Cerebellum

The cerebellum is an organ that receives information from the sensory systems , the spinal cord, and other parts of the brain and is then responsible for regulating motor movements . Coordinates voluntary movements such as posture, balance, coordination, and speech, resulting in smooth, balanced muscle activity.

It is a relatively small portion of the brain, approximately ten percent of the total weight, but containing about half of the neurons of the brain , specialized cells that transmit information via electrical signals.  The cerebellum is not unique to humans as it is also present in animals. Evolutionarily speaking, it is the portion most ancient of the brain.

Histology

The histological pattern of the cortex is basically the same in all areas, and it can be considered to be the sum of a multitude of histo-functional units known as lamellae . The cortex of the cerebellum is a structure that measures approximately 1 mm thick and consists of three main layers: the molecular layer , the granular layer, and an intermediate layer in which the Purkinje cells are located .

These Purkinje cells are unique and have a large number of dendrites , their axons form a pathway for the correct output of information that leaves the cerebellar cortex and distributes the information to neurons in the gray nuclei of the cerebellum.

We find within the cerebellum two different types of sensory input , climbing fibers and mossy fibers , which, in turn, influence Purkinje cells.

When a cut is made in the cerebellum, two types of nerve tissues can be seen, the gray and the white matter . The gray matter creates a thin sheet that covers the cerebellar surface. The union that occurs between the cerebellum and the brain stem is made through the cerebellar peduncles , and they are the entry and exit routes of information.

They can also be found cerebellar afferents are formed in turn by fascicles cerebellar hawthorn , one dorsal and ventral one. We found a molecular layer , a granular layer , the Purkinje axons, mossy and climbing fibers and the white matter .

Characteristics of the cerebellum

The most notable characteristics of the cerebellum are as follows:

• It is ovoid in shape and weighs approximately 150-180 grams.
• A man’s cerebellum is heavier than a woman’s.
• Its approximate size is 8 cm x 5 cm x 5 cm .
• It is covered by liquid cerebrospinal .
• It is made up of two hemispheres with a cavity in the center called the Vermis .
• In the cerebellum we find about 50% of the neurons in the brain.

Location

It is located in the posterior part of the brain at the level of the brainstem bridge , below the occipital lobe , a little above the nape. The peduncles are responsible for joining the cerebellum with the brain.

Parts of the cerebellum

The cerebellum has a surface with transverse grooves. According to these grooves, it has the following parts:

• Anterior lobe : It is located above the Cisura Prima . It is responsible for connecting the cerebellum with the spinal cord. Regulates muscle tone, trunk movement and limbs.
• Posterior lobe : Located between the Prima Fissure and the Posterolateral Fissure, its function is to connect the cortex. Regulates voluntary movements and cognitive functions.
• Flocculonodular lobe : It is below the Posterolateral Fissure and connects the vestibular and reticular nuclei . Promotes balance, position, head movement and eye movements.

Nuclei

The nuclei that exist in the cerebellum are a group of neuronal bodies that work in coordination to carry out a series of functions. The most important nuclei of the cerebellum are:

• Nucleus fastigio : it is also known as the nucleus of the roof and is responsible for receiving the projections of the cortex of the vermis.
• Globose nucleus : called posterior interposition and it is the cortex that is located between the vermis and the two cerebellar hemispheres.
• Emboliform nucleus : receives the projections that are given from the cerebral cortex .
• Serrated nucleus : it is divided into a lateral part , a paleo- serrated part and a non-serrated part .

Function

The primary function of the cerebellum is to coordinate the sensory and motor pathways . This means that the cerebellum is what makes it possible for the muscles to react to different sensory stimuli . It generates reactions or responses quickly when it is generated to a danger signal that comes from the outside and then sends the signal to the brain so that it can react quickly and the reaction occurs .

It also participates in the proper preservation of muscle tone , intervenes and regulates the movements of the human body, both voluntary and involuntary, in addition to the muscles that surround the skeleton.

Diseases and injuries of the cerebellum

The most common lesions in the cerebellum are the following:

• Cancer
• Genetic diseases, such as the Dandy Walker malformation .
• Cell degeneration that occurs when brain cells are defective.
• Hypotonia or muscle tone below normal.
• Movement disorder or ataxias , which is manifested by a lack of muscle control in the legs and arms.
• Cognitive-affective cerebellar syndrome that affects emotions and thinking, attention, memory, language and personality can be affected.