The medulla oblongata, what functions it is responsible for and what diseases it suffers from. Medulla oblongata: basic structure and functioning Medulla oblongata and its functions briefly

The medulla oblongata (myelencephalon) lies at the base of the GM, being a continuation of the SC. Therefore, many features of its structure are similar to SM. The shape of the medulla oblongata resembles a truncated cone. Its length is approximately 30 mm, width at the base - 10 mm, at the top - 24 mm. Its lower border is the exit point of the first pair of spinal nerves. Above the medulla oblongata there is the pons, which on the ventral side looks like a constriction through the brain stem. The medulla oblongata is divided into two symmetrical halves by the anterior median fissure, which passes from the SC, and the posterior median sulcus, which continues a similar groove of the SC.

The medulla oblongata, together with the pons and cerebellum, makes up the hindbrain, the cavity of which is the fourth cerebral ventricle. The bottom of the IV ventricle, formed by the dorsal surface of the medulla oblongata and the pons, is called the rhomboid fossa.

On the ventral surface of the medulla oblongata, on the sides of the median fissure, there are two longitudinal cords of white matter - pyramids (Fig. 6.5). These are fibers of the corticospinal tract coming from the cerebral cortex to the SC (see paragraph 5.4). At the border with the SM, most of the fibers of this tract intersect, forming a pyramidal decussation. This area is the ventral border between the GM and SM.

Lateral to the pyramids lie oval elevations - olives, separated from them by the anterior lateral groove. In the depths of the olives there is gray matter - the inferior olivary complex (nuclei of the inferior olives). The complex consists of the nucleus of the inferior olive (p. olivaris inferior) and two additional nuclei of the inferior olive - medial and dorsal. This is where the spino-olivary tract coming from the SC ends. The inferior olive also receives many other afferents, primarily from the cerebral cortex and the red nucleus of the midbrain. These fibers form a dense capsule surrounding the nucleus. The olives themselves send their efferents to the cerebellar cortex (olivo-cerebellar tract). The olives, together with the cerebellum, are involved in maintaining posture and motor learning.

The VI, VII and VIII pairs of cranial nerves (abducens, facial and glossopharyngeal) emerge from the transverse fissure separating the medulla oblongata from the pons, and the hypoglossal nerve (XII pair) emerges from the anterior lateral sulcus. The glossopharyngeal, vagus and accessory nerves (IX, X and XI pairs) sequentially emerge from the outer edge of the olive.

Rice. 6.5

Roman numerals indicate the corresponding cranial nerves: V - trigeminal;

VI - abducent; VII - facial; VIII - vestibulo-auditory; IX - glossopharyngeal;

X - wandering; XI - additional; XII - sublingual

On the dorsal surface of the medulla oblongata, on the sides of the posterior median sulcus, there are two fascicles - the gentle (more medial) and the wedge-shaped (more lateral) (Fig. 6.6). This is a continuation of the paths of the same name ascending from the SM (see paragraph 5.4). But on the sides of the rhomboid fossa, thickenings are visible on the bundles - tubercles of the tender and wedge-shaped nuclei. Below them lie these nuclei, on which the fibers of the corresponding bundles end. The medial lemniscus begins from the tender and cuneate nuclei (see below). Some of the fibers from here go to the cerebellum.

Let us list the kernels included in gray matter of the medulla oblongata.

1. Nuclei of the trigeminal, facial, vestibulo-auditory, glossopharyngeal, vagus, accessory and hypoglossal nerves (see paragraph 6.2).
2. Gentle and wedge-shaped nuclei.
3. Olive kernels.
4. RF cores (see paragraph 6.7).

White matter occupies a large volume. It includes the so-called transit paths, i.e. ascending and descending tracts passing through the medulla oblongata without interruption (without forming synapses on its neurons). These include all spinal tracts, with the exception of the gentle and sphenoid fasciculi, as well as the spino-olivary tract, which end directly in the medulla oblongata. Transit tracts occupy the ventral and lateral parts of the medulla oblongata.

In addition, several new tracts begin here.

Rice. 6.6.

1. Inferior cerebellar peduncles ( pedunculus cerebellaris inferior)- these are pathways connecting the cerebellum with other brain structures(the cerebellum has three pairs of legs in total). The inferior peduncles include the olivocerebellar tract, the posterior spinocerebellar tract, fibers from the vestibular nuclei of the brainstem, and fibers from the gracile and cuneate nuclei.
2. Ascending tract - medial loop, or medial lemniscus (lemniscus medialis). Its fibers are formed by the axons of the cells of the tender and cuneate nuclei, which first pass to the other side and then go to the thalamus. The medial lemniscus is joined by spinothalamic tracts, as well as fibers from the sensory nuclei of the brain stem (nucleus of the solitary tract and nuclei trigeminal nerve), also ending in the thalamus. As a result, this entire system carries out various types of somatic (pain, skin, muscle, visceral) and also taste sensitivity into the diencephalon, and then into the cerebral cortex.
3. Medial longitudinal fasciculus (fasciculus longitudinalis medialis) starts from the lateral vestibular nucleus (Deiters nucleus). Some of the fibers of this pathway begin in some nuclei of the midbrain, so we will talk about it in more detail below (see paragraph 6.6).

Thus, functions of the medulla oblongata - reflex and conductive.

Conductor function lies in the fact that ascending and descending pathways pass through the brain stem (including through the medulla oblongata), connecting the overlying parts of the brain, up to the cerebral cortex, with the SC. Collaterals from these pathways can end on the nuclei of the medulla oblongata and pons.

Reflex function connected with the nuclei of the brain stem, through which reflex arcs are closed.

It should be noted that in the medulla oblongata (mainly in the reticular nuclei) there are many vital centers - respiratory, vasomotor, centers of food reflexes (salivary, swallowing, chewing, sucking), centers of protective reflexes (sneezing, coughing, vomiting), etc. Therefore, damage to the medulla oblongata (stroke, trauma, edema, hemorrhage, tumors) usually leads to very serious consequences.

Medulla is located in the lower half of the brain stem and connects to the spinal cord, being, as it were, its continuation. It is the most posterior part of the brain. The shape of the medulla oblongata resembles an onion or cone. In this case, the thick part of it is directed upward towards hindbrain, and narrow down to the spinal cord. The longitudinal length of the medulla oblongata is approximately 30-32 mm, its transverse size is about 15 mm, and its anteroposterior size is about 10 mm.

