The human brain occupies a key position in the regulation of all systems of the human body. With the help of this body, communication is carried out between the activities of organs and all systems. Without brain coordination, a person cannot exist.

Thanks to the initially configured work of the central nervous system, we can move, speak and perform many other functions.

The human brain has the most complex structure, and each of its departments is responsible for its own functions. Thus, all brain structures support the work of the organism as a whole.

The main parts of the brain include directly the pons. It contains such centers necessary for human life as:

• Vascular
• Respiratory

Also, it is he who initially forms most of the cranial nerves.

The key component of the main functioning organ is the neuron. It is responsible for receiving, processing and storing data. Whole human brain literally filled with these cells and their processes, which provide signal transmission to the organs. The brain also contains gray and white matter.

The key structural parts of the brain are:

1. Right and left hemisphere (Responsible for our memory, thought processes, imagination)

1. Cerebellum (coordinates and shapes our motor system). It is thanks to the cerebellum that we can move, feel balance, body position

1. Pons

The structure of the pons

The structure of the bridge from the outside is presented in the form of a roller, which includes cranial nerves, arteries, the reticular formation and descending paths. From the inside it appears as a half of the rhomboid fossa.

The basilar sulcus runs along the median path, on the sides of which there are pyramidal eminences. If you make a cross section, then at the cellular level you can see the white matter.

In the lateral section, the nuclei of the upper olive are located, namely in the area of ​​​​the front base and the rear tire. Between these parts there is a line, which is represented by numerous fibers. Specialists distinguish this multiple accumulation of fibers as a trapezoid body, which is responsible for the formation of the auditory pathway.

The border that separates the pons and the middle cerebellar peduncle is called the area where the trigeminal nerve branches off.

Functions

The brain bridge provides a number of important functions for the human body, namely:

• Provides targeted control over body movements
• Allows you to perceive the body in space
• Controls the sensitivity of the tongue, facial skin, nasal mucosa and eye membrane
• Responsible for facial expressions and hearing
• Coordinates the entire act of eating (swallowing, salivation, chewing)

The reflex function that the bridge performs allows the human CNS to respond to various external stimuli (reflex). Reflexes are divided into 2 types:

• Conditional, which are acquired in the process of life with the possibility of adjustment
• Unconditional, which do not give in to consciousness and are laid at the time of birth (chewing, swallowing and other reflexes)

Also, the bridge performs the function of ensuring the relationship of the cerebral cortex and underlying formations. The fibers themselves are directed directly to the cerebellum, spinal cord and oblong section. This transition is possible due to the passage of descending and ascending paths through the bridge.

All important functions of the bridge are achieved with the help of cranial nerves.

For example, the 5th pair of cranial nerves is responsible for the perception of pain and tactile sensations, and also provides the act of chewing. The abducens nerves contain motor fibers, which provide the ability to turn the eyes. The work of the respiratory center of the medulla oblongata also depends on the bridge.

Pathological conditions

It is worth noting that one of the key parts of the brain, the bridge, as well as the brain legs, are affected much more often than the same medulla oblongata. Often they are in a pathological state due to embolism, arthritis or thrombosis. In these places, hemorrhages, tumor formations, infections, for example, tubercles, most often occur.

The presence of such pathologies is quite difficult to diagnose; often, specialists establish an accurate diagnosis using differentiated diagnostics from case to case. However, today there are basic syndromes that are distinguished by a certain clinical picture.

The brain and bridge are distinguished by the following types of syndromes:

1. Inferior pontine syndrome

It is the earliest established pathology. It is located on the entire ventral part of the section of the Varoliyev bridge in its lower sections. In this case, the following clinical picture is observed:

• Hemiplegia of the central type
• Peripheral paralysis of the facial and abducens nerves, also most often the defeat of paired nerves located on the opposite side, that is, on the side of the lesion
• Hemianesthesia, when the facial nerves are affected on the affected side, and the body and limbs are on the opposite side
• Rarely, hemichorrhea and hemiataxia

1. Superior pontine syndrome or Reymond-Sestan syndrome

Pathology is localized in the posterolateral part of the bridge, and the pathological manifestations are as follows:

• Minor hemiparesis without obvious variability in tendon and skin reflexes
• Hyperkinesis - athetosis, tremor
• dysarthria
• Vertical nystagmus
• Frequent dizziness

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Bridge (human brain anatomy)

