Medulla. medulla oblongata and its functions

The medulla oblongata is a continuation of the spinal cord. Its structural and functional organization is more complex than that of the spinal cord. Unlike the spinal cord, it does not have a metameric, repeatable structure; the gray matter in it is located not in the center, but with nuclei to the periphery.

In the medulla oblongata there are olives associated with the spinal cord, the extrapyramidal system and the cerebellum - this is a thin and wedge-shaped nucleus of proprioceptive sensitivity (the nucleus of Gaulle and Burdach). Here are the crossroads of the descending pyramidal paths and ascending paths, formed by thin and wedge-shaped bundles (Goll and Burdakh), reticular formation.

The medulla oblongata is involved in the implementation of vegetative, somatic, gustatory, auditory, vestibular reflexes, provides the performance of complex reflexes that require the sequential inclusion of different muscle groups, which is observed, for example, when swallowing. The nuclei of some cranial nerves are located in the medulla oblongata (8, 9, 10, 11, 12).

Touch functions. The medulla oblongata regulates a number of sensory functions: the reception of skin sensitivity of the face - in the sensory nucleus trigeminal nerve; primary analysis of taste - in the nucleus of the glossopharyngeal nerve; auditory irritations - in the nucleus of the cochlear nerve; vestibular irritations - in the upper vestibular nucleus. In the posterior regions medulla oblongata pass through the paths of skin, deep, visceral sensitivity, some of which switch here to the second neuron (thin and sphenoid nuclei). At the level of the medulla oblongata, the listed sensory functions implement the primary analysis of the strength and quality of stimulation, then the processed information is transmitted to subcortical structures to determine the biological significance of a given irritation.

conductor functions. All ascending and descending pathways of the spinal cord pass through the medulla oblongata: spinal-thalamic, corticospinal, rubrospinal. The vestibulospinal, olivospinal and reticulospinal tracts originate in it, providing tone and coordination of muscle reactions, the paths from the cortex end. big brain- corticoreticular pathways.

Such formations brain like a bridge midbrain, cerebellum, thalamus, hypothalamus and cerebral cortex, have bilateral connections with the medulla oblongata. The presence of these connections indicates the participation of the medulla oblongata in the regulation of tone skeletal muscles, vegetative and higher integrative functions, analysis of sensory stimuli.

reflex functions. In the medulla oblongata are vital centers - respiratory and vasomotor. It organizes and implements a number of protective reflexes: vomiting, sneezing, coughing, lacrimation, closing of the eyelids, reflexes of eating behavior are organized: sucking, chewing, swallowing.

In addition, the medulla oblongata is involved in the formation of postural reflexes. These reflexes are formed by afferentation from the receptors of the vestibule of the cochlea and the semicircular canals to the superior vestibular nucleus; from here, the processed information for assessing the need for a change in posture is sent to the lateral and medial vestibular nuclei. These nuclei are involved in determining which muscular systems, segments of the spinal cord must take part in a change in posture, therefore, from the neurons of the medial and lateral nuclei, along the vestibulospinal pathway, the signal arrives at the anterior horns of the corresponding segments of the spinal cord, innervating the muscles, whose participation in changing the posture in this moment necessary.

Changes in posture, position, movement are provided by static and statokinetic reflexes. Static reflexes regulate skeletal muscle tone in order to maintain a certain body position. Statokinetic reflexes cause a redistribution of the tone of the muscles of the body to maintain posture and position during accelerated rectilinear or rotational movements.

Most of the autonomic reflexes of the medulla oblongata are realized through the nuclei of the vagus nerve located in it, which receive information about the state of the activity of the heart, blood vessels, digestive tract, lungs, etc. In response to this information, motor and secretory reactions of these organs arise. Excitation of the nuclei of the vagus nerve causes an increase in the contraction of the smooth muscles of the stomach, intestines, gallbladder and, at the same time, relaxation of the sphincters of these organs. At the same time, the work of the heart slows down and weakens, the lumen of the bronchi narrows.

The center of salivation is localized in the medulla oblongata, the parasympathetic part of which provides an increase in general secretion, and the sympathetic part - protein secretion of the salivary glands.

The respiratory and vasomotor centers are located in the structure of the reticular formation of the medulla oblongata. The peculiarity of these centers is that their neurons are able to be excited reflexively and under the influence of chemical stimuli.

The respiratory center is localized in the medial part of the reticular formation of each symmetrical half of the medulla oblongata and is divided into two parts, inhalation and exhalation.