The place where the first pair of cervical nerve roots exits is considered the border of the spinal cord and medulla oblongata. The bulbar-pontine groove on the ventral side is the upper border of the medulla oblongata. The stria medullaris (auditory grooves of the medulla oblongata) represent the upper border of the medulla oblongata from the dorsal side. The medulla oblongata is limited from spinal cord on the ventral side there are crosshairs of the pyramids. There is no clear boundary of the medulla oblongata on the dorsal side, and the boundary is considered to be the place where the spinal roots emerge. At the border of the medulla oblongata and the pons there is a transverse groove that separates these two structures along with the medullary stripes.

On the outer ventral side of the medulla oblongata there are pyramids in which the corticospinal tract and olives pass, containing the nuclei of the inferior olive, which are responsible for balance. On the dorsal side of the medulla oblongata there are the wedge-shaped and thin bundles, which end in the tubercles of the wedge-shaped and thin nuclei. Also on the dorsal side is the lower part of the rhomboid fossa, which is the bottom of the fourth ventricle and the lower cerebellar peduncles. The posterior choroid plexus is located in the same place.

Contains many nuclei that are involved in many motor and sensory functions. The medulla contains centers responsible for the functioning of the heart (heart center) and the respiratory center. Through this area The brain controls gag and vasomotor reflexes, as well as autonomic functions of the body, such as breathing, coughing, blood pressure, and heart rate.

The formation of rhombomeres Rh8-Rh4 occurs in the medulla oblongata.

Ascending as well as descending pathways in the medulla oblongata go from the left to the right side and those on the right shall inherit.

The medulla oblongata includes:

glossopharyngeal nerve
part of the fourth ventricle
accessory nerve
nervus vagus
hypoglossal nerve
part of the vestibulocochlear nerve

Lesions and injuries to the medulla oblongata usually always lead to death due to its location.

Functions performed

The medulla oblongata is responsible for certain autonomic functions nervous system, such as:

Breathing controls the level of oxygen in the blood by sending signals to the intercostal muscles, increasing the rate of their contraction to saturate the blood with oxygen.
Reflex functions. This may include sneezing, coughing, swallowing, chewing, and vomiting.
Cardiac activity. Through sympathetic excitation, cardiac activity increases, and parasympathetic inhibition of cardiac activity also occurs. In addition, blood pressure is controlled through vasodilation and vasoconstriction.

Structurally, in terms of the diversity 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 not located in the center, but with its nuclei towards the periphery.

In the medulla oblongata there are olives connected to the spinal cord, the extrapyramidal system and the cerebellum - these are the thin and wedge-shaped nuclei of proprioceptive sensitivity (Gaull and Burdach nuclei). Here are also the intersections of the descending pyramidal paths and the ascending paths formed by the thin and wedge-shaped bundles(Gaull and Burdach), reticular formation.

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

The medulla oblongata contains the nuclei of the following cranial nerves:

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

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

Pair X - the vagus nerve has 3 nuclei: the autonomic innervates the larynx, esophagus, heart, stomach, intestines, digestive glands; sensitive receives information from receptors in the alveoli of the lungs and others internal organs and motor (the so-called mutual) ensures the sequence of contractions of the muscles of the pharynx and larynx during swallowing;

Pair XI - accessory nerve; its nucleus is partially located in the medulla oblongata;

Pair XII 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:

Reception of skin sensitivity of the face - in the sensory nucleus of the trigeminal nerve;

The primary analysis of taste reception is in the nucleus of the glossopharyngeal nerve;

Reception of auditory stimuli - in the nucleus of the cochlear nerve;

Reception of vestibular irritations is in the superior vestibular nucleus.

In the postero-superior parts of the medulla oblongata there are pathways of cutaneous, deep, visceral sensitivity, some of which are switched here to the second neuron (gracilis and cuneate nuclei). At the level of the medulla oblongata, the listed sensory functions implement a primary analysis of the strength and quality of irritation, then the processed information is transmitted to the subcortical structures to determine the biological significance of this irritation.

Conductor functions

All ascending and descending tracts of the spinal cord pass through the medulla oblongata: spinothalamic, corticospinal, rubrospinal. It originates the vestibulospinal, olivospinal and reticulospinal tracts, which provide tone and coordination of muscle reactions. In the medulla oblongata, the tracts from the cerebral cortex end - the corticoreticular tracts. Here the ascending pathways of proprioceptive sensitivity from the spinal cord end: the 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 analysis of sensory stimulation.

Reflex functions

Numerous reflexes of the medulla oblongata are divided into vital and non-vital. However, this idea is quite conditional. The respiratory and vasomotor centers of the medulla oblongata can be classified as 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 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 the command goes to the motor nuclei of the trigeminal, vagus, facial, glossopharyngeal, accessory or hypoglossal nerves, as a result of which 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 the diaphragm, reflexes of eating behavior are organized: sucking, chewing, swallowing.

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

Changes in posture are carried out due to static and statokinetic reflexes. Static reflexes regulate the tone of skeletal muscles in order to maintain a certain body position. Statokinetic reflexes of the medulla oblongata provide redistribution of the tone of the trunk muscles to organize a posture corresponding to the moment of linear or rotational movement.

Most of the autonomous 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 the motor and secretory reactions of these organs.

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

The center of salivation is localized in the medulla oblongata, the parasympathetic part of which ensures increased general secretion, and the sympathetic part ensures increased 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 capable of being 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 there is another vital center - the vasomotor center (regulation of vascular tone). It functions in conjunction with the overlying structures of the brain and primarily 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.

In the middle sections of the reticular formation there are neurons that form the reticulospinal tract, which has an inhibitory effect on the motor neurons of the spinal cord. At the bottom of the fourth ventricle are the neurons of the locus coeruleus. Their transmitter is norepinephrine. These neurons cause activation of the reticulospinal tract during REM sleep, which leads to inhibition of spinal reflexes and decreased muscle tone.

Symptoms of damage. 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 functioning of the muscles of the face and head on the side of the damage. At the same time on opposite side Regarding the side of the injury, disorders of skin sensitivity and motor paralysis of the trunk and limbs are observed. 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.

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Axes and planes of the human body - The human body consists of certain topographic parts and areas in which organs, muscles, vessels, nerves, etc. are located.

Chiselling of walls and cutting of jambs - When there are not enough windows and doors on the house, a beautiful high porch is only in the imagination, you have to climb from the street into the house along a ladder.

Second order differential equations (market model with predicted prices) - B simple models In the market, supply and demand are usually considered to depend only on the current price of the product.

Medulla- the most caudal part of the brain stem, located between the spinal cord and the pons. In the medulla oblongata there are nuclei of the V-XII pairs of cranial nerves, separated by pathways passing through the medulla oblongata, both in the ascending and descending directions.

Reticular formation- a collection of neurons with specific properties, the bulk of which occupies the central part of the medulla oblongata. In the lower part of the medulla oblongata on its dorsal side there are the nuclei of the gentle and sphenoid cords (Gaull and Burdach).

