What is the telencephalon? Telencephalon (human anatomy)

In the course of evolution, the large (terminal) brain appeared later than other departments. Its size and mass are significantly larger than the other segments. The article will feature his photo. associated with the most complex manifestations of intellectual and mental activity. The organ has a rather complex structure. Next, we consider the structure of the telencephalon and its tasks.

Structure

The department in question includes two large segments. The hemispheres of the telencephalon are connected to each other through the corpus callosum. Between these segments there are also commissures: fornix, posterior and anterior. When considering the structure of the telencephalon, you should pay attention to the cavities in this section. They form the lateral ventricles: left and right. Each of them is located in the corresponding segment. One of the walls of the ventricles is formed by a transparent septum.

Segments

The hemisphere is covered on top by a layer of gray matter, which is formed by neurons of more than 50 varieties. Located under the cortex. It consists of myelinated fibers. Most of them connect the cortex with other centers and parts of the brain. The white matter contains clusters of gray - the basal ganglia. The cerebral hemispheres are attached to the cerebral peduncles and thalamus. The layer of white matter that separates the segments from the thalamus of the intermediate section is called the internal capsule. The hemispheres are separated from each other using a longitudinal fissure. Each segment has three surfaces - inferior, lateral and medial - and the same number of edges: temporal, occipital and frontal.

Surface of the raincoat element

In each segment, this part of the brain is divided into lobes by deep grooves and fissures. Primary refers to permanent formations organ. They are formed at the embryonic stage (in the fifth month). The largest fissures include longitudinal (separates the segments) and transverse (separates the cerebellum from the occipital lobes). Secondary and especially tertiary formations determine the individual relief of the segments (it can be seen in the photo). The human brain develops not only during the prenatal period. For example, secondary and tertiary grooves are formed up to 7-8 years after birth. The relief that the telencephalon has, the location of permanent formations and large convolutions are similar in most people. Each segment has six lobes: limbic, insular, temporal, occipital, parietal and frontal.

Lateral surface

The telencephalon in this area includes the Rolandian (central) sulcus. With its help, the parietal and frontal lobes are separated. There is also a Sylvian (lateral) fissure on the surface. Through it, the parietal and frontal lobes are separated from the temporal lobe. A conventional line acts as the anterior-inferior border of the occipital region. It runs from the superior edge of the parieto-occipital sulcus. The line is directed towards the lower end of the hemisphere. lobe) is covered by areas of the temporal, parietal and frontal regions. It lies in the lateral furrow (in depth). Next to the corpus callosum on the medial side is the limbic lobe. It is separated from other areas by the cingulate groove.

Brain: anatomy. Frontal lobe

It contains the following elements:

• Precentral sulcus. The gyrus of the same name is located between it and the central recess.
• Frontal grooves (lower and upper). The first is divided into three zones: orbital (orbital), triangular (triangular), opercular (tegmental). Between the recesses lie the frontal gyri: superior, inferior and middle.
• Horizontal anterior sulcus and ascending branch.
• Frontal medial gyrus. It is separated from the limbic cingulate sulcus.
• Section of the cingulate gyrus.
• Orbital and olfactory grooves. They are located on the lower side in the frontal lobe. The olfactory sulcus contains elements of the same name: bulb, triangle and tract.
• Straight gyrus. It runs between the medial end of the hemisphere and the olfactory sulcus.

The anterior horn corresponds to the frontal lobe.

Tasks of cortical zones

Considering the telencephalon, the structure and functions of this organ, it is necessary to dwell in more detail on the activity of the parts of the frontal lobe:

Parietal lobe

It corresponds to the middle region of the lateral ventricle. The telencephalon in this area includes the postcentral gyrus and sulcus, the parietal lobules - superior and inferior. The precuneus runs behind the parietal lobe. The structure also contains the interparietal sulcus. In the lower region there are gyri - angular and supramarginal, as well as a section of the paracentral lobule.

Tasks of cortical zones in the parietal lobe

Describing the telencephalon, the structure and functions of this structure, it is necessary to highlight such centers as:

• Projection department of general sensitivity. This center is a skin analyzer and is represented by the cortex of the postcentral gyrus.
• Projection section of the body diagram. It corresponds to the edge of the intraparietal sulcus.
• Associative department of "stereognosy". It is represented by the core of recognition of objects by palpation. This center corresponds to the cortex of the parietal superior lobule.
• Associative department of "praxia". This center performs tasks of analyzing habitual, purposeful movements. It corresponds to the cortex of the supramarginal gyrus.
• The associative optical department of speech is a writing analyzer - the center of lexia. This zone corresponds to the cortex of the angular gyrus.

Brain: anatomy. Temporal lobe

On its lateral side there are two grooves: lower and upper. They, together with the lateral one, limit the convolutions. On the lower surface of the temporal lobe there is no clear boundary separating it from the posterior one. Near the lingual gyrus is the occipitotemporal gyrus. From above it is limited by the collateral groove of the limbic region, and laterally by the temporal occipital region. The lobe corresponds to the inferior horn of the lateral ventricle.

Tasks of cortical zones in the temporal region

• In the middle section of the superior gyrus, on its superior side, the cortical section is located. The posterior third of the gyrus includes the auditory speech zone. When this area is injured, the speaker's words are perceived as noise.
• The lower and middle region of the gyri contains the cortical center of the vestibular analyzer. If the functions of the telencephalon are impaired here, the ability to maintain balance when standing will be lost, and the sensitivity of the vestibular apparatus will decrease.

Island

It is located in the side and is limited by a circular groove. Presumably in this area, brain functions are manifested in the analysis of taste and olfactory sensations. In addition, the region's tasks likely include auditory speech perception and somatosensory information processing.

Limbic lobe

This area is located on the medial surface of the hemispheres. It consists of the cingulate, parahippocampal and dentate gyri, and the isthmus. The groove of the corpus callosum acts as one of the boundaries of the lobe. As it descends, it passes into the recess of the hippocampus. Under this groove, in turn, in the inferior horn cavity of the lateral ventricle there is a gyrus. Above the depression in the corpus callosum lies another border. This line - the cingulate sulcus - separates the cingulate gyrus and delimits the parietal and frontal lobes from the limbic lobe. With the help of the isthmus, the cingulate gyrus passes into the parahippocampal gyrus. The last one ends with a hook.

Department tasks

The parahippocampal and cingulate gyri belong directly to the limbic system. Brain functions in this area are associated with the control of a complex of psycho-emotional, behavioral and autonomic reactions to stimuli external environment. The parahippocampal zone and the hook include the cortical region of the olfactory and the hippocampus. At the same time, the hippocampus is associated with learning abilities, it determines the mechanisms of long-term and short-term memory.

Occipital region

On its lateral side there is a transverse groove. There is a wedge in the medial part. It is limited posteriorly by the calcarine groove, and in front by the parieto-occipital groove. The lingual gyrus is also prominent in the medial area. It is bounded above by the calcarine groove and below by the collateral groove. The occipital lobe corresponds to the posterior horn in the lateral ventricle.

Sections of the occipital region

In this zone there are such centers as:

• Projective visual. This segment is located in the cortex, which limits the calcarine groove.
• Associative visual. The center is located in the dorsal cortex.

White matter

It is presented in the form of numerous fibers. They are divided into three groups:

• Projection. This category is represented by bundles of efferent and afferent fibers. Through them, there are connections between the projection centers and the basal, stem and spinal nuclei.
• Associative. These fibers provide connection to the cortical areas within the boundaries of one hemisphere. They are divided into short and long.
• Commissural. These elements connect the cortical zones of the opposite hemispheres. Commissural formations are considered: the corpus callosum, posterior and anterior commissure and commissure of the fornix.

Bark

Its main part is represented by the neocortex. This is the “new cortex,” which phylogenetically is the most recent brain formation. The neocortex occupies about 95.9% of the surface. The rest of the brain is represented as:

• Old cortex - archiocortex. It is located in an area called the horn of ammon, or the hippocampus.
• Ancient crust - paleocortex. This formation occupies an area in the frontal lobe next to the olfactory bulbs.
• Mesocortex. These are small areas adjacent to the paleocortex.

Old and ancient bark appears in vertebrates earlier than others. These formations are distinguished by a relatively primitive internal structure.

Lecture 8

The telencephalon, or cerebrum, in the process of evolution arose later than other parts of the brain. In its mass and size, it significantly exceeds all other parts of the brain and is directly related to the most complex manifestations of human mental and intellectual activity.

The telencephalon consists of two cerebral hemispheres connected to each other by the corpus callosum, the anterior and posterior commissures and the commissure of the fornix. The telencephalon cavities form the right and left lateral ventricles of the brain, each of which is located in the corresponding hemisphere. The medial wall of each lateral ventricle in the rostral region is formed by a transparent septum.

The cerebral hemispheres are covered on top by the cerebral cortex - a layer of gray matter formed by neurons of more than fifty varieties. Under the cerebral cortex in the cerebral hemispheres there is white matter, consisting of myelinated fibers, most of which connect the cortex with other parts and centers of the brain. In the thickness of the white matter of the hemispheres there are accumulations of gray matter - the basal ganglia.

The thalamus and cerebral peduncles are fused with the cerebral hemispheres. The layer of white matter that borders the hemispheres from the thalamus of the diencephalon is called the internal capsule.

The right and left hemispheres of the brain are separated from each other by a longitudinal fissure. In each hemisphere, there are three surfaces - lateral, medial and inferior, as well as three edges - superior, medial and inferior, and three poles - frontal, occipital and temporal.

The surface of the mantle of each hemisphere is divided by slits and grooves into lobes, lobules and convolutions. The fissures and primary sulci are deep and belong to the permanent formations of the brain. They appear in the 5th month of intrauterine development and divide the hemispheres into lobes. The largest fissures are the longitudinal fissure of the brain, which separates the hemispheres from each other, and the transverse fissure, which separates the cerebellum from the occipital lobes. Secondary and especially tertiary grooves determine the individual surface relief of the hemispheres. Their formation occurs from birth to 7-8 years.

For most people, the main relief - the location of deep permanent grooves and large convolutions - is of a similar nature. Large fissures and fissures divide each hemisphere into 6 lobes: frontal, parietal, occipital, temporal, insular and limbic.

On the lateral surface of the hemisphere, there is a central (Rolandian) fissure, which separates the frontal lobe from the parietal lobe, and a lateral (Sylvian) fissure, which separates the temporal lobe from the frontal and parietal lobes. The parietal lobe is bounded from the occipital parieto-occipital sulcus. The anteroinferior border of the occipital lobe is a conventional line drawn from the upper end of the parieto-occipital sulcus down to the lower edge of the hemisphere. Deep in the lateral sulcus is the insular lobe (or insula). This lobe is covered by parts of the frontal, parietal and temporal lobes. On the medial surface of the hemisphere, next to the corpus callosum, is its limbic lobe, separated from the other lobes by the cingulate groove.

