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 ganglia. 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.
Let's study in more detail what is gray and white matter in the brain.
What these substances are 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 is composed of nerve cells with processes. Nerve fibers connect different parts of the central nervous system and nerve centers.
Grey 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 nuclei and are of three types:
- radicular cells;
- beam neurons;
- internal cells.
The white matter of the spinal cord surroundsGray matter. It includes nerve processes that make up three fiber systems:
- intercalary and afferent neurons connecting different parts of the spinal cord;
- sensitive afferents that are long centripetal;
- motor afferent or long centrifugal.
Medulla oblongata
From the course of anatomy, we know that the spinal cord passes into the medulla oblongata. Part of this brain is thicker at the top than at the bottom. Its average length is 25 millimeters, and its 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, coordination of movements.
Hindbrain
This brain is made up of the pons and the cerebellum. Consider the gray and white matter in them. The bridge is a large white ridge at the back of the base. On the one hand, its border 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 the gray nucleus will be very visible here. Transverse fibers divide the pons into ventral and dorsal sections. In the ventral part, the white matter of the pathways is mainly present, and the gray matter here forms its nuclei.
The dorsal part is represented by nuclei: switching, reticular formation, sensory systems and cranial nerves.
The cerebellum is under the occipital lobes. It includes the hemispheres and middlepart called "worm". The gray matter makes up the cerebellar cortex and nucleus, which are hipped, spherical, corky and dentate. The white matter of the brain in this part is located under the cerebellar cortex. It penetrates all the convolutions as white plates and consists of various fibers that either connect the lobules and convolutions, or are directed to the inner nuclei, or connect sections of the brain.
Midbrain
It starts from the middle brain bladder. On the one hand, it corresponds to the surface of the brainstem between the pineal gland and the superior medullary velum, and on the other hand, to the area between the mastoid bodies and the anterior part of the pons.
It includes a cerebral aqueduct, on one side of which the boundary is provided by a roof, and on the other - by a cover of the legs of the brain. In the ventral area, the posterior perforated substance and the cerebral peduncles are distinguished, and in the dorsal area, the roof plate and handles of the lower and upper tubercles are distinguished.
If we consider the white and gray matter of the brain in the cerebral aqueduct, we will see that the white surrounds the central gray matter, consisting of small cells and having a thickness of 2 to 5 millimeters. It consists of the trochlear, trigeminal and oculomotor nerves, along with the accessory nucleus of the latter and the intermediate one.
Diencephalon
It is located between the corpus callosum and the fornix, and fuses with the telencephalon on the sides. The dorsal part consists of optic tubercles, on the upper part of which there is an epithelium, and in the ventr althe lower tubercular region is located.
The gray matter here consists of nuclei that are connected to the centers of sensitivity. White matter is represented by conducting paths in different directions, guaranteeing the connection of formations with the cerebral cortex and nuclei. The diencephalon also includes the pituitary and pineal glands.
Forebrain
Represented by two hemispheres separated by a gap running along them. It is connected in depth by the corpus callosum and adhesions.
The cavity is represented by lateral ventricles located in one and the second hemisphere. These hemispheres are composed of:
- cloak of neocortex or six-layered cortex differing in nerve cells;
- striatum from the basal ganglia - ancient, old and new;
- partitions.
But sometimes there is another classification:
- olfactory brain;
- subcortex;
- cortical gray matter.
Leaving gray matter out of the way, let's focus on white.
On the features of the white matter of the hemispheres
The white matter of the brain occupies the entire space between the gray and basal ganglia. There is a huge amount of nerve fibers here. The white matter contains the following regions:
- central substance of internal capsule, corpus callosum and long fibers;
- radiant crown of divergent fibers;
- semi-oval center in outer parts;
- substance located in the convolutions betweenfurrows.
Nerve fibers are:
- commissural;
- associative;
- projection.
The white matter includes nerve fibers that are connected by the convolutions of one and the other of the cerebral cortex and other formations.
Nerve fibers
Commissural fibers are mainly found in the corpus callosum. They are located in the cerebral commissures that connect the cortex on different hemispheres and symmetrical points.
Associative fibers group areas on one hemisphere. At the same time, short ones connect adjacent gyruses, and long ones - located at a far distance from each other.
Projection fibers connect the cortex with those formations that are located below, and further with the periphery.
If the internal capsule is viewed from the front, the lentiform nucleus and the posterior 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 motor nuclei of nerves;
- fibers that conduct impulses to the muscles of the whole body;
- fibers directed from the cortex to the pontine 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 internal capsule, where the white matter is located between the caudate and lenticular nuclei, as well asthalamus.
There is an extremely complex pattern on the surface, 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 furrows of the brain are deeply individual, they can be very different from person to person.
There are five lobes in the hemispheres:
- frontal;
- parietal;
- temporal;
- occipital;
- islet.
The central sulcus originates at the top of the hemisphere and moves down and forward to the frontal lobe. The area behind the central sulcus is the parietal lobe, which ends in the parietal-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, which are separated from each other.
The furrows of the occipital lobe are variable. But everyone, as a rule, has a transverse one, which is connected to the end of the interparietal sulcus.
On the parietal lobe there is a groove running parallel to the central one horizontally and merging with another groove. Depending on their location, this share is divided into three convolutions.
The island has a triangular shape. It is covered with short convolutions.
Brain lesions
Thanks to the achievements of modern science, high-tech brain diagnostics have become possible. Thus, if there is a pathological focus in the white matter, it can be detected at an early stage andprescribe therapy in a timely manner.
Among the diseases that are caused by the defeat of this substance, there are its violations in the hemispheres, pathologies of the capsule, corpus callosum and mixed syndromes. For example, with damage to the back leg, one half of the human body can be paralyzed. This problem may develop with sensory impairment or a visual field defect. Malfunctions of the corpus callosum lead to mental disorders. At the same time, a person ceases to recognize surrounding objects, phenomena, etc., or does not perform purposeful actions. If the focus is bilateral, swallowing and speech disorders may occur.
The importance of both gray and white matter in the brain cannot be overestimated. Therefore, the sooner the presence of pathology is detected, the more likely it is that the treatment will be successful.
