The brain coordinates absolutely all the processes of our body. Probably everyone knows about the cerebral cortex, hemispheres and medulla oblongata. However, in addition to them, there are many more structures in the brain that perform extremely important functions. These structures include the basal ganglia. 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 depths of the substance of the brain. These accumulations are called the basal nuclei, or the extrapyramidal system. They are not isolated from the rest of the brain, but are constantly interacting with both the cortex and the white matter.
Basal nuclei: varieties
The basal ganglia, or nuclei, include the following structures:
- striate body (striopallidal system),which, in turn, is subdivided into the caudate and lenticular nuclei;
- almond-shaped body;
- fence.
The striatum got its name from the presence of alternating patches of white and gray matter.
Lentil-shaped core: 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 (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, there are many connections from other parts as well.
From the shell, long processes - axons - go to another part of the lenticular ganglion - to the pale ball. Only from it do the processes continue their way to the thalamus, and from there to the cerebral cortex. In addition to these structures, the shell is connected with other formations in the brain: substantia nigra, red nuclei, cerebellum.
The pale ball is made up of larger nerve cells. It is considered the oldest formation among the basal ganglia. Axons of neurons that make up the globus pallidus extend their processes to the thalamus, putamen, caudate nucleus, midbrain, 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 striopallidary 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 for performing a certain action;
- creating the necessary ratio in muscle tone;
- smooth and precise movements;
- their proportionality in space and time.
Lenticular nucleus: possible pathologies
When the striatum is affected, a specific type of movement disorder develops - dyskinesia. Two variants of dyskinesia are possible: hypo- and hyperkinesis.
Hypokinesis means pallor and inexpressiveness of movements. They arise with an increase in the inhibitory, that is, inhibitory, effect of the striatum on the pale ball.
Hyperkinesis - sweeping, disordered, unfocused movements. Arise in the absence of inhibitory influence of the striatal system on the pale ball.
Types of hyperkinesis
When the lentiform is affectednuclei of the brain, the following types of disordered motor activity can occur:
- Athetosis - involuntary movements of the fingers, their twisting, flexion, 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 "Hangtington's chorea". With this pathology, in addition to damage to the basal ganglia, atrophy of the cortex occurs, which leads to mental and intellectual disorders.
- Dystonia - sudden uncontrolled turns of the torso in different directions.
- Myoclonus is a constant short-term contraction of muscle fibers.
- Restless legs syndrome - observed when falling asleep, sudden movements of the legs like kicks, shudders.
- Tick - quick, short, 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 many more types of them, the above are only the most common in neurological practice.
Types of hypokinesis
In case of 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 increasedmuscle tone, mental disorders, stoop, decreased facial activity. In addition, a similar pathology occurs with endocrinological diseases, namely with hypothyroidism - a decrease in the activity of the thyroid gland.
- Apraxia - the inability to make purposeful movements in the presence of normal elementary movements.
- Cataplexy - a sudden drop in muscle tone. Sometimes 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", accompanied by high muscle tone. In this position, the patient can remain for weeks and months.
- Muscle rigidity - increased muscle tone, resulting in 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 malfunction of the lentiform nucleus is just one of many causes. Therefore, the approach to the treatment of dyskinesias should be comprehensive, often, in addition to neurological, psychiatric care 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, thanks to the presence of which we can perform precise actions.
