Brainstem: functions and structures

The brain is almost always associated with some kind of oval with a rough surface full of folds, but below this cerebral cortex are a multitude of very important structures.

In fact, if we were to consider the importance of each of the parts of the brain judging by their relevance to our survival, we would come to the conclusion that the most basic structure is one that does not even have the folded shape of it. cortex, nor oval in shape. Sand it deals with the brainstem, or brainstem, located in the lower part of the brain and in direct contact with the spinal cord.

What is the brainstem?

The brainstem, sometimes called a brainstem, is a cylindrical or elongated cone-shaped part of the brain that it is located between the rest of the brain and the spinal cord. This means that the brainstem is aligned with the neural fibers that run through the spinal cord below the spine; more precisely, it passes in front of the cerebellum.

Therefore, it is the part of the brain that is in an anatomically lower position and close to the neck. In addition, most of the cranial pairs (or cranial nerves) exit from the brainstem.

The brainstem is made up of the two parts of white matter and some areas where gray matter predominates, which means that it is crossed both by connection areas and areas in which the bodies of neurons are concentrated forming control nuclei.

Functions of the brainstem

Although the brainstem is attached to the spinal cord and its shape may be mistaken for an extension of it, its primary function it is not about acting as a simple bridge between the brain and the nerves that cross the human body.

The brainstem is the part of the human brain that houses the most primitive and ancestral functions, and appeared in our evolutionary lineage in species that did not resemble humans. This is part of what, according to Paul MacLean’s 3-brain theory, called “reptilian brain”Precisely because it has been associated with ancestral physiological processes (although MacLean’s ideas are not considered valid, among other things, for being based on a very simplified view of the evolution of the human brain.

Thus, the brainstem is responsible for performing the most basic tasks of the nervous system for our survival, those in which we can hardly voluntarily influence and which have been automated from millions of years of evolution precisely so that our wrong decisions or our distractions do not cost us our lives.

Maintain vital constants

Some of the functions in which the brainstem plays a key role include heart rate regulation and maintenance and automatic breathing control. This is why the brainstem is made up of vital centers which, when damaged, can cause immediate death.

Other brainstem functions that are slightly less important but almost equally primitive are the control of falling, sneezing and coughing, sucking, swallowing, vomiting, and pain sensitivity. It also plays a very important role in regulating arousal levels. More precisely, a network of neurons distributed in part by the brainstem called reticular formation is involved both in the regulation of the circadian cycle (sleep-wake) and in the maintenance of consciousness.

A communication bridge with the spinal cord

In addition to all these features, of course, the brainstem is used to communicate the cranial nerves and the spinal cord with the brain, Thus being the communication channel between the brain and the rest of the body as much in the afferents as in the efferents. It is a more passive role than the previous ones, but just as essential for the survival of the brain and the whole organism in general.

Parts of the brainstem

The brainstem is made up of three main structures: midbrain, brainstem bridge and medulla oblongata.

1. Mesencephalon

the mesencephalon it is the structure of the brainstem located in a higher position and therefore closer to structures located at the top, such as the thalamus. Like other parts of the brainstem, it is involved in such primitive functions as regulating the sleep-wake cycle and body temperature, but it also plays a role in reacting quickly to visual and auditory stimuli by reflex, as well. than in the control of certain movements.

The two basic components of the midbrain are structures called the tectum and tegmentum.

2. Trunk-brain bridge

the truncated brain bridge, Or Varolio Bridge, is located just below the midbrain and above the medulla oblongata. On its posterior surface (closest to the neck) is the cerebellum. This structure is the part of the trunk of the larger brain and its anterior surface is stretched outward as if it were half an egg.

This part of the brainstem intervenes in the control of breathing, in the transition between the phases of sleep and in the regulation of the level of consciousness, Among other basic survival processes.

3. Bulb thorns

the medulla oblongata (Or medulla oblongata) is located in the lower part of the brainstem. It controls all kinds of automatic processes totally necessary for survival, such as heart control or secretion of gastric substances. In addition, it is the part that communicates directly with the spinal cord.

In addition, it is in this part of the brainstem where is the decussation of the pyramidsThat is, the moment when nerve fibers move from the hemibody on the right to the left and vice versa (which is why half of the body is controlled by the opposite half of the brain).

  • If you want to know more about the medulla oblongata and its components, this article may interest you: “Spinal bulb: anatomical structure and functions”.

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