In the reticular formation of the medulla oblongata, another vital center is represented - the vasomotor center (regulation of vascular tone). It functions in conjunction with the overlying structures of the brain and, above all, with the hypothalamus. Excitation of the vasomotor center always changes the rhythm of breathing, the tone of the bronchi, intestinal muscles, Bladder, etc. This is due to the fact that the reticular formation of the medulla oblongata has synaptic connections with the hypothalamus and other centers.

In the middle sections of the reticular formation there are neurons that form the reticulospinal pathway, which has an inhibitory effect on the motor neurons of the spinal cord. At the bottom of the IV ventricle, the neurons of the "blue spot" are located. Their mediator is norepinephrine. These neurons cause activation of the reticulospinal pathway during REM sleep, which leads to inhibition of spinal reflexes and a decrease in muscle tone.

Damage to the medulla oblongata most often leads to lethal outcome. Partial damage to the left or right half of the medulla oblongata above the intersection of the ascending pathways of proprioceptive sensitivity causes disturbances in the sensitivity and work of the muscles of the face and head on the side of the damage. At the same time, on the opposite side relative to the side of the injury, there are violations of skin sensitivity and motor paralysis of the trunk and limbs. This is due to the fact that the ascending and descending pathways from the spinal cord and into the spinal cord intersect, and the nuclei of the cranial nerves innervate their half of the head, i.e. cranial nerves do not cross.

The reticular formation of the bridge is a continuation of the reticular formation of the medulla oblongata and the beginning of the same midbrain system. The axons of the neurons of the reticular formation of the bridge go to the cerebellum, to the spinal cord (reticulospinal pathway). The latter activate the neurons of the spinal cord. The pontine reticular formation affects the cerebral cortex, causing it to activate or sleepy state. There are two groups of nuclei that belong to a common respiratory center. One center activates the inhalation center of the medulla oblongata, the other activates the exhalation center. The neurons of the respiratory center, located in the pons, adapt the work of the respiratory cells of the medulla oblongata in accordance with the changing state of the body.

PHYSIOLOGY OF THE CENTRAL NERVOUS SYSTEM

Spinal cord

brain stem

The brain stem includes the medulla oblongata, pons, midbrain, diencephalon and cerebellum. The brain stem performs the following functions:

1) organizes reflexes that ensure the preparation and implementation various forms behavior; 2) performs a conductive function: paths connecting the structures of the central nervous system pass through the brain stem in an ascending and descending direction; 3) when organizing behavior, it ensures the interaction of its structures with each other, with the spinal cord, basal ganglia and cerebral cortex, i.e., provides an associative function.

Medulla

Features of the functional organization. The human medulla oblongata is about 25 mm long. It is a continuation of the spinal cord. Structurally, in terms of the variety and structure of the nuclei, the medulla oblongata is more complex than the spinal cord. Unlike the spinal cord, it does not have a metameric, repeatable structure; the gray matter in it is located not in the center, but with nuclei to the periphery.

In the medulla oblongata there are olives associated with the spinal cord, the extrapyramidal system and the cerebellum - this is a thin and wedge-shaped nucleus of proprioceptive sensitivity (the nucleus of Gaulle and Burdach). Here are the intersections of the descending pyramidal paths and the ascending paths formed by the thin and wedge-shaped bundles (Gaulle and Burdakh), the reticular formation.

The medulla oblongata, due to its nuclear formations and the reticular formation, is involved in the implementation of autonomic, somatic, gustatory, auditory, and vestibular reflexes. A feature of the medulla oblongata is that its nuclei, being excited sequentially, ensure the implementation of complex reflexes that require the sequential inclusion of different muscle groups, which is observed, for example, when swallowing.

The nuclei of the following cranial nerves are located in the medulla oblongata:

a pair of VIII cranial nerves - the vestibulocochlear nerve consists of the cochlear and vestibular parts. The cochlear nucleus lies in the medulla oblongata;

pair IX - glossopharyngeal nerve (p. glossopharyngeus); its core is formed by 3 parts - motor, sensory and vegetative. The motor part is involved in the innervation of the muscles of the pharynx and oral cavity, sensitive - receives information from the taste receptors of the back third of the tongue; autonomic innervates salivary glands;

pair X - the vagus nerve (n.vagus) has 3 nuclei: the autonomic innervates the larynx, esophagus, heart, stomach, intestines, digestive glands; sensitive receives information from the receptors of the alveoli of the lungs and other internal organs and motor (the so-called mutual) provides a sequence of contraction of the muscles of the pharynx, larynx when swallowing;

pair XI - accessory nerve (n.accessorius); its nucleus is partially located in the medulla oblongata;

pair XII - hypoglossal nerve (n.hypoglossus) is the motor nerve of the tongue, its core is mostly located in the medulla oblongata.