Bridge , pons, is a 25 mm long part of the brain stem that is located between the medulla oblongata and midbrain. Its ventral surface is formed by a white bulge, externally consisting of transversely arranged fibers. The dorsal surface of the bridge makes up the upper part of the bottom of the IV ventricle - the rhomboid fossa, forming its upper triangle. This part of the rhomboid fossa is limited by the superior cerebellar peduncles. The transverse fibers of the anterior surface form the middle cerebellar peduncles, which are immersed in the thickness of the cerebellar hemispheres. The border between the bridge and the middle cerebellar peduncle is the linea trigeminofacialis, which runs between the roots of the trigeminal and facial nerves. In the middle of the ventral surface of the bridge is the main groove, sulcus basilaris. In the lateral part of the ventral surface of the bridge, closer to its front edge, there are roots of the trigeminal nerve. In the region of the pontocerebellar angle (formed by the medulla oblongata, pons and cerebellum) are the roots of the facial, intermediate and vestibulocochlear nerves, and closer to the midline, between the posterior edge of the bridge and the pyramids, are the roots of the abducent nerves.

On the transverse sections of the bridge, a large ventral part, pars ventralis pontis, and a smaller dorsal part, pars dorsalis pontis, are distinguished, the boundary between which is a bundle of transverse fibers - the trapezoid body, corpus trapezoideum. The ventral and dorsal parts of the pons are formed by gray and white matter. However, the ventral part consists predominantly of white matter.

The gray matter of the ventral part is composed of numerous own nuclei of the bridge, nuclei pontis. In these nuclei, the cortical-bridge pathways, tractus corticopontinus, and collaterals from the pyramidal pathways end. The fibers of the cells of the nuclei of the bridge form the transverse fibers of the bridge, fibrae pontis transversae, which, basically, moving to the opposite side, make up the middle legs of the cerebellum and end in the cells of the cortex of its hemispheres. The transverse fibers of the bridge in the ventral part of its lower section form the superficial and deep layers, between which the bundles of the pyramidal path pass. In the upper sections of the bridge, the deep layer of its transverse fibers increases in volume and a third layer appears, dividing the pyramidal pathways into smaller bundles.

The gray matter of the dorsal part of the bridge consists of a centrally located mesh formation, cranial nerve nuclei and switching nuclei. The mesh formation of the bridge is a direct continuation of the formation of the same name in the medulla oblongata.

The nuclei of the following cranial nerves are located in the bridge: abducens, facial, trigeminal, vestibulocochlear.

The nucleus of the abducens nerve, nucleus n. abducentis, formed by large motor cells. It is located near the midline of the bottom of the IV ventricle and has a length of about 3 mm. The processes of the cells of the nucleus exit through the thickness of the bridge between its posterior edge and the pyramid in the form of the root of the abducens nerve.

The nucleus of the facial nerve, nucleus n. facialis, from 2 to 5.6 mm long, is formed by motor cells. It is located in the mesh formation of the dorsal part of the bridge. The processes of the cells of this nucleus form the intracerebral part of the facial nerve root, which has a complex course in the thickness of the bridge. The root from the mesh formation passes along the bottom of the IV ventricle, forms a knee, genu n. facialis, surrounding the nucleus of the abducens nerve and then goes forward through the thickness of the bridge to the region of the cerebellopontine angle. The fibers of the facial nerve are distributed in the mimic muscles and carry out its motor innervation. Somewhat posterior to the nucleus of the facial nerve in the mesh formation of the bridge is the superior salivary nucleus, nucleus salivatorius superior, which is the secretory autonomic center of innervation of the sublingual and submandibular salivary glands and the lacrimal gland. The sensitive nucleus of this nerve is the nucleus of a solitary path, the nucleus tractus solitarii, where the central processes of the intermediate nerve node, the knee node, gangl, terminate. geniculi, located in the canal of the facial nerve of the pyramid of the temporal bone.

The sensory and motor nuclei of the trigeminal nerve are located in the middle and upper parts of the dorsal part of the bridge. The motor nucleus of the trigeminal nerve, nucleus motorius n. trigemini, is formed by large motor cells and is about 4 mm long. The processes of the cells of the motor nucleus form the motor root of the trigeminal nerve and are distributed in the chewing muscles, carrying out its motor innervation. As part of the motor root of the trigeminal nerve, there are also fibers from the nucleus of the trigeminal nerve, located in the midbrain, lateral to the cerebral aqueduct. Superior sensory nucleus of the trigeminal nerve, nucleus sensorius n. trigemini superior, lies outside of the motor nucleus. It is smaller than the nucleus of the spinal tract of the trigeminal nerve. In the cells of this nucleus, the central processes of the sensitive cells of the trigeminal ganglion terminate. These processes form the sensory root of the trigeminal nerve, which, through the thickness of the basal part of the bridge, approaches the superior sensory nucleus. Here, part of the fibers of the root ends, and the remaining fibers pass to the nuclei of the spinal and mesencephalic tracts of the Trigeminal nerve. The processes of the cells of the upper sensory nucleus of the spinal tract (second neurocytes) pass to the opposite side and, as part of the medial loop, enter the optic tubercle.

