Gray and white matter of the brain.

In the brain, gray and white matter are distinguished, but their distribution here is much more complicated than in the spinal cord. Most of the gray matter of the brain is located on the surface of the cerebrum and cerebellum, forming their cortex. A smaller part forms numerous subcortical nuclei surrounded by white matter. All gray matter nuclei are composed of multipolar neurons.

The gray matter contains the bodies of neurons, from which the nuclei of the central nervous system and the cortex are formed. White matter consists of processes of neurons that form bundles and tracts, which are components of the pathways of the central nervous system.

The white matter in the brain occupies the entire space between the gray matter of the cerebral cortex and the basal ganglia. The surface of the hemisphere, the cloak, is formed by a uniform layer of gray matter 1.3–4.5 mm thick, containing nerve cells.

There are four parts in white matter:

the central substance of the corpus callosum, the internal capsule and long associative fibers;

radiant crown (corona radiata), formed by radially diverging fibers entering the inner capsule and leaving it;

the area of white matter in the outer parts of the hemisphere – the semi-oval center;

white matter in the gyri between the sulci.

The nerve fibers of the white matter are divided into projection, associative and commissural.

The white matter of the hemispheres is formed by nerve fibers that connect the cortex of one gyrus with the cortex of other gyri of its own and opposite hemispheres, as well as with underlying formations.

Two cerebral commissures, commissura anterior and commissura fornicis, are much smaller in size, belong to the olfactory brain and connect: commissura anterior – olfactory lobes and both parahippocampal gyrus, commissura fornicis – hippocampi.

The commissural fibers that make up the cerebral commissures, or adhesions, connect not only symmetrical points, but also the cortex belonging to different lobes of opposite hemispheres. Associative fibers connect different parts of the cortex of the same hemisphere. They are divided into short and long fibers.

Short fibers connect adjacent convolutions in the form of arcuate bundles. Long associative fibers connect areas more distant from each other.

The internal capsule is a thick, angled plate of white matter, bounded on the lateral side by the lenticular nucleus, and on the medial side by the head of the caudate nucleus and the thalamus. The internal capsule is formed by projection fibers that connect the cerebral cortex with other parts of the central nervous system. Fibers of the ascending pathways. Diverging in different directions to the cortex of the hemisphere, they form a radiant crown. From top to bottom, the fibers of the descending pathways of the internal capsule in the form of compact bundles are sent to the peduncle of the midbrain. On the frontal section of the brain, the internal capsule looks like an oblique white stripe continuing into the brain stem. In the internal capsule, the anterior leg is distinguished – between the caudate nucleus and the anterior half of the inner surface of the lenticular nucleus, as well as the posterior leg – between the thalamus and the posterior half of the lenticular nucleus and knee. Projection fibers according to their length can be divided into the following three systems:

Fibrae thalamocorticalis et corticothalamici – fibers from the thalamus to the cortex and back from the cortex to the thalamus; conducting excitation towards the cortex and centrifugal (efferent).

Tractus corticonuclearis – pathways to the motor nuclei of the cranial nerves.

Tractus corticospinalis (pyramidalis) – conducts motor volitional impulses to the muscles of the trunk and limbs.

Tractus corticopontini – paths from the cerebral cortex to the nuclei of the bridge. Using these pathways, the cerebral cortex has an inhibitory and regulatory effect on the activity of the cerebellum.

Projection fibers in the white matter of the hemisphere closer to the cortex form a radiant crown, and then their main part converges into the internal capsule.

Medulla.

It contains the nuclei of gray matter, which are related to balance, coordination of movements, as well as to the regulation of metabolism, respiration and blood circulation.

The gray matter of the medulla oblongata is represented by the following nuclei:

1) The nucleus of the olive (nucleus olivaris) has the appearance of a convoluted plate of gray matter, protrudes outward of the medulla oblongata. Lies in the olive. Responsible for balance.

2) The reticular formation (formatio reticularis) is formed from the interweaving of nerve fibers and those lying between the nerve cells. It contains the respiratory and vascular centers. Responsible for ensuring the maintenance of posture and the implementation of locomotion (static vestibular reflexes), the implementation of protective functions (coughing, sneezing, vomiting)

3) The nuclei of the four pairs of lower head nerves (XII – IX).

4) The nuclei of the vagus nerve are the centers of respiration and blood circulation.

