The red nucleus is a very specific structure of the brain related to movement, very prominent, and formed by a large group of nerve cells.
Although some of the functions it performs are known, it is a structure that is still partially unknown, and is still being investigated. In this article we will know the most known functions, its characteristics and the effects it produces in case of injury.
What is the red core of the brain?
This core is part of the tegmentum. The tegmentum, on the other hand, is located in another larger area, the midbrain . And the midbrain, in turn, is part of the brain stem.
The tegméntum is a brain area located in the brain stem , formed by 5 structures, among them the red nucleus.
Specifically, it is formed by: the periaqueductal gray substance (related to defense behavior and pain inhibition), the ventral tegmental area (related to reinforcement), the red nucleus (related to movement), the black substance (also related to movement) and the cerebral peduncles (which coordinate eye movements with the head and neck).
In turn, the red core is divided into two zones: the paleo-rubrum and the neorubrum . It has two portions, a lower magnocellular and an upper parvocellular.
Functions of this part of the brain
The red nucleus intervenes in the control of muscle tone, and inhibits the muscle contraction responsible for the tone . In addition, it participates in the control of the motility of the distal muscles of the arm and the proximal muscles of the legs. On the other hand, it participates in the motor coordination of the shoulder and upper arm.
Another function of the red core is that it participates in the crawling of babies, when they learn to do so. In addition, is responsible for the swinging movement of the arms when we walk . Even certain hand movements are also partially controlled by the red core.
On the other hand, the red nucleus acts as a relay centre for cerebellar and striated reflex pathways , and plays an important role in the cortical extrapyramidal pathways.
It is known that in animals that do not have an important corticospinal tract (involved in the control of voluntary movements), the red nucleus intervenes in their gait.
In addition, it is believed that some animals other than humans make more use of this brain structure. This is because in humans the corticospinal tract is more dominant .
Characteristics and anatomy
The color of the red core is a pink color that can be seen in fresh brain samples. Furthermore, as we have seen, it is formed by a large group of cells (a kind of mass).
This mass of cells is located in the area of the mesencephalic tegment of the midbrain , which extends from the substantia nigra (related to dopamine synthesis) to the brain aqueduct (containing cerebrospinal fluid). More specifically, it is located dorsally to the substantia nigra. Within it there is a rubrospinal tract, which crosses the nucleus itself through axons.
However, even if some things are known, much of the functioning of the red core in humans is unknown.
There is another structure related to movement and to the red nucleus, the rubrospinal tract (fibers that are born in the red nucleus). This is more specialised in the movement of large muscles (such as the arms), unlike the red core, which has more control over the hands.
Fine psychomotor skills (fine control of the fingers), on the other hand, depend on another related structure, the corticospinal tract, related to specific, voluntary movements.
The axons of the red nucleus (most of them) do not project to the spinal cord, but they do transmit information to the cerebellum , which comes from the motor cortex.
Injury and related disorders
What happens if the red core of the brain is injured? A muscular hypertonicity (increased muscle tone) may appear, causing stiffness in the body.
An injury to the tegment may also include the red core; in these cases, motor skills are impaired. Some symptoms that may appear are involuntary tremors , especially in the hands and arms.
Injury to the areas of the brain responsible for controlling, coordinating and managing movement (in addition to the red core), leads to a number of important motor disorders . However, the causes that give rise to this type of disorder are very varied and can go beyond what was initially mentioned.
There are two types of motor disorders: pyramidal (involving paralysis) and extrapyramidal (involving difficulties or alterations in the efficiency of movement). On a psychological level, the latter have more to do with the field of neuropsychology.
In extrapyramidal disorders there is interference in the execution of movements and reflexes . This may result in a loss of fluidity and efficiency of motor activities.
In turn, extrapyramidal disorders can be of three types:
- Rhythmic: tremors.
- Non-rhythmic and stereotyped: tics and stereotypes.
- Non-rhythmic and non-stereotyped: spasms, convulsions, dystonias, dyskinesias, akathisias, etc.
These disorders are related to the injury of some areas of the brain, such as the basal ganglia . They are also closely related to the dopamine (deficiencies of this substance) of the neostriatum, and to lesions in the subthalamic nucleus.
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