The switching nuclei of the dorsal part of the pons include the superior olives, the nuclei of the trapezoid body, and the lateral loop. In all these nuclei, the impulses of the auditory pathway are switched.

The upper olive, oliva superior, is located in the lateral sections of the trapezoid body, which is formed mainly by processes of cells of the ventral nucleus n. vestibulocochlearis. Between the fibers of the trapezoid body there are accumulations of gray matter - the ventral and dorsal nuclei of the trapezoid body, nuclei ventralis et dorsalis corporis trapezoidei. Most of the fibers that arise in the ventral nucleus n. vestibulocochlearis, pass to the opposite side and end in the upper olive and the nuclei of the trapezoid body. A smaller part of these fibers ends in the corresponding nuclei of their side. The processes of the cells of the upper olive form the so-called lateral loop, lemniscus lateralis, among the fibers of which is the core of the lateral loop, nucleus lemnisci lateralis. The side loop is a bundle of fibers of considerable thickness; it consists of processes of cells of the dorsal nucleus n. vestibulocochlearis, as well as processes of cells of the nucleus of the trapezoid body and the nucleus of the lateral loop. The lateral loop ends in the primary auditory centers - the inferior tubercles of the quadrigemina and the medial geniculate body.

The white matter of the bridge consists of endogenous and exogenous fibers. Short endogenous fibers connect the individual nuclei of the bridge and do not go beyond it. Thus, nerve connections have been established between the nuclei of the facial and trigeminal nerves, through which reflex arcs are closed during various facial skin irritations with a response of facial muscles. Long endogenous fibers arise in the nuclei of the bridge and end in other parts of the central nervous system.

This group includes fibers that go from the pontine nuclei to the cerebellum - the transverse fibers of the bridge, fibrae pontis transversae, fibers of the lateral loop, fiber bundles from some cranial nerves. The transverse fibers of the bridge form the middle cerebellar peduncle, through which the cortex of the cerebral hemispheres influences the activity of the cerebellum. 166 ..

The bridge (pons cerebri) is also called the Varolii bridge (pons Varolii) in honor of Costanzo Varoli, an Italian anatomist of the mid-16th century, personal physician of Pope Gregory XIII.

Bridge in the brain, structure and functions of white matter

The bridge is a white matter whose structure is cylindrical, almost entirely consisting of transverse nerve fibers. However, it also contains nuclei from the gray matter of the brain: from the Vth, VIth, VIIth, and VIIIth pair of cranial nerves, as well as the reticular formation. This structure, which refers to structures consisting of bridge neurons, is an intermediate formation between the continuation of the same section in, and its beginning in. The nerve fibers of the bridge connect the cerebellum with the cortex of its own hemispheres, as well as with the cortex hemispheres brain. Thus, the morphological and compensatory connections of the cerebral cortex and cerebellar hemispheres are provided by the structure of the middle cerebellar peduncle.

Thus, the conductive function of the bridge is carried out. In the center of the bridge, in the basilar groove, lies the main artery that provides blood supply to the brain. On both sides of the furrow, pyramidal pathways form thickenings. They look like small oval gray plates on a transverse anatomical section. The nuclei of the trigeminal and vestibulocochlear cranial nerves are responsible for the sensory functions of the pons structure. In this department, the primary analysis of any incoming vestibular signals begins, that is, their direction and intensity are assessed.

• Signals from the membranes of the nose, mouth, teeth, from receptors on the skin of the face and anterior sections of the scalp, the outer part of the eyeball, enter the nucleus of the trigeminal nerve, in its sensitive portion.

• The facial nerve transmits signals from all facial muscles, and the abducent nerve transmits signals from the lateral rectus muscle, due to which the eyeball itself can be retracted forward to the outside.

• Signals from the masticatory muscles and muscles that tense the eardrum, as well as the tense palatine curtain, enter the nucleus of the trigeminal nerve, its motor portion.