THE FRONTAL LOBE contains the following sulci and gyri:

1 Precentral sulcus; between the precentral and central sulcus is the precentral gyrus;

2. The superior and inferior frontal sulci, between which the superior,

middle and inferior frontal gyri. The inferior frontal gyrus is divided into three parts: opercular (tegmental), triangular (triangular) and orbital (orbital).

3. Anterior horizontal sulcus and its ascending branch;

4. The medial frontal gyrus, separated from the limbic lobe by the cingulate sulcus;

5. Part of the cingulate cortex;

6. Olfactory and orbital grooves, located on the lower surface of the frontal lobe. The olfactory sulcus contains the olfactory bulb, olfactory tract and olfactory triangle.

7. Gyrus recta, located between the olfactory sulcus and the medial

edge of the hemisphere.

The frontal lobe corresponds to the anterior horn of the lateral ventricle.

Functional characteristics of the cortical zones of the frontal lobe. 1. In the area of ​​the precentral gyrus of the frontal lobe there is the cortical nucleus of the motor analyzer - the kinesthetic center. This area is also called the sensorimotor cortex. Some of the afferent fibers from the thalamus come here, carrying proprioceptive information from the muscles and joints of the body. Descending pathways to the brain stem and spinal cord also begin here, providing the possibility of conscious regulation of movements (pyramidal tracts). Damage to this area of ​​the cortex leads to paralysis of the opposite half of the body.

2. In the posterior third of the middle frontal gyrus lies the center of writing - the center of graphia, or the associative center of written characters. This zone of the cortex gives projections to the nuclei of the oculomotor cranial nerves, and also, through cortico-cortical connections, communicates with the center of vision in the occipital lobe and the control center for the muscles of the arms and neck in the precentral gyrus. Damage to this center leads to impaired writing skills under visual control (agraphia).

3. In the posterior third of the inferior frontal gyrus there is the speech motor center (Broca's center) - the center of speech articulation. It has pronounced functional asymmetry. When it is destroyed in the right hemisphere, the ability to regulate timbre and intonation is lost, speech becomes monotonous. When the speech motor center on the left is destroyed, speech articulation is irreversibly impaired, up to the loss of the ability to articulate speech (aphasia) and singing (amusia). With partial violations, agrammatism may be observed - the inability to form phrases correctly.

4. In the region of the anterior and middle third of the upper, middle and partially inferior frontal gyri there is an extensive anterior associative zone of the cortex, which programs complex forms of behavior (planning different forms activities, decision making, analysis of the results obtained, volitional reinforcement of activities, correction of the motivational hierarchy). The area of ​​the frontal pole and medial frontal gyrus is associated with the regulation of the activity of emotiogenic areas of the brain included in the limbic system, and is related to the control of psycho-emotional states. Disturbances in this area of ​​the brain can lead to changes in what is commonly called “personality structure” and will affect a person’s character, his value orientations, and intellectual activity.

The orbital region contains the centers of the olfactory analyzer and is closely connected anatomically and functionally with the limbic system of the brain.

5. In the anterior part of the middle frontal gyrus there is a center for combined rotation of the head and eyes.

PARIETAL LOBE. The structure of the parietal lobe includes the postcentral gyrus, postcentral sulcus, interparietal sulcus, superior and inferior parietal lobules; in the inferior parietal lobule - the supramarginal and angular gyri, the posterior part of the paracentral lobule; behind it lies the precuneus; parieto-occipital and subparietal sulci. The parietal lobe corresponds to the central part of the lateral ventricle.

Functional characteristics of the cortical zones of the parietal lobe. The cortical areas of the parietal lobe contain the following centers:

1. Projection center of general sensitivity - skin analyzer of general

sensitivity (tactile, pain, temperature and conscious proprioceptive) - the cortex of the postcentral gyrus.

2. The projection center of the body diagram is the edge of the intraparietal sulcus.

3. Associative center of “stereognosia” - the core of the skin recognition analyzer

objects to the touch - the cortex of the superior parietal lobule.

4. Associative center of “praxia” - analyzer of purposeful habitual

movements (playing the piano, working on a typewriter) - supramarginal cortex

convolutions.

5. Associative optical speech center - visual analyzer of written language

speech - center of lexia (Dejerine) - cortex of the angular gyrus.

TEMPORAL LOBE. In the region of the temporal lobe, on its lateral surface, the superior and inferior temporal sulci are distinguished. These grooves and the lateral sulcus are limited by the superior, middle, and inferior temporal gyri.

On the lower surface, the temporal lobe does not have clear boundaries with the occipital lobe. Next to the lingual gyrus is the lateral occipito-umoral gyrus of the temporal lobe, which is bounded above by the collateral sulcus from the limbic lobe, and laterally by the occipital temporal sulcus. The temporal lobe corresponds to the inferior horn of the lateral ventricle.

Functional characteristics of the cortical zones of the temporal lobe.

1. In the area of ​​the middle part of the superior temporal gyrus, on its upper surface, there is the cortical center of the auditory analyzer. Its damage leads to deafness. The auditory speech center (Wernicke's center) lies in the posterior third of the superior temporal gyrus. Injuries to this area lead to the inability to understand spoken language: it is perceived as noise.

2. In the area of ​​the middle and inferior temporal gyri there is a cortical representation of the vestibular analyzer. Damage to this area leads to imbalance when standing and decreased sensitivity of the vestibular system.

INSALE LOBE (ISLANK). The insular lobe is located deep in the lateral sulcus. The islet is bounded by a circular groove.

Functional characteristics of the cortical zones of the insula. It is believed that the insula is related to the analysis of olfactory and taste sensations, as well as to the processing of somatosensory information and auditory perception of speech.

LIMBIC LOBE. This lobe is located on the medial surface of the hemisphere. It includes the cingulate gyrus, isthmus, dentate and parahippocampal gyri. One of the boundaries of this lobe is the groove of the corpus callosum. This groove, descending, continues into the hippocampal groove. Under the hippocampal sulcus in the cavity of the inferior horn of the lateral ventricle is the hippocampal gyrus, or hippocampus.

Above the sulcus of the corpus callosum there is another boundary of the limbic lobe - the cingulate sulcus, which separates the cingulate gyrus. The cingulate sulcus borders the limbic lobe from the frontal and parietal lobes. The cingulate gyrus passes through the isthmus into the parahippocampal gyrus, which ends in the uncus.

Functional characteristics of the cortical zones of the limbic lobe. The cingulate and parahippocampal gyri are directly related to the limbic system of the brain. This system controls a complex of vegetative and behavioral psycho-emotional reactions to external environmental influences. The cortical representation of the gustatory and olfactory analyzer is located in the uncus and parahippocampal gyrus. At the same time, the hippocampus plays an important role in learning: the mechanisms of short-term and long-term memory are associated with it.

OCCIPITAL LOBE. On the lateral surface of the occipital lobe there is a transverse occipital groove. On the medial surface there are: a wedge, bounded in front by the parieto-occipital groove, and behind by the calcarine groove; lingual gyrus, bounded above by the calcarine groove and below by the collateral groove. The occipital lobe corresponds to the posterior horn of the lateral ventricle.

Functional characteristics of the cortical zones of the occipital lobe. The occipital lobe has the following centers:

The projection center of vision (nucleus of the visual analyzer) is located in the cortex bordering the calcarine sulcus.

The associative center of vision (visual memory analyzer) is located in the cortex of the dorsal surface of the occipital lobe.

WHITE MATTER OF THE HEMISPHERES OF THE BRAIN. The white matter of the cerebral hemispheres is represented by numerous fibers, which are divided into three groups:

1. Projection fibers – bundles of afferent and efferent fibers that connect the projection centers of the cerebral cortex with the basal ganglia, nuclei of the brainstem and spinal cord. Projection fibers form the internal capsule and fornix of the brain.

2. Association fibers connect areas of the cortex within one hemisphere. They are divided into short and long.

3. Commissural fibers connect areas of the cortex of the opposite hemispheres of the brain. Commissural formations include the corpus callosum, anterior commissure of the brain, commissure of the fornix, and posterior commissure of the brain.

STRUCTURE OF THE CEREBRAL CORTEX. The cerebral cortex is

a huge accumulation of neurons and glial cells. The thickness of the cortex ranges from 1.2 to 4.5 mm, and the surface area in an adult is from 1700 to 2200 sq. cm. In the cortex

According to various sources, the large brain contains from 10 to 14 billion neurons.

The main part of the cerebral cortex (95.9% of the entire surface of the hemispheres) is the neocortex - the new cortex. Phylogenetically, this is the most recent formation of the brain. The remaining 4.1% of the area is covered

1. old cortex - archiocortex, located in the temporal lobe, called the hippocampus, or Amon's horn;

2. ancient cortex - paleocortex, which occupies a section of the frontal lobe cortex near the olfactory bulbs;

3. Small zones adjacent to the paleocortex are called mesocortex - interstitial cortex.

Ancient and old bark appear earlier in the phylogeny of vertebrates and carry features of a relatively primitive internal structure. Main feature

These cortical areas are weakly stratified (divided into layers). For example, the hippocampal cortex has five cortical layers, while the dentate gyrus cortex has only three layers. The neurons that form these layers also have a more primitive structure compared to the neurons of the neocortex.

The layer-by-layer arrangement of neurons in the cortex is called cytoarchitecture. In the neocortex of the cerebral hemispheres, neurons are grouped into six to seven cortical layers:

I - external molecular, or pleximorphic;

II - external granular, or external granular;

III - external pyramidal, or ganglionic;

IV - internal granular, or internal granular;

V - internal pyramidal, or internal ganglionic;

VI and VII - layers of polymorphic neurons.

In each of the layers of the cortex, neurons of certain sizes and shapes predominate.

Layer one is poor in cells and contains mainly branches of the apical dendrites of pyramidal neurons of the underlying layers, as well as branching of the axons of neurons. Thanks to the molecular layer, intra- and interhemispheric connections are made between different areas of the cortex.

Layer two includes small pyramidal and stellate (granular) neurons, which provide partial processing of information and its transmission from the structures of the molecular layer to the underlying cortical layers. These neurons are also called interneurons or interneurons.

Granular neurons are also located in layer IV, where they process and transmit information from the endings of afferent fibers coming to the cortex and branching within layer IV to pyramidal neurons of layers III and V.

Layers III and V contain a large number of large pyramidal neurons, the axons of which provide different types intracortical, intercortical and cortical-subcortical connections. The fifth layer in the area of ​​the precentral gyrus contains the largest pyramidal neurons, which are called Betz pyramidal cells. In layers III and V, interneurons of various sizes and shapes are also found in large numbers (double-fascicle cells, long-axonal and short-axonal basket neurons, chandelier cells). Interneurons provide selective intracortical interactions between neurons of different types. This is necessary for:

Transmission of information between afferent fibers arriving in the cortex and

pyramidal neurons;

Exchange of information between neurons located in different cortical layers;

Exchange of information between centers located in different convolutions, lobes and hemispheres;

Storage and reproduction of information.

