike figurative thinking, is based on speech activity);
- analytical and synthetic (since with the help of logical thinking, objects and phenomena are analyzed, while imaginative thinking ensures the integrity of perception);
- successive and simultaneous (since with the help of logical thinking a number of sequential operations are carried out, while imaginative thinking has the ability to simultaneously perceive and evaluate an object).

It is also known that right-hemisphere thinking, which creates a specific spatial-imaginative context, is crucial for creativity. Thus, with organic damage to the left hemisphere of the brain in artists and musicians, their artistic abilities practically do not suffer, and sometimes the level of aesthetic expressiveness of creativity even increases. Damages to the right hemisphere can lead to a complete loss of creativity. At the same time, the issues of the relationship between the leading hand and the leading speech hemisphere, the connection of interhemispheric asymmetry with the emotional sphere and such mental cognitive processes as memory and imagination still remain unclear.

The leading factor in the formation of interhemispheric asymmetry is considered to be genetic predisposition, but in some cases it can be caused by intravital factors, for example, as a result of mild brain damage during childbirth, leading to a temporary predominance of the functional activity of one or another hemisphere. It is generally accepted that interhemispheric asymmetry manifests itself not only in the preference for the right or left hand, but also in the holistic structural and functional organization of brain activity. In the process of ontogenesis, internoluspheric asymmetry is formed in the first years of life and manifests itself primarily in the child’s selection of the leading hand. This occurs, as a rule, at the age of 2-3 years, although in some cases unformed lateralization (lack of a clear preference for one or another hand in actions) can persist up to 6-7 years.

It should be noted that, despite the rich factual material and actively ongoing research, a single theory that explains all aspects of interhemispheric functional asymmetry still does not exist. However, there is no doubt about the expediency of functional asymmetry in the complex organization of the functions of the cerebral cortex, which consists in increasing the diversity of adaptive reactions and development opportunities of human individuals and all of humanity as a biological species.

The dominant hand is the hand most capable of precise, differentiated movements.
The leading hemisphere is considered to be the hemisphere in which the speech centers are localized. Most often this is the left hemisphere in right-handed people and the right hemisphere in left-handed people.

The brain is the main controlling organ of the central nervous system (CNS); a large number of specialists in various fields, such as psychiatry, medicine, psychology and neurophysiology, have been working on the study of its structure and functions for more than 100 years. Despite a good study of its structure and components, there are still many questions about the work and processes that take place every second.

The brain belongs to the central nervous system and is located in the cavity of the cranium. Outside it is reliably protected by the bones of the skull, and inside it is enclosed in 3 shells: soft, arachnoid and hard. Between these membranes, cerebrospinal fluid circulates - cerebrospinal fluid, which serves as a shock absorber and prevents shaking of this organ in case of minor injuries.

The human brain is a system consisting of interconnected sections, each part of which is responsible for performing specific tasks.

To understand its functioning, it is not enough to briefly describe the brain; therefore, to understand how it works, you first need to study its structure in detail.

What is the brain responsible for?

This organ, like the spinal cord, belongs to the central nervous system and plays the role of an intermediary between the environment and the human body. With its help, self-control, reproduction and memorization of information, imaginative and associative thinking, and other cognitive psychological processes are carried out.

According to the teachings of Academician Pavlov, the formation of thoughts is a function of the brain, namely the cerebral cortex, which is the highest organs of nervous activity. The cerebellum, limbic system and some areas of the cerebral cortex are responsible for different types of memory, but since memory varies, it is impossible to single out a specific area responsible for this function.

It is responsible for managing the vegetative vital functions of the body: breathing, digestion, endocrine and excretory systems, control of body temperature.

To answer the question of what function the brain performs, first we should roughly divide it into sections.

Experts distinguish 3 main parts of the brain: the anterior, middle and rhomboid (posterior) sections.

The anterior one performs higher psychiatric functions, such as the ability to cognition, the emotional component of a person’s character, his temperament and complex reflex processes.
The middle one is responsible for sensory functions and processing incoming information from the organs of hearing, vision and touch. The centers located in it are able to regulate the degree of pain, since the gray matter, under certain conditions, is capable of producing endogenous opiates that increase or decrease the pain threshold. It also plays the role of a conductor between the cortex and the underlying sections. This part controls the body through various innate reflexes.
The rhomboid or posterior section is responsible for muscle tone and coordination of the body in space. Through it, targeted movement of various muscle groups is carried out.