Functions of the medulla oblongata:

Defense reflexes (eg, coughing, sneezing); Vital reflexes (eg breathing); Regulation of vascular tone.

Reflex centers of the medulla oblongata: digestion; cardiac activity; protective (coughing, sneezing, etc.); centers for regulating skeletal muscle tone to maintain human posture; shortening or lengthening the spinal reflex time.

Reflexes, carried out by its structures, can be divided into vegetative, somatic, reflexes for the implementation of sensory functions (taste, hearing, vestibular reception).

The functions of the medulla oblongata are highlighted separately, caused by the presence of a reticular formation in it and associated with the regulation of respiration, cardiovascular activity and tonic influences on the spinal cord and cerebral cortex.

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

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

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

pair XI - accessory nerve; its nucleus is partially located in the medulla oblongata;

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

Reflexes:

Vegetative: smooth muscle contraction, secretion – vagus nerve

Somatic: perception, processing, swallowing food, maintaining posture, defense (vomiting, sneezing, coughing, blinking) - glossopharyngeal nerve, accessory nerve, hypoglossal nerve.

Statokinetic: maintaining posture during movement – vestibulocochlear nerve.

12. Integrative functions of the midbrain

Midbrain- part of the brain stem, located between the pons and the diencephalon.

The midbrain includes:

Conducting pathways

Nuclei of the cranial nerves (pair IV - trochlear nerve; pair III - oculomotor nerve),

reticular formation,

Quadrigeminal (upper tubercles - vision; lower tubercles - hearing),

Midbrain nuclei (substantia nigra and red nucleus)

Upper tuberosities of the quadrigeminal:

Indicative alert reflex, pupillary, accommodative, convergence of the ocular axes, rotation of the eyes, body to the light source

The lower tuberosities of the quadrigeminal:

Pricking the ears, turning the head and body towards the sound source

Red kernels:

They receive impulses from the cerebral cortex, subcortical motor nuclei and cerebellum along descending pathways and transmit signals to the rubrospinal pathways to the neurons of the spinal cord.

participate in the regulation of muscle tone

Black substance:

coordinates the acts of chewing and swallowing, also participating in the regulation of plastic tone, and in humans, in small movements of the fingers

The midbrain level of the central nervous system provides:

processing of sensory information; motor regulation; modulation of activity at both diencephalocortical and bulbarnospinal levels

13. Functions and connections of the thalamus

Thalamus - analysis of afferent signals; organization of integrative processes; regulation functional state and higher nervous activity.

It consists of specific and nonspecific nuclei(morphologically and functionally associated with many systems and participate, together with the reticular formation of the brain stem, in the implementation of nonspecific functions)

Specific kernels have a local projection into strictly defined areas of the cortex. They switch afferent impulses from peripheral receptors or from the primary perceptive nuclei of underlying stem structures, as well as from extrasensory sources. Resolution – irreversible loss of sensation or impairment of movement.

These two thalamocortical systems are in constant interaction

the nonspecific system enhances the specific one, and the specific one, on the contrary, suppresses the nonspecific one.

Under the influence of nonspecific impulses, the response of cortical neurons to specific stimulation is noticeably enhanced, i.e. nonspecific thalamic impulses facilitate the activity of cortical neurons, increasing their excitability.

Primary processing of visual, auditory, tactile and information and a sense of equilibrium and balance.

14. Hypothalamus. Location and functions

Hypothalamus or hypothalamus - a section of the diencephalon located below the thalamus, or “visual thalamus”, for which it received its name - is the highest subcortical center integration of autonomic, emotional and motor components of complex reactions.

Includes centers that organize homeostasis (maintaining a constant internal environment) and homeokinesis (adaptation of the internal environment to changes in living conditions)

Centers of the hypothalamus: thermoregulation, hunger and satiety, thirst, regulation of sexual behavior, pleasure, displeasure.

Topic 9. Medulla oblongata.

The brain is divided into 5 sections from bottom to top: medulla oblongata, hindbrain, midbrain, diencephalon and telencephalon.

Rice. 1. Sagittal section of the brain.

1 – medulla oblongata; 2 – hindbrain (pons and cerebellum); 3 – midbrain; 4 – diencephalon; 5 – telencephalon.

Medulla(medulla oblongata) is a direct continuation of the spinal cord and has a cone-shaped shape. It combines the structural features of the spinal cord and brain.

Human medulla oblongata and its most important functions

There are ventral, dorsal and lateral surfaces.

The lower border on the ventral surface is the exit site of the roots of the first pair of cervical nerves of the spinal cord, the upper border is the lower edge of the pons.

On the ventral surface there is a deep median fissure, which is a continuation of the fissure of the same name in the spinal cord. On the sides of it there are two longitudinal rollers - pyramids(pyramides), formed by the nerve fibers of the pyramidal tracts, which form a decussation (decussatio pytamidum) deep in the fissure at the border with the spinal cord. The anterior lateral groove runs along the side of the pyramids, from which the roots of the hypoglossal nerve emerge. In the upper part of the furrow there are convex oval formations - olives(olivae). Lateral to the olive lies the posterior lateral groove of the medulla oblongata, from which the roots of the accessory, vagus and glossopharyngeal nerves emerge.

Fig.2. Transverse section of the medulla oblongata at the level of the inferior olives (view from the ventral surface).

1 – anterior median fissure; 2 – anterolateral groove; 3 – pyramids; 4 – olives; 5 – nucleus of the inferior olive; 6 – gate of the nucleus of the inferior olive; 7 – rhomboid fossa; 8 – inferior cerebellar peduncle; 9 – reticular formation; 10 – double core; 11 – glossopharyngeal nerve; 12 – vagus nerve; 13 – accessory nerve; 14 – hypoglossal nerve

The dorsal surface of the medulla oblongata has a different structure in the lower and upper parts. In its lower third, it is divided by the posterior median sulcus into two symmetrical parts and contains a continuation of the gentle and cuneate fasciculi running in the posterior funiculi of the spinal cord, which end in two protruding tubercles of the same nuclei. Approximately in the middle of the medulla oblongata, the right and left posterior cords diverge upward and to the side and pass into thick ridges - the lower cerebellar peduncles, which plunge into the cerebellum. Top part the dorsal surface of the medulla oblongata is expanded, forming the lower half rhomboid fossa. A median groove runs along the bottom of the diamond-shaped fossa, on the sides of which there are elevations - triangles of the vagus and hypoglossal nerves. In the lateral sections of the fossa, on the border with the bridge there is vestibular field, in the depths of which the auditory and vestibular nuclei are contained.

Fig.3. Dorsal surface of the medulla oblongata.

