Where is the bridge of the brain located. The internal structure of the bridge. How the bridge affects the occurrence of reflexes

The bridge of Varolii performs motor, sensory, integrative and conductive functions. Important functions of the bridge are associated with the presence of cranial nerve nuclei in it.

V pair - trigeminal nerve (mixed). The motor nucleus of the nerve innervates the chewing muscles, the muscles of the palatine curtain and the muscles that strain the eardrum. The sensory nucleus receives afferent axons from the receptors of the skin of the face, the nasal mucosa, teeth, 2/3 of the tongue, the periosteum of the bones of the skull, and the conjunctiva of the eyeball.

VI pair - abducens nerve (motor), innervates the rectus extrinsic muscle, which abducts the eyeball outward.

VII pair - facial nerve (mixed), innervates the facial muscles of the face, sublingual and submandibular salivary glands, transmits information from the taste buds of the anterior part of the tongue.

VIII pair - vestibulocochlear (sensory) nerve. The cochlear part of this nerve ends in the brain in the cochlear nuclei; vestibular - in the triangular nucleus, Deiters' nucleus, Bekhterev's nucleus. Here is the primary analysis of vestibular stimuli, their strength and direction.

All ascending and descending paths pass through the bridge, connecting the bridge with the cerebellum, spinal cord, cerebral cortex and other structures of the central nervous system. The cerebellar cortex controls the cerebellum through the pons through the pons. In addition, there are centers in the bridge that regulate the activity of the centers of inhalation and exhalation located in the medulla oblongata.

The cerebellum, or "small brain", is located behind the bridge and the medulla oblongata. It consists of a middle, unpaired, phylogenetically old part - a worm - and paired hemispheres, characteristic only of mammals. The cerebellar hemispheres develop in parallel with the cerebral cortex and reach a significant size in humans. The worm on the underside is located deep between the hemispheres; its upper surface passes into the hemispheres gradually (Fig. 11.6).

Rice. 11.6.

A: 1 - leg of the brain; 2 – superior surface of the cerebellar hemisphere; 3 – pituitary; 4 - white plates; 5 - bridge; 6 - dentate nucleus; 7 - white matter 8 - medulla; 9 - olive kernel; 10 - the lower surface of the cerebellar hemisphere; 11 – spinal cord.

B: 1 - upper surface of the cerebellar hemisphere; 2 – white plates; 3 - worm; 4 - white matter 5 - tent; 6 - horizontal slot; 7 - the lower surface of the cerebellar hemisphere

In general, the cerebellum has extensive efferent connections with all the motor systems of the brain stem: corticospinal, rubrospinal, reticulospinal, and vestibulospinal. No less diverse are the afferent inputs of the cerebellum.

The entire surface of the cerebellum is divided into lobes by deep grooves. In turn, each lobe is divided into convolutions by parallel grooves; groups of convolutions form the lobules of the cerebellum. The hemispheres and the cerebellar vermis consist of the gray matter lying on the periphery - the cortex - and the white matter located deeper, in which clusters of nerve cells are laid that form the nuclei of the cerebellum - the tent nuclei, spherical, corky and dentate.

The cerebellar cortex has a specific structure that does not repeat anywhere in the central nervous system. All cells of the cerebellar cortex are inhibitory, with the exception of the granular cells of the deepest layer, which have an excitatory effect.

The activity of the neuronal system of the cerebellar cortex is reduced to the inhibition of the underlying nuclei, which prevents the long-term circulation of excitation through the neural circuits. Any excitatory impulse, arriving in the cerebellar cortex, turns into inhibition in a time of about 100 ms. This is how an automatic erasure of previous information takes place, which allows the cerebellar cortex to participate in the regulation of fast movements.

Functionally, the cerebellum can be divided into three parts: archiocerebellum (ancient cerebellum), paleocerebellum (old cerebellum), and neocerebellum (new cerebellum). Archiocerebellum is a vestibular regulator, its damage leads to imbalance. Function paleocerebellum - mutual coordination of posture and purposeful movement, as well as correction of the execution of relatively slow movements by the feedback mechanism. If the structures of this part of the cerebellum are damaged, it is difficult for a person to stand and walk, especially in the dark, in the absence of visual correction. neocerebellum participates in the programming of complex movements, the implementation of which goes without using the feedback mechanism. The result is a purposeful movement performed at high speed, such as playing the piano. When neocerebellum structures are disturbed, complex sequences of movements are disturbed, they become arrhythmic and slowed down.