The structure of the brain cannot be simply briefly described, since each of its parts includes several sections, each of which performs specific functions.

What does the human brain look like?

Brain anatomy is a relatively young science, as it was banned for a long time due to laws prohibiting the dissection and examination of human organs and the head.

The study of the topographic anatomy of the brain in the head area is necessary for accurate diagnosis and successful treatment of various topographic anatomical disorders, for example: skull injuries, vascular and oncological diseases. To imagine what a human GM looks like, you first need to study their appearance.

In appearance, the GM is a yellowish gelatinous mass enclosed in a protective shell, like all organs of the human body, they consist of 80% water.

The large hemispheres occupy almost the volume of this organ. They are covered with gray matter or cortex - the highest organ of human neuropsychic activity, and inside - with white matter, consisting of processes of nerve endings. The surface of the hemispheres has a complex pattern, due to convolutions going in different directions and ridges between them. Based on these convolutions, it is customary to divide them into several sections. It is known that each of the parts performs specific tasks.

In order to understand what a person's brain looks like, it is not enough to examine its appearance. There are several study methods that help to study the brain from the inside in section.

Sagittal section. It is a longitudinal incision that passes through the center of a person’s head and divides it into 2 parts. It is the most informative research method; it is used to diagnose various diseases of this organ.
The frontal section of the brain looks like a cross section of the large lobes and allows you to see the fornix, hippocampus and corpus callosum, as well as the hypothalamus and thalamus, which control the vital functions of the body.
Horizontal section. Allows you to examine the structure of this organ in the horizontal plane.

The anatomy of the brain, as well as the anatomy of the human head and neck, is a rather difficult subject to study for a number of reasons, including the fact that their description requires studying a large amount of material and having good clinical training.

How does the human brain work?

Scientists all over the world study the brain, its structure and the functions it performs. Over the past few years, many important discoveries have been made, however, this part of the body remains incompletely studied. This phenomenon is explained by the difficulty of studying the structure and functions of the brain separately from the skull.

In turn, the structure of the brain structures determines the functions that its departments perform.

It is known that this organ consists of nerve cells (neurons) connected to each other by bundles of filamentous processes, but how their interaction occurs simultaneously as a single system is still unclear.

A diagram of the structure of the brain, based on the study of a sagittal section of the skull, will help to study the sections and membranes. In this figure you can see the cortex, the medial surface of the cerebral hemispheres, the structure of the trunk, cerebellum and corpus callosum, which consists of the splenium, trunk, genu and beak.

The brain is reliably protected externally by the bones of the skull, and internally by 3 meninges: the hard arachnoid and the soft. Each of them has its own device and performs specific tasks.

The deep soft membrane covers both the spinal cord and the brain, while it extends into all the cracks and grooves of the cerebral hemispheres, and in its thickness there are blood vessels that feed this organ.
The arachnoid membrane is separated from the first by a subarachnoid space filled with cerebrospinal fluid (cerebrospinal fluid), which also contains blood vessels. This shell consists of connective tissue, from which thread-like branching processes (cords) extend; they are woven into the soft shell and their number increases with age, thereby strengthening the connection. Between them. Villous outgrowths of the arachnoid membrane protrude into the lumen of the sinuses of the dura mater.
The hard shell, or pachymeninx, consists of connective tissue and has 2 surfaces: the upper one, saturated with blood vessels, and the inner one, which is smooth and shiny. This side of the pachymeninx is adjacent to the medulla, and the outer side is adjacent to the cranium. Between the dura mater and the arachnoid membrane there is a narrow space filled with a small amount of liquid.

About 20% of the total blood volume circulates in the brain of a healthy person, which enters through the posterior cerebral arteries.

The brain can be visually divided into 3 main parts: 2 cerebral hemispheres, brainstem and cerebellum.

Gray matter forms the cortex and covers the surface of the cerebral hemispheres, and a small amount of it in the form of nuclei is located in the medulla oblongata.

In all parts of the brain there are ventricles, in the cavities of which the cerebrospinal fluid that is formed in them moves. In this case, fluid from the 4th ventricle enters the subarachnoid space and washes it.

Brain development begins while the fetus is in utero, and it is finally formed by the age of 25.

Main parts of the brain

What the brain is made of and you can study the composition of the brain of an ordinary person using pictures. The structure of the human brain can be viewed in several ways.

