Cerebellar neurophysiology

2021-06-16 03:29 PM

The cerebellum has the function of regulating muscle tone, thereby maintaining balance for the body. At the same time, the cerebellum is considered a control organ

Structural features

The cerebellum is the part of the central nervous system located in the posterior fossa, just behind the brain stem.

The cerebellum is connected to the brain stem by 3 pairs of cerebellar peduncles:

The upper pair connects to the midbrain.

The middle pair connects to the pons.

The lower pair connects to the medulla oblongata.

In fact, the cerebellar peduncles are the connections of the cerebellum with other parts of the nervous system.

The cerebellum consists of the central pupal lobe and the two cerebellar hemispheres on either side. Each cerebellar hemisphere has an outer layer of gray matter called the cerebellar cortex, inside is white matter containing some important gray nuclei such as the tooth nucleus and the roof nucleus (Fastigial nucleus).

The cerebellar cortex consists of 3 layers:

The outermost layer is the molecular layer that contains neurons.

The middle layer: is the Purkinje cell layer.

The innermost layer is the granular layer containing the Golgi cells.

According to the evolutionary ladder, the cerebellum is divided into 3 parts:

Primordial cerebellum

It is the pupal lobe, this is the earliest part of the evolutionary ladder, the cerebellum is closely related to the vestibular nucleus in the medulla, so it has a major function in regulating muscle tone and maintaining muscle tone. balance for the body.

Cervical cerebellum

This part receives the transmission lines from the spinal cord, in which the important is the unconscious deep sensory tract from which the cerebellum regulates automatic movements, regulates muscle tone and maintains balance for the muscles. body.

New cerebellum

The slowest part of the evolutionary ladder. The cerebellum is newly developed in higher animals and in humans is the most complete.

The neocortex is closely related to the cerebral cortex to contribute to the co-cortical regulation of voluntary movements.

Connections of the cerebellum

The connections to and from the cerebellum all pass through three pairs of cerebellar peduncles:

The pathways terminate in the cerebellar cortex.

The exit lines come from the roof nucleus and the tooth nucleus.

The cerebellar cortex acts as a mediator between these two pathways.

Pathways to the cerebellum

The medulla - cerebellum cross (bundle of Gowers) and the medulla - cerebellum rectilinear (bundle of Flechsig):

These two bundles originate from the receptors in the tendons, muscles, and joints, then enter the spinal cord and terminate in the cerebellar cortex (cervical cerebellum), giving the cerebellum the sensation of muscle tone (sensation of the depth of space). conscious).

Bundle of Goll and Burdach:

These two bundles transmit conscious depth sensation, mainly to the cerebral cortex, but to a small extent into the cerebellum, giving the cerebellum son sensory perception.

Vestibular - cerebellar bundle:

It originates from a balancing receptor in the inner ear, the labyrinth then travels to the vestibular nucleus in the medulla oblongata and ends in the pupal lobe (cerebellum), giving the cerebellum a sense of balance.

cortex - pons - cerebellum:

Originating from the motor areas of the cerebral cortex, then going down to the pons and ending in the cerebellar cortex, conducts motor impulses of the cerebral cortex.

Cerebellar - cerebellar bundle:

Originating from the dentate nucleus of the other cerebellar hemisphere and ending in the lateral cerebellar cortex, this bundle holds the connection between the two cerebellar hemispheres.

Paths out of the cerebellum

Cerebellar - vestibular bundle:

Starting from the roof nucleus, it goes to the vestibular nucleus and then divides into 2: one goes to the oculomotor nerve, one goes down to the spinal cord and then exits along the motor cord.

Cerebellar bundle - medulla oblongata:

Starting from the roof nucleus goes to the reticular structure in the medulla oblongata.

Cerebellar bundle - red nucleus:

Starting from the tooth nucleus, going to the red nucleus in the midbrain, then going down the spinal cord and following the motor roots out.

Cerebellum - thalamus - cerebral cortex:

Originating from the dentate nucleus goes up the thalamus and goes to the motor area of ​​the cerebral cortex.

Functions of the cerebellum

The cerebellum has the function of regulating muscle tone, thereby maintaining balance for the body. At the same time, the cerebellum is considered an organ that controls and regulates both automatic and voluntary movements.

Function to regulate muscle tone and keep the balance for the body

The cerebellum receives the sense of balance from the labyrinth of the inner ear (vestibular bundle - cerebellum) and receives the sensation of muscle tone from the deep unconscious sensory tract (medullary bundle - cerebellum diagonal and straight).

The cerebellum will transmit impulses downward (through the cerebellum - vestibular bundles, cerebellum - red nucleus) to regulate muscle tone and balance the body.

Automatic movement regulation function

The extrapyramidal tract originating from the premotor area of ​​the cerebral cortex and the subcortical Gray nuclei before descending to the spinal cord both send impulses to the cerebellum, from which the cerebellum contributes to the regulation of automatic movements.

Active movement regulation function

Active movement is controlled by the cerebral cortex (motor area). However, impulses from the cortical motor area before descending to the spinal cord are partially sent to the cerebellum. At the same time, the cerebellum also receives part of the conscious depth sensation from below (Goll and Burdach bundles). Therefore, the cerebellum is also involved in the regulation of active movements.

When the cerebellum is damaged, the active movements will be disturbed.

Cerebellar syndrome

When the cerebellum is damaged (tumour, infection, trauma...) will appear pathological symptoms. This collection of pathological symptoms is called cerebellar syndrome. A complete cerebellar syndrome includes the following:

Decreased muscle tone.

Syndrome 3 wrong: wrong range, wrong direction, wrong rhythm.

Run: run when working, the more complicated the movement, the more shaking.

Eyeball twitch.

Loss of balance: wobbling, falling easily, walking in a zigzag pattern.

Pronunciation disorders: speaking when fast and slow, when loud when small, difficult to speak.