Touch functions. The medulla oblongata regulates a number of sensory functions: the reception of skin sensitivity of the face - in the sensory nucleus of the trigeminal nerve; primary analysis of taste reception - in the nucleus of the glossopharyngeal nerve; reception of auditory stimuli - in the nucleus of the cochlear nerve; reception of vestibular stimuli - in the upper vestibular nucleus. In the posterior superior sections of the medulla oblongata, there are paths of skin, deep, visceral sensitivity, some of which switch here to the second neuron (thin and sphenoid nuclei). At the level of the medulla oblongata, the enumerated sensory functions implement the primary analysis of the strength and quality of stimulation, then the processed information is transmitted to the subcortical structures to determine the biological significance of this stimulation.

conductor functions. Through the medulla oblongata pass all ascending and descending paths spinal cord: dorsal-thalamic, corticospinal, rubrospinal. The vestibulospinal, olivospinal and reticulospinal tracts originate in it, providing tone and coordination of muscle reactions. In the medulla, the paths from the cerebral cortex end - the corticoreticular paths. Here ends the ascending pathways of proprioceptive sensitivity from the spinal cord: thin and wedge-shaped. Brain formations such as the pons, midbrain, cerebellum, thalamus, hypothalamus, and cerebral cortex have bilateral connections with the medulla oblongata. The presence of these connections indicates the participation of the medulla oblongata in the regulation of skeletal muscle tone, autonomic and higher integrative functions, and the analysis of sensory stimuli.

reflex functions. Numerous reflexes of the medulla oblongata are divided into vital and non-vital, but such a representation is rather arbitrary. The respiratory and vasomotor centers of the medulla oblongata can be attributed to vital centers, since a number of cardiac and respiratory reflexes are closed in them.

The medulla oblongata organizes and implements a number of protective reflexes: vomiting, sneezing, coughing, tearing, closing of the eyelids. These reflexes are realized due to the fact that information about irritation of the receptors of the mucous membrane of the eye, oral cavity, larynx, nasopharynx through the sensitive branches of the trigeminal and glossopharyngeal nerves enters the nuclei of the medulla oblongata, from here comes the command to the motor nuclei of the trigeminal, vagus, facial, glossopharyngeal, accessory or hypoglossal nerves, as a result, one or another protective reflex is realized. In the same way, due to the sequential inclusion of muscle groups of the head, neck, chest and diaphragm are organized reflexes of eating behavior: sucking, chewing, swallowing.

In addition, the medulla oblongata organizes postural reflexes. These reflexes are formed by afferentation from the receptors of the vestibule of the cochlea and the semicircular canals to the superior vestibular nucleus; from here, the processed information for assessing the need for a change in posture is sent to the lateral and medial vestibular nuclei. These nuclei are involved in determining which muscle systems, segments of the spinal cord should take part in a change in posture, therefore, from the neurons of the medial and lateral nuclei along the vestibulospinal pathway, the signal arrives at the anterior horns of the corresponding segments of the spinal cord, innervating the muscles, whose participation in changing the posture in necessary at the moment.

Posture change is carried out due to static and statokinetic reflexes. Static reflexes regulate skeletal muscle tone in order to maintain a certain body position. The statokinetic reflexes of the medulla oblongata provide a redistribution of the tonus of the trunk muscles to organize a posture corresponding to the moment of rectilinear or rotational movement.

Most of the autonomic reflexes of the medulla oblongata are realized through the nuclei of the vagus nerve located in it, which receive information about the state of activity of the heart, blood vessels, digestive tract, lungs, digestive glands, etc. In response to this information, the nuclei organize motor and secretory reactions of these organs.

Excitation of the nuclei of the vagus nerve causes an increase in the contraction of the smooth muscles of the stomach, intestines, gallbladder and, at the same time, relaxation of the sphincters of these organs. At the same time, the work of the heart slows down and weakens, the lumen of the bronchi narrows.

The activity of the nuclei of the vagus nerve is also manifested in increased secretion of the bronchial, gastric, intestinal glands, in the excitation of the pancreas, secretory cells of the liver.

The respiratory center is localized in the medial part of the reticular formation of each symmetrical half of the medulla oblongata and is divided into two parts, inhalation and exhalation.

In the reticular formation of the medulla oblongata, another vital center is represented - the vasomotor center (regulation of vascular tone). It functions in conjunction with the overlying structures of the brain and, above all, with the hypothalamus. Excitation of the vasomotor center always changes the rhythm of breathing, the tone of the bronchi, intestinal muscles, bladder, ciliary muscle, etc. This is due to the fact that the reticular formation of the medulla oblongata has synaptic connections with the hypothalamus and other centers.