Long-term circulation of excitation in the cortex and in associated parts and centers of the brain with the participation of interneurons accompanies cognitive operations and others. higher forms mental activity. In the end, everything information processes, occurring in the structures of the brain, are integrative, systemic in nature and are mediated by many interneurons.

The lowest cortical layers VI and VII differ mainly in the density of cells in the section: layer VI is more densely cellular and contains larger neurons than layer VII. The lower layers are older in origin than the rest, and therefore contain polymorphic cells that differ in shape from the pyramidal neurons and interneurons of the overlying layers. Neurons of layers VI and VII provide U-shaped connections between the cortex in adjacent gyri and projectional corticothalamic connections.

In addition to cellular elements (neurons and glia), the gray matter of the cortex contains branching fibers of various origins. Among them, associative, commissural and projection fibers are distinguished. The layer-by-layer arrangement of fibers in the cortex is called myeloarchitecture.

MODULAR ORGANIZATION OF THE LARGE HEMISPHERES CORTEX. The cortical module (neural ensemble) is a group of neurons, as well as glial cells and blood vessels, specially located in space and functionally interconnected. This module ensures the processing and storage of incoming information in the cerebral cortex. It has the appearance of a discrete columnar block of cells with a diameter of 300-600 microns, covering all cortical layers in the vertical direction. Associated with the module is a certain set of afferent fibers that bring information, which it subjects to standard discrete processing, as well as a set of efferent fibers that deliver it to certain areas of the brain. Various modules of the cortex are closely connected to each other via interneurons and intracortical fibers. The principle of modular structural and functional organization is valid for all departments of the central nervous system.

Forebrain. In its development, the forebrain is associated with the olfactory receptor. As other analyzers emerge and improve, it grows and turns into a department of the central nervous system, which controls all the vital functions of the body. The forebrain consists of the telencephalon and diencephalon.

Telencephalon. In mammals, the cortex occupies most of the surface of the hemispheres, significant structural transformations occur in it, and six cellular layers are formed. The surface area of ​​the cerebral cortex is about 220 thousand mm2, it depends on the availability large quantity grooves and convolutions. Moreover, the convex parts of the gyri account for less than 1/3, and the lateral and lower walls of the grooves account for more than 2/3 of the entire area of ​​the cortex. In humans, more than 95% of the cortex is neocortex. In the process of evolution, not only does the brain grow and its structure become more complex, but also the ratio of individual lobes changes. The frontal lobes reach special development in humans; their surface makes up about 29% of the entire surface of the cortex, and their mass is more than 50% of the mass of the brain. The hemispheres of the cerebrum are separated from each other by the longitudinal fissure of the cerebrum, in the depth of which the corpus callosum, formed by white matter, connecting them can be seen.

Three edges (superior, inferior and medial) divide the hemispheres into three surfaces: superolateral, medial and inferior. Each hemisphere is divided into lobes. The central sulcus (Rolandova) separates the frontal lobe from the parietal lobe, the lateral sulcus (Sylvian sulcus) separates the temporal from the frontal and parietal, the parieto-occipital sulcus separates the parietal and occipital lobes. The insular lobe is located deep in the lateral sulcus. Smaller grooves divide the lobes into convolutions. U lower mammals the surface of the hemispheres is smooth (for example, marsupials, insectivores, rodents). The increasing complexity of the relief as evolution progresses is associated with the development of the crust. In the prenatal period, gyrification (formation of convolutions) gradually occurs. On the initially smooth cerebral cortex of the fetus, first-order grooves gradually appear: lateral - by the 4th month, parieto-occipital and central - by the 6th month; on the 7th-8th - less deep furrows of the second order, before birth and during the 1st month after it - furrows of a third of its order, shallow, characterized by individual variability and inconstancy. Superolateral surface of the cerebral hemisphere. Frontal lobe. A number of grooves divide it into gyri: almost parallel to the central sulcus, in front of it runs the precentral sulcus, which separates the pre-central gyrus. From the precentral sulcus, two grooves run forward more or less horizontally, separating the superior, middle and inferior frontal gyri. Parietal lobe. The postcentral sulcus separates the gyrus of the same name; The horizontal intraparietal sulcus separates the superior and inferior parietal lobules. Occipital lobe is divided into several convolutions by grooves, of which the most constant is the transverse occipital groove. Temporal lobe. Two longitudinal grooves - superior and inferior temporal - separate three temporal gyri: superior, middle

and bottom. Insula located in the depth of the lateral groove. A deep circular groove of the insula separates it from other parts of the hemisphere. Medial surface of the cerebral hemisphere. All of its lobes, except the insular lobe, take part in the formation of the medial surface of the cerebral hemisphere. The groove of the corpus callosum goes around it from above, separating the corpus callosum from the cingulate gyrus, goes down and forward and continues into the groove of the hippocampus. The cingulate groove runs above the cingulate gyrus, which begins anteriorly and inferiorly to the beak of the corpus callosum, rises upward, turns back, running parallel to the groove of the corpus callosum. At the level of its ridge, its marginal part extends upward from the cingulate sulcus, and the sulcus itself continues into the subparietal sulcus. The marginal part of the cingulate groove limits the pericentral lobule posteriorly, and the precuneus anteriorly. Inferiorly and posteriorly through the isthmus, the cingulate gyrus passes into the parahippocampal gyrus, which ends anteriorly with a hook and is bounded superiorly by the hippocampal sulcus. The cingulate gyrus, isthmus and parahippocampal gyrus are collectively called the vaulted gyrus. The dentate gyrus is located deep in the hippocampal sulcus. The medial surface of the occipital lobe is separated from the parietal lobe by the parieto-occipital sulcus. A calcarine groove runs from the posterior pole of the hemisphere to the isthmus of the vaulted gyrus, which limits the lingual gyrus above. Between the parieto-occipital groove in front and the calcarine groove below there is a wedge facing an acute angle anteriorly. Inferior surface of the cerebral hemisphere has the most difficult terrain. In front is the lower surface of the frontal lobe, behind it is the temporal pole and the lower surface of the temporal and occipital lobes, between which there is no clear boundary. On the bottom surface frontal lobe The olfactory groove runs parallel to the longitudinal fissure, to which the olfactory bulb and the olfactory tract, which continues into the olfactory triangle, are adjacent below. Between the longitudinal fissure and the olfactory sulcus there is a straight gyrus. Lateral to the olfactory sulcus lie the orbital gyri. The lingual gyrus of the occipital lobe is bounded by a collateral sulcus, which passes to the inferior surface of the temporal lobe, separating the parahippocampal and medial occipitotemporal gyri. Anterior to the collateral groove is the nasal groove, which bounds the anterior end of the parahippocampal gyrus - the uncus.

73 Structure of the cerebral cortex. The cerebral cortex is formed by gray matter, which lies along the periphery (on the surface) of the cerebral hemispheres. The thickness of the cortex in different parts of the hemispheres ranges from 1.3 to 5 mm. For the first time, Russian scientist V. A. Bets showed that the structure and relative position of neurons is not the same in different parts of the cortex, which determines the neurocytoarchitecture of the cortex. Cells of more or less the same structure are arranged in the form of separate layers (plates). In the neocortex, the cell bodies of neurons form six layers. The thickness of the layers, the nature of their boundaries, the size of cells, their number, etc. vary in different sections. The 1st - molecular - layer is located outside, it contains small multipolar associative neurons and many fibers - processes of neurons of the underlying layers. The 2nd layer - the outer granular layer - is formed by many small multipolar neurons. The 3rd - the widest, pyramidal layer contains pyramidal-shaped neurons, the bodies of which increase in the direction from top to bottom. The 4th layer, internal granular, is formed by small stellate-shaped neurons. In the 5th layer - the internal pyramidal layer, which is most well developed in the precentral gyrus, there are pyramidal cells discovered by V. A. Betz in 1874. These are very large nerve cells (up to 125 microns). In the 6th layer - polymorphic cells there are neurons various shapes and sizes (Fig. 186). The number of neurons in the cortex reaches 10-14 billion. In each cell layer, in addition nerve cells, nerve fibers are located. The structure and density of their occurrence is also different in different parts of the crust; Features of the distribution of fibers in the cerebral cortex are defined by the term “myeloarchitecture.” K. Brodman in 1903-1909 identified 52 cytoarchitectonic fields in the cortex. O. Vogt and C. Vogt (1919-1920), taking into account the fiber structure, described 150 myeloarchitectonic areas in the cerebral cortex. The Brain Institute of the USSR Academy of Medical Sciences created detailed maps cytoarchitectonic fields of the human cerebral cortex (I, N. Filimonov, S. A. Sarkisov).

Localization of functions in the cerebral cortex. In the cerebral cortex, all stimuli that come from the surrounding external and internal environment are analyzed. Largest number afferent impulses enter through the nuclei of the thalamus to the cells of the 3rd and 4th layers of the cerebral cortex. The cerebral cortex contains centers that regulate the performance of certain functions. I. P. Pavlov considered the cerebral cortex as a set of cortical ends of analyzers. The term “analyzer” refers to a complex complex of anatomical structures, which consists of a peripheral receptor (perceiving) apparatus, conductors of nerve impulses and a center. In the process of evolution, functions are localized in the cerebral cortex. The cortical end of the analyzers is not any strictly defined zone. In the cerebral cortex, a “core” of the sensory system and “scattered elements” are distinguished. The core is the area where the largest number cortical neurons, in which all structures of the peripheral receptor are accurately projected. Scattered elements are located near the nucleus and at varying distances from it. If the kernel implements higher analysis and synthesis, then in dispersed elements, is simpler. At the same time, the zones of “scattered elements” of various analyzers do not have clear boundaries and overlap each other. Let us consider the localization of the nuclei of some analyzers in accordance with the cytoarchitectonic maps of the Brain Institute of the USSR Academy of Medical Sciences. In the cortex of the postcentral gyrus and superior parietal lobule lie nuclei of the cortical analyzer of proprioceptive and general sensitivity(temperature, pain, tactile) of the opposite half of the body. In this case, the cortical ends of the sensitivity analyzer are located closer to the longitudinal fissure of the brain. the lower extremities and lower parts of the torso, and the receptor fields of the upper parts of the body and head are projected lowest at the lateral sulcus. Motor analyzer core located mainly in the precentral gyrus and paracentral lobule on the medial surface of the hemisphere (“motor cortex”). In the upper parts of the precentral gyrus and paracentral lobule, the motor centers of the muscles of the lower extremities and the lowermost parts of the body are located. In the lower part, near the lateral groove, there are centers that regulate the activity of the muscles of the face and head. The motor areas of each hemisphere are connected to the skeletal muscles of the opposite side of the body. The muscles of the limbs are connected in isolation to one of the hemispheres, the muscles of the trunk, larynx and pharynx are connected to the motor areas of both hemispheres. In both centers described, the size of the projection zones of various organs depends not on the size of the latter, but on their functional significance. Thus, the zone of the hand in the cerebral hemisphere cortex is much larger than the zones of the trunk and lower limbs combined. On the surface of the middle part of the superior temporal gyrus facing the insula there is auditory analyzer core. Conducting pathways from the hearing organ receptors on both the left and right sides approach each hemisphere. Visual analyzer core located on the medial surface of the occipital lobe of the cerebral hemisphere on both sides (“along the banks”) of the calcarine groove. The nucleus of the visual analyzer of the right hemisphere is connected by pathways with the lateral half of the retina of the right eye and the medial half of the retina of the left eye, the left - with the lateral half of the retina of the left eye and the medial half of the retina of the right eye.