5) Wedge-shaped and thin nuclei – switching nuclei.

The white matter of the medulla oblongata contains long and short fibers. The long ones include descending pyramidal tracts passing into the anterior cords of the spinal cord. In the nuclei of the posterior cords are the bodies of the second neurons of the ascending sensory pathways. In the medulla oblongata there are two intersections of long pathways: ventral motor and dorsal sensory.

Short paths include bundles of nerve fibers that connect individual nuclei of gray matter, as well as the nuclei of the medulla oblongata with neighboring parts of the brain.

Hind brain.

It consists of two parts: the bridge and the cerebellum. The bridge contains longitudinal and transverse fibers, between which their own nuclei of gray matter are scattered. Longitudinal fibers belong to the pyramidal tracts, which are connected with their own nuclei of the bridge, from which the transverse fibers originate, going to the cerebellar cortex. The surface of the cerebellum is covered with a layer of gray matter that makes up the cerebellar cortex. There are three layers in the cortex:

1 outer, or molecular – contains various cellular elements, but few neurons. It consists mainly of intertwining basilar fibers, i.e. unmyelinated, and contains a small number of irregularly scattered small cell nuclei. It contains parallel fibers and many dendrites of Purkinje cells. Basket neurons and stellate neurons are also located here.

2 ganglionic – contains large pear-shaped cells (Purkinje cells) located in 1 row .. One axon departs from each such cell, extending deep into the cerebellum, and dendrites form a tree above the cell, their branching is perpendicular to the convolutions. These dendrites are equipped with spines.

3 granular, or granular – contains many granular cells. These are the smallest neurons. Their body is mainly occupied by the nucleus, around which there is a narrow layer of protoplasm. There are also two types of Golgi cells: short-axon and long-axon. The former are involved in the formation of the cerebellar lumen, and the latter, entering the white matter of the cerebellum, connect various areas of its cortex. Behind the granular layer is white matter, which contains subcortical nuclei. Allocate:

Globular nucleus (nucleus globosus)

Corky nucleus (n. emboliformis)

Tent Core (n.fastigii)

Dentate nucleus (n.dentatus).

There are two types of afferent fibers in the cerebellum: moss and liana. Cerebellar fibers form three pairs of legs:

Lower legs (to medulla oblongata)

Middle legs (to the bridge)

Upper legs (to the roof of the midbrain).

Midbrain.

The midbrain consists of the quadrigemina, which includes 2 pairs of upper and lower hillocks. The midbrain also includes 2 pairs of knobs of the hillocks. The upper colliculi contain the visual nuclei, and the lower colliculi contain the auditory nuclei. It contains red nuclei and black matter, which belong to a fiber system that does not pass through the pyramid of the medulla oblongata. They regulate automatic unconscious movements. The substantia nigra secretes the hormone dopamine, which suppresses the excessive activity of the motor nuclei of the telencephalon. The nuclei of the III and IX cranial nerves are located in the central gray matter.

The white matter of the midbrain is a descending tract connecting the red nuclei and the anterior horns of the spinal cord. The bundles, at the exit from the red nucleus, intersect with each other, forming a ventral decussation of the tegmentum. The tegmentum contains longitudinal ascending fibers that form a continuation of the medial and lateral loops in the midbrain. As part of these loops, sensitive impulses go to the large brain. In the midbrain there is a medial longitudinal bundle, which is associative. It connects the various nuclei of the nerves of the eye muscles with each other. Another of its functions is associated with the movement of the eyes and head during stimulation of the vestibular apparatus.

Intermediate brain.

The diencephalon consists of the thalamus, epithalamus, thalamus, and hypothalamus.

The thalamus is a large paired ovoid-shaped accumulation of gray matter. These accumulations are located in the lateral walls of the diencephalon on the sides of the third ventricle. Their medial surface, covered with a thin layer of gray matter, protrudes freely into the cavity of the third ventricle, being its lateral wall; on this surface passes the hypothalamic groove (sulcus hypothalamicus), delimiting the thalamus from the hypothalamus. The dorsal surface is covered with a thin layer of white matter. The gray matter, which is part of the thalamus, forms the nuclei of the thalamus. The main nuclei of the thalamus are: 1. Anterior nucleus (nucleus anterior thalami); 2. Medial nucleus (nucleus medialis thalami); 3. Lateral nucleus (nucleus lateralis).

