Midbrain: characteristics, parts and functions

The midbrain is one of the most important parts of the brain, in many ways. On the one hand, it is located almost in the center of the brain, occupying a part of its deepest area, and for consequently establishes direct communication with many of the major structures of the nervous system central.

On the other, it is the area that joins the brainstem to the diencephalon and parts of the cerebral cortex. Without the midbrain we could not survive.

Next we will see what are the characteristics of this region of the brain, we will review its main functions and its different anatomical components, and we will see what happens when certain injuries or diseases alter its functioning.

• Related article: "Parts of the human brain (and functions)"

What is the midbrain?

The midbrain is one of the parts of the brain stem. It is located in its upper area, on the bridge of Varolio (or protuberance), and just below the diencephalon, composed mainly of the thalamus and the hypothalamus. It is the part of the brainstem closest to the center of the brain, while the pons and the medulla oblongata are more oriented towards the spinal cord.

Also, the midbrain It is crossed by a narrow canal called Silvio aqueduct, through which the cerebrospinal fluid from the third ventricle to the fourth. This liquid has the function of isolating and protecting various structures of the nervous system.

• You may be interested: "Brainstem: functions and structures"

Your anatomy

The shape of the midbrain is that of a trapezium, with a base narrower than its upper part, and with the Silvio aqueduct (a small canal through which cerebrospinal fluid circulates) through it from above under.

The border between the midbrain and the diencephalon is marked by the optic bands (the continuation of the nerve fibers of the optic nerves), while its lower limit, which separates it from the bridge of Varolio, it is marked by the pontomesencephalic sulcus.

In addition, on its anterior face (close to the face) you can distinguish a vertical cleft called the interpeduncular fossa, which divides two bodies of nerve fibers that go up to the brain, called cerebral peduncles.

Parts of the midbrain

The two fundamental structures that make up the midbrain are the tectum and the tegmentum.

Tectum

It is located in the dorsal area of ​​the midbrain, facing the neck, and etymologically means “roof”. Its functions are related to automatic reactions to auditory and sound stimuli.

It is made up of two pairs of bundles, one located on top of the other. These lumps are called colliculi, or quadrigeminal tubercles., and the superiors play a role in vision and in the orientation of the eyes towards visual stimuli, while the inferiors are involved in involuntary reactions to sounds.

Tegmentum

In the ventral area of ​​the midbrain is the tegmentum. It contains three main regions, each associated with a color: the black substance, the periaqueductal gray substance and the red nucleus.

The black substance

The substantia nigra is located in the upper area of ​​the midbrain, and is distributed on both sides of this structure, following the division of the cerebral hemispheres. It has many associated functions, linked especially to movements and muscle tone.

• You may be interested: "Substance nigra: what it is, functions and related disorders"

Red core

It is another of the important elements of the motor system. Its function is related to the coordination of movements.

Periaqueductal gray matter

The periaqueductal gray substance, which as its name suggests is located around the aqueduct of Silvio, intervenes in the habituation to pain and in analgesic processes in general.

Midbrain functions

The location of the midbrain means that the main functions of this structure have to do with the integration between different types of information. On the one hand, it collects nerve impulses linked to motor commands that have to be executed by muscles, and on the other it receives sensory data.

In the same way, the quadrigeminal tubers located in the tectum are responsible for coordinating this kind of information so that they can give rise to sequences of action adjusted to what the senses register in time real.

On the other hand, certain regions of the midbrain are associated with processes of regulation of consciousness and sleep, being crossed by the reticular formation. The midbrain is also involved in homeostatic functions aimed at keeping the body in a good balance, and therefore, for example, has a role in temperature regulation bodily.

Thus, the midbrain is responsible for carrying out processes of vital importance for the organism to continue to function, to the point that the activity in this structure of the nervous system is what indicates more clearly if there is brain death or there isn't.

Associated diseases and injuries

Any injury that affects the lower areas of the brain can reach the midbrain. The consequences of this kind of accident are almost always very serious, producing coma or death.

The reason is that the midbrain is a section of the nervous system whose importance is crucial for coordinating functions. basic physiological factors of the organism, and also serves so that various types of nerve impulses reach the groups of neurons superiors. Like the midbrain acts as a link between many areas, the presence of anomalies in this area affects many others.

With regard to the diseases that affect these brain structures, the most common are Alzheimer's disease and that of Parkinson's. Both are neurological disorders that interfere with the functioning of large areas of the nervous system, including the midbrain, and can lead to mobility and cognition problems.