Cortical end of the olfactory analyzer- this is a hook, as well as old and ancient bark. old bark located in the area hippocampus and dentate gyrus, ancient- in the region anterior perforated space, septum pellucidum and olfactory gyrus. Due to the close location of the nuclei of the olfactory and gustatory analyzers, the senses of smell and taste are closely related. The nuclei of the taste and olfactory analyzers of both hemispheres are connected by pathways with receptors on both the left and right sides.

The described cortical ends of the analyzers carry out the analysis and synthesis of signals coming from the external and internal environment of the body, constituting the first signal system of reality (I. P. Pavlov). Unlike the first, the second signaling system is found only in humans and is closely related to the development of articulate speech.

Human speech and thinking are carried out with the participation of the entire cortex. At the same time, in the human cerebral cortex there are zones that are centers of a number of special functions related to speech. Motor analyzers of oral and written speech are located in areas of the frontal lobe cortex adjacent to the precentral gyrus near the nucleus of the motor analyzer. Analyzers for visual and auditory speech perception are located near the cores of the vision and hearing analyzers. In this case, speech analyzers in right-handers are localized only in the left hemisphere, and in left-handers - only in the right.

74 Basal (subcortical central) nuclei and white matter of the telencephalon . In the thickness of the white matter of each cerebral hemisphere there are accumulations of gray matter, forming separate nuclei that lie closer to the base of the brain. These nuclei are called basal (subcortical central). These include the striatum, which in lower vertebrates constitutes the predominant mass of the hemispheres; fence and amygdala. The striatum consists of the caudate and lenticular nuclei. The caudate nucleus is located lateral and superior to the thalamus, being separated from it by the stria terminalis. The nucleus has a head located in the frontal lobe and protruding into the anterior horn of the lateral ventricle, a body lying under the parietal lobe, limiting the central part of the lateral ventricle on the lateral side, and a tail participating in the formation of the roof of the lower horn of the lateral ventricle. The lentil nucleus is located lateral to the caudate. A layer of white matter, the internal capsule, separates the lenticular nucleus from the caudate and from the thalamus. In the lenticular nucleus, the globus pallidus (medially) and the putamen (laterally) are distinguished. The outer capsule (a narrow strip of white matter) separates the shell from the enclosure. The nuclei of the striatum form the striopallidal system, which, in turn, belongs to the extrapyramidal system involved in the control of movements and the regulation of muscle tone.

The fence is located in the white matter of the hemisphere lateral to the lenticular nucleus between it and the insular cortex. The amygdala lies in the white matter of the temporal lobe of the hemisphere, 1.5-2 cm posterior to its temporal pole. The white matter of the hemisphere includes the internal capsule and fibers passing through the cerebral commissures (corpus callosum, anterior commissure, fornix commissure) and heading to the cortex and basal ganglia, fornix, as well as systems of fibers connecting areas of the cortex and subcortical centers within one half of the brain (hemisphere). The anterior end of the corpus callosum, its genu, the continuation of which is the beak, bends forward; rear - roller, rounded; the body is located between them. The beak passes below into the mentioned terminal plate. Under the corpus callosum lies the vault (also consisting of white matter) in the form of two arches connected in the middle, which converge in front, forming the columns of the vault, descending through the subtubercle into the mastoid bodies. At the back, the legs of the arch diverge and are connected to each other by adhesions. The peduncle, going down, becomes the fimbria, which reaches the lower horn of the lateral ventricle, where it joins the hippocampus. The lower surface of the corpus callosum in the middle fuses with the body of the fornix. Between the lower surface of the anterior half of the corpus callosum (including its knee and beak) and the columns of the fornix in the sagittal plane there are two plates of the transparent septum, limiting its narrow cavity.

75 Reticular formation is a collection of cells, cell clusters and nerve fibers located in the brain stem (medulla oblongata, pons and midbrain) and forming a network. The reticular formation is connected to all sense organs, motor and sensory areas of the cerebral cortex, the thalamus and hypothalamus, and the spinal cord. It regulates the level of excitability and tone of various parts of the central nervous system, including the cerebral cortex, and is involved in the regulation of the level of consciousness, emotions, sleep and wakefulness, autonomic functions, and purposeful movements.

On the medial and lower surfaces there are a number of formations related to limbic system. The limbic system includes the olfactory bulb, olfactory tract, olfactory triangle, anterior perforated substance, located on the lower surface of the frontal lobe (peripheral part of the olfactory brain), as well as the cingulate, parahippocampal (together with the hook) and dentate gyri. This receives sensory information from the olfactory structures, the fibers of which begin in the olfactory bulb. In addition, the function of zakl is in organizing the behavioral reactions of the individual in response to the influence of the external environment.

76 Diencephalon(diencephalon) located under the corpus callosum, consists of the thalamus, epithalamus, metathalamus and hypothalamus.

Thalamus(visual tubercle) - paired, ovoid, formed mainly by gray matter. Its medial and posterior surfaces are free, therefore clearly visible on a section of the brain, the anterior one is fused with the hypothalamus, the lateral one is adjacent to the internal capsule. The thalamus is the subcortical center of all types of sensitivity. The anterior end (anterior tubercle) of the thalamus is pointed, the posterior (cushion) is rounded. The medial surface of the right and left thalami, facing each other, form side walls the cavities of the diencephalon are the third ventricle, they are connected to each other by interthalamic fusion. Epithalamus includes the pineal gland, leashes and leash triangles. The pineal body, or pineal gland, which is an endocrine gland, is suspended, as it were, on two leashes, interconnected by a commissure and connected to the thalamus through triangles of leashes. The triangles of the leashes contain nuclei related to the olfactory analyzer.

Metathalamus formed by paired medial and lateral geniculate bodies lying behind each thalamus. The medial geniculate body is located behind the thalamic cushion; it is, along with the lower colliculi of the midbrain roof plate (quadrigeminal), the subcortical center of the auditory analyzer. The lateral one is located downward from the pillow; it, together with the upper colliculi of the roof plate, is the subcortical center of the visual analyzer. The nuclei of the geniculate bodies are connected with the cortical centers of the visual and auditory analyzers.

77 Hypothalamus, representing the ventral part of the diencephalon, located anterior to the cerebral peduncles and includes a number of structures that have different origins - the anteriorly located visual part is formed from the telencephalon (optic chiasm, optic tract, gray tubercle, infundibulum, neurohypophysis); from the intermediate - the olfactory part (mammillary bodies and the subthalamic region itself - the hypothalamus). The functional role of the hypothalamus is very large. It contains the centers of the autonomic part of the nervous system, the neurons of the hypothalamus secrete neurohormones (vasopressin and oxytocin), as well as factors that stimulate or inhibit the production of hormones by the pituitary gland. The hypothalamus is the center for the regulation of endocrine functions; it combines nervous and endocrine regulatory mechanisms into a common neuroendocrine system, coordinates nervous and hormonal mechanisms for regulating the functions of internal organs. The hypothalamus contains neurons of the usual type and neurosecretory cells. Both produce protein secretions and mediators, but in neurosecretory cells protein synthesis predominates, and neurosecret is released into the lymph and blood (B.V. Aleshin). These cells transform the nerve impulse into a neurohormonal one. The hypothalamus and the pituitary gland form a single functional complex, in which the former plays a regulatory and the latter an effector role. The hypothalamus has more than 30 pairs of nuclei. Large neurosecretory cells of the supraoptic and paraventricular nuclei of the anterior hypothalamic region produce neurosecretions of a peptide nature (the first is vasopressin, or antidiuretic hormone, the second is oxytocin), which enter the posterior lobe of the pituitary gland along the branches of the axons of the neurosecretory cells, from where they are carried by the blood. Small neurons of the nuclei of the medial hypothalamic zone (arcuate, gray tuberous, ventromedial, infundibular, previsual field) produce releasing factors, or liberins, as well as inhibitory factors, or statins, entering the adenohypophysis, which transmits these signals in the form of its tropic hormones to peripheral endocrine glands. Releasing factors promote the release of thyroid-, luteo-, corticotropin, prolactin, follitropin, somatotropin and melanotropin. Statins inhibit the release of the latter two hormones and prolactin. The medial hypothalamus contains neurons that perceive all changes occurring in the blood and cerebrospinal fluid (temperature, composition, hormone content, etc. ). The medial hypothalamus is also connected to the lateral hypothalamus. The latter does not have nuclei, but has bilateral connections with the overlying and underlying parts of the brain. The medial hypothalamus is a link between the nervous and endocrine systems. In recent years, enkephalins and endorphins (peptides), which have a morphine-like effect, have been isolated from the hypothalamus. They are believed to be involved in the regulation of behavior and vegetative processes. Anterior to the posterior perforated substance lie two small spherical mastoid bodies formed by gray matter covered with a thin layer of white. The nuclei of the mammillary bodies are the subcortical centers of the olfactory analyzer. Lower vertebrates do not have formed mammillary bodies; Mammals (before primates) have one body, and only primates have two bodies. Anterior to the mastoid bodies is a gray tubercle, which is limited in front by the optic chiasm and the optic tract; it is a thin plate of gray matter at the bottom of the third ventricle, which is extended downward and anteriorly and forms a funnel. Its end passes into the pituitary gland - an endocrine gland located in the pituitary fossa of the sella turcica. The optic chiasm, located in front of the gray tuberosity, continues anteriorly into the optic nerves, posteriorly and laterally into the optic tracts, which reach the right and left lateral geniculate bodies. The nuclei of the autonomic nervous system lie in the gray mound. They also influence a person's emotional reactions. The part of the diencephalon, located below the thalamus and separated from it by the hypothalamic groove, constitutes the hypothalamus itself. The coverings of the cerebral peduncles continue here, the red nuclei and the black substance of the midbrain end here. Diencephalon cavity - III ventricle(ventriculus tertius) is a narrow, slit-like space located in the sagittal plane, bounded laterally by the medial surfaces of the thalamus, below by the hypothalamus, in front by the columns of the fornix, the anterior commissure and the terminal plate, behind by the epithalamic (posterior) commissure, above by the fornix, above which the callosum is located body. The upper wall itself is formed by the vascular base of the third ventricle, in which its choroid plexus lies. The cavity of the third ventricle passes posteriorly into the midbrain aqueduct, and in front on the sides through the interventricular foramina communicates with the lateral ventricles.