1 – rhomboid fossa; 2 – brain stripes; 3 – posterior median groove; 4 – posterolateral groove; 5 – posterointermediate groove; 6 – thin beam; 7 – tubercle of a thin bundle; 8 – wedge-shaped bundle; 9 – tubercle of the wedge-shaped bundle; 10 - lateral cord; 11 – inferior cerebellar peduncle.

The lateral surface of the medulla oblongata contains a continuation of the lateral cords of the spinal cord and in the upper part ends with the trigeminal tubercle.

Internal structure of the medulla oblongata. If you make a transverse section of the medulla oblongata at the level of the middle of the olives, a number of structures will be visible on the section (Fig. 2). The gray and white matter, and as you move up, the nature of their relative position gradually changes. Gray matter gradually loses its butterfly shape and is divided by conductive pathways into separate nuclei.

Four groups of nuclei of the medulla oblongata can be distinguished. The first group is the nuclei of the posterior funiculi, thin and wedge-shaped, located in the thickness of the tubercles of the same name. The neurons of these nuclei end with fibers of the thin and wedge-shaped fasciculi, which transmit information from the proprioceptors of the body and limbs. The axons of the cells of the thin and wedge-shaped nuclei form two ascending tracts: the larger one - bulbothalamic, which in the form of a medial loop is directed to the nuclei of the thalamus and bulbocerebellar, which is sent to the cerebellum as part of the inferior cerebellar peduncles.

The second group of nuclei - olive kernels. The neurons of this nucleus terminate the descending fibers coming from the red nucleus of the midbrain. Functionally, the core is associated with maintaining posture and balance and is part of the extrapyramidal system. From it begins the large olivo-cerebellar tract, which goes to the cerebellum as part of the inferior cerebellar peduncles, and the smaller olivo-spinal tract, which descends into the spinal cord.

The third group of nuclei is represented by the nuclei of the cranial nerves. In the depths of the medulla oblongata lie the nuclei of the YIII-XII pair of cranial nerves. They are mainly located on the dorsal surface of the medulla oblongata in the region of the rhomboid fossa. Cores vestibulocochlear nerve (YIII pair) lie in the lateral parts of the rhomboid fossa in the region of the vestibular field. They are divided into 4 vestibular nuclei and 2 cochlear (auditory) nuclei. The auditory nuclei (ventral and dorsal) lie in the lateral section auditory field. The axons of the neurons of the spiral ganglion end on their cells, through which information from the organ of hearing (cochlea) is transmitted. The axons of the neurons of the auditory nuclei are directed to the nuclei of the trapezoidal body of the bridge. Three vestibular nuclei (lateral, medial and inferior) are also located at the level of the medulla oblongata, the fourth, the superior vestibular nucleus, is considered part of the pontine nuclei. They receive information from the receptors of the semicircular canals, the organ of balance, along the axons of the vestibular ganglion. The vestibular nuclei are distinguished by an abundance of outputs. They start from them vestibulo-spinal And vestibulocerebellar pathways functionally associated with the coordination of skeletal muscle activity depending on vestibular afferentation. Some of the bundles responsible for visual-motor coordination (image stabilization on the retina) go to the nuclei of the III, IY and YI pairs of cranial nerves. There are also pathways to the reticular formation and thalamus. Glossopharyngeal nerve (IX pair)- mixed: has sensitive, motor and autonomic nuclei located in the medulla oblongata. The sensory nucleus of the glossopharyngeal nerve is nucleus of the solitary tract(n. solitarius), which stretches along the wall of the IY ventricle in the dorsal part of the medulla oblongata. This nucleus is the common sensory nucleus for the YII, IX and X pairs of cranial nerves. This nucleus collects information from the taste buds of the tongue, as well as from the receptors of the internal organs and the eardrum. Afferents from the nucleus are sent to the thalamus and hypothalamus, as well as to the motor nuclei of the cranial nerves and to the reticular formation. Motor core - double core(n. ambiguous), located in the ventrolateral parts of the medulla oblongata. It is the common motor nucleus for the IX and X pairs of cranial nerves. It has inputs from the sensory nuclei of the Y, IX and X pairs of cranial nerves, as well as from the cerebral cortex. The axons of the neurons of this nucleus end on motor neurons that innervate the muscles of the larynx and pharynx. Participates in sneezing, swallowing and coughing. Cortical input provides voluntary muscle activity and coordination during speech. Vegetative nucleus is called inferior salivary nucleus(n. salivatorius inferior). It receives axons from neurons in the nucleus of the solitary tract and vestibular nuclei, as well as from neurons in the cerebral cortex. The core regulates the work parotid glands. X pair - nervus vagus(n. vagus) - also mixed: motor, sensitive, vegetative. The motor nucleus - the double, and the sensitive - the nucleus of the solitary tract were discussed above. Vegetative nucleus - posterior nucleus of the vagus nerve, is located on the dorsal surface of the medulla oblongata in the region of the triangle of the vagus nerve.

On the neurons of this nucleus, the axons of the neurons of the nucleus of the solitary tract and the sensory nuclei of the trigeminal nerve end. The axons of the vagal neurons end on the neurons of the parasympathetic ganglia of the internal organs of the abdominal and chest cavity. The nucleus participates in the regulation of the functioning of internal organs and carries out the gag reflex. XI pair - accessory nerve(n. accessorius) – motor. The nucleus is located medially in the lower corner of the rhomboid fossa, connected with the anterior horns of the spinal cord and close to them in structure. Regulates the work of the muscles of the shoulder girdle. XII pair - hypoglossal nerve(n. hypoglossus) - motor. The nucleus is located in the area of the sublingual triangle of the rhomboid fossa. Some of the fibers of the cortical-nuclear tract, as well as the axons of the neurons of the sensory nuclei of the trigeminal and vagus nerves, end on its neurons. Functionally, the core is associated with the coordination of tongue movements during chewing. The presence of cortical inputs ensures voluntary movement of the tongue during speech.

The last group of nuclei are nuclei of the reticular formation. Large nuclei located within the medulla oblongata act as centers for such complex reflex acts as breathing, heartbeat, vascular tone, etc. Distinctive features reticular centers - poor differentiation, lack of clear boundaries, a large number of inputs and projections to various brain structures. They are located in the central parts of the medulla oblongata. Within the medulla oblongata there are vitally important centers of respiration and circulation. Therefore, if the medulla oblongata is damaged, death can occur.

Fig.5. Projection of the nuclei of the cranial nerves onto the rhomboid fossa.