In the so-called bridge cover, there is a bundle of fibers of the medial loop, as well as a trapezoid body, or rather its part, represented by the anterior and posterior nuclei. In this department, the initial analysis of the signals coming from the organ of hearing takes place, then the signals from it come to, to their posterior tubercles. Here in the tire are located two leading nerve tracts: medial and tectospinal. The reticulospinal path is formed with the help of axons of the reticular formation going to. This section of the bridge has a direct effect on the cerebral cortex. Under its influence, awakening occurs, or vice versa - "falling asleep" of the cortex. Here, in the reticular formation, there is also a group of nuclei responsible for the activation of the inhalation center located in the medulla oblongata, and the second group, respectively, responsible for the exhalation center. They belong to the respiratory center of the bridge. The neurons of this center bring the activity of the respiratory cells from the medulla oblongata in line with the constantly changing general state of the body, in fact, adapting them. structures white matter especially clearly can be seen in the anatomical section. It can be seen that into two parts: the basilar part and the tire, the structure of the bridge is divided by its central formation - the trapezoid body. Anatomically, it is a thick bundle of transverse fibers, and functionally, it is, as already mentioned, a conductive tract that transmits signals from the auditory analyzer. The basilar part of the bridge arose in mammals during evolution. The more developed the cerebral cortex, the larger both the cerebellar hemispheres and the bridge itself turn out to be.

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 involved in programming complex movements, the execution 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 big number 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 deep violation 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 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 participates in the provision of smell and the interaction of various brain systems. 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 represented by the main part of the cerebral cortex and carries out highest level coordination of the brain and the formation of complex forms of behavior. The greatest development of the functions of the new cortex is noted in humans, its thickness in adulthood ranges from 1.5 to 4.5 mm and is maximum in the anterior central gyrus.

10.1. BRAIN BRIDGE

Bridge of the brain (pons cerebri, pons) - part of the brain stem, located between the medulla oblongata and midbrain. The pons of the brain can be considered as a direct continuation of the medulla oblongata. If both of these sections of the brain stem are approximately equal in length, then the thickness of the brain bridge is much greater, mainly due to the thickening of its base.

At the base of the bridge, in addition to the pyramidal and cortical-nuclear pathways, there are numerous cortical-bridge fibers that go to the own nuclei of the brain bridge located here scattered between the pathways. In addition to these longitudinally located conductors, there are a large number of transverse fibers at the base of the brain bridge, which are axons of the cells of the bridge's own nuclei. These fibers, which make up the cerebellopontine pathways, cross the longitudinal conductors, while stratifying their bundles into numerous groups, pass to the opposite side and form the middle cerebellar peduncles, which have only a conditional border with the bridge of the brain, passing through the places where the roots of the trigeminal nerve exit from the bridge. The cortical-bridge and cerebellopontine fibers form the cortical-bridge-cerebellar pathways. The presence at the base of the bridge of numerous transversely pontine fibers causes the transverse striation of its basal surface.

From the medulla oblongata, on the ventral side, the bridge separates the transverse bulbar-pontine groove, from which the roots of the VIII, VII, and VI cranial nerves emerge. The posterior surface of the bridge is formed mainly by the upper triangle of the rhomboid fossa, which makes up the bottom of the IV ventricle of the brain.

In the lateral corners of the rhomboid fossa are auditory fields (areae acustici), which correspond to the location of the nuclei of the VIII cranial nerve (n. vestibulocochlearis). The auditory field is located at the junction of the medulla oblongata and the bridge, and the nuclei of the VIII cranial nerve partially enter the substance of the medulla oblongata. In the auditory field, the nuclei of the auditory portion of the VIII cranial nerve occupy the most lateral sections of the rhomboid fossa - the so-called lateral eversion of the IV ventricle of the brain, between which the so-called auditory strips (striae acustici) pass in the transverse direction. The medial parts of the auditory fields correspond to the location of the vestibular nuclei.

On the sides of the median sulcus, passing through the upper triangle of the rhomboid fossa, there is an elevation elongated along it (eminentia

medialis). In the lower part, this elevation is divided longitudinally into two sections, the outer of which corresponds to the location of the nucleus of the abducens nerve. Lateral to middle third eminentia medialis, at the bottom of the IV ventricle, a small depression is visible - fovea Superior, under which the motor nucleus of the trigeminal nerve is located. In front of this depression, in the upper part of the rhomboid fossa on the sides of the midline, there are areas of brain tissue that are gray with a bluish tint due to the presence of abundantly pigmented cells here - a bluish place (locus ceruleus).

For a more detailed consideration of the structure of the bridge, you can cut it into three parts: the lower one, which contains the nuclei of the VIII, VII and VI cranial nerves, the middle one, in which two of the three nuclei of the V cranial nerve are located, and the upper part, which is the site of the transition of the bridge in the midbrain and sometimes called the isthmus of the brain (istmus cerebri).

Due to the fact that the foundation of the bridge at all levels has a more or less identical structure and the basic information about it has already been presented, in the future, attention will be paid mainly to the structure of the different levels of the bridge cover.

The bottom of the bridge. In the lower part of the bridge (Fig. 10.1), on the border between its tire and base, there is a continuation of the medial loop, consisting of axons of the second sensory neurons heading to the thalamus.