78 Midbrain (mesencephalon). During evolution, the midbrain has undergone fewer changes than other parts of the brain. Its development is associated with the visual and auditory analyzers. The midbrain includes the cerebral peduncles and the roof of the midbrain. Brain stems- these are white rounded (rather thick) cords emerging from the pons and heading forward to the cerebral hemispheres. Between the legs below there is an interpeduncular fossa, at the bottom of which the posterior perforated substance is visible. The oculomotor nerve (III pair of cranial nerves) emerges from the groove on the medial surface of each peduncle. Each leg consists of a tire and a base, the border between them is a black substance. The color depends on the abundance of melanin in its nerve cells. The substantia nigra belongs to the extrapyramidal system, which is involved in maintaining muscle tone and automatically regulates muscle function. The base of the pedicle is formed by nerve fibers running from the cerebral cortex to the spinal and medulla oblongata and the pons. The tegmentum of the cerebral peduncles contains mainly ascending fibers heading to the thalamus, among which the nuclei lie. The largest are the red nuclei, from which the motor red nuclear-spinal cord tract begins. In addition, the reticular formation and the nucleus of the dorsal longitudinal fasciculus (intermediate nucleus) are located in the tegmentum. In the roof of the midbrain a roof plate (quadrigeminal) is distinguished, consisting of four whitish hillocks - two upper (subcortical centers of the visual analyzer) and two lower (subcortical centers of the auditory analyzer). The pineal body lies in the depression between the superior colliculi. Handles extend from each colliculus on the sides to the diencephalon: the handle of the superior colliculus goes to the lateral colliculus, and the handle of the lower colliculus goes to the medial geniculate body. The quadrigeminal region is a reflex center for various types of movements that occur mainly under the influence of visual and auditory stimuli. From the nuclei of these hillocks a conducting path originates, ending on the cells of the anterior horns of the spinal cord. Midbrain plumbing(Aqueduct of Sylvius) - a narrow canal that connects the III and IV ventricles, it is limited on top by the roof plate, the bottom is the tire of the cerebral peduncles, its length does not exceed 2 cm. Around the aqueduct there is a central gray matter, which contains the reticular formation, nuclei III and IV pairs of cranial nerves, as well as the paired accessory autonomic nucleus (Yakubovich), the unpaired median nucleus and the nucleus of the midbrain tract of the trigeminal nerve. Isthmus of the rhombencephalon(isthmus rhombencephali) is formed by the superior cerebellar peduncles, the superior medullary velum and the triangle of the lemniscus. The superior medullary velum is a thin plate located between the cerebellum at the top and the superior cerebellar peduncles at the sides. The latter, together with the velum, form the anterosuperior part of the roof of the fourth ventricle of the brain. The lemniscus triangle is bounded anteriorly by the manubrium of the inferior colliculus, superiorly and posteriorly by the superior cerebellar peduncle, and laterally by the lateral groove present on the outer surface of the cerebral peduncle. In the thickness of the loop triangle there is a lateral (auditory) loop, which is part of the auditory pathway.

79 Hindbrain

Bridge ( The pons) appears only in mammals in connection with the development of the brain cloak; in humans it reaches its greatest development. The bridge looks like a transversely thickened ridge, from the lateral side of which the middle cerebellar peduncles extend to the right and left. The posterior surface of the pons, covered by the cerebellum, participates in the formation of the rhomboid fossa, the anterior surface (adjacent to the base of the skull) borders the medulla oblongata below and the cerebral peduncles above. It is transversely striated due to the transverse direction of the fibers that go from the pontine nuclei to the middle cerebellar peduncles. On the anterior surface of the bridge along the midline there is a basilar groove located longitudinally, in which the artery of the same name passes. In a frontal section through the bridge, two of its parts are visible: the anterior (main basilar) and posterior (tegmental). The bridge consists of many nerve fibers that form pathways, among which are cellular clusters of the nucleus. The pathways of the anterior (basilar) part connect the cerebral cortex with the spinal cord and the cerebellar cortex. The bridge's own cores lie between the fibers. In the posterior part of the bridge (tegmentum) there are ascending pathways and partially descending ones, the reticular formation, the nuclei of the V, VI, VII, VIII pairs of cranial nerves are located. On the border between both parts of the bridge lies a trapezoidal body formed by the nuclei and transversely running fibers of the conductive path of the auditory analyzer.

80 Hindbrain(metencephalon). The hindbrain includes the ventrally located pons and the cerebellum lying behind the pons.

Cerebellum (cerebellum) plays a major role in maintaining body balance and coordination of movements. All vertebrates have a cerebellum, the development of which depends on the nature of the animal’s movements. The cerebellum reaches its greatest development in humans in connection with upright posture and the adaptation of the hand to work. In this regard, humans have highly developed hemispheres ( new part ) cerebellum. The two convex surfaces of the cerebellum - superior and inferior - are separated by its transverse posterior edge, under which runs a deep horizontal fissure. In the lateral sections, the horizontal groove originates at the place where its middle peduncles enter the cerebellum. In the cerebellum there are two hemispheres and an unpaired middle phylogenetically old part - the vermis. The size of the cerebellar hemispheres correlates with the size of the cerebral hemispheres and the pons. The surfaces of the hemispheres and the vermis are separated by transverse parallel grooves, between which there are narrow long leaves of the cerebellum. Due to this, its surface area in an adult is on average 850 cm2. The cerebellum is divided into anterior, posterior and floculonodular lobes, separated by deeper fissures. They are formed by the lobules of the cerebellum. The grooves of the cerebellum are continuous and pass from the vermis to the hemispheres, so each lobe of the vermis is connected with the right and left lobes of the hemispheres. Flocculi are the most isolated and phylogenetically oldest lobules of the hemispheres, which are adjacent on each side to the ventral surface of the middle cerebellar peduncle and are connected to the vermis node by the flocculus leg, which passes into the inferior medullary velum. The cerebellum consists of gray and white matter. The white matter (brain body), penetrating between the gray matter, seems to branch, forming white stripes, resembling the figure of a branching tree in the median section - the “tree of life” of the cerebellum. The cerebellar cortex consists of gray matter, 1-2.5 mm thick. In addition, in the thickness of the white matter there are accumulations of gray - paired nuclei: the largest, newest - the dentate nucleus, located laterally within the cerebellar hemisphere; medial to it is cork-shaped, even more medial is spherical, and the most medial is the tent core. Afferent and efferent fibers connecting the cerebellum with other parts form three pairs of cerebellar peduncles: the lower ones go to the medulla oblongata, the middle ones to the pons, the upper ones to the quadrigemulus. Each leaf (gyrus) of the cerebellum is a thin layer of white matter covered with cortex (gray matter). There are three layers in the cortex: the outer - molecular, the middle - layer of piriform neurons (ganglionic) and the inner - granular (Fig. 195). The molecular and granular layers contain mainly small neurons. Large piriform neurons (Purkinje cells) measuring up to 40 microns, located in the middle layer in one row, are efferent neurons of the cerebellar cortex. Their axons, extending from the base of the bodies, form the initial link of the efferent pathways. They are directed to the neurons of the cerebellar nuclei, and the dendrites are located in the superficial molecular layer. The remaining neurons of the cerebellar cortex are intercalary, associative, which transmit nerve impulses to piriform neurons. Thus, all nerve impulses entering the cerebellar cortex reach the piriform neurons. By the time of birth, the cerebellum is less developed than the telencephalon (especially the hemisphere), but in the first year of life it develops faster than other parts of the brain. A pronounced enlargement of the cerebellum is observed between the 5th and 11th months of life, when the child learns to sit and walk. The mass of the cerebellum of a newborn is about 20 g, at 3 months it doubles, at 5 months it increases 3 times, at the end of the 9th month - 4 times. Then the cerebellum grows more slowly, and by the age of 6 its weight reaches the lower limit of the adult norm (for boys - 142-150 g, for girls - 125-135 g). The mass of the cerebellum of an adult is 120-160 g.

81 Medulla oblongata (medulla oblongata) is a direct continuation of the spinal cord. Its lower boundary is considered to be the place of exit of the roots of the 1st cervical spinal nerve or the decussation of the pyramids, the upper is the posterior edge of the bridge, its length is about 25 mm, its shape approaches a truncated cone, “facing upward with its base. The anterior surface is divided by the anterior median fissure, along on the sides of which there are pyramids formed by bundles of nerve fibers of the pyramidal tracts, partially intersecting (the cross of the pyramids) in the depths of the described gap at the border with the spinal cord. Fibers of the pyramidal tracts connect the cerebral cortex with the nuclei of the cranial nerves and the anterior horns of the spinal cord. Pyramids are absent in the lower ones. vertebrates, are formed in connection with the development of the new cortex and are best expressed in humans. On each side of the pyramid there is an olive, separated from the pyramid by the anterior lateral groove. The posterior surface of the medulla oblongata is divided by the posterior median groove, on the sides of which there are continuations of the posterior cords of the spinal cord. brain, which diverge upward, passing into the lower cerebellar peduncles. The latter limit the rhomboid fossa from below. The posterior funiculus consists of two bundles - wedge-shaped (lateral) and thin (medially), which, near the lower corner of the rhomboid fossa, end in corresponding tubercles containing the wedge-shaped and thin nuclei. The medulla oblongata is built of white and gray matter, the latter is represented by the nuclei of the IX-XII pairs of cranial nerves, olives, centers of respiration and circulation, and the reticular formation. White matter is formed by long and short fibers that make up the corresponding pathways.

82 Ventricular system

Lateral ventricle(ventriculus lateralis). The cavities of the cerebral hemispheres are the lateral ventricles (I and II), located in the thickness of the white matter under the corpus callosum.

The telencephalon consists of two hemispheres of the cerebrum, separated from each other by a longitudinal fissure. In the depths of the gap is the corpus callosum connecting them. In addition to the corpus callosum, the hemispheres are also connected by the anterior, posterior commissures and the fornix commissure. Each hemisphere has three poles: frontal, occipital and temporal. Three edges (superior, inferior and medial) divide the hemisphere into three surfaces: superolateral, medial and inferior. Each hemisphere is divided into lobes. The central sulcus (Rolandic) separates the frontal lobe from the parietal lobe, the lateral sulcus (Sylvian) separates the temporal from the frontal and parietal, the parieto-occipital sulcus separates the parietal and occipital lobes. The insular lobe is located deep in the lateral sulcus. Smaller grooves divide the lobes into convolutions.

Superolateral surface of the cerebral hemisphere. The frontal lobe, located in the anterior section of each cerebral hemisphere, is bounded below by the lateral (Sylvian) fissure, and behind by the deep central groove (Rolandic), located in the frontal plane. Anterior to the central sulcus, almost parallel to it, is the precentral sulcus. From the precentral sulcus forward, almost parallel to each other, the superior and inferior frontal sulci run forward, dividing the superolateral surface of the frontal lobe into convolutions. Between the central sulcus behind and the precentral sulcus in front is the precentral gyrus. Above the superior frontal sulcus lies the superior frontal gyrus, which occupies the upper part of the frontal lobe.

