The cerebellum ("little brain") is a structure located at the back of the brain, at the base of the occipital and temporal cortex. Although the cerebellum makes up approximately 10% of the volume of the brain, it contains more than 50% of the total number of neurons in it.
The cerebellum has long been considered the motor structure of a person, because damage to it leads to deterioration in coordination of movements, balance of the body.
The figure above shows the brain. The cerebellum is indicated by an arrow.
This is how the small brain looks in section.
The cerebellum of the brain performs the following functions.
Maintain balance and posture
The cerebellum is very important for maintaining balance in the human body. It receives data from vestibular and proprioceptor receptors, and then modulates commands to motor neurons, as if warning them of changes in body position or excessive muscle load. People with damage to the cerebellum suffer from balance disorders.
Movement coordination
Most body movements involve several different muscle groups interacting together. It is the cerebellum that is responsible for coordinating movements in our body.
Motor learning
The cerebellum is of great importance for our learning. It plays an important role in adapting and fine-tuning motor programs to make movements precise through a process of trial and error (such as teaching baseball and other games that require body movement).
Cognitive processes (cognitive)
Although the cerebellum is most considered in terms of its contributions to the motor control unit, it is also involved in certain cognitive functions such as language. These functions of the cerebellum of the brain have not yet been studied so well that they can be discussed in more detail.
Thus the cerebellum has historically been considered part of the motor system, but its functions don't stop there.
Structure of the cerebellum
It consists of two main parts connected by a worm (intermediate zone). These two parts are filled with white matter covered by a thin layer of gray cortex (cerebellar cortex). Also in the white matter there are small accumulations of gray matter - the nucleus. Along the edge of the worm is a small particle - the cerebellar tonsil. It is involved in the coordination of movements, helps maintain balance. We offer a closer 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 take a closer look at only the mostbig parts.
The figure shows the cerebellum. The numbers indicate the hemispheres of the cerebellum and not only:
1 - anterior lobe; 2 - midbrain; 3 - varoli bridge; 4 - flocculent-nodular share; 5 - posterolateral crack; 6 - back share.
The numbers correspond to:
1 - cerebellar vermis; 2 - anterior share; 3 – main crack; 4 - hemisphere; 5 - posterolateral crack; 6 - flocculent-nodular share; 7 - back share.
Parts of the cerebellum
Two major fissures running mediolaterally divide the cerebellar cortex into three main lobes. A posterolateral fissure separates the flocculent lobe from the medulla, while the main fissure divides the medulla into anterior and posterior lobes.
The cerebellum of the brain is also divided sagittally into three zones - two hemispheres and the middle section (worm). The vermis is an intermediate zone between the two hemispheres (there are no clear morphological boundaries between the intermediate zone and the lateral hemispheres; the amygdala of the cerebellum is located between the vermis and the hemispheres).
Cerebellar nuclei
The cerebellum of the brain transmits all signals not without the help of the cerebellar deep nuclei. Thus, damage to the cerebellar nuclei has the same effect as complete damage to the entire cerebellum. There are several types of cores:
- The nuclei of the tent are the most medially located nuclei of the cerebellum. They receive signals from the afferents (nerve impulses) of the cerebellum, carrying vestibular, somatosensory, auditory and visual information. Localized inmainly in the white matter of the worm.
- The next type of cerebellar nuclei includes two types of nuclei at once - spherical and corky. They also receive signals from the intermediate zone (vermis) and cerebellar afferents, which carry spinal, somatosensory, auditory, and visual information.
- The dentate 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 cerebellar afferents, which carry information from the cerebral cortex (via the pontine nuclei).
- The vestibular nuclei are located outside the cerebellum, in the medulla oblongata. Therefore, they are not strictly cerebellar nuclei, but are considered functionally equivalent to these nuclei because their structures are identical. The vestibular nuclei receive signals from the flocculo-nodular lobe and from the vestibular labyrinth.
In addition to these signals, all nuclei and all parts of the cerebellum receive special impulses from the inferior olive of the medulla oblongata.
Let's clarify that the anatomical location of the cerebellar nuclei correspond to the areas of the cortex from which they receive signals. Thus, in the middle, the nuclei of the shart receive impulses from the worm located in the middle; lateral spherical and corky nuclei receive information from the lateral part of the intermediate zone (the same worm); and the lateralmost dentate nucleus receives signals from one or the other hemisphere of the cerebellum.