The first divides it into the components that make up the brain:

The terminal one is represented by 2 cerebral hemispheres, united by the corpus callosum;
intermediate;
average;
oblong;
the posterior one borders on the medulla oblongata, and the cerebellum and pons extend from it.

It is also possible to distinguish the basic composition of the human brain, namely, it includes 3 large structures that begin to develop during embryonic development:

diamond-shaped;
average;
forebrain.

In some textbooks, the cerebral cortex is usually divided into sections, so that each of them plays a specific role in the higher nervous system. Accordingly, the following parts of the forebrain are distinguished: frontal, temporal, parietal and occipital zones.

Large hemispheres

First, let's look at the structure of the cerebral hemispheres.

The human telencephalon controls all vital processes and is divided by a central sulcus into 2 cerebral hemispheres, covered on the outside with cortex or gray matter, and on the inside consisting of white matter. Between themselves, in the depths of the central gyrus, they are united by the corpus callosum, which serves as a connecting and transmitting link between other departments.

The structure of gray matter is complex and, depending on the area, consists of 3 or 6 layers of cells.

Each lobe is responsible for performing certain functions and coordinating the movement of the limbs on its part, for example, the right part processes non-verbal information and is responsible for spatial orientation, while the left one specializes in mental activity.

In each hemisphere, experts distinguish 4 zones: frontal, occipital, parietal and temporal, they perform certain tasks. In particular, the parietal cortex of the cerebral hemispheres is responsible for visual function.

The science that studies the detailed structure of the cerebral cortex is called architectonics.

Medulla

This section is part of the brain stem and serves as a link between the spinal cord and the terminal pons. Since it is a transitional element, it combines the features of the spinal cord and the structural features of the brain. The white matter of this section is represented by nerve fibers, and the gray matter in the form of nuclei:

The olive nucleus, a complementary element of the cerebellum, is responsible for balance;
The reticular formation connects all sense organs with the medulla oblongata and is partially responsible for the functioning of some parts of the nervous system;
The nuclei of the nerves of the skull, these include: glossopharyngeal, vagus, accessory, hypoglossal nerves;
The nuclei of respiration and circulation, which are connected with the nuclei of the vagus nerve.

This internal structure is due to the functions of the brain stem.

It is responsible for the body's defense reactions and regulates vital processes such as heartbeat and blood circulation, so damage to this component leads to instant death.

Pons

The brain includes the pons, which serves as a link between the cerebral cortex, the cerebellum and the spinal cord. It consists of nerve fibers and gray matter, in addition, the bridge serves as a conductor for the main artery that supplies the brain.

Midbrain

This part has a complex structure and consists of the roof, the midbrain part of the tegmentum, the Sylvian aqueduct and the legs. In the lower part it borders on the posterior section, namely the pons and cerebellum, and at the top there is the diencephalon, connected to the telencephalon.

The roof consists of 4 hills, inside of which nuclei are located; they serve as centers for the perception of information received from the eyes and organs of hearing. Thus, this part is part of the area responsible for receiving information and belongs to the ancient structures that make up the structure of the human brain.

Cerebellum

The cerebellum occupies almost the entire back part and repeats the basic principles of the structure of the human brain, that is, it consists of 2 hemispheres and an unpaired formation connecting them. The surface of the cerebellar lobules is covered with gray matter, and inside they consist of white matter; in addition, the gray matter in the thickness of the hemispheres forms 2 nuclei. The white matter, with the help of three pairs of legs, connects the cerebellum with the brain stem and spinal cord.

This brain center is responsible for coordinating and regulating the motor activity of human muscles. It also helps to maintain a certain posture in the surrounding space. Responsible for muscle memory.

Bark

The structure of the cerebral cortex has been studied quite well. Thus, it is a complex layered structure 3-5 mm thick, which covers the white matter of the cerebral hemispheres.

The cortex is formed by neurons with bundles of filamentous processes, afferent and efferent nerve fibers, and glia (provide impulse transmission). It contains 6 layers, different in structure:

grainy;
molecular;
external pyramidal;
internal granular;
internal pyramidal;
the last layer consists of spindle-shaped cells.

It occupies about half the volume of the hemispheres, and its area in a healthy person is about 2200 square meters. cm. The surface of the bark is dotted with grooves, in the depths of which a third of its entire area lies. The size and shape of the grooves in both hemispheres are strictly individual.

