Midbrain: characteristics, parts and functions.

A part of the brain essential for our survival and maintenance of consciousness.

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

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

In the following 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.

What is the midbrain?

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

In addition, the midbrain is traversed by a narrow canal called the aqueduct of Sylvius, through which fluid flows.through which cerebrospinal fluid flows from the third ventricle to the fourth ventricle. This fluid has the function of isolating and protecting various structures of the nervous system.

Its anatomy

The shape of the midbrain is that of a trapezoid, with a base narrower than its upper part, and with the aqueduct of Sylvius (a small channel through which cerebrospinal fluid circulates) crossing it from top to bottom.

The boundary between the midbrain and the diencephalon is marked by the optic girdles (the continuation of the nerve fibers of the optic nerves), while its lower boundary, which separates it from the pons, is pontomesencephalic sulcus, which separates it from the pons..

In addition, on its anterior aspect (close to the face) it is possible to distinguish a vertical fissure called the interpeduncular fossawhich divides two bodies of nerve fibers that go up to the brain, called cerebral peduncles.

Parts of the midbrain

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

Tectum

It is located in the dorsal area of the midbrain, oriented towards the nape of the neck, and etymologically means "roof". Its functions are related to automatic reactions to auditory and sound stimuli.

It is formed by two pairs of lumps, one located above the other. These lumps are called colliculi, or quadrigeminal tubercles.The upper ones play a role in vision and in the orientation of the eyes to visual stimuli, while the lower ones are involved in involuntary reactions to sounds.

Tegmentum

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

The substantia nigra

The substantia nigra is located in the superior 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, especially linked to movement and Muscle tone..

Red nucleus

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 Sylvius, is involved in pain habituation and analgesic and in analgesic processes in general.

Functions of the midbrain

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 to be executed by muscles, and on the other it receives sensory data.

Similarly, the quadrigeminal tubercles 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 are registering in real time.

On the other hand, certain regions of the midbrain are associated with processes of regulation of consciousness and sleep, since they are crossed by the formationas they are traversed by the reticular formation. The midbrain is also involved in homeostatic functions aimed at keeping the organism in good equilibrium, and thus, for example, plays a role in the regulation of body temperature.

Thus, the midbrain is responsible for carrying out processes of vital importance for the organism to continue functioning, to the point that the activity in this structure of the nervous system is what signals more clearly whether there is brain death or not.

Diseases and associated lesions

Any injury affecting the lower parts of the brain can reach the midbrain. The consequences of this kind of accidents 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 basic physiological functions of the organism, and also serves for various types of nerve impulses to reach the upper neuron groups. As the midbrain acts as a nexus between many areasAs the midbrain acts as a link between many areas, the presence of abnormalities in this area affects many others.

As far as diseases affecting this brain structure are concerned, the most common are Alzheimer's disease and Parkinson's disease. 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.