Pedicles of the cerebellum
Information to and from the nuclei of the cerebellum is transmitted with the help of legs. There are two types of pathways - afferent and efferent(going to and from the cerebellum, respectively).
- The inferior cerebellar peduncle (also called the rope body) mainly contains afferent fibers from the medulla oblongata, as well as efferents from the vestibular nuclei.
- The middle cerebellar peduncle (or pontine shoulder) mainly contains afferent fibers from the nuclei of the pons.
- The superior cerebellar peduncle (or connecting shoulder) primarily contains efferent fibers from the cerebellar nuclei, as well as some afferent fibers from the spinocerebellar tracts.
Thus, information is transmitted to the cerebellum mainly through the lower and middle cerebellar peduncles, and from the cerebellum is transmitted primarily through the superior cerebellar peduncle.
Here, parts of the cerebellum are shown in more detail. The drawing captures even the structure of the brain regions, more precisely, the structure of the midbrain. Numbers are:
1 - tent cores; 2 - spherical and corky nuclei; 3 - jagged nuclei; 4 - coarse nuclei of the cerebellum; 5 - superior colliculus of the midbrain; 6 - lower colliculus; 7 - upper medullary sail; 8 - superior cerebellar peduncle; 9 - middle cerebellar peduncle; 10 - lower cerebellar peduncle; 11 - tubercle of a thin nucleus; 12 - barrier; 13 - bottom of the fourth ventricle.
Functional divisions of the cerebellum
The anatomical divisions described above correspond to the three main functional divisions of the cerebellum.
Archicerebellum (vestibulocerebellum). This part includes the flocculent-nodular lobe and its connectionswith lateral vestibular nuclei. In phylogenesis, the vestibulocerebellum is the oldest part of the cerebellum.
Paleocerebellum (spinocerebellum). It includes the intermediate zone of the cerebellar cortex, as well as the tent nuclei, spherical and corky nuclei. As can be understood by the name, it receives the main signals from the spinocerebellar tracts. It is involved in the integration of sensory information with motor commands, producing adaptations of motor coordination.
Neocerebellum (pontocerebellum). Neocerebellum is the largest functional section, including the lateral hemispheres of the cerebellum and the dentate nuclei. Its name comes from the extensive connections to the cerebral cortex via the nuclei of the pons (afferents) and the 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 Purkinje cell layer, consists of a single row of large cells. The outer layer, the molecular layer, is made up of axons of granular cells and dendrites of Purkinje cells, as well as several other cell types. The Purkinje cell layer forms the boundary between the granular and molecular layers.
Granular cells. Very small, densely packed neurons. Cerebellar granule cells make up more than half of the neurons in the entire brain. These cells receive information from mossy fibers andproject it to Purkinje cells.
Purkinje cells. They are one of the brightest cell types in the mammalian brain. 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 cell types. In addition to the main types (granular and Purkinje cells), the cerebellar cortex also contains various types of interneuron, including the Golgi cell, basket cell and stellate cell.
Signaling
The cerebellar cortex has a relatively simple, stereotyped pattern of signaling capability that is identical throughout the entire cerebellum. Information can be entered into the cerebellum in two ways:
- Mossy fibers are produced in the pontine nuclei, 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 "tufts" when they come into contact with granular cells. Each mossy fiber innervates hundreds of granular cells. Granular cells send axons up towards the surface of the cortex. Each axon branches out in the molecular layer, sending signals in different directions. These signals travel along fibers that are called parallel because they run parallel to the folds of the cerebellar cortex, inpathways producing synapses with Purkinje cells. Each parallel fiber comes into contact with hundreds of Purkinje cells.
- Climbing fibers are produced exclusively in the inferior olive and transmit impulses to the cerebellar nuclei and Purkinje cells of the cerebellar cortex. They are called climbers because their axon rise and wrap around the dendrites of the Purkinje cell is like a climbing vine. Each Purkinje cell receives a single, extremely strong impulse from a single climbing fiber. Unlike mossy 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 transmission from the cerebellar cortex (note the difference between Purkinje cells, which transmit signals from the cerebellar cortex, and the cerebellar nuclei, which transmit 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. Perhaps everyone has experienced a state of intoxication? So, alcohol affects Purkinje cells quite strongly, because of which, in fact, a person loses balance and is not able to move normally while intoxicated with alcohol.
Even from this, we can conclude that the large cerebellum (occupying about 10% of the total mass of the brain) plays a large role in the human body.