1 – nucleus of the oculomotor nerve; 2 – nucleus of the trochlear nerve; 3 – motor nucleus of the trigeminal nerve; 4 – sensitive nucleus of the trigeminal nerve; 5 – motor nucleus of the glossopharyngeal nerve; 6 – motor nucleus of the vagus nerve; 7 – nucleus of the abducens nerve; 8 – motor nucleus of the facial nerve; 9 – nucleus of the accessory nerve; 10, 11 – nuclei of the vestibulo-cochlear nerve; 12 – sensitive nucleus of the vagus nerve; 13 – sensitive nucleus of the glossopharyngeal nerve; 14 – nucleus of the hypoglossal nerve; 15,16,17 – cerebellar peduncles; 18 – facial mound; 19 – brain stripes

White matter The medulla oblongata is represented mainly by longitudinally running nerve fibers. Many of them are transit, i.e. pass without switching. Ascending fibers follow from the spinal cord. This - thin and wedge-shaped beams, which, having switched in the nuclei of the same name, form bulbo-thalamic and bulbo-cerebellar tracts. Along the lateral surface of the medulla oblongata there are anterior and posterior spinocerebellar tracts. The first continues into the pons, the second, as part of the inferior cerebellar peduncle, enters the cerebellum. Passes in transit more medially spinothalamic tract, formed by fibers of the anterior and lateral spinal cord tracts of the same name. Descending fibers are represented by bundles coming from various motor nuclei of the brain. The largest is pyramidal tract, running along the ventral surface of the medulla oblongata, its fibers will form lateral and anterior corticospinal tracts. Passes dorsal to the pyramids reticulospinal tract, and more laterally – vestibulospinal. Near the dorsal surface of the medulla oblongata there are posterior and medial longitudinal beams . Ahead of them is located tegnospinal tract. Mediolaterally passes red nucleus spinal tract. In addition, pathways are formed in the medulla oblongata that connect its sensory nuclei with the overlying centers of the brain - nuclear-thalamic and nuclear-cerebellar pathways. The first one is transmitted general information from head receptors and internal organs receptors. According to the second, unconscious proprioceptive impulses from the head area. On the neurons of the motor nuclei of the cranial nerves of the medulla oblongata they end fibers of the corticonuclear tract.

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Human medulla oblongata

Medulla is located in the lower half of the brain stem and connects to the spinal cord, being, as it were, its continuation. It is the most posterior part of the brain. The shape of the medulla oblongata resembles an onion or cone. In this case, its thick part is directed upward to the hindbrain, and the narrow part downward to the spinal cord. The longitudinal length of the medulla oblongata is approximately 30-32 mm, its transverse size is about 15 mm, and its anteroposterior size is about 10 mm.

Medulla oblongata: basic structure and functioning

The stria medullaris (auditory grooves of the medulla oblongata) represent the upper border of the medulla oblongata from the dorsal side. The medulla oblongata is limited from the spinal cord on the ventral side by the crosshairs of the pyramids. There is no clear boundary of the medulla oblongata on the dorsal side, and the boundary is considered to be the place where the spinal roots emerge. At the border of the medulla oblongata and the pons there is a transverse groove that separates these two structures along with the medullary stripes.

On the outer ventral side of the medulla oblongata there are pyramids in which the corticospinal tract and olives pass, containing the nuclei of the inferior olive, which are responsible for balance.

On the dorsal side of the medulla oblongata there are the wedge-shaped and thin bundles, which end in the tubercles of the wedge-shaped and thin nuclei. Also on the dorsal side is the lower part of the rhomboid fossa, which is the bottom of the fourth ventricle and the lower cerebellar peduncles. The posterior choroid plexus is located in the same place.

Contains many nuclei that are involved in many motor and sensory functions. The medulla contains centers responsible for the functioning of the heart (heart center) and the respiratory center. Through this part of the brain, gag and vasomotor reflexes are controlled, as well as autonomic functions of the body, such as breathing, coughing, blood pressure, and the frequency of contractions of the heart muscle.

The formation of rhombomeres Rh8-Rh4 occurs in the medulla oblongata.

Ascending as well as descending pathways in the medulla oblongata go from the left to the right side and are inherited from the right.

The medulla oblongata includes:

glossopharyngeal nerve
part of the fourth ventricle
accessory nerve
nervus vagus
hypoglossal nerve
part of the vestibulocochlear nerve

Lesions and injuries to the medulla oblongata usually always lead to death due to its location.

Functions performed

The medulla oblongata is responsible for certain functions of the autonomic nervous system, such as:

Breathing controls the level of oxygen in the blood by sending signals to the intercostal muscles, increasing the rate of their contraction to saturate the blood with oxygen.
Reflex functions. This may include sneezing, coughing, swallowing, chewing, and vomiting.
Cardiac activity. Through sympathetic excitation, cardiac activity increases, and parasympathetic inhibition of cardiac activity also occurs. In addition, blood pressure is controlled through vasodilation and vasoconstriction.

Features of functional organization. The medulla oblongata in humans is about 25 mm long. It is a continuation of the spinal cord. Structurally, in terms of the diversity 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 not located in the center, but with its nuclei towards the periphery.

In the medulla oblongata there are olives connected to the spinal cord, the extrapyramidal system and the cerebellum - these are the thin and wedge-shaped nuclei of proprioceptive sensitivity (Gaull and Burdach nuclei). Here are the intersections of the descending pyramidal tracts and the ascending tracts formed by the thin and wedge-shaped fascicles (Gaull and Burdach), the reticular formation.

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

The medulla oblongata contains the nuclei of the following cranial nerves:

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 (n.

Medulla oblongata: anatomy, structure of nuclei and functions

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

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

Sensory functions. The medulla oblongata regulates a number of sensory functions: 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 irritations - in the superior vestibular nucleus. In the postero-superior parts of the medulla oblongata there are pathways of cutaneous, deep, visceral sensitivity, some of which are switched here to the second neuron (gracilis and cuneate nuclei). At the level of the medulla oblongata, the listed sensory functions implement a primary analysis of the strength and quality of irritation, then the processed information is transmitted to the subcortical structures to determine the biological significance of this irritation.

Reflex functions. Numerous reflexes of the medulla oblongata are divided into vital and non-vital, but this idea is quite arbitrary. The respiratory and vasomotor centers of the medulla oblongata can be classified as 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 the eyelids. These reflexes are realized due to the fact that information about the 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 activation of the muscle groups of the head, neck, chest and diaphragm, reflexes of eating behavior are organized: sucking, chewing, swallowing.

Static reflexes Statokinetic reflexes

Most of the autonomous reflexes of the medulla oblongata are realized through the vagus nerve nuclei 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 the motor and secretory reactions of these organs.

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

Localized in the medulla oblongata salivary center the parasympathetic part of which ensures increased general secretion, and the sympathetic part ensures increased protein secretion of the salivary glands.

Respiratory center 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.

Another vital center is represented in the reticular formation of the medulla oblongata - vasomotor center(regulation of vascular tone). It functions together 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.

