Brainstem: functions and structures

What is the brainstem and why is it so important in our nervous system?

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

In fact, if we were to consider the importance of each of the parts of the brain by judging them according to how relevant they are to our survival, we would conclude that the most fundamental structure is one that is neither the folded shape of the cortex nor the shape of an oval. St is the brainstem, or brainstem, located in the lowest part of the brain and in direct contact with the spinal cord.

What is the brainstem?

The brainstem, sometimes referred to as the brain stemis a part of the brain that is shaped like a cylinder or elongated cone, and that 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 along the spinal cord under the spinal column; specifically, it passes in front of the cerebellum.

Therefore, it is the part of the brain that is anatomically lower and closer to the neck. In addition, most of the cranial nerves (or cranial nerves) emerge from the brainstem.

The brainstem is composed of both white matter parts and some areas dominated by gray matter, which means that areas in which the bodies of neurons are concentrated, forming control nuclei. forming control nuclei.

Functions of the brainstem

Although the brainstem is attached to the spinal cord and may be mistaken for an extension of the spinal cord because of its shape, its main function is to is not to act as a simple bridge between the brain and the nerves that run through the human body..

The brain stem is the part of the human brain that houses the most primitive and ancestral functions, and it appeared in our evolutionary lineage in species that were nothing like humans. It is part of what, according to Paul MacLean's theory of the 3 brains, has been called the "reptilian brain"precisely because it has been associated with ancestral physiological processes (although MacLean's ideas are not considered valid, among other things, because they are based on a very simplified view of the evolution of the human brain.

Thus, the brainstem is responsible for performing the tasks of the nervous system that are most basic to our survival, those that we can barely influence voluntarily. which we can hardly influence voluntarily and which have been automated. The evolution of the human body is based on millions of years of evolution, precisely so that our unwise decisions or our distractions do not cost us our lives.

Maintaining vital signs

Among the functions in which the brainstem plays a fundamental role are regulation and maintenance of Heart rate and automatic control of respiration.. This is why the brainstem is composed of vital centers which, when damaged, can cause immediate death.

Other functions of the brainstem that are somewhat less important but just as primitive are the control of hiccups, sneezing and coughing, sucking, swallowing, vomiting and sensitivity to pain. It also has a very important role in the regulation of arousal levels.. Specifically, a network of neurons distributed in part throughout the brainstem called the reticular formation is involved in both the regulation of the circadian cycle (sleep-wakefulness) and the maintenance of consciousness.

A communication bridge with the spinal cord

In addition to all these functions, of course, the brain stem serves to communicate the cranial nerves and the spinal cord with the brain, thus being the communication pathway between the cranial nerves and the spinal cord.Thus, it is the communication pathway between the brain and the rest of the body in both afferent and efferent directions. This is a more passive role than the previous ones, but equally essential for the survival of the brain and the whole organism in general.

Parts of the brainstem

The brain stem is composed of three main structures: the midbrain, the brainstem bridge and the medulla oblongata..

1. Midbrain

The midbrain is the structure of the brainstem located highest in the brain stem and therefore closest to structures located higher up, such as the thalamus. Like other parts of the brainstem, it is involved in such primitive functions as the regulation of the sleep-wake cycle and body temperature, but it also plays a role in reacting quickly to visual and auditory stimuli in a reflex manner, as well as in the control of certain movements.

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

2. Brainstem bridge

The brainstem bridge, o ponsis located just below the midbrain and above the medulla oblongata. On its posterior face (the one closest to the nape of the neck) is the cerebellum. This structure is the most bulky part of the brainstem, and its anterior side bends outward like half of an egg.

This part of the brain stem is involved in the control of breathing, in the transition between sleep phases and in the regulation of the level of consciousness, among other basic survival processes.among other basic survival processes.

3. Medulla oblongata

The medulla oblongata (o medulla oblongata) is located in the lowest part of the brainstem. It controls all kinds of automatic processes that are totally necessary for survival, such as cardiac control or the 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 the decussation of the pyramids is located.The spinal cord is the point at which nerve fibers change from right to left and vice versa (which explains that one 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 parts, this article may interest you: "Medulla oblongata: anatomical structure and functions".