The cerebellum is involved in the regulation of movements, making them smooth, precise, proportionate, providing a correspondence between the intensity of muscle contraction and the task of the movement being performed. The cerebellum also affects a number of autonomic functions, such as the gastrointestinal tract, blood pressure, and blood composition.

For a long time, the cerebellum was considered a structure responsible solely for the coordination of movements. Today, its participation in the processes of perception, cognitive and speech activity is recognized.

midbrain located above the bridge and represented by the legs of the brain and the quadrigemina. The legs of the brain consist of a base and a tire, between which there is a black substance containing highly pigmented cells. The nuclei of the trochlear (IV pair) and oculomotor (III pair) nerves are located in the tegmentum of the brain. The cavity of the midbrain is represented by a narrow canal - the Sylvian aqueduct, which connects the III and IV cerebral ventricles. The length of the midbrain in an adult is about 2 cm, weight - 26 g. In the process of embryonic development, the midbrain is formed from the midbrain bladder, the lateral protrusions of which move forward and form the retina of the eye, structurally and functionally representing the nerve center of the midbrain placed on the periphery.

The largest nuclei of the midbrain are the red nuclei, the scooping substance, the nuclei of the cranial (oculomotor and trochlear) nerves, and the nuclei of the reticular formation. Through the midbrain, ascending paths pass to the thalamus, cerebral hemispheres and cerebellum and descending paths to the medulla oblongata and spinal cord.

The midbrain performs conduction, motor and reflex functions.

Conductor function of the midbrain lies in the fact that all ascending paths to the overlying departments pass through it: the thalamus (medial loop, spinothalamic path), cerebrum and cerebellum. Descending paths go through the midbrain to the medulla oblongata and spinal cord. This pyramidal tract, cortical-bridge fibers, rubroreticulo-spinal tract.

Motor function of the midbrain It is realized due to the nuclei of the trochlear nerve, the nuclei of the oculomotor nerve, the red nucleus, the substantia nigra.

red cores, receiving information from the motor zone of the cerebral cortex, subcortical nuclei and the cerebellum about the upcoming movement and the state of the musculoskeletal system, they regulate muscle tone, preparing its level for the emerging voluntary movement. scoop substance connected with the basal ganglia underlying the forebrain hemispheres - the striatum and the pale ball - and regulates the acts of chewing, swallowing (their sequence), provides fine regulation of the plastic muscle tone and precise movements of the fingers of the hand, for example, when writing. Neurons of nuclei oculomotor and trochlear nerves regulate the movement of the eye up, down, out, towards the nose, and down towards the corner of the nose. The neurons of the accessory nucleus of the oculomotor nerve (Yakubovich's nucleus) regulate the lumen of the pupil and the curvature of the lens. Also associated with the midbrain implementation of rectifier and statokinetic reflexes. The rectifying reflexes consist of two phases: the lifting of the head and the subsequent lifting of the torso. The first phase is carried out due to the reflex influences of the receptors of the vestibular apparatus and skin, the second one is associated with the proprioreceptors of the muscles of the neck and trunk. Statokinetic reflexes are aimed at returning the body to its original position when the body moves in space, during rotation.

Functionally independent structures of the midbrain are tubercles of the quadrigemina. The upper ones are involved in the activity of the primary subcortical centers of the visual analyzer, the lower ones are involved in the auditory. In them, the primary switching of visual and auditory information occurs. The main function of the tubercles of the quadrigemina is the organization alert reactions and the so-called start reflexes on sudden, not yet recognized, visual (superior colliculus) or sound (inferior colliculus) signals. Activation of the midbrain under the action of alarming factors through the hypothalamus leads to an increase in muscle tone, an increase in heart rate; there is a preparation for avoidance or for a defensive reaction. In addition, if the quadrigeminal reflex is impaired, a person cannot quickly switch from one type of movement to another.

diencephalon located under the corpus callosum and fornix, growing together on the sides with the cerebral hemispheres. It includes: thalamus (visual tubercles), hypothalamus (hypothalamic area), epithalamus (supratuberous area) and metathalamus (extratuberous area) (Fig. 11.7). The cavity of the diencephalon is the third ventricle of the brain.