In the middle sections of the reticular formation there are neurons that form the reticulospinal tract, which has an inhibitory effect on the motor neurons of the spinal cord. At the bottom of the fourth ventricle are the neurons of the locus coeruleus. Their mediator is norepinephrine. These neurons cause activation of the reticulospinal tract during REM sleep, which leads to inhibition of spinal reflexes and decreased muscle tone.

Symptoms of damage. 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 functioning of the muscles of the face and head on the side of the damage. At the same time, on the opposite side to the side of the injury, disorders of skin sensitivity and motor paralysis of the trunk and limbs are observed. 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.

21. Static (positional, straightening reflexes) and statokinetic reflexes, mechanism of formation, their significance.

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

Changes in posture are carried out due to static and statokinetic reflexes. Static reflexes regulate the tone of skeletal muscles in order to maintain a certain body position. Statokinetic reflexes the medulla oblongata provide redistribution of the tone of the trunk muscles to organize a posture corresponding to the moment of linear or rotational movement.

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Blood supply to the brain

Brain malformations

Brain tumors

The brain is the anterior part of the central nervous system, located in the cranial cavity. Consists of the hemispheres and the brain stem with the cerebellum.

Anatomy
The brain is divided into five sections: 1) medulla oblongata (myelencephalon, or medulla oblongata); 2) the hindbrain (metencephalon), consisting of the pons (varoliev) and the cerebellum; 3) the midbrain (mesencephalon), in which the cerebral peduncles and quadrigeminal region are located; 4) the diencephalon (diencephalon), consisting of the visual thalamus (thalamus), epithalamus, hypothalamus and subthalamus; 5) telencephalon, or cerebral hemispheres.

Just as in the spinal cord (see), gray and white matter are distinguished in the brain. From gray matter- accumulations of nerve cells - the nuclei and cortex of the cerebral hemispheres and cerebellum are formed in the brain. White matter is bundles of long and short nerve fibers that connect various structures of the brain to the spinal cord. In the brain stem there are clusters of nerve cells with short, numerous fibers - a reticular formation (formatio reticularis).

Medulla is a direct continuation of the spinal cord. Important cranial nerves (glossopharyngeal, vagus, accessory and hypoglossal) originate in the nuclei of the medulla oblongata. Paths that carry impulses from the spinal cord to the brain (centripetal) and from the brain to the spinal cord (centrifugal) pass through it. One important pathway is the pyramidal tract, which connects the motor area of the cerebral cortex with the motor cells of the anterior horn of the spinal cord. At the border of the medulla oblongata and the spinal cord, the pyramidal tracts cross, which causes functional disorders with damage to one or another area of the brain. When the pyramidal fascicle is damaged above the chiasm, hemiplegia (see) develops on the opposite side of the body; if the cranial nerves are simultaneously affected, their function is impaired on the side of the body of the same name as the lesion (see Alternating syndromes).

The pons also contains the nuclei of the cranial nerves - trigeminal, abducens, facial and statoacoustic (vestibular-cochlear).

Regulation is carried out through the medulla oblongata and the pons blood pressure and breathing and reflexes such as chewing, swallowing, vomiting, coughing, sneezing, blinking.

The junction of the pons, medulla oblongata and cerebellum is called the pontocerebellar angle. It is located at the base of the brain in the posterior cranial fossa. In this area, the facial and statoacoustic nerves emerge from the surface of the brain. With tumors in the area of the cerebellopontine angle, the nearest parts of the medulla oblongata, pons and cerebellum are compressed and corresponding clinical symptoms develop.

Part midbrain includes the quadrigeminal peduncle and cerebral peduncles. The quadrigeminal region is located on the dorsal surface of the midbrain. The anterior tubercles of the quadrigeminal are the primary visual centers, and the posterior ones are the auditory centers. The cerebral peduncles contain the red nucleus and the substantia nigra, which take part in the regulation of the plastic tone of the muscles of the body, and at the bottom of the cerebral (Sylvian) aqueduct are the nuclei of the oculomotor and trochlear cranial nerves. Through the cerebral peduncles there are ascending pathways that carry impulses to the thalamus opticus and the cerebral hemispheres, and descending pathways that carry impulses to the medulla oblongata and spinal cord. The mesencephalon also contains the reticularis substance (see above).

Main formations diencephalon- visual hillocks, which are the collector of all sensory pathways (except olfactory) passing to the cerebrum, hypothalamus (see Hypothalamus), geniculate bodies with subcortical visual and auditory centers and the pineal body with adjacent formations.

In each part of the brain there are cavities - the ventricles of the brain.

Ascending upward, the central canal of the spinal cord, expanding, passes into the IV ventricle, the bottom of which is a rhomboid fossa formed by the medulla oblongata and the pons. In the thickness of the bottom of the IV ventricle there are nuclei of the cranial nerves (from the V to the XII pairs). The cerebellum is located above the IV ventricle (see). Externally, the IV ventricle is bounded by the cerebellar peduncles, superiorly by the vascular plate, superior and inferior medullary velum. Upwards, the IV ventricle narrows and in the region of the midbrain passes into the cerebral (Sylvian) aqueduct, surrounded by gray matter. The cerebral aqueduct at the top passes into the third ventricle - the cavity of the diencephalon. The lateral walls of the third ventricle are the visual tuberosities; upper - epithelial plate (roof of the third ventricle), above which lies the fornix and corpus callosum of the cerebral hemispheres; anterior - anterior commissure and columns of the arch. Between the columns of the fornix and the anterior part of the corpus callosum there is a transparent septum. The bottom of the third ventricle consists of the hypothalamus: lamina terminalis, optic chiasm, infundibulum, pituitary gland, gray tubercle, mamillary bodies.

The cavity of the third ventricle is connected through the interventricular foramina with the lateral ventricles of the cerebral hemispheres. In the lateral ventricles, the anterior, posterior and inferior horns of the lateral ventricles are distinguished. Just like in the IV and III ventricles, they contain choroid plexuses.

The choroid plexuses produce cerebrospinal fluid (see), which fills the ventricles of the brain and the cavity of the central spinal canal. Through the openings of the inferior medullary velum, cerebrospinal fluid enters from the cavity of the fourth ventricle into the subarachnoid space (see Meninges) and also washes the outer surface of the brain and spinal cord. If the patency of these openings is impaired, as well as when the cerebral aqueduct is compressed by a tumor, occlusive hydrocephalus may develop (see).

