Cerebrospinal Brain. Structure and function of the cerebellum

The cerebellum ("small brain") is a structure that is located in the back of the brain, at the base of the occipital and temporal lobes of the cortex. Although the cerebellum is approximately 10% of the brain volume, it contains more than 50% of the total number of neurons in it.

Long since the cerebellum was considered a motor structure of a person, because its damage leads to impairment of coordination of movements, balance of the body.

The picture above shows the brain. The cerebellum is indicated by an arrow.

This is how the small brain looks in a cut.

The cerebellum cerebrum performs the following functions.

Maintaining balance and posture

The cerebellum is very important for maintaining balance in the human body. He receives data from the vestibular receptors and proprioceptors, and then modulates the commands for the motor neurons, as if warning them of changes in the position of the body or an unnecessary strain on the muscles. People with cerebellar lesions suffer from a balance disorder.

Coordination of movements

In most body movements, several different muscle groups participate, interacting together. It is the cerebellum that is responsible for the coordination of movements in our body.

Motor training

The cerebellum is of great importance for our learning. It plays an important role in adapting and tuning motor programs to make movements precise through trial and error (for example, learning baseball and other games for which body movement is required).

Cognitive processes

Although the cerebellum is most viewed from the point of view of its contributions to the movement control device, it is also involved in certain cognitive functions, for example, such as language. These functions of the cerebellum of the brain have not yet been studied so well that they can be described in more detail.

Thus, the cerebellum is historically regarded as part of the motor system, but its functions do not end there.

Structure of the cerebellum

It consists of two main parts connected by a worm (intermediate zone). These two parts are filled with a white substance, covered with a thin layer of gray cortex (the cerebellar cortex). Also in the white matter there are small accumulations of gray matter - the nucleus. At the edge of the worm is a small particle - the amygdala of the cerebellum. It participates in coordination of movements, helps to maintain balance. We offer a more detailed look at the structure of the cerebellum.

The cerebellum is divided into many small parts, each of which has its own name, but in the article we will consider in more detail only the largest parts.

The figure shows a cerebellum. Numbers indicate the hemispheres of the cerebellum and not only:

1 - anterior lobe; 2 - the middle brain; 3 - the varioli bridge; 4 - scrapie-nodal lobe; 5 - posterolateral fissure; 6 - posterior lobe.

The figures correspond to:

1 - the worm of the cerebellum; 2 - anterior lobe; 3 - the main crack; 4 - hemisphere; 5 - posterolateral fissure; 6 - scrapie-nodal lobe; 7 - posterior lobe.

Parts of the cerebellum

Two major cracks, running mediolaterally, divide the cerebellar cortex into three major lobes. The zadnobokovaya fissure separates the scrapie-nodular portion from the medulla, and the main fissure divides the medulla into the anterior and posterior lobes.

The cerebellum also divides sagittally into three zones - the two hemispheres and the middle section (the worm). The worm is an intermediate zone between the two hemispheres (there are no distinct morphological boundaries between the intermediate zone and the lateral hemispheres, the amygdala of the cerebellum lies between the worm and hemispheres).

Cerebellar cores

All signals cerebellum of the brain transmits, not without the help of cerebellar deep cores. Thus, damage to the cerebellar cores has the same effect as complete damage to the entire cerebellum. There are several types of cores:

1. The tent core is the most medially located nucleus of the cerebellum. They receive signals from the afferents (nerve impulses) of the cerebellum, carrying the vestibular, somatosensory, auditory and visual information. They are localized mainly in the white matter of the worm.
2. The next kind of nucleus of the cerebellum includes at once two types of nuclei - globose and cork-shaped. They also receive signals from the intermediate zone (worm) and the afferents of the cerebellum, which carry spinal, somatosensory, auditory and visual information.
3. Toothed nuclei are the largest in the cerebellum and are located on the side of the previous type. They receive signals from the lateral hemispheres and afferents of the cerebellum, which carry information from the cerebral cortex (using the nuclei of the brain bridge).
4. Vestibular nuclei are located outside the cerebellum, in the medulla oblongata. Consequently, they are not strictly nuclei of the cerebellum, but are considered functionally equivalent to these nuclei, because their structures are identical. Vestibular nuclei receive signals from the scrapie-nodal lobe and from the vestibular labyrinth.

In addition to these signals, all nuclei and all parts of the cerebellum receive special impulses from the lower olive of the medulla oblongata.

Let us specify that the anatomical location of the cerebellar cores corresponds to the areas of the cortex from which they receive signals. Thus, in the middle, the located core of the shart receives impulses from a worm located in the middle; Lateral globular and cork-shaped nuclei receive information from the lateral part of the intermediate zone (the same worm); And the most lateral jagged nucleus receives signals from one or the other hemisphere of the cerebellum.

Cerebellum legs

Information to the nuclei and from the nuclei of the cerebellum is transmitted with the help of the legs. There are two types of pathway: afferent and efferent (reaching the cerebellum and from it, respectively).