The middle frontal gyrus runs between the superior and inferior frontal sulci. Down from the inferior frontal sulcus is the inferior frontal gyrus, into which the ascending and anterior branches of the lateral sulcus project from below, dividing the lower part of the frontal lobe into small gyri. The tegmental part (frontal tegmentum), located between the ascending branch and the lower part of the lateral sulcus, covers the insular lobe, which lies deep in the sulcus. The orbital part lies inferior to the anterior ramus, continuing onto the inferior surface of the frontal lobe. At this point, the lateral sulcus widens, passing into the lateral fossa of the cerebrum.

The parietal lobe, located posterior to the central sulcus, is separated from the occipital parieto-occipital sulcus, which is located on the medial surface of the hemisphere, extending deeply into its upper edge. The parieto-occipital groove passes into the superolateral surface, where the border between the parietal and occipital lobes is a conventional line - the continuation of this groove downwards. The inferior border of the parietal lobe is the posterior branch of the lateral sulcus, separating it from the temporal lobe. The postcentral sulcus runs behind the central sulcus, almost parallel to it.

Between the central and postcentral sulci there is a postcentral gyrus, which at the top passes to the medial surface of the cerebral hemisphere, where it connects with the precentral gyrus of the frontal lobe, forming together with it the precentral lobule. On the superior lateral surface of the hemisphere below, the postcentral gyrus also passes over the precentral gyrus, covering the central sulcus from below. The intraparietal sulcus extends posteriorly from the postcentral sulcus, parallel to the superior edge of the hemisphere. Above the intraparietal sulcus there is a group of small convolutions called the superior parietal lobule; Below is the inferior parietal lobule.

The smallest occipital lobe is located behind the parieto-occipital sulcus and its conventional continuation on the superolateral surface of the hemisphere. The occipital lobe is divided into several convolutions by grooves, of which the transverse occipital groove is the most constant.

The temporal lobe, which occupies the inferolateral parts of the hemisphere, is separated from the frontal and parietal lobes by the lateral sulcus. The insular lobe is covered by the edge of the temporal lobe. On the lateral surface of the temporal lobe, almost parallel to the lateral sulcus, lie the superior and inferior temporal gyri. On the upper surface of the superior temporal gyrus, several weakly defined convolutions (Heschl's gyri) are visible. Between the superior and inferior temporal sulci is the middle temporal gyrus. Below the inferior temporal sulcus is the inferior temporal gyrus.

The insula (insula) is located deep in the lateral sulcus, covered by a operculum formed by parts of the frontal, parietal and temporal lobes. The deep circular fissure of the insula separates the insula from the surrounding parts of the brain. The inferoanterior part of the insula is devoid of grooves and has a slight thickening - the threshold of the insula. On the surface of the insula, a long and a short gyrus are distinguished.

Medial surface of the cerebral hemisphere. All of its lobes, except the insular lobe, take part in the formation of the medial surface of the cerebral hemisphere. The groove of the corpus callosum goes around it from above, separating the corpus callosum from the lumbar gyrus, goes down and forward and continues into the groove of the hippocampus.

The cingulate groove runs above the cingulate gyrus, which begins anteriorly and inferiorly to the beak of the corpus callosum. As it rises, the groove turns back and runs parallel to the groove of the corpus callosum. At the level of its ridge, its marginal part extends upward from the cingulate sulcus, and the sulcus itself continues into the subparietal sulcus. The marginal part of the cingulate sulcus limits the pericentral lobule behind, and the precuneus, which belongs to the parietal lobe, in front. Inferiorly and posteriorly through the isthmus, the cingulate gyrus passes into the parahippocampal gyrus, which ends anteriorly with a hook and is bounded superiorly by the hippocampal sulcus. The cingulate gyrus, isthmus and parahippocampal gyrus are combined under the name vaulted gyrus. The dentate gyrus is located deep in the hippocampal sulcus. At the level of the splenium of the corpus callosum, the marginal part of the cingulate groove branches upward from the cingulate sulcus.

The lower surface of the cerebral hemisphere has the most complex relief. In front is the surface of the frontal lobe, behind it is the temporal pole and the lower surface of the temporal and occipital lobes, between which there is no clear boundary. Between the longitudinal fissure of the hemisphere and the olfactory sulcus of the frontal lobe there is a straight gyrus. Lateral to the olfactory sulcus lie the orbital gyri. The lingual gyrus of the occipital lobe is limited on the lateral side by the occipitotemporal (collateral) groove. This groove passes to the inferior surface of the temporal lobe, separating the parahippocampal and medial occipitotemporal gyri. Anterior to the occipitotemporal sulcus is the nasal sulcus, which bounds the anterior end of the parahippocampal gyrus - the uncus. The occipitotemporal sulcus separates the medial and lateral occipitotemporal gyri.

On the medial and lower surfaces there are a number of formations related to the limbic system (from the Latin Limbus-border). These are the olfactory bulb, olfactory tract, olfactory triangle, anterior perforated substance, mammillary bodies located on the lower surface of the frontal lobe (peripheral part of the olfactory brain), as well as the cingulate, parahippocampal (together with the hook) and dentate gyri. The subcortical structures of the limbic system are the amygdala, septal nuclei and anterior thalamic nucleus.

The limbic system is connected to other areas of the brain: with the hypothalamus, and through it with the midbrain, the temporal cortex and the frontal lobe. The latter, apparently, regulates the functions of the limbic system. The limbic system is a morphological substrate that controls a person’s emotional behavior and controls his general adaptation to environmental conditions. All signals coming from the analyzers, on their way to the corresponding centers of the cerebral cortex, pass through one or more structures of the limbic system. Descending signals from the cerebral cortex also pass through the limbic structures.

The structure of the cerebral cortex. The cerebral cortex is formed by gray matter, which lies along the periphery (on the surface) of the cerebral hemispheres. The cerebral cortex is dominated by the neocortex (about 90%) - the new cortex, which first appeared in mammals. Phylogenetically more ancient areas of the cortex include the old cortex - the archecortex (dentate gyrus and base of the hippocampus) as well as the ancient cortex - the paleocortex (preperiform, preamygdala and entorhinal regions). The thickness of the cortex in different parts of the hemispheres ranges from 1.3 to 5 mm. The thickest cortex is located in the upper parts of the precentral and postcentral gyri and at the paracentral lobule. The cortex of the convex surface of the gyri is thicker than that of the lateral and bottom of the grooves. The surface area of ​​the cerebral cortex of an adult reaches 450,000 cm2, one third of which covers the convex parts of the gyri and two thirds - the lateral and lower walls of the sulci. The cortex contains 10-14 billion neurons, each of which forms synapses with approximately 8-10 thousand others.

For the first time, domestic scientist V.A. Betz showed that the structure and interaction of neurons is not the same in different parts of the cortex, which determines its neurocytoarchenics. Cells of more or less the same structure are arranged in the form of separate layers (plates). In the neocortex, the cell bodies of neurons form six layers. In different sections, the thickness of the layers, the nature of their boundaries, the size of the cells, their number, etc. vary. The cerebral cortex is dominated by pyramidal cells of various sizes (from 10 to 140 µm). Small pyramidal cells located in all layers of the cortex are associative or commissural interneurons. Larger ones generate impulses of voluntary movements, directed to the skeletal muscles through the corresponding motor nuclei of the brain and spinal cord.

On the outside there is a molecular layer. It contains small multipolar associative neurons and many fibers - processes of neurons in the underlying layers, running as part of the tangential layer parallel to the surface of the cortex. The second layer - the outer granular layer - is formed by many small multipolar neurons, the diameter of which does not exceed 10-12 microns. Their dendrites are directed to the molecular layer, where they pass as part of the tangential layer. The third layer of bark is the widest. This is a pyramidal layer that contains pyramidal-shaped neurons, the bodies of which increase in the direction from top to bottom from 10 to 40 µm. This layer is best developed in the precentral gyrus. The axons of large cells of this layer, covered with a myelin sheath, are directed into the white matter, forming association or commissural fibers. The axons of small neurons do not leave the cortex. Large dendrites extending from the top of the pyramidal neurons are directed to the molecular layer, the remaining small dendrites form synapses within the same layer.

The fourth layer - the internal granular layer - is formed by small stellate-shaped neurons. This layer is developed unevenly in different parts of the cortex. The fifth layer - the internal pyramidal layer, which is most well developed in the precentral gyrus - contains pyramidal cells discovered by V.A. Betz in 1874. These are very large nerve cells (up to 80-125 microns), rich in chromatophilic substance. The axons of these cells leave the cortex and form the descending corticospinal and corticonuclear (pyramidal) tracts. Collaterals depart from the axons and go to the cortex, basal ganglia, red nucleus, reticular formation, pontine and olivary nuclei. The sixth layer - polymorphic cells - contains neurons of various shapes and sizes. The axons of these cells are directed into the white matter, and the dendrites into the molecular layer. However, not all of the cortex is built this way. On the medial and lower surfaces of the cerebral hemispheres, sections of the old (archecortex) and ancient (paleocortex) cortex, which has a two- and three-layer structure, have been preserved.

In addition to nerve cells, each cell layer contains nerve fibers. The structure and density of their occurrence are also different in different parts of the crust. Features of the distribution of fibers in the cerebral cortex are defined by the term “myeloarchitecture.” K. Brodman in 1903-1909 identified 52 cytoarchitectonic fields in the cerebral cortex.

O. Vogt and C. Vogt (1919-1920), taking into account the fiber structure, described 150 myeloarchitectonic areas in the cerebral cortex. The Brain Institute of the Academy of Medical Sciences created detailed maps of the cytoarchitectonic fields of the human cerebral cortex (I.N. Filimonov, S.A. Sarkisov). The fibers of the cerebral cortex are divided into commissural, which connect parts of the cortex of both hemispheres, associative, which connect various functional zones of the cortex of the same hemisphere, and projection, which connect the cerebral cortex with the underlying parts of the brain. They form radially oriented layers that end on the cells of the pyramidal layer. In the molecular, internal granular and pyramidal layers there are tangential plates of myelin fibers that form synapses with cortical neurons.

J. Szentagothai (1957) developed the concept of a modular structure of the cerebral cortex. The module is a vertical cylindrical column of the cortex with a diameter of about 300 μm, the center of which is the corticocortical association or commissural fiber extending from the pyramidal cell. They end in all layers of the cortex, and in the first layer they branch into horizontal branches. In the human cerebral cortex there are about 3 million modules.