Rice. 10.1.Section at the border of the medulla oblongata and the pons.

1 - medial longitudinal bundle; 2 - medial loop; 3 - the core of the efferent nerve; 4 - vestibular nerves; 5 - lower cerebellar peduncle; 6 - the nucleus of the descending root of the V cranial nerve; 7 - nuclei of the auditory nerve; 8 - the nucleus of the facial nerve; 9 - anterior spinocerebellar pathway; 10 - lower olive; 11 - cortico-spinal (pyramidal) path; VI - abducens nerve; VII - facial nerve; VIII - vestibulocochlear nerve; 13 - cortical-spinal (pyramidal) path.

positive ways. The medial loop is crossed by transverse fibers of the trapezius body (corpus trapezoideum), related to the auditory analyzer system. Along the course of these fibers are small accumulations of gray matter - the so-called own nuclei of the trapezoid body. (nuclei corporis trapezoidei). In them, as well as in the accumulations of gray matter located on the sides of the medial loop, known as the lower olives (olivae inferior), the axons of the second neurons of the auditory pathways end. Axons, however, extending from the bodies located in the listed structures of the third neurons form a lateral, or auditory, loop, located outward from the medial loop, taking an ascending direction and reaching the subcortical auditory centers.

Outward and dorsally from the lower olive are the fibers of the spinal cord of the trigeminal (V cranial) nerve and the cells of the nucleus of the same name surrounding it, also known as nucleus of the spinal tract (lower nucleus) of the trigeminal nerve. Above these formations is the reticular formation and the central gray matter lining the bottom of the IV ventricle. In it, on the sides of the midline are located nucleus of the VI cranial nerve. Nuclei of the facial (VII) nerve located deep in the reticular formation. The axons of the motor cells embedded in them (the roots of the facial nerve) first rise upward, go around the nucleus of the VI cranial nerve, then, going next to the root of the VI cranial nerve, go down to the back of the basal surface of the bridge and leave the brain stem, leaving the groove, separating the basal surfaces of the bridge and the medulla oblongata.

The upper lateral sections of the lower part of the tegmentum of the bridge and the upper sections of the tegmentum of the medulla oblongata are occupied hearing field, in which the auditory and vestibular nuclei are located, related to the system of the VIII cranial nerve. The auditory nuclei are located in the part of the auditory field, the rhomboid fossa, adjacent to the lower cerebellar peduncle, extending to its dorsal surface. One of the auditory nuclei - anterior (dorsal) nucleus, or the nucleus of the auditory tubercle, located on the posterolateral surface of the inferior cerebellar peduncle, and the other - posterior (ventral) nucleus - in the region of transition of the lower cerebellar peduncle to the cerebellum. In these nuclei, the axons of the first neurons end and the bodies of the second neurons of the auditory pathways are located.

The vestibular nuclei are located under the floor of the lateral part of the IV ventricle. Above and lateral to other nuclei is superior vestibular nucleus (core Bekhterev), in which the ascending part of the vestibular portion of the VIII cranial nerve ends. Behind Bechterew's nucleus is localized large cell lateral vestibular nucleus (vestibular nucleus Deiters), giving rise to the vestibulospinal tract, and more medially - medial, or triangular nucleus (core Schwalbe), occupying a large area of ​​the auditory field. inferior vestibular nucleus (core Roller) located lower in the part of the rhomboid fossa related to the medulla oblongata.

The middle part of the bridge. The middle part of the bridge tire (Fig. 10.2) contains motor nucleus (nucl. motorius nervi trigemini) and pavement(nucl. pontinus nervi trigemini), or the upper sensitive nucleus of the V cranial nerve (the nucleus of the mesencephalic pathway of the trigeminal nerve), consisting of the second neurons of the pathways of deep and tactile sensitivity. These nuclei are located deep in the lateral part of the tegmentum, on the border of the upper and middle thirds of the pons, and the motor nucleus lies ventral to the sensory one.

Rice. 10.2.Cut at the level of the middle third of the bridge.

1 - medial longitudinal bundle; 2 - medial loop; 3 - motor nucleus of the V nerve; 4 - the final nucleus of the trigeminal nerve (the core of deep sensitivity); 5 - lateral (auditory) loop; 6 - cortico-spinal (pyramidal) path; V - trigeminal nerve.

On the border between the tire and the base of the bridge are ascending fibers that make up the medial and lateral loops. The posterior longitudinal and occlusal-spinal tract, as well as at other levels of the bridge and the medulla oblongata, are located under the bottom of the IV ventricle, close to the midline.

The rest of the bridge cover is mainly occupied by the reticular formation that has increased in volume.