1. The lower cerebellar pedicle (also called the rope body) basically contains afferent fibers from the medulla oblongata, as well as the efferents of the vestibular nuclei.
2. The middle cerebellar pedicle (or bridge shoulder) mainly contains afferent fibers from the nuclei of the variolium bridge.
3. The upper cerebellar pedicle (or connecting shoulder) primarily contains efferent fibers from the cores of the cerebellum, as well as some afferent fibers from the spinocerebellar tracts.

Thus, information in the cerebellum is transmitted mainly through the lower and middle cerebellar legs, and from the cerebellum is transmitted primarily through the upper cerebellar pedicle.

Here the parts of the cerebellum are shown in more detail. Figure captures even the structure of the brain, or rather, the structure of the midbrain. The numbers are:

1 - the core of the tent; 2 - spherical and cork-shaped nuclei; 3 - serrated nuclei; 4 - coarse nuclei of the cerebellum; 5 - upper diochloria of the midbrain; 6 - lower dysthonia; 7 - upper cerebral sail; 8 - upper cerebellar pedicle; 9 - middle cerebellar pedicle; 10 - lower cerebellar pedicle; 11-tubercle of a thin nucleus; 12 - barrier; 13 - bottom of the fourth ventricle.

Functional subdivisions of the cerebellum

The anatomical units described above correspond to the three main functional divisions of the cerebellum.

Archiscerebellum (vestibulocerebellum). This part includes the scrapie-nodular lobe and its connections with the lateral vestibular nuclei. In phylogenesis, vestibulocerebellum is the oldest part of the cerebellum.

Paleocerebellum (Spinocerebellum). It includes an intermediate zone of the cerebellar cortex, as well as tent core, globose and cork-shaped nuclei. What can be understood by name, it receives the main signals from the spinocerebellar tracts. He participates in the integration of sensory information from motor teams, producing an adaptation of motor coordination.

Neocerebellum (pontocerebellum). Nocerebellum is the largest functional section, including the lateral hemispheres of the cerebellum and the jagged nuclei. Its name comes from extensive connections with the cortex of the brain with the help of the nuclei of the bridge (afferents) and ventrolateral thalamus (efferents). He participates in planning the time of movement. In addition, this section is involved in the cognitive function of the cerebellum of the brain.

Histology of the cerebellar cortex

The cerebellar cortex is divided into three layers. The inner layer, granular, is made of 5 x 1010 small, tightly connected cells in the form of granules. The middle layer, the layer of Purkinje cells, consists of one row of large cells. The outer layer, molecular, is made of axons of granular cells and dendrites of Purkinje cells, as well as several other types of cells. The Purkinje cell layer forms the boundary between the granular and molecular layers.

Granular cells. Very small, tightly packed neurons. Cerebellar granular cells make up more than half of the neurons in the entire brain. These cells receive information from mossy fibers and design it to the Purkinje cells.

Purkinje cells. They are one of the most striking types of cells in the brain of mammals. Their dendrites form a large fan of finely branched processes. It is noteworthy that this dendritic tree is almost two-dimensional. In addition, all Purkinje cells are oriented in parallel. This device has important functional considerations.

Other types of cells. In addition to the main types (granular and Purkinje cells), the cerebellar cortex also contains various types of interneuron, including the Golgi cell, the basilar and star-shaped cell.

Signaling

The cerebellar cortex has a relatively simple, stereotyped pattern of signal transmission capability that is identical throughout the entire cerebellum. Information entry into the cerebellum can be carried out in two ways:

1. Mossy fibers are produced in the nuclei of the bridge, spinal cord, brainstem and vestibular nuclei, they transmit signals to the cerebellar nuclei and granular cells in the cerebellar cortex. They are called mossy fibers because of the appearance of "crests" when they come into contact with granular cells. Each mossy fiber innervates hundreds of granular cells. Granular cells send axons upward toward the surface of the cortex. Each axon branches into the molecular layer, sending signals in different directions. These signals go through the fibers, which are called parallel, because they run parallel to the folds of the cerebellar cortex, making synapses with Purkinje cells along the way. Each parallel fiber comes into contact with hundreds of Purkinje cells.
2. The climbing fibers are produced exclusively in the lower olive and transmit pulses to the cerebellar nuclei and cells of the Purkinje cerebellar cortex. They are called climbing, because their ascent of axons and wrapping around the dur- drits of the Purkinje cell is like a climbing vine. Each Purkinje cell receives a single, extremely strong impulse from a single climbing fiber. Unlike moss fibers and parallel fibers, each climbing fiber binds to 10 Purkinje cells on average, making ~300 synapses with each cell.

The Purkinje cell is the only source of information transmitted from the cerebellar cortex (note the difference between the Purkinje cells that transmit signals from the cerebellar cortex and the cerebellar cores that give information from the entire cerebellum).

Now you have an idea of what the cerebellum of the brain is. Its functions in the body are really very important. Probably everyone was experiencing a state of intoxication? So, alcohol strongly influences the Purkinje cells, because of what, in fact, a person loses his balance and is not able to move normally during alcohol intoxication.

Even from this it can be concluded that a large cerebellum (occupying about 10% of the total mass of the brain) plays a large role in the human body.