Damage symptoms. Damage to the left or right half of the medulla oblongata above the intersection of the ascending pathways of proprioceptive sensitivity causes disturbances in the sensitivity and work of the muscles of the face and head on the side of the injury. At the same time, on the opposite side relative to the side of the injury, there are violations of skin sensitivity and motor paralysis of the trunk and limbs. This is explained by the fact that the ascending and descending pathways from the spinal cord and into the spinal cord intersect, and the nuclei of the cranial nerves innervate their half of the head, i.e., the cranial nerves do not intersect.

Bridge

The bridge (pons cerebri, pons Varolii) is located above the medulla oblongata and performs sensory, conductive, motor, integrative reflex functions.

The structure of the bridge includes the nuclei of the facial, trigeminal, abducens, vestibular-cochlear nerve (vestibular and cochlear nuclei), the nuclei of the vestibular part of the vestibular-cochlear nerve (vestibular nerve): lateral (Deiters) and superior (Bekhterev). The reticular formation of the bridge is closely related to the reticular formation of the middle and medulla oblongata.

An important structure of the bridge is the middle cerebellar peduncle. It is she who provides functional compensatory and morphological connections of the cerebral cortex with the cerebellar hemispheres.

The sensory functions of the bridge are provided by the nuclei of the vestibulocochlear, trigeminal nerves. The cochlear part of the vestibulocochlear nerve ends in the brain in the cochlear nuclei; the vestibular part of the vestibulocochlear nerve - in the triangular nucleus, Deiters' nucleus, Bekhterev's nucleus. Here is the primary analysis of vestibular stimuli of their strength and direction.

The sensory nucleus of the trigeminal nerve receives signals from receptors in the skin of the face, the anterior scalp, mucous membranes of the nose and mouth, teeth, and the conjunctiva of the eyeball. The facial nerve (p. Facialis) innervates all facial muscles of the face. The abducens nerve (n. abducens) innervates the rectus lateral muscle, which abduces eyeball outside.

The motor portion of the nucleus of the trigeminal nerve (n. trigeminus) innervates chewing muscles, a muscle that stretches the tympanic membrane, and a muscle that stretches the palatine curtain.

The conductive function of the bridge. Provided with longitudinal and transverse fibers. Transversely located fibers form the upper and lower layers, and between them pass the pyramidal paths coming from the cerebral cortex. Between the transverse fibers are neuronal clusters - the nuclei of the bridge. From their neurons, transverse fibers begin, which go to the opposite side of the bridge, forming the middle cerebellar peduncle and ending in its cortex.

In the tire of the bridge there are longitudinally running bundles of fibers of the medial loop (lemniscus medialis). They are crossed by transversely running fibers of the trapezoid body (corpus trapezoideum), which are axons of the cochlear part of the vestibulocochlear nerve opposite side, which end in the core of the upper olive (oliva superior). From this nucleus, the paths of the lateral loop (lemniscus lateralis) go to the posterior quadrigemina of the midbrain and to the medial geniculate bodies of the diencephalon.

The anterior and posterior nuclei of the trapezoid body and the lateral loop are localized in the tegmentum of the brain. These nuclei, together with the superior olive, provide the primary analysis of information from the organ of hearing and then transmit information to the posterior colliculus of the quadrigemina.

The tegmentum also contains a long medial and tectospinal tract.

The intrinsic neurons of the pons structure form its reticular formation, the nuclei of the facial and abducens nerves, the motor portion of the nucleus, and the middle sensory nucleus of the trigeminal nerve.

The pontine reticular formation affects the cerebral cortex, causing it to awaken or sleep. In the reticular formation of the bridge there are two groups of nuclei that belong to a common respiratory center. One center activates the inhalation center of the medulla oblongata, the other activates the exhalation center. The neurons of the respiratory center, located in the pons, adapt the work of the respiratory cells of the medulla oblongata in accordance with the changing state of the body.

Medulla oblongata, myelencephalon, medulla oblongata, represents a direct continuation of the spinal cord into the brainstem and is part of the rhomboid brain. It combines the features of the structure of the spinal cord and initial department head, which justifies its name myelencephalon.

Medulla oblongata has the appearance of a bulb, bulbus cerebri (hence the term "bulbar disorders"); the upper extended end borders the bridge, and lower bound serves as an exit point for the roots of the first pair cervical nerves or the level of the foramen magnum.