Finite brain is divided by a longitudinal groove into two hemispheres, connected by the corpus callosum, fornix and anterior commissure. The corpus callosum is a powerful bundle of fibers connecting the hemispheres of the brain. The arch is divided anteriorly into columns, and posteriorly into legs. Between the legs of the vault lies the commissure of the vault. The columns of the fornix are directed into the mamillary bodies, from inner core which originates from a bundle going to the optic thalamus. The cerebral hemispheres are divided into frontal, parietal, temporal, occipital lobes and insula. The surface of the cerebral hemisphere - the cloak (pallium) - is cut by grooves, between which lie convolutions. The deepest lateral (Sylvian) fissure separates the temporal lobe from the frontal and parietal lobes. An island is located deep in the lateral sulcus. The part of the frontal and parietal lobes above the lateral sulcus is called the central operculum. The frontal and parietal lobes are separated from each other by the central (Rolandic) sulcus. Around the central sulcus lie the precentral and postcentral gyri. The frontal lobe has two or three frontal grooves; its lower surface is cut through by the orbital and olfactory grooves. The latter contains the olfactory tract.

The parietal lobe is divided into inferior and superior lobules and is cut through by the interparietal groove. On the inner surface of the occipital lobe there are calcarine and parieto-occipital grooves. Between them there is a so-called wedge. The groove of the corpus callosum and the cingulate groove run along the inner surface of the hemisphere; between them lies the cingulate gyrus, which is part of the limbic region.

Under the gray matter of the hemispheres - the cerebral cortex - lie the white matter and basal ganglia. The white substance, consisting of fibers, forms the outer and inner bursae.

In the cerebral cortex there is a representation of various functions (cortical centers). According to the teachings of I.P.

Medulla oblongata, structure, functions and development

Pavlov, the cortex is the cortical end of the analyzers. The visual analyzer is represented in the occipital region, the auditory analyzer is represented in the temporal region, general sensitivity is represented in the postcentral region, and the motor analyzer is represented in the precentral region.

The limbic region is related to autonomic functions. Areas such as the frontal, inferior parietal, temporo-parietal-occipital subregion belong to the inter-analyzer zones that carry out higher mental and speech functions, as well as subtle purposeful movements of the hands.

Rice. 1. Sagittal section of the brain: 1 - frontal lobe of the hemisphere; 2- cingulate gyrus; 3 - corpus callosum; 4 - transparent partition; 5 - vault; 6 - anterior commissure; 7 - optic chiasm; 8 - pituitary gland; 9 - temporal lobe of the hemisphere; 10 - bridge; 11 - medulla oblongata; 12 - cerebellum; 13 - fourth ventricle; 14 - occipital lobe of the hemisphere; 15 - parietal lobe of the hemisphere; 16 - quadrigeminal; 17 - pineal body; 18 - cerebral aqueduct; 19 - visual thalamus; 20-subtubercular region.

Rice. 2. Brain. Side view: 1- frontal lobe; 2 - temporal lobe; 3 - medulla oblongata; 4 - cerebellum; 5- occipital lobe; b - parietal lobe; 7 - lateral groove; 8 - central groove.

Rice. 3. Brain. Top view: 1 - frontal lobes hemispheres; 2 - parietal lobes of the hemispheres; 3 - occipital lobes of the hemispheres; 4 - longitudinal fissure of the brain.

Rice. 4. Brain stem. Top view: 1st optic tubercle; 2 - pineal body; 3 - quadrigeminal; 4 - trochlear nerve; 5 - trigeminal nerve; 6 - upper cerebral velum; 7-superior cerebellar peduncle; 8 - middle cerebellar peduncle; 9 - facial nerve; 10 - diamond-shaped fossa; 11 - glossopharyngeal nerve; 12 - vagus nerve; 13 - accessory nerve; 14 - medulla oblongata; 15 - inferior cerebellar peduncle; 16 - cerebral peduncle.

Rice. 5. Base of the brain: 1 - frontal lobes of the hemisphere; 2 - olfactory tract; 3 - optic nerve; 4 - temporal lobe of the hemisphere; 5 - oculomotor nerve; 6 - trochlear nerve; 7 - bridge; 8 - trigeminal nerve; 9 - abducens nerve; 10 - facial and vestibulocochlear nerves; 11 - glossopharyngeal nerve; 12 - vagus nerve; 13 - accessory nerve; 14 - cerebellum; 15 - occipital lobes of the hemisphere; 16 - pyramids of the medulla oblongata; 17 - hypoglossal nerve; 18 - mastoid body; 19 - gray tubercle and funnel; 20 - optic chiasm.

Search Lectures

Lecture No. 18-20 “Functional anatomy of the brain. ChMN."

1. Structural organization of the brain, its physiological role.

2. Medulla oblongata - structural features, physiological role.

3. Hindbrain - structural features, physiological role.

4. Midbrain - structural features, physiological role.

5. Diencephalon - structural features, physiological role.

6. CMN region and nature of innervation.

7. Anatomical and physiological features of the cerebral cortex.

8. Liquor formation, composition, functions.

Structural organization of the brain, its physiological role.

The brain is the main regulator of all functions of a living organism. It is one of the elements of the central nervous system. The human brain consists of 25 billion neurons. These cells are the gray matter. Inside the brain there are cavities called ventricles. Paired cranial nerves (12 pairs) depart from it to different parts of the body.

During evolution, a strong cranium was formed around the human brain, protecting this organ. The brain occupies more than 90% of the space of the skull. It consists of three main parts:

· cerebral hemispheres;

·brain stem;

· cerebellum.

It is also customary to distinguish five parts of the brain:

Forebrain (cerebral hemispheres);

hindbrain (cerebellum, pons);

·medulla;

midbrain;

diencephalon.

The first section located above the spinal cord is medulla, it is actually its continuation.

Medulla oblongata: its structure, nuclei and functions

The medulla oblongata consists of gray and white matter.
Next comes Pons- This is a roller of nerve transverse fibers and gray matter. The main artery that supplies the brain passes through it. It starts above the medulla oblongata and passes into the cerebellum.
Cerebellum consists of two hemispheres and a worm, as well as white matter and gray matter covering it. This section is connected by pairs of “legs” to the medulla oblongata and midbrain.
Midbrain consists of two visual hillocks and two auditory hillocks (quadrigeminal). Nerve fibers extending from these tubercles connect the brain with the spinal cord.
Large hemispheres of the brain separated by a deep fissure with the corpus callosum inside, which connects these two sections of the brain. Each hemisphere has the following areas:

Temporal,

Parietal and

Occipital.

The hemispheres are covered by the cerebral cortex.
In addition, there are three membranes of the brain:

·hard, representing the periosteum of the inner surface of the skull; a large number of pain receptors are concentrated in this shell;

· arachnoid, which is closely adjacent to the cerebral cortex, but does not line the gyri; the space between it and the dura mater is filled with serous fluid, and the space between it and the cerebral cortex is filled with cerebrospinal fluid;

soft, consisting of a system blood vessels And connective tissue, in contact with the entire surface of the brain matter and nourishing it.