Rice. 11.7. :

1 - medulla; 2 - bridge; 3 - legs of the brain; 4 – thalamus; 5 - pituitary gland; 6 – projection of the nuclei of the hypothalamic region; 7 - corpus callosum; 8 – epiphysis; 9 – tubercles of the quadrigemina; 10 - cerebellum

Epithalamus includes endocrine glands epiphysis (pineal body). In the dark, it produces the hormone melatonin, which is involved in the organization of the daily rhythm of the body, affects the regulation of many processes, in particular, the growth of the skeleton and the rate of puberty (see Fig. Endocrine system).

Metathalamus represented by external and median geniculate bodies. Outer geniculate body is the subcortical center of vision, its neurons react differently to color stimuli, turning on and off the light, i.e. can perform a detective function.

Median geniculate body subcortical, thalamic center of hearing. Efferent paths from the medial geniculate bodies go to the temporal lobe of the cerebral cortex, reaching the primary auditory zone there.

thalamus, or visual tubercle, - a paired organ of an ovoid shape, the anterior part of which is pointed (anterior tubercle), and the posterior expanded part (pillow) hangs over the geniculate bodies. The median surface of the thalamus faces the cavity of the third ventricle of the brain.

The thalamus is called the "collector of sensitivity", since afferent (sensory) pathways from all receptors, except for olfactory ones, converge to it. In the nuclei of the thalamus, the information coming from various types of receptors is switched to the thalamocortical pathways that begin here, facing the cerebral cortex.

The main function of the thalamus is the integration (unification) of all types of sensitivity. To analyze the external environment, signals from individual receptors are not enough. In the thalamus, the information received through various channels is compared and its biological significance is assessed. There are about 40 pairs of nuclei in the visual tubercle, which are divided into specific (the ascending afferent pathways end on the neurons of these nuclei), non-specific (nuclei of the reticular formation) and associative.

Individual neurons of specific nuclei of the thalamus are excited by receptors of only their own type. From specific nuclei, information about the nature of sensory stimuli enters strictly defined areas of III–IV layers of the cerebral cortex. (somatotopic localization). Violation of the function of specific nuclei leads to the loss of specific types of sensitivity, since the nuclei of the thalamus, like the cerebral cortex, have somatotopic localization. Signals from the receptors of the skin, eyes, ear, and muscular system go to the specific nuclei of the thalamus. This also receives signals from the interoreceptors of the projection zones of the vagus and celiac nerves, the hypothalamus.

Neurons of nonspecific nuclei form their connections according to the mesh type. Their axons rise to the cerebral cortex and contact with all its layers, forming not local, but diffuse connections. Nonspecific nuclei receive connections from the reticular formation of the brain stem, hypothalamus, limbic system, basal ganglia, and specific thalamic nuclei. An increase in the activity of nonspecific nuclei causes a decrease in the activity of the cerebral cortex (development of a sleepy state).

The complex structure of the thalamus, the presence of interconnected specific, nonspecific and associative nuclei in it, allows it to organize such motor reactions as sucking, chewing, swallowing, laughing, and to provide a connection between vegetative and motor acts.

Through the associative nuclei, the thalamus is connected with all the motor nuclei of the subcortex - the striatum, globus pallidus, hypothalamus and with the nuclei of the middle and medulla oblongata. The thalamus is the center of organization and realization of instincts, drives, emotions. The ability to receive information about the state of many body systems allows the thalamus to participate in the regulation and determination of the functional state of the body as a whole.

Hypothalamus (hypertuberosity) - the structure of the diencephalon, which is part of the limbic system and organizes the emotional, behavioral, homeostatic reactions of the body. The hypothalamus has a large number of nerve connections with the cerebral cortex, basal ganglia, thalamus, midbrain, pons, medulla oblongata and spinal cord. The nuclei of the hypothalamus have a powerful blood supply, its capillaries are easily permeable to high-molecular protein compounds, which explains the high sensitivity of the hypothalamus to humoral changes.