On the anterior (ventral) surface of the medulla oblongata along the midline passes fissura mediana anterior, which is a continuation of the sulcus of the spinal cord of the same name. On either side of it, on either side, there are two longitudinal strands - pyramids, pyramides medullae oblongatae, which, as it were, continue into the anterior funiculi of the spinal cord. Pyramid bundles nerve fibers partly cross in the depths of the fissura mediana anterior with similar fibers of the opposite side - decussatio pyramidum, after which they descend in the lateral funiculus on the other side of the spinal cord - tractus corticospinal (pyramidalis) lateralis, partly remain uncrossed and descend in the anterior funiculus of the spinal cord on their side - tractus corticospinalis (pyramidalis) anterior. Pyramids are absent in lower vertebrates and appear as the new cortex develops; therefore, they are most developed in humans, since the pyramidal fibers connect the cerebral cortex, which has reached its highest development in humans, with the nuclei of the cranial nerves and the anterior horns of the spinal cord. Lateral to the pyramid lies an oval elevation - olive, oliva, which is separated from the pyramid by a groove, sulcus anterolateral.

On the posterior (dorsal) surface of the medulla oblongata the sulcus medianus posterior stretches - a direct continuation of the sulcus of the spinal cord of the same name. On the sides of it lie the posterior cords, limited laterally on both sides of the weakly expressed sulcus posterolaterals. In the upward direction, the posterior cords diverge to the sides and go to the cerebellum, being part of its lower legs, pedunculi cerebellares inferiores, bordering the diamond-shaped fossa from below. Each posterior funiculus is subdivided by means of an intermediate furrow into medial, fasciculus gracilis, and lateral, fasciculus cuneatus. At bottom corner rhomboid fossa thin and wedge-shaped bundles acquire thickenings - tuberculum gracilum and tuberculum cuneatum. These thickenings are due to the nuclei of gray matter, the nucleus gracilis and the nucleus cuneatus, which are similar to the bundles. In these nuclei, the ascending fibers of the spinal cord (thin and wedge-shaped bundles) passing in the posterior cords terminate. The lateral surface of the medulla oblongata, located between the sulci posterolateralis et anterolateralis, corresponds to the lateral funiculus. From the sulcus posterolateralis behind the olive exit the XI, X and IX pairs of cranial nerves. The medulla oblongata contains Bottom part rhomboid fossa.

The internal structure of the medulla oblongata. The medulla oblongata arose in connection with the development of the organs of gravity and hearing, as well as in connection with the gill apparatus, which is related to breathing and blood circulation. Therefore, it contains the nuclei of gray matter, which are related to balance, coordination of movements, as well as to the regulation of metabolism, respiration and blood circulation.

Nucleus olivaris, olive kernel, has the appearance of a convoluted plate of gray matter, open medially (hilus), and causes a protrusion of the olive from the outside. It is associated with the dentate nucleus of the cerebellum and is an intermediate balance nucleus, most pronounced in humans, vertical position which needs a perfect gravitational apparatus. (There is also nucleus olivaris accessorius medialis.)
Formatio reticularis, reticular formation, formed from the interweaving of nerve fibers and the nerve cells lying between them.
Nuclei of four pairs of inferior cranial nerves (XII-IX) related to the innervation of derivatives of the gill apparatus and viscera.
Vital centers of respiration and circulation associated with the nuclei of the vagus nerve. Therefore, if the medulla oblongata is damaged, death can occur.

White matter of the medulla oblongata contains long and short fibers.

The long ones include descending pyramidal tracts passing in transit into the anterior funiculi of the spinal cord, partly crossing in the area of \u200b\u200bthe pyramids. In addition, in the nuclei of the posterior cords (nuclei gracilis et cuneatus) are the bodies of the second neurons of the ascending sensory pathways. Their processes go from the medulla oblongata to the thalamus, tractus bulbothalamicus. The fibers of this bundle form a medial loop, lemniscus medialis, which in the medulla oblongata crosses, decussatio lemniscorum, and in the form of a bundle of fibers located dorsal to the pyramids, between the olives - the inter-olive loop layer - goes further.

Thus, in the medulla oblongata there are two intersections of long pathways: the ventral motor, decussatio pyramidum, and the dorsal sensory, decussatio lemniscorum.

Short paths include bundles of nerve fibers that connect individual nuclei of gray matter, as well as the nuclei of the medulla oblongata with neighboring parts of the brain. Among them, it should be noted tractus olivocerebellaris and fasciculus longitudindlis medialis lying dorsally from the interolive layer. The topographic relationships of the main formations of the medulla oblongata are visible on a cross section drawn at the level of the olives. Outgoing from the nuclei of the sublingual and vagus nerve roots divide the medulla oblongata on both sides into three regions: posterior, lateral, and anterior. In the back lie the nuclei of the posterior funiculus and the lower legs of the cerebellum, in the lateral - the nucleus of the olive and formatio reticularis, and in the anterior - the pyramids.

