The lenticular nucleus of the brain (nucleus lentiformis): functions, structure, possible pathologies

Head brain - the center of coordination of all functions of the human body. It is a complexly organized system with many departments and fields responsible for different processes.

The lenticular nucleus of the brain is an area that is part of the subcortical structures that make up forebrain. Located closer to its base.

Basal nuclei and their varieties

Basal nuclei Are accumulations of bodies neuronsresponsible for the regulation of movements and the formation of motivation. Macroscopically, they are represented by areas gray matter. Located between the frontal lobes and above the brainstem.

These structures are responsible for the following functions:

• automatic, involuntary coordination of muscle tone, complex movements;
• regulation of motor manifestations of emotions;
• maintaining posture;
• implementation of mining, defensive and other unconditioned reflexes;
• participation in the control of memory, attention.

Subcortical formations are closely related to other parts of the brain. These are paired structures separated by white matter. The latter is a formation of nerve fibers - conductors of signals from the nervous system.

Neural connections are realized through the synthesis and release of certain neurotransmitters:

• serotonin;
• dopamine;
• GABA (gamma-aminobutyric acid);
• acetylcholine;
• neuropeptides - vasoactive intestinal polypeptide, substance P, somatostatin.

Each of the presented elements has its own unique structure and function. Their interaction ensures complete regulation both in the brain itself and in the body as a whole.

Basal nuclei are usually divided into two systems according to their functional purpose:

1. The striopallidal system consists of three structures: the pallidum, the caudate nucleus, and the shell. The latter two, in turn, are combined under the name "striatum“, Since both elements have a layered structure. The shell and the globus pallidus also have a common name - the lenticular nucleus.
2. Part of the limbic system is formed by basal nuclei such as the amygdala and the enclosure. Its other elements are related to cortical structures.

The function of the striatum is to reduce muscle tone. It takes part in such areas as food-gathering behavior, the work of internal organs, the formation of conditioned reflexes.

The limbic system is responsible for emotions, memory, sleep and wakefulness cycles. The amygdala is associated with the manifestation of reactions such as fear, caution, and aggression.

Core structure

The lenticular nucleus of the brain was named for its external similarity to lentil seeds. It has the shape of an angle with a capsule in the middle. On the frontal cut, it is located wedge-shaped.

Topographically, the structure lies lateral (closer to the outside) of such formations as the caudate nucleus and thalamus and is separated from them by an inner capsule. It is divided by two parallel vertical layers of white matter into three sections:

1. The most lateral is putamen (shell). The largest nucleus of the basal ganglia. Outwardly, it has a darker color compared to other parts. Refers to the neostriatum, a newer formation of the brain. Consists of type II Golgi cells - small, with short dendrites and thin axons.
2. Lateral globus pallidus - part diencephalon. Located between the medial and lateral medulla plates, consisting of white matter.
3. The medial globus pallidus is located inward from the medial cerebral plate. Like the lateral one, it consists of large neurons, like motoneurons, and small intercalary - with short processes.

The term "lenticular nucleus" in modern literature is used for topographic designation of specific formations. When they talk about the functional purpose of the above structures, they use the term "striopallidal system".

The main functions of the lenticular kernel

The functional significance of the nucleus lentiformis should be considered according to the function of its constituents. The shell, being a later formed formation, has an inhibitory effect on the pallidum.

The latter, in turn, is responsible for the following processes:

• regulation of movement and muscle tone;
• the activity of mimic muscles, emotional reactions;
• participation in the regulation of the work of internal organs, especially the heart, blood vessels, gastrointestinal tract;
• integration of the activities of various systems of the body.

Accordingly, the shell reduces the aforementioned pallidus effects. She also takes part in the organization of eating behavior.

The striopallidal system affects the muscle in the following way:

• selects the most comfortable poses for a specific situation;
• regulates the ratio of the tone of different muscle groups;
• determines the proportionality of movements in time and space;
• controls the accuracy and smooth execution of actions.

It is this system that coordinates the work of all basal nuclei.

Possible pathologies

In violation of the activity of the nucleus, a separate group of pathologies develops - dyskinesia. They can be accompanied by both a decrease and an increase in function: hypokinesis and hyperkinesis, respectively.

Hyperkinesis

If the inhibitory effect on the globus pallidus is insufficient, hyperkinesis develops. They are characterized by sweeping, multidirectional, disordered movements.

The most common hyperkinesis are:

Name	Clinical picture	Provoking pathologies
Chorea	Swing legs and arms in different directions and with different intensities	Chorea Huntington Rheumatism Carbon monoxide poisoning Recurrent tonsillitis
Athetosis	Extension, flexion, twisting of the fingers	Wilson's disease, Lesha-Nihana, Huntington Birth trauma of a newborn Prematurity Fetal hypoxia A brain tumor Traumatic brain injury
Myoclonus	Short-term repetitive muscle contractions	Myoclonus (cortical myoclonus) Ketoacidosis, uremia Hyperosmolar coma Alpers disease Teya-Sachs Epilepsy Amyloidosis, hemochromatosis
Dystonia	Sudden turns of the body in different directions	Hypertonicity/ Muscle hypotension
Tremor	Shaking hands and feet	Multiple sclerosis Traumatic brain injury Parkinson's disease Tumor, brain abscess
Teak	Various fast simple movements	Psychotrauma Intoxication Tourette's syndrome
Restless legs syndrome	Shuddering legs, usually when falling asleep	Iron-deficiency anemia Diseases of the thyroid gland Arthritis Avitaminosis (group B) Magnesium deficiency

Certain viral diseases (in most cases, encephalitis) can also be complicated by the above symptoms.

Hypokinesis

Hypokinesis occurs when the striatum, shell and caudate nucleus begin to excessively inhibit the activity of the globus pallidus. They are of the following types:

1. Apraxia- the inability to make purposeful movements. At the same time, the ability to reproduce simple actions, of which complex ones are composed, is preserved.
2. Akinesia lies in the impossibility of performing arbitrary movements or changing them in volume, strength, speed. Partial loss of this ability, weakening of motor activity is called bradykinesia. A similar symptom is observed in hypothyroidism and Parkinson's disease.
3. Cataplexy - paroxysmal movement disorder. There is a sharp decrease in muscle tone.
4. Muscle stiffness - a state opposite to the previous one. There is a sudden increase in muscle tone, limiting motor activity.
5. Catatonia manifests itself by the "freezing" of a person for a long time in one position with increased muscle tone.

The above disorders are not an isolated manifestation of the disease. Similar conditions are observed both with damage to the lenticular nucleus, and with other diseases. Treatment of dyskinesias must be carried out in a comprehensive manner, affecting the cause of the development of the disease.

Neural connections and the functional significance of the lenticular nucleus, as well as its role in the development of pathologies, continues to be actively studied.