In humans, the hypothalamus finally matures by the age of 13-14, when the formation of the hypothalamic-pituitary neurosecretory connections ends. Due to powerful afferent connections with the olfactory brain, basal ganglia, thalamus, hippocampus, cerebral cortex, the hypothalamus receives information about the state of almost all brain structures. At the same time, the hypothalamus sends information to the thalamus, the reticular formation, the autonomic centers of the brain stem and spinal cord.

The neurons of the hypothalamus have features that determine the specifics of the functions of the hypothalamus itself.

These include the absence of a blood-brain barrier between neurons and blood, the high sensitivity of hypothalamic neurons to the composition of the blood washing them, and the ability to secrete hormones and neurotransmitters. This allows the hypothalamus to influence the autonomic functions of the body through humoral and nervous pathways.

In general, the hypothalamus regulates the functions of the nervous and endocrine systems, it houses the centers of homeostasis, thermoregulation, hunger and satiety, thirst and its satisfaction, sexual behavior, fear, rage. A special place in the functions of the hypothalamus is occupied by the regulation of the activity of the pituitary gland. In the hypothalamus and pituitary gland, neuroregulatory substances are formed - enkephalins, endorphins, which have a morphine-like effect and help reduce stress.

The neurons of the nuclei of the anterior group of the hypothalamus produce vasopressin, or antidiuretic hormone (ADH), oxytocin and other hormones that enter the posterior lobe of the pituitary gland, the neurohypophysis, along the axons. The neurons of the nuclei of the middle group of the hypothalamus produce the so-called releasing factors that stimulate (liberins) and inhibit (statins) the activity of the anterior pituitary gland - the adenohypophysis, in which somatotropic, thyroid-stimulating and other hormones are formed (see Fig. Endocrine system). The neurons of the hypothalamus also have the function of a homeostasis detector: they respond to changes in blood temperature, electrolyte composition and plasma osmotic pressure, the amount and composition of blood hormones. The hypothalamus is involved in the implementation of sexual function and puberty, in the regulation of the wake-sleep cycle: the posterior hypothalamus activates wakefulness, stimulation of the anterior causes sleep, damage to the hypothalamus can cause so-called lethargic sleep.

telencephalon is the youngest in phylogenetic terms. It consists of two hemispheres, each of which is represented by a cloak, an olfactory brain, and basal or subcortical ganglia (nuclei). The length of the hemispheres is on average 17 cm, height - 12 cm. The cavity of the telencephalon is the lateral ventricles located in each of the hemispheres. The hemispheres of the brain are separated from each other by a longitudinal fissure of the brain and are connected using the corpus callosum, the anterior and posterior commissures, and the commissure of the fornix. The corpus callosum consists of transverse fibers, which in the lateral direction go to the hemispheres, forming the radiance of the corpus callosum.

Olfactory brain represented by olfactory bulbs, olfactory tubercle, transparent septum and adjacent areas of the cortex (preperiform, periamygdala and diagonal). This is a smaller part of the telencephalon, it provides the function of the first sense organ that appeared in living beings - the function of smell, and, in addition, is part of the limbic system. Damage to the structure of the limbic system causes profound impairment of emotions and memory.

(kernels of gray matter) are located in the depths of the cerebral hemispheres. They make up about 3% of their volume. The basal ganglia form numerous connections both between the structures that make up them and other parts of the brain (cerebral cortex, thalamus, substantia nigra, red nucleus, cerebellum, motor neurons of the spinal cord). The basal ganglia include a strongly elongated and curved caudate nucleus and a lenticular nucleus embedded in the thickness of the white matter. With two white plates, it is divided into a shell and a pale ball. Together, the caudate nucleus and the putamen are called the striatum, are anatomically connected and are characterized by the alternation of white and gray matter (Fig. 11.8).