The brain performs the most important features in the human body and is the main organ of the central nervous system. When its activity ceases, even if breathing is supported by artificial ventilation lungs, doctors ascertain clinical death.

Anatomy

The medulla oblongata is located in the posterior cranial notch and looks like an inverted bulb. From below, through the occipital foramen, it connects to the spinal cord, from above it has common border Where is the medulla oblongata located cranium, is clearly shown in the picture posted later in the article.

In an adult, the organ in its widest part is approximately 15 mm in diameter, in full length it reaches no more than 25 mm. Outside, the medulla oblongata envelops and inside it is filled with gray matter. In its lower part there are separate clots - nuclei. Through them, reflexes are carried out, covering all body systems. Let's take a closer look at the structure of the medulla oblongata.

outer part

The ventral surface is the outer anterior part of the medulla oblongata. It consists of paired cone-shaped lateral lobes, expanding upward. The departments are formed by pyramidal tracts and have a median fissure.

The dorsal surface is the posterior outer portion of the medulla oblongata. It looks like two cylindrical thickenings, separated by a median sulcus, consists of fibrous bundles that connect to the spinal cord.

Inner part

Consider the anatomy of the medulla oblongata, which is responsible for the motor functions of skeletal muscles and the formation of reflexes. The core of the olive is a sheet of gray matter with jagged edges and resembles the shape of a horseshoe. It is located on the sides of the pyramidal parts and looks like an oval elevation. Below is the reticular formation, consisting of plexuses of nerve fibers. The medulla oblongata includes the nuclei of the cranial nerves, centers of respiration and blood supply.

Nuclei

Contains 4 nuclei and affects the following organs:

throat muscles;
palatine tonsils;
taste receptors on the back of the tongue;
salivary glands;
drum cavities;
auditory tubes.

The vagus nerve includes 4 nuclei of the medulla oblongata and is responsible for:

organs of the abdomen and chest;
muscles of the larynx;
skin receptors of the auricle;
internal glands of the abdominal cavity;
neck organs.

Accessory nerve has 1 nucleus, controls the sternoclavicular and trapezius muscle. contains 1 core and affects the muscles of the tongue.

What are the functions of the medulla oblongata?

The reflex function acts as a barrier against the ingress of pathogenic microbes and external stimuli, regulates muscle tone.

Protective reflexes:

When too much food, toxic substances enter the stomach, or when irritated vestibular apparatus the vomiting center in the medulla gives the body a command to empty it. When the gag reflex is triggered, the contents of the stomach exit through the esophagus.
Sneezing is unconditioned reflex, which removes dust and other irritating agents from the nasopharynx by accelerated exhalation.
The secretion of mucus from the nose performs the function of protecting the body from the penetration of pathogenic bacteria.
Cough is a forced exhalation caused by contraction of the muscles of the upper respiratory tract. It cleans the bronchi from sputum and mucus, protects the trachea from foreign objects entering it.
Blinking and tearing are protective eye reflexes that occur upon contact with foreign agents and protect the corneas from drying out.

Tonic reflexes

The centers of the medulla oblongata are responsible for tonic reflexes:

static: body position in space, rotation;
statokinetic: adjusting and rectifying reflexes.

Food reflexes:

secretion of gastric juice;
sucking;
swallowing.

What are the functions of the medulla oblongata in other cases?

cardiovascular reflexes regulate the functioning of the heart muscle and blood circulation;
respiratory function provides ventilation of the lungs;
conductive - is responsible for the tone of skeletal muscles and acts as an analyzer of sensory stimuli.

Symptoms on injury

The first descriptions of the anatomy of the medulla are found in the 17th century after the invention of the microscope. The organ has a complex structure and includes the main centers of the nervous system, in case of violation of which the whole organism suffers.

Hemiplegia (cross paralysis) - paralysis right hand and the left lower half of the body, or vice versa.
Dysarthria - restriction of the mobility of the organs of speech (lips, palate, tongue).
Hemianesthesia - a decrease in the sensitivity of the muscles of one half of the face and numbness of the lower opposite part of the trunk (limbs).

Other signs of medulla oblongata dysfunction:

stop mental development;
unilateral paralysis of the body;
violation of sweating;
memory loss;
paresis of facial muscles;
tachycardia;
decreased ventilation of the lungs;
retraction of the eyeball;
pupil constriction;
inhibition of the formation of reflexes.

