Medulla oblongata (medulla oblongata): anatomy, structure and functions, for which the nerve centers are responsible

The brain is one of the few most essential and interesting human organs responsible for most of the vital functions of the human body.

The departments of this body are not easy to study. Let's analyze one of the sections - the medulla oblongata, its structure and functions.

The structure of the medulla oblongata

The medulla oblongata (translated from the Latin myelencephalon, medulla oblongata) is an extension spinal cord and makes up a fragment of the rhombencephalon. In infants, this department is larger in size in relation to other departments. The development of the structure ends in a person by the age of 7-8.

External structure

Located at the junction of the spinal cord, combining it with the brain. The appearance of the myelencephalon resembles the shape of an onion, has a conical shape and is a couple of centimeters long.

In the center of its front side, the anterior median fissure extends - an elongation of the main sulcus of the spinal cord. On the side of this gap are pyramids, passing into the facial ropes of the medulla spinalis, which include accumulations of nerve cells.

On the posterior side of the medulla oblongata is the dorsal middle groove, which also connects to the groove of the spinal cord. The ascending paths of the medulla spinalis go to the caudal cords located nearby.

The dorsal border is the junction of the roots of the highest cervical spinal nerve, and the basal border is the junction with the brain. The border zone of the medulla oblongata and the spinal cord is the passage of the first branch of the roots of the cervical nerves.

Internal structure

The internal structure of the elongated section includes gray and white matter. The anatomy of the medulla oblongata is close to the structure of the medulla spinalis, but unlike the structure of the spinal cord, in the oblong white the substance turns out to be outside, and the gray is located from the inside and consists of a concentration of nerve cells that form certain kernels.

In the underlying areas of the myelencephalon originates reticular formation, stretching further into the dorsal areas.

The reticular formation coordinates the receipt of impulses from all sense centers, which it conducts into the cerebral cortex. The structure controls the degree of excitability, is central to the work of consciousness, thinking, memory and other mental formations.

Near the pyramidal tract in medulla oblongata are olive trees that cover:

• subcortical department, coordinating the processes of balance;
• branches of the hypoglossal nerve connected to the lingual muscle tissue;
• nerve congestion;
• the gray matter that forms the nuclei.

Thin efferent pathways are responsible for the connection with the spinal cord and surrounding areas: the cortical-spinal pathway, the thin and wedge-shaped bundles.

The main nuclei of the medulla oblongata

The nerve centers of the medulla oblongata organize pairs of cranial nerve nuclei:

1. IX pair - glossopharyngeal nerves, composed of three parts: motor, affective and autonomic. The motor site is responsible for the movement of the muscles of the pharyngeal canal and oral cavity. The affective section receives signals from the digestive sensory system of the back of the tongue. Vegetative regulates saliva secretion.
2. X pair — nervus vagus, which includes three nuclei: the vegetative is responsible for the regulation of the larynx, esophagus, cardiovascular system, gastrointestinal tract and digestive glands. The nerve contains afferent and efferent fibers. The sensitive nucleus picks up signals from receptors in the lungs and other internal systems. The motor nucleus controls the contraction of the muscles in the oral cavity during swallowing. There is also a mutual core (n. ambiguus), whose axons are activated when a person coughs, sneezes, vomits stomach contents and changes the intonation of the voice.
3. XI pair - accessory nerve, divided into 2 parts: the first is closely interconnected with the vagus nerve, and the second is directed to the muscles of the sternum, key and trapezius muscles. With the pathology of the XI pair, head movement disorders occur - it is thrown back or shifted to one side.
4. XII pair - the hypoglossal nerve, which is responsible for the motor skills of the tongue. Regulates muscles such as the styloid, chin, as well as the rectus and transverse muscles of the tongue. The functions of the XII pair include, in part, the reflexes of swallowing, chewing and sucking. The composition includes mainly motor neurons. The nuclei control lingual motor skills in the process of eating and chopping food, the movement of the mouth and tongue during a conversation.

The structure also contains wedge-shaped and tender nuclei, along the paths of which signals are transferred to the somatosensory area of ​​the cortex. The cochlear nuclei regulate the auditory system. The nuclei of the underlying olives control the transmission of impulses to the cerebellum.

In the underlying caudal region of the myelencephalon is the center of hemodynamics, which interacts with the fibers of the 5th pair of nerves. It is assumed that it is from this area that excitatory activating signals of sympathetic fibers to the cardiovascular system are born. This fact is confirmed by studies on the intersection of the caudal regions of the medulla oblongata, after which the level of blood pressure did not change.

