The human brain is made up of white and gray matter. The first is everything that is filled between the gray matter on the cortex and the basal nuclei. On the surface there is a uniform layer of gray matter with nerve cells, the thickness of which is up to four and a half millimeters.
We will study in more detail what gray and white matter is in the brain.
What are these substances made of?
CNS substance is of two types: white and gray.
White matter consists of many nerve fibers and processes of nerve cells, the shell of which is white.
Gray matter consists of nerve cells with processes. Nerve fibers connect different parts of the central nervous system and nerve centers.
Gray and white matter of the spinal cord
The heterogeneous substance of this organ is gray and white. The first is formed by a huge number of neurons that are concentrated in the nucleus and are of three types:
- radicular cells;
- bundle neurons;
- internal cells.
The white matter of the spinal cord surrounds the gray matter. It includes the nerve processes, comprising three systems of fibers:
- intercalary and afferent neurons connecting different parts of the spinal cord;
- sensitive afferent, which are long centripetal;
- motor afferent or long centrifugal.
Medulla
From the course of anatomy, we know that the spinal cord goes into the medulla oblongata. The part of this brain above is thicker than below. Its average length is 25 millimeters, and the shape resembles a truncated cone.
It develops gravitational and auditory organs associated with breathing and blood circulation. Therefore, the nuclei of gray matter here regulate balance, metabolism, blood circulation, respiration, and coordination of movements.
Hind brain
This brain consists of a bridge and cerebellum. Consider the gray and white matter in them. The bridge is a large white roller at the back of the base. On the one hand, its boundary with the legs of the brain is expressed, and on the other, with the oblong. If you make a cross-section, then the white matter of the brain and gray nucleus here will be visible very well. Transverse fibers divide the bridge into the ventral and dorsal sections. In the ventral part, white matter of the pathways is mainly present, and gray forms its nucleus here.
The dorsal part is represented by the nuclei: switching, reticular formation, sensory systems and cranial nerves.
The cerebellum is located under the occipital lobes. It includes the hemispheres and the middle part called the "worm". The gray matter makes up the cerebral cortex and nucleus, which are tent-like, spherical, cork-like and dentate. The white matter of the brain in this part is located under the cerebellar cortex. It penetrates into all convolutions as white plates and consists of different fibers that either bind lobules and convolutions, or are directed to the inner nuclei, or connect sections of the brain.
Midbrain
It starts from the middle brain bubble. On the one hand, it corresponds to the surface of the brain stem between the pineal gland and the superior cerebral sail, and on the other, to the area between the mastoid bodies and the anterior part of the bridge.
It includes cerebral aqueduct, on the one side of which the border is provided by the roof, and on the other, by the cover of the legs of the brain. On the ventral section, the posterior perforated substance and the legs of the large brain are distinguished, and on the dorsal one, the roof plate and the handles of the lower and upper tubercles.
If we consider the white and gray matter of the brain in the brain water supply, we will see that white surrounds the central gray matter, consisting of small cells and having a thickness of 2 to 5 millimeters. It consists of the block, trigeminal and oculomotor nerves along with the additional nucleus of the latter and the intermediate.
Diencephalon
It is located between the corpus callosum and the arch, and on the sides it grows together with the final brain. The dorsal section consists of visual tubercles, on the upper part of which there is an elevation, and in the ventral region there is a lower tubercle region.
The gray matter here is made up of nuclei that are connected to centers of sensitivity.
White substances are represented by pathways of different directions, guaranteeing the connection of formations with the cerebral cortex and nuclei. The pituitary and pineal gland also enter the diencephalon.
End brain
It is represented by two hemispheres, which are separated by a gap running along them. It connects deep in the corpus callosum and commissures.
The cavity is represented by lateral ventricles located in one and the second hemisphere. These hemispheres consist of:
- a cloak from a neocortex or a six-layer cortex, distinguished by nerve cells;
- striatum of basal nuclei - ancient, old and new;
- partitions.
But sometimes there is another classification:
- olfactory brain;
- subcortex;
- gray matter bark.
Without touching the gray matter, we dwell immediately on white.
About the features of the white matter of the hemispheres
The white matter of the brain occupies the entire space between the gray and basal nuclei. There is a huge amount of nerve fibers. In the white matter there are the following areas:
- the central substance of the inner capsule, corpus callosum, and long fibers;
- radiant crown of diverging fibers;
- semi-oval center in the outer parts;
- a substance located in the convolutions between the furrows.
Nerve fibers are:
- commissural;
- associative;
- projection.
Nerve fibers enter the white matter, which are connected by convolutions of one and the other cortex of the hemispheres and other formations.
Nerve fibers
Most commissural fibers are part of the corpus callosum. They are located in the brain commissures that connect the cortex in different hemispheres and symmetrical points.
Associative fibers group sites in one hemisphere. At the same time, short gyruses connect adjacent gyruses, and long ones are located at a distant distance from each other.
Projection fibers bind the cortex to those formations that are located below, and further to the periphery.
If you look at the inner capsule in the section from the front, the lenticular nucleus and hind leg will be visible. Projection fibers are divided into:
- fibers located from the thalamus to the cortex and in the opposite direction, they excite the cortex and are centrifugal;
- fibers directed to the motor nuclei of the nerves;
- fibers that conduct impulses to the muscles of the whole body;
- fibers directed from the cortex to the bridge nuclei, providing a regulatory and inhibitory effect on the work of the cerebellum.
Those projection fibers that are located closest to the cortex create a radiant crown. Then their main part passes into the inner capsule, where the white matter is located between the caudate and lenticular nuclei, as well as the thalamus.
On the surface there is an extremely complex pattern where grooves and ridges alternate between them. They are called convolutions. Deep furrows divide the hemispheres into large sections, which are called lobes. In general, the grooves of the brain are deeply individual, they can be very different in different people.
There are five lobes in the hemispheres:
- frontal;
- parietal;
- temporal lobe;
- occipital;
- island.
The central groove originates at the top of the hemisphere and moves down and forward to the frontal lobe. The area posterior to the central sulcus is the parietal lobe, which ends with the parieto-occipital sulcus.
The frontal lobe is divided into four convolutions, vertical and horizontal.
In the temporal lobe, the lateral surface is represented by three convolutions that are delimited from each other.
Furrows of the occipital lobe are variable. But all, as a rule, have a transverse one, which is connected to the end of the inter-dark furrow.
On the parietal lobe there is a furrow running parallel to the central horizontal and merging with another furrow. Depending on their location, this fraction is divided into three convolutions.
The island has a triangular shape. It is covered with short convolutions.
Brain damage
Thanks to the achievements of modern science, it has become possible to conduct high-tech brain diagnostics. Thus, if there is a pathological focus in the white matter, it can be detected at an early stage and therapy can be prescribed in a timely manner.
Among the diseases that are caused by the defeat of this substance, its disturbances in the hemispheres, pathology of the capsule, corpus callosum and mixed syndromes are distinguished. For example, with damage to the hind leg, one half of the human body can be paralyzed. This problem can develop with a violation of sensitivity or a defect in the field of view. Malfunctioning of the corpus callosum leads to mental disorders. At the same time, a person ceases to recognize surrounding objects, phenomena, etc., or does not perform targeted actions. If the focus is bilateral, disorders of swallowing and speech may be observed.
It is impossible to overestimate the importance of both gray and white matter in the brain. Therefore, the sooner the presence of pathology is detected, the more likely it is that the treatment will be successful.