The cortex was formed relatively recently, but is the center of the entire higher nervous system. Experts identify several parts in its composition:

neocortex (new) main part covers more than 95%;
archicortex (old) – about 2%;
paleocortex (ancient) – 0.6%;
intermediate cortex, occupies 1.6% of the total cortex.

It is known that the localization of functions in the cortex depends on the location of nerve cells that capture one of the types of signals. Therefore, there are 3 main areas of perception:

Sensory.
Motor.
Associative.

The last region occupies more than 70% of the cortex, and its central purpose is to coordinate the activity of the first two zones. It is also responsible for receiving and processing data from the sensory area, and purposeful behavior caused by this information.

Between the cerebral cortex and the medulla oblongata there is the subcortex, or in other words, subcortical structures. It includes the visual thalamus, hypothalamus, limbic system and other nerve nodes.

Main functions of brain parts

The main functions of the brain are to process data received from the environment, as well as control the movements of the human body and his mental activity. Each part of the brain is responsible for performing specific tasks.

The medulla oblongata controls the body's protective functions, such as blinking, sneezing, coughing and vomiting. It also controls other vital reflex processes - breathing, secretion of saliva and gastric juice, swallowing.

With the help of the Varoliev bridge, coordinated movement of the eyes and facial wrinkles is carried out.

The cerebellum controls the motor and coordination activity of the body.

The midbrain is represented by the peduncle and quadrigeminal (two auditory and two visual hillocks). With its help, orientation in space, hearing and clarity of vision are achieved, and is responsible for the muscles of the eyes. Responsible for the reflexive turn of the head towards the stimulus.

The diencephalon consists of several parts:

The thalamus is responsible for the formation of feelings, such as pain or taste. In addition, he is in charge of tactile, auditory, olfactory sensations and rhythms of human life;
The epithalamus consists of the pineal gland, which controls circadian biological rhythms, dividing daylight into the time of wakefulness and the time of healthy sleep. Has the ability to detect light waves through the bones of the skull, depending on their intensity, produces the corresponding hormones and controls metabolic processes in the human body;
The hypothalamus is responsible for the functioning of the heart muscles, normalizing body temperature and blood pressure. With its help, a signal is given to release stress hormones. Responsible for feelings of hunger, thirst, pleasure and sexuality.

The posterior lobe of the pituitary gland is located in the hypothalamus and is responsible for the production of hormones on which puberty and the functioning of the human reproductive system depend.

Each hemisphere is responsible for performing its own specific tasks. For example, the right cerebral hemisphere accumulates data about the environment and experience of communicating with it. Controls the movement of the limbs on the right side.

The left cerebral hemisphere contains the speech center, which is responsible for human speech; it also controls analytical and computational activities, and abstract thinking is formed in its cortex. Similarly, the right side controls the movement of the limbs on its side.

The structure and function of the cerebral cortex directly depend on each other, so the gyri conditionally divide it into several parts, each of which performs certain operations:

temporal lobe, controls hearing and charisma;
the occipital part regulates vision;
touch and taste are formed in the parietal;
The frontal parts are responsible for speech, movement and complex thought processes.

The limbic system consists of the olfactory centers and the hippocampus, which is responsible for adapting the body to changes and regulating the emotional component of the body. It creates lasting memories by associating sounds and smells with a specific period of time during which sensory shocks occurred.

In addition, it controls restful sleep, storage of data in short-term and long-term memory, intellectual activity, control of the endocrine and autonomic nervous system, and participates in the formation of the reproductive instinct.

How does the human brain work?

The work of the human brain does not stop even in sleep; it is known that people in a coma also have some parts functioning, as evidenced by their stories.

The main work of this organ is carried out with the help of the cerebral hemispheres, each of which is responsible for a specific ability. It has been noted that the hemispheres are unequal in size and function - the right side is responsible for visualization and creative thinking, usually larger than the left side, responsible for logic and technical thinking.

It is known that men have a larger brain mass than women, but this feature does not affect mental abilities. For example, Einstein's figure was below average, but his parietal area, which is responsible for cognition and the creation of images, was large, which allowed the scientist to develop the theory of relativity.

Some people are endowed with super abilities, this is also the merit of this organ. These features manifest themselves in high speed of writing or reading, photographic memory and other anomalies.