Part of the processes of thalamic neurons goes to the nuclei of the striatum of the telencephalon (in this regard, the thalamus is considered as a sensitive center of the extrapyramidal system), and part – thalamocortical bundles (fasciculi thalamocorticales) – to the cerebral cortex.

The epithalamus includes the triangle of the leash (trigonum habenulae), the leash (habenula), the commissure (adhesion) of the leashes (commissura habenularum), and the pineal body (corpus pineale).

The leash includes a triangle of the leash and a soldering of the leashes. In the triangle of the leash lies an accumulation of gray matter – the core of the leash, in the cells of which most of the fibers of the brain strip of the thalamus terminate. A smaller part of the fibers passes through the commissure of the leash; at the same time, some of them connect with the cells of the node of the leash of the opposite side, others reach the upper tubercle of the roof of the midbrain, the opposite side;

Anterior and inferior to the pineal body is a bundle of transverse fibers – the epithalamic commissure. It is a curved plate protruding into the cavity of the third ventricle. Between the epithalamic commissure and the commissure of the leashes, a shallow blind pocket protrudes into the anterior upper part of the pineal body, at its base – the pineal depression.

Metathalamus includes geniculate bodies – paired formations in which the ascending fibers of the auditory system switch to the auditory cortex and the ascending optic fibers to the visual cortex. Distinguish between the medial geniculate body and the lateral geniculate body.

The hypothalamus unites formations located ventrally under the bottom of the third ventricle; lies down from the visual hillock, under the hypotuberous furrow (sulcus hypothalamicus). The entire hypothalamus is divided into two sections – anterior and posterior. The anterior section includes a gray tubercle, consisting of a thin plate of gray matter. In the posterior section is the optic chiasm, formed by the optic chiasm, and the mastoid bodies. These are two small elevations of irregular spherical shape. Outside, they are covered with white matter, and inside each there are two (medial and lateral) gray nuclei. By function, the mastoid bodies belong to the subcortical olfactory centers.

The gray matter of the hypothalamus forms nuclei, which are divided into five groups: preoptic, anterior, middle, outer and posterior groups.

telencephalon

The telencephalon consists of two hemispheres of the large brain, separated by a longitudinal fissure and interconnected in the depths of this fissure with the help of the corpus callosum, anterior and posterior commissures, and also the commissure of the fornix. The composition of the hemispheres of the telencephalon includes three components: the cloak of the telencephalon (pallium), the striatum (corpus striatum) and the septum (septum). The cloak consists of the neocortex – the new cortex, which has six layers, differing from each other mainly in the shape of the nerve cells included in them.

The derivatives of the striatum are the basal nuclei:

The ancient striatum is a pale ball.

Old striatum – amygdala complex

New striatum – caudate nucleus, fence, shell.

In the hemispheres, the following groups of centers are distinguished:

1. The olfactory brain (rhinencephalon) is the oldest and at the same time the smallest part located ventrally.

2. Basal, or central, nuclei of the hemispheres, “subcortex” – the old part of the telencephalon, hidden in the depths.

3. The gray matter of the bark is the youngest, and at the same time the largest part, covering the rest with a kind of cloak, hence its name “cloak”, or mantle.

The cerebral cortex (cloak) is the most highly differentiated part of the nervous system. The cortex is most developed in the region of the central gyrus. The surface area of the cortex increases due to the many furrows. The surface area of both hemispheres is about 1650 cm 2 .

In the cerebral cortex, 11 cytoarchitectonic regions are distinguished, including 52 fields. These fields differ in the composition of neurons and different fibrous structures. The cerebral cortex consists of a huge number of nerve cells, which, according to morphological features, can be divided into six layers:

I. molecular layer

II. outer granular layer

III. outer pyramidal layer

IV. inner granular layer

V. internal pyramidal

VI. polymorphic layer

The surface of the hemisphere – raincoat (pallium) is formed by gray matter 1.3 – 4.5 mm thick. The cloak is divided into main lobes, which differ both in location and in function:

– frontal lobe, lobus frontalis; this is the part of the hemisphere located rostral to the central (Roland) sulcus. The lower edge of the frontal lobe is limited by the anterior edge of the Sylvian furrow;