Localization of functions in the cerebral cortex. In the cerebral cortex, all stimuli that come from the surrounding external and internal environment are analyzed. The largest number of afferent impulses enters through the nuclei of the thalamus to the cells of the third and fourth layers of the cerebral cortex. The cerebral cortex contains centers that regulate the performance of certain functions. I.P. Pavlov considered the cerebral cortex as a set of cortical ends of analyzers. The term “analyzer” refers to a complex complex of anatomical structures, which consists of a peripheral receptor (perceiving) apparatus, conductors of nerve impulses and a center. The cortical end of the analyzer is not any strictly defined zone. In the cerebral cortex, a “core” of the sensory system and “scattered elements” are distinguished. The nucleus is the area where the largest number of cortical neurons are located, to which impulses come from peripheral receptor structures. Scattered elements are located near the nucleus and at various distances from it. If higher analysis and synthesis are carried out in the nucleus, then simpler ones are carried out in scattered elements. At the same time, the zones of “scattered elements” of various analyzers do not have clear boundaries and overlap each other. Let's consider the localization of the cores of some analyzers.

In the cortex of the postcentral gyrus and superior parietal lobule lie the nuclei of the cortical analyzer of proprioceptive and general sensitivity (temperature, pain, touch) of the opposite half of the body. In this case, the cortical ends of the sensitivity analyzer of the lower extremities and lower parts of the body are located closer to the longitudinal fissure of the brain, and the receptor fields of the upper parts of the body and head are projected lowest at the lateral sulcus.

The nucleus of the motor analyzer is located mainly in the precentral gyrus and paracentral lobule on the medial surface of the hemisphere (“motor area of ​​the cortex”). In the upper parts of the precentral gyrus and paracentral lobule, the motor centers of the muscles of the lower extremities and the lowermost parts of the body are located. In the lower part, near the lateral groove, there are centers that regulate the activity of the muscles of the face and head. The motor areas of each hemisphere interact with the skeletal muscles of the opposite side of the body. The muscles of the limbs are connected in isolation to one of the hemispheres, the muscles of the trunk, larynx and pharynx are connected to the motor areas of both hemispheres. In both described centers, the size of the projection zones of various organs depends not on the size of the latter, but on the functional significance. Thus, the zone of the hand in the cerebral hemisphere cortex is much larger than the zones of the trunk and lower limbs combined. I.P. Pavlov called the motor area of ​​the cerebral cortex receptor, since it also contains the analysis of proprioceptive (kinetic) stimuli perceived by receptors embedded in skeletal muscles, tendons, fascia and joint capsules.

In the depths of the lateral sulcus, on the superficial middle part of the superior temporal gyrus facing the insula, there is the nucleus of the auditory analyzer (Heschl's gyrus). Paths from the hearing organ receptors of both the left and right sides approach each hemisphere, so unilateral damage to this nucleus does not cause a complete loss of the ability to perceive sounds.

The nucleus of the visual analyzer is located on the medial surface of the occipital lobe of the cerebral hemisphere on both sides (“along the banks”) of the calcarine sulcus. The nucleus of the visual analyzer of the right hemisphere is connected by pathways with the lateral half of the retina of the right eye and the medial half of the retina of the left eye, the left - with the lateral half of the retina of the left eye and the medial half of the retina of the right eye.

In the region of the inferior parietal lobule, in the supramarginal gyrus, there is an asymmetrical (for right-handers - in the left, and for left-handers - only in the right hemisphere) nucleus of the motor analyzer, which coordinates all purposeful complex combined movements.

In the cortex of the superior parietal lobule there is the nucleus of the cutaneous analyzer of stereognosis (recognition of an object by touch). The cortical end of this analyzer in each hemisphere is connected to the opposite upper limb.

The cortical end of the olfactory analyzer is the hook, as well as the old and ancient cortex. The old cortex is located in the area of ​​the hippocampus and the dentate gyrus, the ancient cortex is located in the area of ​​the anterior perforated space, the septum pellucidum and the olfactory gyrus. Due to the close location of the nuclei of the olfactory and gustatory analyzers, the senses of smell and taste are closely related to each other. In addition, part of the taste analyzer nucleus is also located in the lower parts of the postcentral gyrus. The nuclei of the taste and olfactory analyzers of both hemispheres are connected by pathways with receptors on both the left and right sides.

The described cortical ends of the analyzers carry out the analysis and synthesis of signals coming from the external and internal environment of the body, constituting the first signal system of reality (I.P. Pavlov).

Unlike the first, the second signaling system is found only in humans and is closely related to the development of articulate speech.

Human speech and thinking are carried out with the participation of the entire cortex. At the same time, in the human cerebral cortex there are zones that are centers of a number of special functions related to speech. The nucleus of the motor analyzer of voluntary movements associated with writing is located in the posterior part of the middle frontal gyrus near the areas of the cortex of the precentral gyrus that control the movement of the hand and the combined rotation of the head and eyes in the opposite direction. The nucleus of the motor analyzer of speech articulation, or speech motor analyzer, is located in the posterior sections of the inferior frontal gyrus (Broca's center), near the sections of the precentral gyrus, which are analyzers of movements produced by contraction of the muscles of the head and neck. The speech motor analyzer analyzes the movements of all muscles involved in the act of articulate speech (pronunciation of words and sentences). In the center of the inferior frontal gyrus there is the nucleus of the speech analyzer associated with singing.

The core of the auditory analyzer of oral speech is closely connected with the cortical center of the auditory analyzer and is also located in the region of the superior temporal gyrus, in its posterior sections on the surface facing the lateral sulcus of the cerebral hemisphere. Its function is to coordinate the auditory perception and understanding of another person's speech and to control one's own speech.

In the middle third of the superior temporal gyrus there is the cortical end of the auditory analyzer, which belongs to the centers of the second signaling system, perceiving the verbal designation of objects, actions, phenomena, i.e. sensing signal signals.

Near the nucleus of the visual analyzer is the nucleus of the visual analyzer of written speech, located in the angular gyrus of the inferior parietal lobule. Speech analyzers in right-handed people are localized only in the left hemisphere, and in left-handed people - only in the right.

In humans, like other mammals, there are large areas in the neocortex that are not cortical centers of sensory or motor functions (nonspecific, or associative, areas), but their area significantly exceeds the area of ​​the motor and sensory centers. Associative areas provide poorly developed connections between sensory and motor centers and, most importantly, are the morphological substrate of mental activity (consciousness, thinking, learning, memory, emotions). This primarily applies to the frontal lobes. The frontal lobes also play a critical role in developing human behavior strategies. The associative cortex of the parietal and temporal lobes are involved in the formation of speech, in the perception and assessment of the location of one’s own body and its parts in space, as well as the three-dimensional spatial external world.

Basal ganglia and white matter of the telencephalon. In the thickness of the white matter of each cerebral hemisphere there are accumulations of gray matter, forming separately lying nuclei. These nuclei lie closer to the base of the brain and are called basal (subcortical, central). These include the striatum, which in lower vertebrates constitutes the predominant mass of the hemispheres, the fence and the amygdala.

The striatum (corpus striatum) in sections of the brain looks like alternating stripes of gray and white matter. Most medially and anteriorly is the caudate nucleus, located lateral and superior to the thalamus, being separated from it by the knee of the internal capsule. The nucleus has a head located in the frontal lobe, protruding into the anterior horn of the lateral ventricle and adjacent to the anterior perforated substance. The body of the caudate nucleus lies under the parietal lobe, limiting the central part of the lateral ventricle on the lateral side. The tail of the nucleus participates in the formation of the roof of the inferior horn of the lateral ventricle and reaches the amygdala, which lies in the anteromedial parts of the temporal lobe (posterior to the anterior perforated substance). The lenticular nucleus is located lateral to the caudate nucleus. A layer of white matter - the internal capsule - separates the lenticular nucleus from the caudate nucleus and from the thalamus. The lower surface of the anterior part of the lentiform nucleus is adjacent to the anterior perforated substance and is connected to the caudate nucleus. The medial part of the lenticular nucleus in a horizontal section of the brain narrows and is angled towards the knee of the internal capsule, located on the border of the thalamus and the head of the caudate nucleus. The convex lateral surface of the lenticular nucleus faces the base of the insular lobe of the cerebral hemisphere.

On the frontal section of the brain, the lenticular nucleus also has the shape of a triangle, the apex of which faces the medial side and the base faces the lateral side. Two parallel vertical layers of white matter divide the lenticular nucleus into three parts. The darker shell lies most laterally, the “globus pallidus” is located more medially, consisting of two plates: medial and lateral. The caudate nucleus and putamen belong to phylogenetically newer formations, while the globus pallidus belongs to older ones. The nuclei of the striatum form the striopallidal system, which, in turn, belongs to the extrapyramidal system involved in the control of movements and the regulation of muscle tone.

A thin vertically located fence, lying in the white matter of the hemisphere on the side of the shell, between it and the cortex of the insula, is separated from the shell by the outer capsule, and from the insular cortex by the outermost capsule. The amygdala lies in the white matter of the temporal lobe of the hemisphere, approximately 1.5 - 2 cm posterior to the temporal pole.

The white matter of the hemisphere includes the internal capsule and fibers that have different directions. These are fibers passing to the other hemisphere of the brain through its commissures (corpus callosum, anterior commissure, fornix commissure) and heading to the cortex and basal ganglia of the other side (commissural), as well as projection nerve fibers running from the cerebral hemisphere to its underlying parts and to the spinal cord and in the opposite direction from these formations.

The corpus callosum is formed by commissural fibers connecting both hemispheres. The free upper surface of the corpus callosum, facing the longitudinal fissure of the cerebrum, is covered with a thin plate of gray matter. The middle part of the corpus callosum - its trunk - bends downwards in front, forming the knee of the corpus callosum, which, thinning, passes into the beak, which continues downwards into the terminal (border) plate. The thickened posterior section of the corpus callosum ends freely in the form of a ridge. The fibers of the corpus callosum form its radiance in each hemisphere of the cerebrum. The genu fibers of the corpus callosum connect the cortex of the frontal lobes of the right and left hemispheres. Brainstem fibers connect the gray matter of the parietal and temporal lobes. The roller contains fibers connecting the cortex of the occipital lobes. The areas of the frontal, parietal and occipital lobes of each hemisphere are separated from the corpus callosum by the fissure of the same name.

Under the corpus callosum there is a thin white plate - the vault, consisting of two arched cords connected in its middle part by a transverse commissure of the vault. The body of the vault, gradually moving away in the anterior part from the corpus callosum, arches forward and downward and continues into the column of the vault. The lower part of each column of the fornix first approaches the terminal plate, and then the columns of the fornix diverge laterally and are directed downward and posteriorly, ending in the mastoid bodies.

Between the crura of the fornix at the back and the terminal plate at the front there is a transverse anterior (white) commissure, which, along with the corpus callosum, connects both hemispheres of the cerebrum.

Posteriorly, the body of the fornix continues into the flat peduncle of the fornix, fused with the lower surface of the corpus callosum. The crus of the fornix gradually moves laterally and downwards, separates from the corpus callosum, becomes even more dense and on one side fuses with the hippocampus, forming the hippocampal fimbria. The free side of the fimbria, facing the cavity of the inferior horn of the lateral ventricle, ends in the hook, connecting the temporal lobe of the telencephalon with the diencephalon.