Upper part of the bridge. At this level, the IV ventricle is already significantly narrowed (Fig. 10.3). Its roof here is the anterior medullary velum, in which, in addition to the anterior spinal cerebellar pathway of Gowers passing to the opposite side, there are also crossing fibers of the IV cranial nerve. The volume of the pontine tire decreases, and at the same time, its base reaches its greatest development, in which the longitudinally descending pyramidal pathways are dissected into bundles of various thicknesses by numerous transverse fibers directed to the middle cerebellar peduncles, which no longer fall into this section, because they go to the fibers from here turn rather sharply back. The middle cerebellar peduncles are replaced by the superior cerebellar peduncles on this section, limiting the upper triangle of the rhomboid fossa and heading upward and medially. Plunging deep into the tire of the bridge, the upper cerebellar legs at this level begin to form a decussation.

On the border between the tire and the base of the bridge, as at the previously considered levels, there are medial and lateral loops, which are here

Rice. 10.3.Cut at the level of the upper third of the bridge.

1 - superior cerebellar peduncle; 2 - medial longitudinal bundle; 3 - lateral loop; 4 - medial loop; 5 - cortical-spinal (pyramidal) path; IV - trochlear nerve.

begin to diverge. At the bottom of the rhomboid fossa at this level of the trunk is a pigmented area - a bluish place (locus ceruleus), outside of it is the nucleus of the mesencephalic pathway of the trigeminal nerve. The rest of the bridge cover is occupied reticular formation and transit paths passing through the bridge.

10.2. CRANIAL NERVES OF THE BRIDGE

10.2.1. Vestibulocochlear (VIII) nerve (n. vestibulocochlearis)

The vestibulocochlear nerve is sensitive. It conducts impulses from receptors located in a complex fluid-filled structure called the labyrinth, which is located in the petrous part of the temporal bone. The labyrinth includes the cochlea, which contains auditory receptors, and the vestibular apparatus, which provides information about the severity of gravity and acceleration, about head movements, and promotes orientation in space. The VIII cranial nerve, therefore, consists of two parts or portions that are different in function: auditory (cochlear, cochlear) and vestibular (pre-door), which may well be considered

Rice. 10.4.Vestibulocochlear (VIII) nerve.

1 - olive; 2 - trapezoid body; 3 - vestibular nuclei; 4 - posterior cochlear nucleus; 5 - anterior cochlear nucleus; 6 - vestibular root; 7 - cochlear root; 8 - internal auditory opening; 9 - intermediate nerve; 10 - facial nerve; 11 - knee assembly; 12 - cochlear part; 13 - vestibule; 14 - vestibular node; 15 - anterior membranous ampulla; 16 - lateral membranous ampulla; 17 - elliptical bag; 18 - posterior membranous ampulla; 19 - spherical bag; 20 - cochlear duct.

Xia as peripheral parts of independent (auditory and vestibular) systems (Fig. 10.4).

10.2.1.1. auditory system

Together with concentrating (outer ear) and sound-transmitting (middle ear) formations cochlear part of the inner ear (cochlea) in the process of evolution, it acquired a high sensitivity to sound stimuli, which are air vibrations. In young people Normally, the auditory analyzer is sensitive to air vibrations in the range from 20 to 20,000 Hz, and the maximum sensitivity is recorded at frequencies close to 2000 Hz. Thus, the human ear perceives sounds in a very wide range of intensities without saturation or overload. In the middle frequency band, sound can cause pain in the ear only when its energy exceeds the threshold by 10 12 times. sound intensity, reflecting the energy relations of the impact sound vibrations on the structures of the hearing aid, measured in decibels (dB). Under normal conditions, a person can detect changes in the intensity of a continuously sounding tone by 1 dB. The frequency of sound waves determines the tone of the sound, and the shape of the sound wave determines its timbre. In addition to the intensity, pitch and timbre of sounds, a person can determine and the direction of their sources, this function is provided thanks to binaural reception sound signals.

Sounds are concentrated to some extent by the auricle, enter the external auditory canal, at the end of which there is a membrane - bar-

bath membrane, separating the cavity of the middle ear from the outer space. Pressure in the middle ear is balanced by the auditory (Eustachian) tube, which connects it to the back of the throat. This tube is usually in a collapsed state and opens when swallowing and yawning.

Vibrating under the influence of sounds, the eardrum sets in motion located in the middle ear is a chain of small bones - the hammer, anvil and stirrup. It is possible to amplify the sound energy by about 15 times. The regulation of sound intensity is facilitated by contraction of the muscle that stretches the eardrum (m. tensor tympani), and stirrup muscles. Spreading through the auditory ossicles sound energy reaches the oval window of the cochlea of ​​the inner ear, causing the perilymph to vibrate.