– parietal lobe, lobus parientalis; located caudal to the central sulcus. The lower edge of the parietal lobe is limited by the posterior edge of the Sylvian furrow. The boundary between the parietal and occipital lobes is conditionally considered to be a line drawn from the point of intersection of the dorsal edge of the hemisphere by the upper end of the parietal-occipital sulcus to the anterior edge of the cerebellum;

– occipital lobe, lobus occipitalis; located behind the parietal-occipital sulcus and its conditional continuation on the upper lateral surface of the hemisphere. Furrows and convolutions of the outer surface of the occipital lobe are very variable;

– temporal lobe, lobus temporalis; rostro-dorsally limited by the Sylvian groove, and the caudal border is drawn according to the same principles as in the parietal lobe;

– insular lobe, lobus insularis (insula); located under the lid of the islet (operculum). The composition of the cover includes small areas of the temporal, parietal and frontal lobes.

The main surface of the lobes of the cloak are furrows and convolutions. Furrows are deep folds of the cloak containing stratified bodies of neurons – the cortex (the gray matter of the cloak) and the processes of cells (the white matter of the cloak). The sulci of the cloak of the telencephalon are divided into 3 main categories, which reflect their depth, occurrence and stability of outlines.

Permanent furrows (I order). A person has 10 of them. These are the deepest folds on the surface of the brain, which change the least in different people. Furrows of the first order appear in the process of early development and are a species trait.

Irregular furrows of the II order. They have a characteristic place and direction, but can vary individually within very wide limits or even be absent. The depth of these furrows is quite large, but much less than that of the furrows of the first order.

Non-permanent furrows of the III order are called grooves. They rarely reach significant sizes, their outlines are variable, and their topology has ethnic or individual characteristics. As a rule, grooves of the III order are not inherited.

The entire space between the gray matter of the cerebral cortex and the basal ganglia is occupied by white matter. It consists of a large number of nerve fibers running in different directions and forming pathways of the telencephalon. Nerve fibers can be divided into 3 systems: associative, commissural and projection waves.

window.

CONCLUSION

So, we can conclude that in the human body the work of all its organs is closely interconnected, and therefore the body functions as a single whole. The coordination of the functions of the internal organs is provided by the nervous system, which, in addition, communicates the body as a whole with the external environment and controls the work of each organ.

The nervous system plays an important role in the regulation of body functions. It ensures the coordinated work of cells, tissues, organs and their systems. In this case, the body functions as a whole. Thanks to the nervous system, the body communicates with the external environment.

The activity of the nervous system underlies feelings, learning, memory, speech and thinking – mental processes with the help of which a person not only cognizes the environment, but can also actively change it.

Distinguish between the central nervous system (brain and spinal cord) and the peripheral, represented by nerves extending from the brain and spinal cord and other elements that lie outside the spinal cord and brain. The entire nervous system is divided into somatic and autonomic.

The brain is made up of gray and white matter. Gray matter is a collection of neurons and their short processes. In the spinal cord, it is located in the center, surrounding the spinal canal. In the brain, on the contrary, the gray matter is located on its surface, forming a cortex and separate clusters, called nuclei, concentrated in the white matter. The white matter is under the gray and is composed of sheathed nerve fibers. Nerve fibers, connecting, compose nerve bundles, and several such bundles form individual nerves. The spinal cord is located in the spinal canal and looks like a white cord stretching from the occipital foramen to the lower back. Longitudinal grooves are located along the anterior and posterior surfaces of the spinal cord, in the center there is a spinal canal, around which gray matter is concentrated – an accumulation of a huge number of nerve cells that form the contour of a butterfly. On the outer surface of the cord of the spinal cord is white matter – an accumulation of bundles of long processes of nerve cells.

LIST OF USED LITERATURE

1. Bets L.V. Lectures on the anatomy of the central nervous system (compendium)

2. Sinelnikov R.D. Atlas of human anatomy, volume 3. Medicine, Moscow 1974.

3. S.V. Saveliev, M.A. Negasheva. Workshop on the anatomy of the human brain. Lead, Moscow, 2001.

4. Baritonov I.S. Structure and functions of the cerebral cortex. Science 1969.

5. Sapin M. R. Human anatomy. Book 2. Higher School 1996.

6. Rassolimo T. E. Anatomy of the CNS Reader.

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