Rice. 11.8.

striatum takes part in the organization and regulation of movements and ensuring the transition of one type of movement to another. Stimulation caudate nucleus inhibits the perception of visual, auditory and other types of sensory information, inhibits the activity of the cortex, subcortex, unconditioned reflexes (food, defensive, etc.) and the development of conditioned reflexes, leads to the onset of sleep. With a lesion of the striatum, there is a loss of memory for events preceding the injury. Bilateral damage to the striatum induces the desire to move forward, unilateral - leads to arena movements (walking in a circle). With a violation of the functions of the striatum, a disease of the nervous system is associated - chorea (involuntary movements of the facial muscles, muscles of the arms and torso). Shell provides organization of eating behavior. When it is damaged, trophic skin disorders are observed, and its irritation causes salivation and a change in respiration. Functions pale ball consist in provoking an orienting reaction, movement of the limbs, eating behavior (chewing, swallowing).

Cloak, or cerebral cortex, - a plate of gray matter, separated from the cavity of the ventricles by white matter, which contains a huge amount of nerve fibers, divided into three groups:

  • 1. Pathways connecting different parts of the cerebral cortex within one hemisphere - association paths. There are short, or arcuate, associative fibers that connect two adjacent gyruses, and long ones that stretch from one lobe to another, remaining within the same hemisphere.
  • 2. commissural, or adhesive, fibers connect the cortex of both hemispheres. The largest commissure in the brain is the corpus callosum.
  • 3. Projection Paths connect the cerebral cortex with the periphery. There are centrifugal (efferent, motor) fibers that carry nerve impulses from the cortex to the periphery, and centripetal (afferent, sensory) fibers that carry impulses from the periphery to the cerebral cortex.

The cerebral cortex is the highest division of the CNS. It provides a perfect organization of animal behavior on the basis of congenital and ontogenesis-acquired functions. It is divided into ancient ( archicortex ), old ( paleocortex ) and new ( neocortex ). ancient bark involved in the provision of smell and interaction various systems brain. old bark includes the cingulate gyrus, the hippocampus and is involved in the implementation of innate reflexes and the emotional and motivational sphere. New bark It is represented by the main part of the cerebral cortex and carries out the highest level of coordination of the brain and the formation of complex forms of behavior. The greatest development of functions new cortex noted in humans, its thickness in adulthood ranges from 1.5 to 4.5 mm and is maximum in the anterior central gyrus.

The medulla oblongata is a direct continuation of the spinal cord to the brain stem and is part of the rhomboid brain. It combines the features of the structure of the spinal cord and the initial part of the brain, has the appearance of a bulb, the upper extended end borders on the bridge, and the lower border is the exit point of the roots of the first pair of cervical nerves or the level of the large foramen occipitalis.

On the anterior surface of the medulla oblongata, the fissura mediana anterior passes along the midline, 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, which, as it were, continue into the anterior cords of the spinal cord. The bundles of nerve fibers that make up the pyramid partly intersect in depth with similar fibers of the opposite side, after which they descend in the lateral funiculus on the other side of the spinal cord, partly remain uncrossed and descend in the anterior funiculus of the spinal cord on their side. 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 - an olive, which is separated from the pyramid by a groove,

On the posterior (dorsal) surface of the medulla oblongata, there is 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, bordering the rhomboid fossa from below. Each posterior funiculus is subdivided by means of an intermediate furrow into medial and lateral. At the lower corner of the rhomboid fossa, thin and wedge-shaped bundles become thickened. These thickenings are due to the gray matter nuclei of the same name as 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 corresponds to the lateral funiculus. Cranial nerves XI, X and IX emerge from behind the olive. The lower part of the rhomboid fossa is part of the medulla oblongata.

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.

The core of the olive has the appearance of a convoluted plate of gray matter, open medially and causes the protrusion of the olive from the outside. It is connected with the dentate nucleus of the cerebellum and is an intermediate nucleus of balance, most pronounced in a person whose vertical position requires a perfect gravitational apparatus. reticular formation, formed from the interweaving of nerve fibers and the nerve cells lying between them.

The nuclei of the four pairs of lower cranial nerves (XII-IX), which are related to the innervation of the derivatives of the branchial 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.

The 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, the bodies of the second neurons of the ascending sensory pathways are located in the nuclei of the posterior cords. Their processes go from the medulla oblongata to the thalamus. The fibers of this bundle form a medial loop, which crosses in the medulla oblongata, 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 crossroads of long pathways: ventral motor and dorsal sensory.