The area bounded above and in front by the corpus callosum, below by its beak, terminal plate and anterior commissure, and behind by the crus of the fornix, is occupied on each side by a sagittally located thin plate - a transparent septum. Between the plates of the transparent septum there is a narrow sagittal cavity of the same name, containing a transparent liquid. The lamina pellucidum is the medial wall of the anterior horn of the lateral ventricle.

The internal capsule (capsula interna) is a thick, angled plate of white matter, bounded on the lateral side by the lentiform nucleus, and on the medial side by the head of the caudate nucleus (in front) and the thalamus (back). The internal capsule is formed by projection fibers connecting the cerebral cortex with other parts of the central nervous system. The fibers of the ascending pathways, diverging in different directions to the cerebral cortex, form the corona radiata. Downward, the fibers of the descending pathways of the internal capsule in the form of compact bundles are directed to the peduncle of the midbrain.

Lateral ventricle (ventriculus lateralis). The cavities of the cerebral hemispheres are the lateral ventricles (1st and 2nd), located in the thickness of the white matter under the corpus callosum. Each ventricle has four parts: the anterior horn lies in the frontal lobe, the central part in the parietal lobe, the posterior horn in the occipital lobe, and the inferior horn in the temporal lobe. The anterior horn of both ventricles is separated from the adjacent one by two plates of a transparent septum. The central part of the lateral one bends from above around the thalamus, forms an arc and passes posteriorly into the posterior horn, downward into the inferior horn. The medial wall of the inferior horn is the hippocampus (a section of the ancient cortex), corresponding to the deep groove of the same name on the medial surface of the hemisphere. The fimbria stretches medially along the hippocampus, which is a continuation of the crus of the fornix. On the medial wall of the posterior horn of the lateral ventricle of the brain there is a protrusion - a bird's spur, corresponding to the calcarine groove on the medial surface of the hemisphere. The choroid plexus protrudes into the central part and lower horn of the lateral ventricle, which through the interventricular foramen connects with the choroid plexus of the 3rd ventricle.

The choroid plexus of the lateral ventricle is formed by protrusion into the ventricle through the vascular fissure of the pia mater of the brain with the blood vessels it contains.

Plan

Introduction

1.Anatomy of the telencephalon

2. Physiology of the telencephalon

3. Limbic system

4.Associative zones of the cortex

Conclusion

List of used literature

Introduction

The brain is located in the cranial cavity. Its upper surface is convex, and its lower surface - the base of the brain - is thickened and uneven. At the base of the brain, 12 pairs of cranial (or cranial) nerves arise from the brain. The brain is divided into the cerebral hemispheres (the most recent part in evolutionary development) and the brainstem with the cerebellum. The weight of the adult brain is on average 1375 g for men, 1245 g for women. The weight of the brain of a newborn is on average 330 - 340 g. In the embryonic period and in the first years of life, the brain grows rapidly, but only by the age of 20 it reaches its final size. Brain and The spinal cord develops on the dorsal (dorsal) side of the embryo from the outer germ layer (ectoderm). At this point, the neural tube is formed with an expansion in the head section of the embryo. Initially, this expansion is represented by three brain vesicles: anterior, middle and posterior (diamond-shaped). Subsequently, the anterior and rhomboid vesicles divide and five brain vesicles are formed: terminal, intermediate, middle, posterior and oblong (accessory). During development, the walls of the brain vesicles grow unevenly: either thickening, or remaining thin in some areas and pushing into the cavity of the vesicle, participating in the formation of the choroid plexuses of the ventricles. The remnants of the cavities of the brain vesicles and the neural tube are the cerebral ventricles and the central canal of the spinal cord. From each brain vesicle certain parts of the brain develop. In this regard, out of the five cerebral vesicles in the brain, five main sections are distinguished: medulla oblongata, hindbrain, midbrain, diencephalon and telencephalon.

1.Anatomy of the telencephalon

The telencephalon develops from the forebrain and consists of highly developed paired parts - the right and left hemispheres and the middle part connecting them. The hemispheres are separated by a longitudinal fissure, in the depth of which lies a plate of white matter, consisting of fibers connecting the two hemispheres - the corpus callosum. Under the corpus callosum there is a vault, which consists of two curved fibrous cords, which are connected to each other in the middle part, and diverge in front and behind, forming the pillars and legs of the vault. Anterior to the columns of the arch is the anterior commissure. Between the anterior part of the corpus callosum and the fornix is ​​a thin vertical plate of brain tissue - a transparent septum.

The hemisphere is formed by gray and white matter. It contains the largest part, covered with grooves and convolutions - a cloak formed by the gray matter lying on the surface - the cortex of the hemispheres; the olfactory brain and accumulations of gray matter inside the hemispheres - the basal ganglia. The last two sections constitute the oldest part of the hemisphere in evolutionary development. The cavities of the telencephalon are the lateral ventricles. In each hemisphere, three surfaces are distinguished: the superolateral (superolateral) is convex according to the cranial vault, the middle (medial) is flat, facing the same surface of the other hemisphere, and the bottom is irregular in shape. The surface of the hemisphere has a complex pattern, thanks to grooves running in different directions and ridges between them - convolutions. The size and shape of the grooves and convolutions are subject to significant individual fluctuations. However, there are several permanent grooves that are clearly expressed in everyone and appear earlier than others during the development of the embryo. They are used to divide the hemispheres into large areas called lobes. Each hemisphere is divided into five lobes: the frontal, parietal, occipital, temporal and hidden lobe, or insula, located deep in the lateral sulcus. The boundary between the frontal and parietal lobes is the central sulcus, and between the parietal and occipital lobes is the parieto-occipital sulcus. The temporal lobe is separated from the rest by the lateral sulcus. On the superolateral surface of the hemisphere in the frontal lobe, there is a precentral sulcus, separating the precentral gyrus, and two frontal sulci: superior and inferior, dividing the rest of the frontal lobe into the superior, middle and inferior frontal gyri. In the parietal lobe there is a postcentral sulcus, separating the postcentral gyrus, and an intraparietal sulcus, dividing the rest of the parietal lobe into the superior and inferior parietal lobes. In the lower lobule, the supramarginal and angular gyri are distinguished. In the temporal lobe, two parallel grooves - the superior and inferior temporal - divide it into the superior, middle and inferior temporal gyri. In the region of the occipital lobe, transverse occipital sulci and gyri are observed. On the medial surface, the sulcus of the corpus callosum and the cingulate are clearly visible, between which the cingulate gyrus is located. Above it, surrounding the central sulcus, lies the paracentral lobule. Between the parietal and occipital lobes runs the parieto-occipital sulcus, and behind it is the calcarine sulcus. The area between them is called a wedge, and the one lying in front is called a pre-wedge. At the point of transition to the lower (basal) surface of the hemisphere lies the medial occipitotemporal, or lingual, gyrus.

On the lower surface, separating the hemisphere from the brain stem, there is a deep groove of the hippocampus (seahorse groove), lateral to which is the parahippocampal gyrus. Laterally, it is separated by a collateral groove from the lateral occipitotemporal gyrus. The insula, located deep in the lateral (side) sulcus, is also covered with grooves and convolutions.

The cerebral cortex is a layer of gray matter up to 4 mm thick. It is formed by layers of nerve cells and fibers arranged in a certain order. The most typically structured areas of the phylogenetically newer cortex consist of six layers of cells; the old and ancient cortex has fewer layers and is simpler in structure. Different areas of the cortex have different cellular and fibrous structures. In this regard, there is a doctrine of cellular structure cortex (cytoarchitectonics) and fibrous structure (myeloarchitectonics) of the cerebral hemisphere cortex.

The olfactory brain in humans is represented by rudimentary formations, well expressed in animals, and constitutes the oldest parts of the cerebral cortex.

The basal ganglia are clusters of gray matter within the hemispheres. These include the striatum, consisting of the caudate and lenticular nuclei, interconnected. The lenticular nucleus is divided into two parts: the shell, located on the outside, and the globus pallidus, which lies on the inside. They are subcortical motor centers.

Outside the lenticular nucleus there is a thin plate of gray matter - the fence; in the anterior part of the temporal lobe lies the amygdala. Between the basal ganglia and the optic thalamus there are layers of white matter, the inner, outer and outermost capsules. Conducting pathways pass through the internal capsule.

The lateral ventricles (right and left) are cavities of the telencephalon, lie below the level of the corpus callosum in both hemispheres and communicate through the interventricular foramina with the third ventricle. They have irregular shape and consist of anterior, posterior and lower horns and a central part connecting them. The anterior horn lies in the frontal lobe; it continues posteriorly into the central part, which corresponds to the parietal lobe. At the back, the central part passes into the posterior and inferior horns, located in the occipital and temporal lobes. In the lower horn there is a cushion - the hippocampus (seahorse). From the medial side, the choroid plexus invaginates into the central part of the lateral ventricles, continuing into the inferior horn. The walls of the lateral ventricles are formed by the white matter of the hemispheres and the caudate nuclei. The thalamus is adjacent to the central part below.

The white matter of the hemispheres occupies the space between the cortex and the basal ganglia. It consists of a large number of nerve fibers going into different directions. There are three systems of fibers of the hemispheres: associative (combinative), connecting parts of the same hemisphere; commissural (commissural) connecting parts of the right and left hemispheres, which in the hemispheres include the corpus callosum, anterior commissure and commissure of the fornix, and projection fibers, or pathways connecting the hemispheres with the underlying parts of the brain and spinal cord.

2. Physiology of the telencephalon

The telencephalon, or the cerebral hemispheres, which have reached their highest development in humans, is rightly considered the most complex and most amazing creation of nature.

The functions of this section of the central nervous system are so different from the functions of the trunk and spinal cord that they are allocated to a special chapter of physiology called higher nervous activity. This term was introduced by I.P. Pavlov. The activity of the nervous system, aimed at uniting and regulating all organs and systems of the body, was called lower nervous activity by I. P. Pavlov. By higher nervous activity he understood behavior, activity aimed at adapting the body to changing environmental conditions, at balancing with environment. In the behavior of an animal, in its relationships with the environment, the leading role is played by the telencephalon, the organ of consciousness, memory, and in humans - the organ of mental activity and thinking.

The great achievements of I. P. Pavlov in the field of studying the functions of the cerebral hemispheres are explained by the fact that he proved the reflex nature of the activity of the cortex and discovered a new, qualitatively higher type of reflexes inherent only in it, namely conditioned reflexes. Having discovered the basic mechanism of activity of the cerebral cortex, he thereby created a fruitful, progressive method for studying its functions - the method of conditioned reflexes. As it turned out later, conditioned reflexes are those elementary acts, those “bricks” from which a person’s mental activity, or behavior, is built.