Midbrain: structure, function, structure

The midbrain (or mesencephalon), the structure and functions of which is difficult even to list - irreplaceable, multifaceted, unique and important GM department, present in almost all chordates animals. Nature has provided for the most secure location of all structures of the brain inside a strong cranium as the main means of preventing damage.

Without the activity of the SM, the cyclicity of the most important processes ceases, the reflexes of the human body, the ability to maintain the relative balance of the system in an unstable environment is lost environment.

Location

The Greek term (mesencephalon) unambiguously indicates its location - inside the head, its etymology - from the roots meaning "middle" and "brain". The Greek term "enkephalos" literally means - inside the head.

The Russian language contains the maximum information content - an indication of the main belonging to a complex complex of brain structures and its location.

As part of the brain stem, the CM is located between intermediate (part of the hypothalamic-pituitary system) and Varoliyev bridge (sometimes referred to simply as a bridge for simplicity).

The description of the anatomy of the midbrain, starting with the precise location of the object in the complex interweaving of brain formations, indicates its location as follows:

• caudal direction - border with metencephalon or hindbrain;
• rostral - border with diencephalon (intermediate);
• the trunk of a large GM consists of the nuclei of the middle, pons and diencephalon, as part of the formed structures trunk, mesencephalon can be detected by focusing on the area of ​​1 and 2 cervical vertebrae and the occipital fossa;
• an obsolete understanding of the middle complex of important components, now separated into a separate structure - a specific layer between the Varoliyevy bridge and the diencephalon.

Previously, the mesencephalon was not given the same importance as in modern neurology, it was simply called the tubercle of the medulla.

Studies carried out using special devices have shown that the reflex activity of the midbrain, as part of a complex system of interactions, makes it an irreplaceable part of the entire physiological functionality of the human body.

Without its independent structures, it is impossible to see and hear normally: neurons the hillocks of the midbrain quadruple are responsible for eye movement, regulation of the lens and the lumen of the pupil, start reflexes are the key to the survival of the organism. Because they are the ones who react even to those signals that are not recognized by the auditory or visual center.

The structure and function of the midbrain

The two-centimeter element of the brain stem, according to the anatomists who study GM, is not complicated at all. For visual study, it is usually suggested to study its cut, and mnemonic techniques are recommended to be memorized as a bear's face turned upside down with its ears.

The cross section helps to see clearly all the departments from which it is formed, but the connections with the upper and lower structures passing through the mesencephalon of communication and tracts, significantly complicate the idea of ​​a small parts of GM.

The structure is roughly divided into seven segments, but if you delve deeper into its structure, it turns out that everything is much more complicated than you might imagine. This is due to the polyfunctionality of education, for the implementation of which nature has provided for such a whimsical architectonics.

Quadruple

Structural formation in the upper part of the mesencephalon, which is responsible for processing information that has not yet reached the rest of the brain nuclei, the number of which in the human GM is quite significant, represented by paired tubercles (back and front), but not in all creatures, inhabiting the Earth.

For example, fish and reptiles have only two of them. In higher chordates, it plays the role of a sentinel center, which is extremely important for the preservation of the biological species. The anterior ones are tuned to receive visual information from the retina or geniculate nuclei, while the posterior ones are tuned to the one supplied by hearing and the nuclei responsible for auditory and vestibular signals.

Biological expediency consists in the primary processing of unconscious information, its processing before it will go further, and the formation of a sudden defense reaction faster than other structures of the NM will process it and feed it signals.

Hence the possibility for the higher chordates to perform unexpected but necessary actions - to scream, jump up, run, at the same time, simultaneously form a chain of signals for transmission to other centers, which form a reaction for more conscious.

Initially, there were two of them, but as they developed, they transformed into four hillocks, which are visualized as protrusions on the back of the CM.

In anatomy, they can be described as the upper and lower colliculus, since they differ in structure and function, but are considered a complex structure located on the roof of the midbrain.

The location of the four-hillock structure is the reason why the SM roof is sometimes called a quadruple plate.

Nearwire gray matter

Periaqueductal, or central Gray matter - an integral part of the tire, which is found under cerebral plumbing.