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. The topographic relationships of the main formations of the medulla oblongata are visible on a cross section drawn at the level of the olives. The roots extending from the nuclei of the hypoglossal and vagus nerves 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 bridge is a thick white shaft from the side of the base of the brain, bordering behind the upper end of the medulla oblongata, and in front - with the legs of the brain. The lateral border of the bridge is an artificially drawn line through the roots of the trigeminal and facial nerves. Laterally from this line are the middle cerebellar peduncles, plunging into the cerebellum on both sides. The dorsal surface of the bridge is not visible from the outside, as it is hidden under the cerebellum, forming the upper part of the rhomboid fossa (the bottom of the IV ventricle). The ventral surface of the pons is fibrous in nature, with the fibers generally running transversely. A gentle groove runs along the midline of the ventral surface,

The internal structure of the bridge. On cross sections of the bridge, one can see that it consists of a larger anterior, or ventral, part, and a smaller dorsal part. The boundary between them is a thick layer of transverse fibers - the trapezoid body, the fibers of which belong to the auditory pathway. In the region of the trapezoid body, there is a nucleus, which is also related to the auditory pathway. contains longitudinal and transverse fibers, between which are scattered their own nuclei of gray matter. Longitudinal fibers belong to the pyramidal tracts, which are connected with their own nuclei of the bridge, from which the transverse fibers originate, going to the cerebellar cortex. This entire system of pathways connects the cortex of the cerebral hemispheres with the cortex of the cerebellum through the bridge.

The more developed the cerebral cortex, the more developed the bridge and the cerebellum. Naturally, the bridge is most pronounced in humans, which is a specific feature of the structure of his brain. which is a continuation of the same formation of the medulla oblongata, and on top of the reticular formation - the bottom of the rhomboid fossa lined with ependyma with the nuclei of the cranial nerves (VIII-V pairs) lying underneath.

Bridge, pons, represents a thick white shaft from the side of the base of the brain, bordering behind the upper end of the medulla oblongata, and in front - with the legs of the brain. The lateral border of the bridge is an artificially drawn line through the roots of the trigeminal and facial nerves, linea trigeminofacialis. Laterally from this line are the middle cerebellar peduncles, pedunculi cerebellares medii, plunging on both sides into the cerebellum. The dorsal surface of the bridge is not visible from the outside, as it is hidden under the cerebellum, forming the upper part of the rhomboid fossa (the bottom of the IV ventricle). The ventral surface of the pons is fibrous in nature, the fibers generally running transversely and running into the pedunculi cerebellares medii. A gentle groove, sulcus basilaris, runs along the midline of the ventral surface, in which lies a. basilaris.

The internal structure of the bridge. On the transverse sections of the bridge, you can see that it consists of a larger anterior, or ventral, part, pars ventralis pontis, and a smaller dorsal, pars dorsalis pontis. The boundary between them is a thick layer of transverse fibers - the trapezoid body, corpus trapezoideum, the fibers of which belong to the auditory pathway. In the region of the trapezoid body, there is a nucleus, which is also related to the auditory pathway, the nucleus dorsalis corporis trapezoidei. Pars ventralis contains longitudinal and transverse fibers, between which are scattered their own nuclei of gray matter, nuclei pontis. The longitudinal fibers belong to the pyramidal tracts, to the fibrae corticopontine, which are connected with their own nuclei of the bridge, from which the transverse fibers originate, going to the cerebellar cortex, tractus pontocerebellaris. This entire system of pathways connects the cortex of the cerebral hemispheres with the cortex of the cerebellum through the bridge.

The more developed the cerebral cortex, the more developed the bridge and the cerebellum. Naturally, the bridge is most pronounced in humans, which is a specific feature of the structure of his brain. In pars dorsalis there is a formatio reticularis pontis, which is a continuation of the same formation of the medulla oblongata, and on top of the reticular formation is the bottom of the rhomboid fossa lined with ependyma with the nuclei of the cranial nerves (VIII-V pairs) lying underneath. In the pars dorsalis, the pathways of the medulla oblongata also continue, located between the midline and the nucleus dorsalis corporis trapezoidei and are part of the medial loop, lemniscus medialis; in the latter, the ascending paths of the medulla oblongata, tractus bulbothalamicus, cross.

