The brain coordinates absolutely all the processes of our body. Probably everyone knows about the cerebral cortex, hemispheres and medulla oblongata. However, besides them, there are many more structures in the brain that perform extremely important functions. These structures include the basal nucleus. And one of the constituent parts of this structure is the lenticular nucleus.
Basal nuclei: what is it?
The bulk of the gray matter formed by the bodies of nerve cells, or neurons, is located in the cerebral cortex. However, there is an accumulation of bodies of neurons in the back of the brain. These clusters are called basal nuclei, or extrapyramidal system. They are not isolated from the rest of the brain, but constantly interact with both the cortex and the white matter.
Basal nuclei: varieties
The basal ganglia, or nuclei, include the following structures:
- striatum (striopallidar system), which, in turn, is divided into a caudate and lenticular nucleus;
- amygdala ;
- fence.
The striped body got its name due to the presence of successive sections of white and gray matter.
Lenticular nucleus: structure
The structure of this part of the basal nucleus should be considered in the context of the caudate nucleus, since some of their parts have a similar histological structure.
The core itself consists of two parts:
- shells (the darker part);
- pale ball (lighter).
It is the shell that is similar in structure to the caudate ganglion. Their nerve cells are characterized by the presence of short dendrites and one thin long process (axon). From above, the shell receives connections from the cerebral cortex, mainly from its extrapyramidal part. However, many links also come from other parts.
From the shell, the long processes - axons - go to the other part of the lenticular ganglion - to the pale ball. Only from it the processes continue their path to the thalamus, and from there to the cerebral cortex. In addition to these structures, the shell is associated with other formations in the brain: substantia nigra, red nuclei, and cerebellum.
A pale ball consists of larger nerve cells. It is considered the oldest formation among the basal ganglia. The axons of the neurons that make up the pale ball stretch their processes to the thalamus, shell, caudate nucleus, midbrain, and hypothalamus.
Such a large number of connections between the lenticular nucleus and other structures of the brain confirms its great functional significance.
Main functions
The functions of the lenticular nucleus, as well as its structure, should also be considered together with the caudate nucleus, since they are inextricably linked with each other. The striopallid system is the basis of all the basal ganglia, coordinating their work. It really performs a huge number of functions in the body, the main of which is the regulation of motor activity, the implementation of precise movements. With the participation of the striatum, it becomes possible:
- creating the optimal posture to perform a certain action;
- creating the necessary ratio in muscle tone;
- smoothness and accuracy of movements;
- their proportionality in space and time.
Lenticular nucleus: possible pathologies
When the striatum is damaged, a specific type of movement disorder develops - dyskinesia. There are two possible options for dyskinesia: hypo-and hyperkinesis.
Hypokinesis means pallor and inexpressive movements. They occur with an increase in the inhibitory, that is, inhibitory, effect of the striatum on a pale ball.
Hyperkinesis - sweeping, disordered, defocused movements. In the absence of inhibitory effect, the striatal system affects a pale ball.
Types of Hyperkinesis
When the lenticular nucleus of the brain is damaged, the following types of disordered motor activity may occur:
- Athetosis - involuntary movements of the fingers, their twisting, bending, extension.
- Chorea - sweeping swings of arms and legs in different planes and directions. They can be both weakly expressed and strong. A characteristic disease manifested by this hyperkinesis is called “Gangtington’s chorea.” With this pathology, in addition to the defeat of the basal ganglia, cortical atrophy occurs, which leads to mental and intellectual disorders.
- Dystonia - sudden uncontrolled turns of the body in different directions.
- Myoclonia is a permanent short-term contraction of muscle fibers.
- Restless legs syndrome - observed when falling asleep, sudden movement of the legs according to the type of strokes, trembling.
- Tick - fast, short-term, simple movement.
- Tremor - trembling movements of the limbs.
It is characteristic that all these movements are involuntary, that is, they cannot be controlled by consciousness. In fact, there are much more types of them; the above are only the most common in neurological practice.
Types of hypokinesis
With damage to the lenticular nucleus, the following types of hypokinesis are also possible:
- Akinesia - a complete lack of motor activity, bradykinesia - a decrease in motor activity. This is most characteristic of Parkinson's disease, where the deviation is combined with increased muscle tone, mental disorders, stoop, and a decrease in facial activity. In addition, a similar pathology occurs with endocrinological diseases, namely with hypothyroidism - a decrease in thyroid activity.
- Apraxia - the lack of the ability to make targeted movements in the presence of normal elementary movements.
- Cataplexy - a sudden drop in muscle tone. Sometimes it leads to a fall and injury to the patient.
- Catatonia - "freezing" of the patient for a long time in the position in which he was "left" is accompanied by a high muscle tone. In this position, the patient can remain for weeks and months.
- Muscular rigidity - increased muscle tone, which leads to a decrease in the number of movements.
The conditions listed above are not independent diseases. As a rule, dyskinesia is just one of many symptoms that can lead to a correct diagnosis. The origin of many of these pathologies is not fully known, and the disruption of the lenticular nucleus is only one of many reasons. Therefore, the approach to the treatment of dyskinesias should be comprehensive, often, in addition to neurological, psychiatric help is needed.
Thus, the article provides an answer to the question of what it is - a lenticular nucleus. In short, this is a complex, complexly organized structure, one of the components of the extrapyramidal system, due to the presence of which we can perform accurate actions.