Alternating syndromes

The study of the anatomy of the medulla oblongata showed that when the left or right side of the organ is damaged, alternating (alternating) syndromes occur. Diseases are caused by a violation of the conduction functions of the cranial nerves on the one hand.

Jackson Syndrome

Develops with dysfunction of the nuclei hypoglossal nerve, the formation of blood clots in the branches of the subclavian and vertebral arteries.

Symptoms:

paralysis of the muscles of the larynx;
impaired motor response;
paresis of the tongue on one side;
hemiplegia;
dysarthria.

Avellis syndrome

Diagnosed with damage to the pyramidal regions of the brain.

Symptoms:

paralysis of the soft palate;
swallowing disorder;
dysarthria.

Schmidt syndrome

Occurs with dysfunction of the motor centers of the medulla oblongata.

Symptoms:

paralysis of the trapezius muscle;
incoherent speech.

Wallenberg-Zakharchenko syndrome

It develops in violation of the conductive ability of the fibers of the muscles of the eye and dysfunction of the hypoglossal nerve.

Symptoms:

vestibular-cerebellar changes;
paresis of the soft palate;
decreased sensitivity of the skin of the face;
skeletal muscle hypertonicity.

Glick syndrome

Diagnosed with extensive damage to the brain stem and nuclei of the medulla oblongata.

Symptoms:

decreased vision;
spasm of mimic muscles;
violation of swallowing function;
hemiparesis;
pain in the bones under the eyes.

The histological structure of the medulla oblongata is similar to the spinal cord, with damage to the nuclei, a violation of the formation conditioned reflexes and motor functions of the body. For determining accurate diagnosis conduct instrumental and laboratory studies: tomography of the brain, sampling of cerebrospinal fluid, X-ray of the skull.

AT medulla oblongata there are centers of both relatively simple and more complex reflexes, in the implementation of which various muscle groups, vessels and many internal organs participate. These reflexes arise in response to impulses coming from the spinal cord, as well as from the receptor systems of the glossopharyngeal, auditory, vestibular, trigeminal and vagus nerves. The reflexes, the arcs of which pass through the hindbrain, are more perfect and more complexly coordinated than the reflexes of the spinal cord. Such, for example, are tonic reflexes of body position. In the performance of many complex reflex acts of the hindbrain, various groups neurons that are covered by excitation in a certain regular order. An example is the swallowing and sneezing reflexes.

Medulla It has importance in the regulation of respiration, cardiac activity, the state of blood vessels, sweating, and the functions of the digestive organs. The centers of all these functions are located in the medulla oblongata. A feature of some centers - respiratory, regulating cardiac activity, vasomotor - is that they are excited as a reflex nerve impulses coming from the periphery, and chemical irritants acting directly on them.

Here we will consider the reflexes and centers of the medulla oblongata associated with the activity of predominantly skeletal muscles. The role of the medulla oblongata in the regulation of internal organs and vessels innervated by the autonomic nervous system will be considered below.

formed by several groups of neurons located in different parts of the medulla oblongata, and is a single functional system. The respiratory center is located between the upper border of the pons and lower section medulla oblongata in the area related to the reticular formation. There is still no consensus on whether to consider respiratory center an independent anatomical formation, i.e., a semblance of a separate nucleus, or it should be considered as a part of the reticular formation, specialized in the regulation of respiratory movements. Essential parts respiratory center as a whole are pneumotaxic, expiratory and inspiratory centers. Impulses from the respiratory center are sent to the motor neurons of the spinal cord, innervating the diaphragm and intercostal muscles. That is why the transection of the spinal cord above the 4th cervical segment, where the neurons are located, the processes of which form the phrenic nerve, stops breathing.

The rhythmic activity of the respiratory center affects the state of other centers of the oblong and . The connection between the respiratory center and the center of regulation of cardiac activity is especially pronounced, resulting in a respiratory-cardiac reflex, or the so-called respiratory arrhythmia - a correctly periodic slowdown in cardiac activity at the end of exhalation before the start of the next breath. The connection between the respiratory center and the centers of the spinal cord is shown in the experience of L. A. Orbeli and K. I. Kuntsman, who observed that after deafferentation of one paw in a dog, i.e., after cutting the posterior roots, through which impulses from this paw, the latter produced rhythmic movements that coincided with breathing.

Deafferentation disrupted the inhibitory processes in the corresponding parts of the spinal cord, as a result of which the motor centers of the spinal cord reacted with excitation to impulses from the respiratory center coming to them along the reticulo-spinal pathways.