Snailis a tube coiled into a spiral, divided longitudinally into 3 channels or stairs: stairs vestibule And tympanic ladder, containing perilymph and located outside the membranous part of the cochlea, and middle stairs (cochlea's own canal), containing endolymph and is part of the membranous labyrinth located in the cochlea. These ladders (channels) are separated from each other by the basal lamina and the vestibular membrane (Reissener's membrane).

The receptors of the auditory analyzer are located in the inner ear, more precisely in the membranous labyrinth located there, containing the spiral organ. (organum spirale), or organ of corti located on the basilar plate and facing the middle scala filled with endolymph. Actually receptor apparatus are the hair cells of the spiral organ, which are irritated by the vibration of its basilar plate (lamina basilaris).

The vibrations caused by the sound stimulus are transmitted through the oval window to the perilymph of the cochlear labyrinth. Spreading along the curls of the cochlea, they reach its round window, are transmitted to the endolymph of the membranous labyrinth, causing vibration of the basilar plate (main membrane) and irritation of the receptors, in which mechanical wave vibrations are transformed into bioelectric potentials.

It should be noted that, besides described, the so-called air conduction of sound vibrations, their transmission through the bones of the skull is also possible - bone conduction; an example of this is the transmission of sound caused by the vibration of a tuning fork, the leg of which is installed on the crown or mastoid process of the temporal bone.

The nerve impulses arising in the auditory receptors move in a centripetal direction along the dendrites of the first neurons of the auditory pathway to the spiral node (ganglion spirale), or cochlear node, in which their bodies are located. Further, the impulses travel along the axons of these neurons, forming a cochlear portion of a single trunk of the VIII cranial nerve, consisting of approximately 25,000 fibers. The trunk of the VIII cranial nerve exits the temporal bone through the internal auditory canal, passes the lateral cistern of the pons (cerebellopontine space) and enters the brainstem in the lateral part of the bulbar-pontine sulcus, located on its base and delimiting the bridge from the medulla oblongata.

In the brain stem cochlear portion VIII cranial nerve separates from the vestibular and ends in two auditory nuclei: posterior (ventral) and anterior (dorsal) (Fig. 10.5). In these nuclei, impulses pass through synaptic connections from the first neuron to the second. Axons of posterior cells (vent-

Rice. 10.5.Conducting paths of impulses of auditory sensitivity.

1 - fibers coming from the receptor apparatus of the cochlea; 2 - cochlear (spiral) node;

3 - posterior cochlear nucleus;

4 - anterior cochlear nucleus;

5 - upper olive core; 6 - trapezoid body; 7 - brain strips; 8 - lower cerebellar peduncle; 9 - superior cerebellar peduncle; 10 - middle cerebellar peduncle;

11 - branches to the cerebellar vermis; 12 - reticular formation; 13 - lateral loop; 14 - lower colliculus; 15 - pineal body; 16 - or rather double colliculus; 17 - medial geniculate body; 18 - cochlear path leading to the cortical center of hearing in the superior temporal gyrus.

ral) nuclei are involved in the formation of the trapezoid body, located on the border between the base and the tire of the bridge. The axons of the anterior (dorsal) auditory nucleus are sent to the midline in the form of cerebral (auditory) strips of the IV ventricle (striae medullares ventriculi quarti). Most of the axons of the second neurons of the auditory pathways end in the nuclei of the trapezoid body or in the superior olives of the opposite side of the brainstem. Another, smaller, part of the axons of the second neurons does not undergo decussation and ends in the upper olive of the same side.

In the upper olives and nuclei of the trapezoid body, the third neurons of the auditory pathways are located. Their axons form a lateral, or auditory, loop, consisting of crossed and uncrossed auditory fibers that rise up and reach the subcortical auditory centers - the medial geniculate bodies, located in the diencephalon, more precisely its metathalamic department, and inferior tubercles of the quadrigemina, related to the midbrain.

In these subcortical auditory centers lie the bodies of the last neurons of the auditory pathway to the corresponding projection cortical fields. Along the axons of these neurons, impulses are directed through the sublenticular part (pars sublenticularis) internal capsule and the radiant crown to the cortical end of the auditory analyzer, which is located in cortex of the transverse convolutions of Heschl, located on the lower lip of the lateral (Sylvian) groove formed by the superior temporal gyrus (cytoarchitectonic fields 41 and 42).

The defeat of the auditory analyzer can cause various hearing impairments. When the function of the sound-conducting structures and the receptor apparatus of the auditory analyzer is impaired, usually there are hearing loss (hypacusis, hearing loss) or deafness (anacusis, surditas), often accompanied by tinnitus.