One way or another, the activity of this organ is of great importance in the conscious control of the human body, and the presence of the cortex distinguishes humans from other mammals.

What, according to scientists, constantly arises in the human brain

Experts who study the psychological capabilities of the brain believe that the performance of cognitive and mental functions occurs as a result of biochemical currents, however, this theory is currently being questioned because this organ is a biological object and the principle of mechanical action does not allow us to fully understand its nature.

The brain is a kind of steering wheel of the whole organism, performing a huge number of tasks every day.

The anatomical and physiological features of the structure of the brain have been the subject of study for many decades. It is known that this organ occupies a special place in the structure of the human central nervous system (CNS), and its characteristics are different for each person, so it is impossible to find 2 people who think absolutely alike.

Video

The main regulator of the body's functioning is the brain. In this article we will briefly talk about the structure and functions of the parts of the human brain. Using this material, you can quickly and easily recall the topics covered in grade 8 and prepare additional information for the lesson.

general characteristics

The brain is one of the constituent organs of the central nervous system. Doctors are still studying it. It consists of 25 billion neurons, which are presented in the form of gray matter.

Rice. 1. Sections of the brain.

In addition, this organ of the nervous system is covered with the following types of membrane:

soft;
hard;
arachnoid (cerebrospinal fluid circulates in it - cerebrospinal fluid, which serves as a kind of shock absorber and protects against impacts).

The brains of men and women differ in their mass. In representatives of the stronger sex, its weight is 100 g more. However, mental development does not depend in any way on this indicator.

The functions of generator and impulse transmission are performed by neurons. There are ventricles (cavities) inside the brain, from which paired cranial nerves extend to different parts of the human body. There are a total of 12 such pairs in the body.

Structure

The main organ of the nervous system consists of three parts:

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two hemispheres;
trunk;
cerebellum.

It also has five departments:

final, constituting 80% of the mass;
intermediate;
rear;
average;
oblong.

Each section consists of a specific set of cells (white and gray matter).

White matter is presented in the form of nerve fibers, which can be of three types:

association - connect cortical areas in one hemisphere;
commissural - connect the two hemispheres;
projection - connect the cortex with the underlying formations.

Gray matter consists of neuron nuclei, their functions include the transmission of information.

Rice. 2. Lobes of the cerebral cortex.

The following table will help you understand in more detail the structure and functions of the brain:

Table “Structure and functions of the brain”

*Department*	*Structure*	*Functions*
Finite	Located from the occipital to the frontal bone. It consists of two hemispheres, which have many grooves and convolutions. On top they are covered with a bark consisting of lobes.	The right hemisphere is responsible for the left side of the body, and the left hemisphere is responsible for the right side. The temporal lobe of the cerebral cortex regulates hearing and smell, the occipital lobe regulates vision, the parietal lobe regulates taste and touch; frontal - speech, thinking, movement.
Intermediate	Consists of the hypothalamus and thalamus.	The thalamus is a mediator in the transmission of stimuli to the hemispheres and helps to adequately adapt to changes in the environment. The hypothalamus regulates the functioning of metabolic processes and endocrine glands. Manages the work of the cardiovascular and digestive systems. Regulates sleep and wakefulness, manages food and drink needs.
	It consists of the cerebellum and the pons, which is presented in the form of a white thick cushion located above the oblongata. The cerebellum is located behind the pons and has two hemispheres, the inferior and superior surfaces and the vermis.	This section provides a conductive function during the transmission of impulses. The cerebellum controls the coordination of movements.
	Located from the anterior edge of the bridge to the optic tracts.	Responsible for hidden vision, as well as the work of the orienting reflex, which ensures the body turns in the direction of the heard sharp noise.
Oblong	Presented as a continuation of the spinal cord.	Controls coordination of movements, balance, regulates metabolic processes, breathing, blood circulation. Controls the process of coughing and sneezing.

Rice. 3. Functions of parts of the brain.

The brainstem consists of the medulla oblongata, midbrain, diencephalon and pons. The trunk is the connecting link between the spinal and head sections of the central nervous system. Its functions include controlling articulate speech, heartbeat and breathing.

What have we learned?

The brain is a complex mechanism that controls the work of all internal systems of the body. It consists of five departments, each of which performs certain functions. Without the work of this part of the central nervous system, it is difficult to imagine the vital activity of the entire organism.

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