The brain and spinal cord are one of the independent structures in the human body, but not many people know that for their normal functioning and interaction with each other, the Varolii bridge is necessary.

What is Varolii formation and what functions does it perform, you can learn all this from this article.

General information

The pons varolii is a formation in the nervous system, which is located in the gap between the midbrain and the medulla oblongata. Through it stretch the bundles of the upper parts of the brain, as well as veins and arteries. In the pons itself, there are nuclei of the central nerves in the cranial brain, which are responsible for the masticatory function of a person. In addition, it helps to ensure the sensitivity of the entire face, as well as the mucous membranes of the eyes and sinuses. Education performs two functions in the human body: binding and conducting. The bridge got its name in honor of the Bolognese anatomist Constanzo Varolia.

The structure of the varoli formation

Education is located on the surface of the brain.
If we talk about the internal structure of the bridge, then it contains an accumulation of white matter, where the nuclei of gray matter are located. In the back of the formation are the nuclei, consisting of 5,6,7, and 8 pairs of nerves. One of the most important buildings located on the bridge is reticular formation. It performs a particularly important function, it is responsible for the activation of all departments located above.
The pathways are represented by thickened nerve fibers that connect the pons to the cerebellum, thus forming the brooks of the formation itself and the cerebellar peduncles.

It saturates with blood the Varolian bridge of the artery of the vertebrobasilar basin.
Outwardly, it looks like a roller, which is attached to the brain stem. The cerebellum is attached to it from the back. In its lower part there is a transition to the medulla oblongata, and from the upper part to the middle. The main characteristic feature of the Varolii formation is that it contains a mass of pathways and nerve endings in the brain.

Four pairs of nerves diverge directly from the bridge:

  • ternary;
  • diverting;
  • facial;
  • auditory.

Formation in the prenatal period

The formation of varoli begins to form even in the embryonic period from the rhomboid bladder. The bubble, in the process of its maturation and formation, is also divided into oblong and posterior. In the process of formation, the hindbrain gives rise to the origin of the cerebellum, and the bottom and its walls become the components of the bridge. The cavity of the rhomboid bladder will subsequently be common.
The nuclei of the cranial nerves at the stage of formation are located in the medulla oblongata and only with time do they move directly to the bridge.

When the baby is born, the bridge is located just above the back of the Turkish saddle. Only after 2-3 years, he begins to rise and thus is fixed in a permanent place for him - the upper part of the skull.

At the age of 8, all spinal fibers begin to grow in a myelin sheath in a child.

VM functions

As mentioned earlier, the Varoliev bridge contains a lot of different functions necessary for normal functioning. human body.

Functions of the Varolii education:

  • controlling function, behind purposeful movements in the entire human body;
  • perception of the location of the body in space and time;
  • taste sensitivity, skin, as well as the mucous membranes of the nose and eyeballs;
  • facial expression;
  • eating: chewing, salivation and swallowing;
  • conductor, through its paths nerve endings pass to the cerebral cortex, as well as the spinal cord; interactive.
  • CM is used to communicate between the anterior and posterior parts of the brain;
  • hearing perception.

It contains the centers from which the cranial nerves exit. They are responsible for swallowing, chewing and the perception of skin sensitivity.
The nerves extending from the bridge contain motor fibers (provide the rotation of the eyeballs).

Triple nerves of the fifth pair affect the tension of the muscles of the palate, as well as the tympanic membrane in the cavity of the auricle.

The nucleus of the facial nerve is located in the Varolium formation, which is responsible for the motor, autonomic and sensory functions. In addition, the center of the respiratory system of the medulla oblongata depends on its normal functioning.

VM pathologies

Like any organ in the human body, the VM can also stop functioning and the following diseases become the reason for this:

  • cerebral artery stroke;
  • multiple sclerosis;
  • head injury. Can be obtained at any age, including during childbirth;
  • tumors (malignant or benign) of the brain.

