Myelencephalon: Characteristics, Functions And Development Phases
The myelencephalon is an embryonic vesicle, that is, it is a part of the nervous system in formation. Although it cannot be found in the adult brain as such, it is the precursor of a fundamental structure, since it fulfills several basic functions for our survival.
Next we are going to see in more depth what the myelencephalon is, what it corresponds to in the postnatal brain, what phases of neurological development it goes through and what functions are associated with the structure it ends up becoming.
The myelencephalon is a secondary vesicle of the neural tube, that is, the embryonic nervous system in formation, which is located in the area of the hindbrain
Throughout embryonic development, this part of the brain extends until it becomes the medulla oblongata, also known as the medulla oblongata, in addition to forming part of the central canal. Despite having a small size, the myelencephalon becomes a part that contributes to several systems and functions.
The myelencephalon is also included in part of the fourth ventricle, specifically in the lower part of it. On the other hand, in its interior we can find the reticular formation, a part of the brain that is involved in the regulation of several basic functions.
As with other structures formed from the hindbrain, the myelencephalon and, specifically, its matured structure, the medulla oblongata, plays a very important role in the control of the most basic human impulses such as alertness, attention and the sleep-wake cycle, in addition to being behind several reflexes essential for survival.
In many aspects, the myelencephalon is a passage structure between what will be the brain, that is, the cerebrum and cerebellum, and the spinal cord. This can be seen based on the functional organization and the shape it presents, very similar to those of the spinal cord.
embryological development
As we have mentioned, the myelencephalon is a secondary vesicle of the embryonic tube, halfway between the primary vesicles of the same tube and the more or less developed structures later during embryological development. That is to say, it is not a part of the adult brain but a part of the adult brain is formed from this structure, specifically the medulla oblongata.
There are two phases that can be highlighted in terms of its development.
1. First phase: from the neural tube to the myelencephalon
When the fetus begins to form, inside the mother’s womb, it presents a structure that will be the precursor of the nervous system: the neural tube. This tube will become more specialized as the weeks go by forming more complex neurological structures, such as the mature brain and nerves.
However, before the neural tube becomes the postnatal nervous system as we know it, it has to be segmented into different parts:
The first three parts are known as primary vesicles, which form approximately three weeks after conception: the forebrain, midbrain, and hindbrain
Then, the primary vesicles segment, forming secondary vesicles. The forebrain is segmented into two parts, the telencephalon and the diencephalon, and the hindbrain is divided into the metencephalon and the myelencephalon. This part of neurological development occurs at the fifth week.
2. Second phase: from the myelencephalon to the spinal cord
As we have mentioned, the myelencephalon is a structure that could be located halfway between the brain itself and the spinal cord This develops until it becomes the medulla oblongata, clearly distinguishable from the rest of the brain and spinal cord from the 20th week of gestation.
Although the myelencephalon is an embryonic structure, its adult version, the medulla oblongata or medulla oblongata, It can be found in the brain stem, serving as a connection between the spinal cord and the brain, being located at the Varolio point. We can see that this structure is the apparent origin or contains part of the following components:
Features
As a precursor of the medulla oblongata, we could consider that the myelencephalon is part of the autonomic nervous system The medulla oblongata is responsible for regulating a multitude of basic functions related to survival reflexes. In addition, it also participates in more complex brain functions, such as attention, alertness or the sleep-wake cycle. Below we explain them in more detail.
1. Breathing
The myelencephalon is related to the regulation of the respiratory cycle The medulla oblongata constantly monitors the acidification levels in the blood, preventing them from reaching levels that imply organic damage.
Once the medulla oblongata detects that this is happening, it sends nerve signals to the intercostal muscle tissues, that is, the muscles found between the ribs, activating them to carry out respiratory movements.
This way These muscles can increase their rate of contraction causing more oxygen to enter the blood and for it to acquire the appropriate pH levels so that no damage occurs to the body.
2. Cardiovascular control
In addition to the respiratory function, the medulla oblongata It is responsible for regulating various components of cardiac activity and, consequently, of the circulatory system Although it is not the only structure that is responsible for regulating the activity of the heart, it is one of the most important.
The medulla oblongata is responsible for exciting the sympathetic nervous system so that it increases the rate of heartbeat. This is especially important for those situations in which greater physical effort is required, such as when we play sports or are faced with a threatening situation, to facilitate the activation of fight or flight responses.
But, in addition, it is responsible for producing the opposite effect, that is, decrease heart rate by activating the parasympathetic nervous system As expected, this function will be necessary in opposite situations, such as relaxation or states of low alertness.
In addition to increasing and decreasing the heart rate, the medulla oblongata regulates blood pressure through mechanisms of vasodilation and vasoconstriction.
3. Alertness and reflexes
Due to the function of the medulla oblongata on the sympathetic and parasympathetic systems, the development of the midbrain is of utmost importance for the regulation of all processes that have to do with attention, alertness and, as we have already mentioned previously, the sleep-wake cycle.
Finally, the adult structure of the midbrain It is directly related to the realization of several reflexes and instincts fundamental for survival, which occur, automatically and unconsciously, in the presence of various stimuli. Based on research, it is known that the medulla oblongata is the main brain component behind partially involuntary behaviors, such as coughing, sneezing, the swallowing reflex, vomiting and gagging, or the masseteric reflex.