Within the structure is also the center of the "blue spot" - this is the area of ​​the reticular formation. Blue spot axons secrete a hormone norepinephrine, which affects the excitability of nerve cells. This center controls reactions such as tension and anxiety.

The control of the respiration processes is carried out thanks to the respiratory center, which is located between the higher region Varoliev's bridge and the underlying medulla oblongata. Violations of this center lead to cessation of breathing and death.

What are the functions of the medulla oblongata?

The medulla oblongata regulates important manifestations of the body and the brain, even a minor insignificant violation of any area will lead to serious pathologies.

Sensory

The sensory department regulates the reception of afferent impulses, which are perceived by sensory receptors from the external or internal world. Receptors can be composed of:

• sensorepithelial cells (taste and vestibular process);
• nerve fibers afferent neurons (pain, pressure, temperature changes).

The signals from the respiratory centers are analyzed - the structure and composition of the blood, the structure of the lung tissue, according to the results of which not only respiration, but also metabolic processes are assessed. Sensory functionality also means controlling the sensitivity of the face, taste, hearing, and receiving information from the food processing system.

The result of the analysis of all these indicators is the resulting further reaction in the form of reflex regulation, which is activated by the centers of the medulla oblongata.

For example, the accumulation of gas in the blood and a decrease in oxygen becomes the reason for ensuing behavioral manifestations: negative feelings, lack of air and others that motivate the body to find a source air.

Conductor

The presence of conduction promotes the transmission of nerve stimuli from the medulla oblongata to the nerve tissues of other areas CNS and to motor nerve cells. Information arrives at the myelencephalon via fibers of 8-12 pairs of nerves from various receptors.

Further, the information is transmitted to the nuclei of the cranial nerves, where the processing and occurrence of counter reflex signals takes place. Motor signals from neuronal nuclei can be transmitted to the next nuclei of other departments for the emergence of the following complex manifestations of the central nervous system.

Through the myelencephalon, pathways stretch from the dorsal region to such departments as cerebellum, visual hillocks and nuclei of the brain stem.

The following types of pathways are activated here:

• thin and wedge-shaped in the posterior region;
• spinocerebellar;
• spinothalamic;
• cortical-dorsal in the ventral region;
• descending olivospinal, tectospinal, Monakov's bundle in the lateral section.

White matter is the place of localization of the listed paths, most of them fall into the opposite direction in the area of ​​the pyramids, that is, they intersect.

Integrative

Integration involves the interaction of the centers of the medulla oblongata with parts of other types of the nervous system.

This relationship is manifested in complex reflexes - for example, the movement of the eyeballs during head vibrations, which is possible due to the joint work of the vestibular and oculomotor centers with the intervention of the posterior longitudinal beam.

Reflex

Reflex functionality is manifested in the regulation of muscle tone, body position, and defense reactions. The main types of reflexes of the oblong section:

1. Rectifier - resume the pose of the body and skull. They act thanks to the vestibular centers and receptors for muscle distortion, as well as mechanoreceptors in the epidermis.
2. Labyrinth - help in fixing a certain position of the skull. These reflexes are tonic and phasic. The former fix the pose in a certain form for a certain period of time, while the latter do not allow given a pose, be disturbed in the absence of balance, adjusting the instantaneous transformations of voltage in muscles.
3. Cervical - coordinate the activity of the muscles of the arms and legs with the assistance of the proprioceptors of the efferent center of the cervical spine.
4. Tonic posture reflexes are noticeable in the process of head rotation to the right and left. They arise due to the presence of the vestibular center and muscle stretch receptors. The visual centers are also involved.

Defense reactions are another central function of the medulla oblongata, which is noticeable from the first days of life. Defensive reflexes include:

1. Sneeze occurs during a sharp exhalation of air in response to physical or chemical irritation of the nasal cavity. There are two stages of this reflex. The first stage is nasal, which activates at the moment of direct impact on the mucous membranes. The second stage is respiratory, it is activated in a situation when the impulses entering the sneezing department are sufficient for the occurrence of motor nervous reactions.
2. Eruption of stomach contents - vomiting. It arises in a situation when sensory impulses from taste receptors arrive at the neurons of the vomiting center. The response of this reflex is also possible thanks to the motor nuclei, which are responsible for the contraction of the pharyngeal muscles.
3. Swallowing it is realized by the passage of food mass mixed with saliva. This requires contraction of the lingual muscles and the muscles of the larynx. This reflex occurs due to complex joint contractions and tensions of many muscles, as well as clusters of neurons that represent the center of swallowing in the medulla oblongata.