Cerebellum

Synonym

Medical: Cerebellum (lat.)

  • Nucleus dentatus
  • Nucleus emboliformis
  • Nucleus globosus
  • Nucleus fastigii

Another anatomically distinct area of the cerebellum is the so-called cerebellar tonsils. Although they are not functionally significant (at least no particular function has been attributed to them so far), they do play an important role in everyday clinical practice.

This is for the following reason: In the event of increased intracranial pressure, which can occur, for example, as a result of disturbed cerebrospinal fluid outflow (cerebrospinal fluid or liquor for short), the brain does not have much opportunity to avoid the pressure because of the inelastic bony calotte surrounding it. Actually, such an evasion is only possible in two places. Either brain mass is pressed into the cerebellar tent, which is known as the upper incarceration, or the aforementioned cerebellar tonsils are pressed down through the foramen magnum (opening in the base of the skull) and out (lower incarceration).

In both cases there is an acute danger of brain tissue damage, but the lower incarceration, i.e. that of the tonsils, is more dreaded and can become acutely life-threatening, since the respiratory center (located in the extended medulla, i.e. the medulla oblongata, which corresponds to the lowest part of the brain stem) is located in the immediate vicinity of the incarceration and can also be compressed if necessary, leading to immediate respiratory arrest. Functionally (i.e. not according to purely external aspects, but according to various functional attributions) the cerebellum is divided into three parts:

  • 1.

    spinocerebellum – anatomically it includes the worm and adjacent hemisphere areas on both sides

  • 2. pontocerebellum – corresponds anatomically to the lateral parts of the two hemispheres
  • 3. vestibulocerebellum – anatomically corresponds to the lobus flocculonodularis

This subdivision has the following reason: The Cerebellum receives information and sends information.

They reach or leave it in the form of nerve cell fibers. Fibers that enter the cerebellum and send information to it are called afferences (from afferre, lat = supply). Those that leave the cerebellum to take information generated here to another place are called efferences (from efferens, lat = to lead out).

These incoming and outgoing fibers each run in one of the three so-called cerebellar stems. Now, each of the three parts of the cerebellum mentioned above receives its afferences from different parts of the body, so it makes sense to structure them accordingly. The following table gives a handy overview of the three parts of the cerebellum and their inputs.

In addition, the names of the afferent fiber tracts are listed: cerebellar part | afferences from… | name of the fiber web Spinocerebellum | spinal cord | Tractus spinocerebellaris Pontocerebellum (Cerebrocerebellum) | cerebrum via bridge (Pons) | Tractus pontocerebellaris Vestibulocerebellum | brainstem centers of the organ of equilibrium (so-called Vestibular nuclei) | Tractus vestibulocerebellaris The names of the fibrous tracts (Tractus, lat. = strand) can be easily derived, they are each composed of two words. The first word describes the place where the fibers originate, the second word the place where they end.

For example, the Tractus pontocerebellaris: It goes from the bridge (Pons) to the cerebellum (Cerebellum), i.e. ponto-cerebellaris. Confusingly, there is now a further classification of the cerebellum, neither functional nor anatomical, but phylogenetic, i.e. according to phylogenetic development. The following table shows a short summary of how the anatomical, functional and phylogenetic classification is now related: Anatomical | Functional | phylogenetic Worm and adjacent hemisphere parts | Spinocerebellum | Palaeocerebellum Lateral hemisphere parts | Pontocerebellum | Neocerebellum Lobus flocculonodularis | Vestibulocerebellum | Archicerebellum The Archicerebellum is the phylogenetically oldest, the Neocerebellum (neo, Greek = new) the youngest part of the cerebellum.

While the medulla of the cerebellum, i.e. the part deep inside, contains mainly nerve fibers that move from one place to another in the central nervous system, the cerebellar cortex (cortex cerebelli) contains many cells.Although the cerebellum – as the name suggests – is by far not the largest part of the CNS in terms of size, the cortex contains about 50% of all CNS nerve cells. The cerebellum can be divided into three layers, each of which contains specific cell types. While the molecular layer contains the cell bodies of star cells and basket cells in particular, the Purkinje cell layer contains the cell bodies of Purkinje cells, the typical cells of the cerebellum.

Finally, the granular layer contains the somata of granule cells and Golgi cells. Nerve cells are distinguished between excitatory and inhibitory ones, depending on which neurotransmitter they pass on as “information” to the next cell after they have become excited themselves. All cells of the cerebellum are inhibitory nerve cells with GABA (short for gamma-amino-butyric acid) as neurotransmitter.

Only the granule cells are excitatory. Their neurotransmitter is glutamate.

  • Molecular layer (stratum moleculare) – outermost layer
  • Purkinje cell layer (Stratum purkinjense) – middle layer
  • Könerschicht (Stratum granulosum) – innermost layer, adjacent to the medulla