The cerebellum (the "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 accounts for approximately 10% of the brain volume, it contains more than 50% of the total number of neurons in it.
From time immemorial, the cerebellum was considered the motor structure of a person, because its damage leads to impaired coordination of movements, body balance.
The image above shows the brain. The cerebellum is indicated by an arrow.
This is what a small brain looks like in a section.
The cerebellum of the brain performs the following functions.
Maintaining balance and posture
The cerebellum is very important for maintaining balance in the human body. It receives data from vestibular receptors and proprioreceptors, after which it modulates commands for motor neurons, as if warning them of changes in body position or excessive muscle strain. People with cerebellar injuries suffer from an imbalance.
Motion coordination
Most body movements involve several different muscle groups 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 training. It plays an important role in adapting and tuning motor programs to make movements accurate through trial and error (for example, teaching baseball and other games that require body movement).
Cognitive processes (cognitive)
Although the cerebellum is most viewed in terms of its contributions to the motion control device, 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 could be described in more detail.
Thus, the cerebellum has historically been considered as part of the motor system, but its functions do not end there.
Cerebellum structure
It consists of two main parts connected by a worm (intermediate zone). These two parts are filled with white matter, covered with a thin layer of gray cortical substance (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 tonsil of the cerebellum. She participates in 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 largest parts.
The picture shows the cerebellum. The numbers indicate the cerebellar hemisphere and not only:
1 - anterior lobe; 2 - midbrain; 3 - Varoliev bridge; 4 - rag-nodular lobe; 5 - posterolateral crack; 6 - a back share.
The numbers correspond to:
1 - cerebellar worm; 2 - anterior lobe; 3 - the main crack; 4 - the hemisphere; 5 - posterolateral crack; 6 - rag-nodular lobe; 7 - a back share.
Cerebellar parts
The two main cracks running mediolaterally divide the cerebellar cortex into three main lobes. The posterolateral fissure separates the shredded-nodular lobe from the cerebral body, and the main fissure divides the cerebral body 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 worm is an intermediate zone between the two hemispheres (there are no clear morphological boundaries between the intermediate zone and the lateral hemispheres, and the cerebellar tonsil is located between the worm and the hemispheres).
Cerebellar nuclei
The cerebellum transmits all the signals with 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 nucleus of the tent is the most medially located nucleus of the cerebellum. They receive signals from afferents (nerve impulses) of the cerebellum, which carry vestibular, somatosensory, auditory and visual information. They are localized mainly in the white matter of the worm.
- The next type of cerebellar nuclei includes immediately two types of nuclei - spherical and cork-shaped. They also receive signals from the intermediate zone (worm) and afferents of the cerebellum, which carry dorsal, 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 afferents of the cerebellum, which carry information from the cerebral cortex (using the nuclei of the brain bridge).
- The vestibular nuclei are located outside the cerebellum, in the medulla oblongata. Therefore, they are not strictly cerebellum nuclei, but are considered functionally equivalent to these nuclei because their structures are identical. The vestibular nuclei receive signals from the shredded-nodular lobe and from the vestibular maze.
In addition to these signals, all nuclei and all parts of the cerebellum receive special impulses from the lower olive of the medulla oblongata.
We clarify that the anatomical location of the cerebellar nuclei corresponds to the regions of the cortex from which they receive signals. Thus, in the middle, the located nuclei of the chart receive impulses from the worm located in the middle; lateral spherical and cork-shaped nuclei receive information from the lateral part of the intermediate zone (the same worm); and the most lateral gear nucleus receives signals from one or the other hemisphere of the cerebellum.
Cerebellum legs
Information to and from the nuclei of the cerebellum is transmitted through the legs. There are two types of pathway - afferent and efferent (going to and from the cerebellum, respectively).
- The inferior cerebellar peduncle (also called the cord body) mainly contains afferent fibers from the medulla oblongata, as well as efferents of the vestibular nuclei.
- The middle cerebellar peduncle (or shoulder of the bridge) mainly contains afferent fibers from the nuclei of the warolium bridge.
- The superior cerebellar pedicle (or connective shoulder) primarily contains efferent fibers from the cerebellar nuclei, as well as some afferent fibers from the spinocerebellar tract.
Thus, information is transmitted mainly to the cerebellum through the lower and middle cerebellar legs, and from the cerebellum is transmitted primarily through the superior cerebellar pedicle.
Parts of the cerebellum are shown in more detail here. The drawing even captures the structure of the parts of the brain, more precisely, the structure of the midbrain. The numbers indicate:
1 - the core of the tent; 2 - spherical and cork-shaped nuclei; 3 - dentate nuclei; 4 - coarse cerebellar nuclei; 5 - upper dvuhlmie midbrain; 6 - lower dvuhme; 7 - upper cerebral sail; 8 - upper cerebellar pedicle; 9 - the middle cerebellar pedicle; 10 - lower cerebellar pedicle; 11 - tubercle of the thin nucleus; 12 - a barrier; 13 - the bottom of the fourth ventricle.
Functional units of the cerebellum
The anatomical units described above correspond to the three main functional units of the cerebellum.
Architserebellum (vestibulocerebellum). This part includes a patchy-nodular lobe and its connections with the lateral vestibular nuclei. In phylogenesis, vestibulocerebellum is the oldest part of the cerebellum.
Paleocerebellum (spinocerebellum). It includes the intermediate zone of the cerebellar cortex, as well as the nucleus of the tent, spherical and cork-shaped nuclei. What can be understood by name, it receives the main signals from the spinocerebellar tracts. He is involved in the integration of sensory information with motor commands, adapting motor coordination.
Neocerebellum (Pontocerebellum). Neocerebellum is the largest functional section, including the lateral cerebral hemispheres and dentate nuclei. Its name comes from extensive connections with the cerebral cortex using the nuclei of the bridge (afferents) and ventrolateral thalamus (efferents). He is involved in planning movement times. In addition, this section is involved in the cognitive function of the cerebellum.
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 layer of Purkinje cells forms the boundary between the granular and molecular layers.
Granular cells. Very small, tightly packed neurons. Cerebellar granular cells comprise more than half of the neurons in the entire brain. These cells receive information from mossy fibers and project it to Purkinje cells.
Purkinje cells. They are one of the most striking 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 a Golgi cell, a basket and a star-shaped cell.
Signal transmission
The cerebellar cortex has a relatively simple, stereotypical pattern of signal transmission that is identical throughout the cerebellum. The input of information into the cerebellum can be carried out in two ways:
- Mossy fibers are produced in the nuclei of the bridge, spinal cord, brain stem and vestibular nuclei; they transmit signals to the cerebellar nuclei and granular cells in the cerebellar cortex. They are called mossy fibers due to the appearance of "crests" in their contacts 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 through fibers, which are called parallel, because they travel parallel to the folds of the cerebellar cortex, producing synapses with Purkinje cells along the way. Each parallel fiber comes into contact with hundreds of Purkinje cells.
- Climbing fibers are produced exclusively in the lower olive and transmit impulses to the cerebellar nuclei and Purkinje cells of the cerebellar cortex. They are called climbers because their axon lift and wrapping around the Purkinje cell dendrites is like a rising 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 information from the cerebellar cortex (note the difference between the 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. Probably everyone on himself experienced a state of intoxication? So, alcohol influences Purkinje cells quite strongly, due to which, in fact, a person loses balance and is not able to move normally during alcohol intoxication.
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.