Afferent impulses coming to the respiratory center from the receptors of the lungs, respiratory tract and respiratory muscles are important in maintaining a certain level of activity of the reticular formation and, therefore, are important not only in the regulation of breathing, but in the activity of the entire central nervous system due to the activating effect reticular formation.

Nuclei medulla oblongata take part in the performance of reflex acts of chewing, sucking, swallowing, vomiting, sneezing, coughing, blinking, etc. These reflexes are observed even in children born without most of the brain (anencephalos).

sucking movements occur when touching the lips of a newborn. This reflex is carried out when the sensitive endings of the trigeminal nerve are stimulated, the excitation from which switches in the medulla oblongata to motor nuclei facial and hypoglossal nerves.

Chewing is a motor act that can be carried out reflexively in response to irritation of the receptors of the oral cavity and consists in moving the lower jaw relative to the upper. According to R. Magnus, the center of this reflex is located in the medulla oblongata and therefore chewing can be induced in bulbar animals. Finer regulation of the act of chewing is achieved only when the thalamus and motor cortex are intact.

swallowing is a complexly coordinated reflex act. Many muscles of the oral cavity, pharynx and the beginning of the esophagus are involved in its implementation. The act of swallowing consists of two phases: 1) formation food bolus and bringing it to the cavity of the pharynx and 2) swallowing it, in which the muscles of the pharynx contract and at the same time the palatine curtain rises, and the epiglottis descends. The first part of this mechanism is regulated arbitrarily, and the second - involuntarily - unconditioned reflex. The act of swallowing involves the afferent systems of the trigeminal, glossopharyngeal and vagus nerves. The swallowing center is a functional association of many nuclei that ensure the implementation of this reflex act.

Vomit is a reflex act that occurs when the receptors of the pharynx and stomach are irritated, as well as when the vestibuloreceptors are irritated (p. 461) and some others. Impulses coming from these receptors along afferent fibers in the medulla oblongata pass to many effector neurons located both in the medulla oblongata and in the spinal cord.

Vomiting can be caused not only by reflex, but also by direct irritation of certain parts of the medulla oblongata with a growing tumor, inflammation, or an increase in intracranial pressure. The center of vomiting can also be irritated in a humoral way, that is, by substances dissolved in the blood, for example, microbial toxins and some drugs (apomorphine), which, when injected subcutaneously, cause vomiting.

During the act of vomiting, the entrance to the stomach opens, the muscles of the intestine and the walls of the stomach contract, and the muscles contract. abdominals and diaphragm, muscles of the pharynx, larynx, tongue and mouth, secretion of saliva and tears.

During the act of vomiting, the state of many centers of the central nervous system changes due to the participation of the reticular formation of the brain stem in it. The latter, with its multiple connections, ensures the functional unification and coordination of the activity of neurons located in different parts of the medulla oblongata and spinal cord, and changes the state of the overlying centers.

Sneeze is a complex expiratory reflex act that occurs when the receptors of the trigeminal nerve in the nose are irritated. At the beginning of a sneeze soft sky rises and closes the internal nasal opening; then contraction of the expiratory muscles creates high blood pressure in the chest cavity, after which the nasal opening suddenly opens and all the air forcefully exits through the nose, removing the substance that irritated the mucous membrane of the post. In the act of sneezing, efferent fibers of the glossopharyngeal, vagus, hypoglossal, and some epipal nerves take part.

Cough, like sneezing, is a protective respiratory reflex that occurs when the mucous membrane of the larynx, trachea and bronchi is irritated. When coughing, unlike sneezing, it is not the posterior opening that closes, but the glottis, which, after creating the necessary pressure in the lungs, suddenly opens and a strong stream of air removes annoying factor. The same efferent fibers are involved in the act of coughing as in the act of sneezing, and afferent signals are transmitted along the fibers of the vagus first.

blinking- also a protective reflex - occurs when the cornea and conjunctiva of the eye are irritated, innervated by afferent fibers of the trigeminal nerve. The impulses coming from them in the medulla oblongata switch to the motor nucleus facial nerve, the fibers of which innervate the circular muscle of the eye; as a result, the eyelids close. In addition to all the listed reflex acts, the medulla oblongata is involved in reflex mechanisms, due to which orientation in the surrounding world and the regulation of muscle tone are achieved. Afferent impulses that cause the corresponding reflexes come along the V-XII cranial nerves (in particular, along the vestibular), as well as spinal nerves, which conducts impulses from the receptors of the muscles of the face, neck, limbs and torso.

Thus, a bulbar animal with a medulla oblongata and a pons varolii is capable of more complex reactions to external influences than spinal. All the main vital functions in these animals are united by more perfect control and are more coordinated.