The structural features of this segment of the CM suggest that the conductive function is carried out by it both up and down.

The spinothalamic pathway ascending along the nerve fibers carries pain and temperature signals to the thalamus, to the line of the medulla oblongata and the bluish spot, and the descending one delivers information through it to the spinal to the brain.

White and gray matter are also building materials striatum, in which they alternate in stripes.

Red core

The nuclei of the midbrain are presented in variable forms, for example, the neural structures of the same name at the border of the oblong or the quadruple, also sometimes referred to them, are geniculate.

Red coreshaped like a sausage, not round. It consists of two parts - caudal and rostral.

Through it, important signals are transmitted by the centers of regulation of skeletal muscles, the spinal cord (more precisely, its motor nuclei), the extrapyramidal system, the cerebellum, the aqueduct and the pallidum.

The activity of the rubrospinal and corticorubal tract would also be impossible without the caudate nucleus of a conditionally red color.

Black substance

The second name is black matter. Regulates vegetative and statokinetic functions, takes an active part in vegetation - work respiratory and cardiovascular systems, is responsible for part of the work of maintaining the tone of the walls of the blood vessels.

Located in the space between the bridge and the diencephalon, next to legs, deployed to the right and left (according to the location of each leg.

It has been proven that neuromelanin is involved in the synthesis of dopamine, and the substance itself projects neuroleptides onto important parts of the central nervous system.

Even during the discovery of the structure, it was noted that it is abundantly permeated with vessels, which indicates its long-standing origin and importance for the work of the SM.

Reticular formation

The literal translation from Latin means "mesh formation". A complex complex localized along the trunk of the GM, activating its cortex and controlling spinal reflex functionality.

The RF cores are responsible for the production of norepinephrine, acetylcholine and serotonin. The importance of this structure of midbrain formation is undeniable. She is responsible for some types of behavior, functions of internal organs, takes part in initiation and maintenance of the wakefulness regime, attention, thanks to it, a person has indicative reflexes.

Starting from the thalamus and down to the lower part of the medulla oblongata, it directs its processes to other areas, cavities and zones, communicates with them in ways of various directions.

Ventral and dorsal tegmental areas

They are located near the substantia nigra and red nuclei, are a cluster of numerous nerve pathways, from here the mesocortical, mesolimbic and dopamine pathways start.

The ventral communicates with reward systems. The structures of the lining of the midbrain include: the substantia nigra, the reticular formation in its spinal cord, red nuclei and all areas, including the central, dorsal and ventral. It enters, according to some researchers, into the legs of the brain, and according to others, it adjoins them and limits the structure.

The tegmentum, or the lining of the brain, the basal or plantar part of the CM, it is the ventral and the dorsal region, while the opposing tectum (roof) is located in the opposite direction.

Brain legs

The most important anatomical formation responsible for visual orientation taken by a person posture, reflex muscle tone and associated in variable ways with other areas and formations of GM.

The vegetative centers of the spinal cord, medulla oblongata and midbrain, located in different areas, carry out communication through the legs with other important structures and cannot work if at least a bruise is observed education.

And if atrophy occurs, a person loses the ability to respond to external stimuli, cannot provide for himself and literally turns into a vegetable.

Age features of the midbrain

In a newborn, the average volume is slightly more than two grams, and in girls it is not much less than in boys, but it is formed in approximately the same form as an adult.

In intrauterine development, the nuclei of the oculomotor nerve are already ready and red, however, the specific color of the latter appears only by the age of 2 years and is finally visualized not earlier than 4 years.

Myelin is already present in the substantia nigra in an infant, but in not very significant quantities, its active development starts from six months and is finally formed only by adulthood (at 16).

It is not by chance that a person is considered an adult starting from this age: the black substance is responsible for respiration, CVS, vascular tone, regulates motor and performs statokinetic functions, this is an important component of extrapyramidal systems.

The midbrain and diencephalon play an undeniably important role in the activity of the human body. They contain important formations and structures whose duties include the regulation of the functions of the somatic, autonomic and central nervous systems, the brain and spinal cord.