In addition to the main causes that can provoke brain pathologies, it is necessary to know the symptoms of such a lesion:

  • the process of swallowing and chewing is disturbed;
  • loss of sensitivity of the skin;
  • nausea and vomiting;
  • - these are eye movements in one specific direction, as a result of such movements, the head can often begin to spin, up to loss of consciousness;
  • can double in the eyes, with sharp turns of the head;
  • violations at work motor system, paralysis of certain parts of the body, muscles or tremor in the hands;
  • in case of violations in the work of the facial nerves, the patient may experience complete or partial anemia, lack of strength in the facial nerve;
  • speech disorders;
  • asthenia - a decrease in the strength of muscle contraction, rapid muscle fatigue;
  • - incompatibility between the task of the performed movement and muscle contraction, for example, when walking, a person can raise his legs much higher than necessary or, on the contrary, can stumble over small bumps;
  • snoring, in cases where it has never been observed before.

Conclusion

From this article, we can draw such conclusions that the Varoli formation is an integral part of the human body. Without this education, all parts of the brain cannot exist and perform their functions.

Without the Varoliev bridge, a person could not: eat, drink, walk and perceive the world around him as it is. Therefore, there is only one conclusion, this small formation in the brain is extremely important and necessary for every person and living being in the world.

The spinal cord and brain are independent structures, however, in order for them to interact together, one formation is required - the pons Varolii. This element of the central nervous system acts as a collector, a connecting structure that articulates together the brain and spinal cord. That is why education is called bridge, from what connects two key organs of the central and peripheral nervous system. The pons is part of the structure of the hindbrain, to which the cerebellum is also attached.

Structure

Varolii education is located on the basal surface of the brain. This is the location of the bridge in the brain.

Speaking about the internal structure - the bridge consists of clusters, where their own cores (clusters) are located. On the back of the bridge lie the nuclei of the 5th, 6th, 7th and 8th pairs of cranial nerves. An important structure lying on the territory of the bridge is considered to be the reticular formation. This complex is responsible for the energy activation of the higher located elements of the brain. Also, mesh formation is responsible for activating the state of wakefulness.

Outwardly, the bridge resembles a roller and is part of the brain stem. The cerebellum is attached behind it. Below the bridge goes into, and from above - into the middle one. Features of the structure of the bridge of the brain are the presence in it of cranial nerves and many pathways.

On the posterior surface of this structure is rhomboid fossa- It's a small hole. The upper part of the bridge is limited by the brain strips, on which the facial mounds lie, and even higher - by the medial eminence. A little to the side of it is a blue spot. This color formation is involved in many emotional processes: anxiety, fear and rage.

Functions

After studying the location and structure of the bridge, Costanzo Varoliy wondered what function the bridge performs in the brain. In the 16th century, during his lifetime, the equipment of European individual laboratories did not allow answering the question. However, modern research has shown that the Varoliyev bridge is responsible for the implementation of many tasks. Namely: sensory, conductive, reflex and motor functions.

located in it VIII pair cranial nerves performs a primary analysis of sounds coming from outside. Also, this nerve processes vestibular information, that is, it controls the location of the body in space (8).

Task facial nerve- innervation of facial muscles of the human face. In addition, the axons of the VII nerve branch off and innervate the salivary glands located under the jaw. Axons also extend from the tongue (7).

5th nerve- trinity. Its tasks include the innervation of the masticatory muscles, the muscles of the palate. Sensory branches of this nerve transmit information from receptors in the skin, nasal mucosa, surrounding skin of the apple and teeth (5).

In the pons Varoliy there is a center that activates exhalation center, which is located in the adjacent structure below - the medulla oblongata (10).

Damage symptoms

Violations of the activity of the Varoily bridge are determined by its structure and functions:

  • Dizziness. It can be systemic - a subjective sensation of the movement of surrounding objects in any direction, and non-systemic - a feeling of loss of control over one's body.
  • nystagmus- translational movements of the eyeballs in a certain direction. This pathology may be accompanied by dizziness and nausea.
  • In the case when the areas of the nuclei are affected, the clinical picture corresponds to the damage to these nuclei. For example, with a disorder of the facial nerve, the patient will manifest amimia(complete or sluggish) - lack of muscle strength of the facial muscles. People who have such a lesion have a "stone face".

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