Medulla oblongata - structural features, physiological role.

The medulla oblongata, medulla oblongata, is a direct continuation of the spinal cord. Its lower border is considered to be the place of exit of the roots of the first cervical spinal nerve, the upper border is the posterior edge of the bridge. The length of the medulla oblongata is about 25 mm, the shape approaches a truncated cone, with the base facing upward. The anterior surface is divided by the anterior median fissure, on the sides of which there are elevations - pyramids, formed by bundles of nerve fibers of the pyramidal pathways. These fibers partially intersect (pyramid decussation) in the depth of the described fissure at the border with the spinal cord. On each side of the pyramid there is an olive approximately 1.5 cm long, containing the nuclei of gray matter. The medulla oblongata is built of white and gray matter, the latter is represented by the nuclei of the IX–XII pairs of cranial nerves, olives, reticular formation, respiratory and circulatory centers. White matter, which is formed by long and short fibers that make up the corresponding pathways, should be distinguished from gray matter.

The medulla oblongata regulates a number of sensory functions: skin sensitivity of the face - in the sensory nucleus of the trigeminal nerve; primary analysis of taste - in the nucleus of the glossopharyngeal nerve; auditory stimulation - in the nucleus of the cochlear nerve; vestibular stimulation - in the superior vestibular nucleus. At the level of the medulla oblongata, the listed sensory functions undergo a primary analysis of the strength and quality of irritation, then the processed information is transmitted to the subcortical structures to determine the biological significance of this irritation.

It should be noted that the medulla oblongata organizes and implements a number of protective reflexes: vomiting, sneezing, coughing, lacrimation, closing eyelids. These reflexes are realized due to the fact that information about the 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 activation of the muscle groups of the head, neck, chest and diaphragm, reflexes of eating behavior are organized: sucking, chewing, swallowing.

Excitation of the vagus nerve nuclei causes increased contraction of the smooth muscles of the stomach, intestines, and 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, and the lumen of the bronchi narrows. The activity of the vagus nerve nuclei is also manifested in increased secretion of the bronchial, gastric, intestinal glands, and in the stimulation of the pancreas and secretory cells of the liver.

The main centers of the medulla oblongata:

- salivary center, the parasympathetic part of which ensures increased general secretion, and the sympathetic part ensures increased protein secretion of the salivary glands;

-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.

-vasomotor center(regulation of vascular tone) - this vital center is also localized in the reticular formation of the medulla oblongata; it functions together 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.

The medulla oblongata is a direct continuation of the spinal cord. Its lower border is the exit point of the first pair of spinal nerves. The length of the medulla oblongata is about 25 mm. The cranial nerves from the IX to the XII pairs depart from the medulla oblongata. In the medulla oblongata there is a cavity (a continuation of the spinal canal) - the fourth cerebral ventricle, filled with cerebrospinal fluid.

Functions medulla oblongata: conductive and reflex, some also distinguish sensory.

Sensory function. The medulla oblongata regulates a number of sensory functions: 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 irritations - in the superior vestibular nucleus. In the postero-superior parts of the medulla oblongata there are pathways of cutaneous, deep, visceral sensitivity, some of which are switched here to the second neuron (gracilis and cuneate nuclei). At the level of the medulla oblongata, the listed sensory functions implement a primary analysis of the strength and quality of irritation, then the processed information is transmitted to the subcortical structures to determine the biological significance of this irritation.

Conductor function: Ascending and descending nerve tracts pass through the medulla oblongata, connecting the brain and spinal cord.

In the medulla oblongata there are olives connected to the spinal cord, the extrapyramidal system and the cerebellum - these are the thin and wedge-shaped nuclei of proprioceptive sensitivity (Gaull and Burdach nuclei). Here are the intersections of the descending pyramidal tracts and the ascending tracts formed by the thin and wedge-shaped fascicles (Gaull and Burdach), the reticular formation.

Rice. 9 Medulla oblongata:

1 - olivocerebellar tract;

2 - olive kernel;

3 - olive kernel gate;

5 - pyramidal tract;

6 - hypoglossal nerve;

7 - pyramid;

8 - anterior lateral groove;

9 - accessory nerve

The nuclei of the medulla oblongata include the nuclei of the cranial nerves (from VIII to XII pairs) and switching nuclei:

Cranial nerve nuclei include:

Motor nuclei XII, XI, X;

Vagal nuclei (vegetative, sensory nucleus of the solitary tract and reciprocal – motor nucleus of the pharynx and larynx);

Nuclei of the glossopharyngeal nerve (IX) (motor nucleus, sensory nucleus - taste of the posterior third of the tongue) and autonomic nucleus (salivary glands);

Nuclei of the vestibulocochlear nerve (VIII) (cochlear nuclei and vestibular nuclei - medial Schwalbe, lateral Deiters, superior Bechterew).

Switching Cores include:

Gaulle and Burdakh - to the thalamus;

Reticular formation (from the cortex and subcortical nuclei - to the spinal cord);

Olivary nuclei - from the cortex and subcortical nuclei and cerebellum - to the spinal cord, and from the spinal cord - to the cerebellum, thalamus and cortex; from the auditory nuclei - to the midbrain and quadrigeminal region.

Reflex function: The centers of many important reflexes for human life are located in the medulla oblongata.

Centers of the medulla oblongata:

Autonomic (vital) centers

Respiratory (center of inhalation and exhalation);

Cardiovascular (maintains optimal lumen of arterial vessels, ensuring normal blood pressure and cardiac activity);

Most of the vegetative 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 the visceral organs.

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

Defense reflex centers

Tears;

These reflexes are realized due to the fact that information about the 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.

Eating Behavior Reflex Centers:

Salivation (the parasympathetic part ensures increased general secretion, and the sympathetic part ensures increased protein secretion of the salivary glands);

Swallowing;

Posture reflex centers.

These reflexes are formed due to afferentation from the receptors of the vestibule of the cochlea and the semicircular canals to the superior vestibular nucleus; from here, processed information assessing the need to change posture is sent to the lateral and medial vestibular nuclei. These nuclei are involved in determining which muscular systems and segments of the spinal cord should take part in changing posture, therefore, from the neurons of the medial and lateral nuclei along the vestibulospinal tract, the signal arrives to the anterior horns of the corresponding segments of the spinal cord, innervating the muscles that participate in changing posture in necessary at the moment.

Symptoms of damage. 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 functioning of the muscles of the face and head on the side of the damage. At the same time, on the opposite side to the side of the injury, disorders of skin sensitivity and motor paralysis of the trunk and limbs are observed. 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.