The defeat of the trunk of the VIII cranial nerve, as well as its nuclei in the tire of the bridge, can also lead to hearing loss on the side of the pathological focus and the occurrence of lateralized noise.

If the auditory pathways are affected on one side above the place of their incomplete intersection in the bridge, then deafness does not occur, but some hearing loss is possible on both sides, mainly on the side opposite to the pathological focus, in such cases moderate, unstable noise in the head is possible.

If the pathological focus irritates the cortical end of the auditory analyzer, auditory hallucinations are possible, which in such cases may also represent the auditory aura of an epileptic seizure.

When examining the state of the auditory analyzer, it is necessary to pay attention to the patient's complaints: are there any information among them that could indicate hearing loss, distortion of sounds, noise in the ear, auditory hallucinations.

When checking hearing, it should be borne in mind that with normal hearing, a person hears whispered speech at a distance of 5-6 m. Since the hearing of each ear must be checked separately, the patient should cover the other ear with a finger or damp cotton. If hearing is reduced (hypacusia) or absent (anacusia), then it is necessary to clarify the cause of his disorder.

It should be taken into account that hearing in a patient can be reduced due to damage not only to the sound-perceiving, but also to the sound-conducting apparatus of the middle ear. In the first case, we are talking about deafness of the inner ear or about neural deafness, in the second - about deafness of the middle ear or about conductive form of hearing loss. The cause of the conductive form of hearing loss can be any form of damage to the middle (rarely - outer) ear - otosclerosis, otitis media, tumors, etc., while hearing loss and noise in the ear are possible. The neural form of hearing loss is a manifestation of a dysfunction of the inner ear (spiral, or Corti's, organ), cochlear portion of the VIII cranial nerve, or brain structures related to the auditory analyzer.

With conductive hearing loss, there is usually no complete deafness and the patient hears sounds transmitted to the spiral organ through the bone; with hearing loss of the neural type, the ability to perceive sounds transmitted both through the air and through the bone suffers.

The following additional studies can be applied to differentiate hearing loss by conductive and neural types.

1. The study of hearing using tuning forks with different frequencies. Usually used tuning forks C-128 and C-2048. When the outer and middle ear are damaged, the perception of mainly low-frequency sounds is disturbed, while when the function of the sound-perceiving apparatus is impaired, the perception of sound of any tone occurs, but hearing for high sounds suffers more significantly.

2. Air and bone conduction studies. When the sound-conducting apparatus is damaged, air conduction is disturbed, while bone conduction remains intact. In case of damage to the sound-perceiving apparatus, the

both air and bone conduction are affected. To check the state of air and bone conduction, the following samples with a tuning fork can be used (the C-128 tuning fork is more often used).

Weber's experience is based on the possible lateralization of the duration of sound perception through bone. When conducting this experiment, the leg of a sounding tuning fork is placed in the middle of the patient's crown. If the sound-conducting apparatus is damaged, the patient will hear the sound of the tuning fork on the affected side for a longer time with the diseased ear, i.e. there will be a lateralization of the sound towards the diseased ear. If the sound-perceiving apparatus is damaged, the sound will lateralize towards the healthy ear.

Renne's experience is based on comparing the duration of air and bone sound perception. It is checked by finding out how long the patient hears a sounding tuning fork, the leg of which stands on the mastoid process of the temporal bone, and a tuning fork brought to the ear at a distance of 1-2 cm. Normally, a person perceives sound through the air approximately 2 times longer than through the bone. In this case, the Renne experience is said to be + (positive). If the sound is perceived through the bone for a longer time, Renne's experience is (negative). The negative experience of Renne indicates a probable damage to the sound-conducting apparatus (the apparatus of the middle

ear).

Schwabbach's experience is based on measuring the duration of the patient's sound perception of a tuning fork through the bone and comparing it with normal bone sound conduction. The test is carried out as follows: the leg of the sounding tuning fork is placed on the mastoid process of the temporal bone of the patient. After the patient stops hearing the sound of the tuning fork, the examiner places the stem of the tuning fork against his mastoid process. In the case of shortening of the patient's bone conduction, i.e. dysfunction of the sound-perceiving apparatus (apparatus of the inner ear), the examiner will still feel vibration for some time, while it is considered that the examiner has normal hearing.

3. Audiometric study. More accurate information about the state of air and bone conduction can be obtained by audiometric research, which allows you to find out and get a graphic image of the threshold of hearing of sounds of various frequencies through the air and bone. To clarify the diagnosis, audiometry is used in an extended frequency range, including high-frequency and low-frequency spectra, as well as various suprathreshold tests. Audiometry is carried out using a special audiometer apparatus in an otoneurological room.

10.2.1.2. vestibular system

The term is derived from the concept labyrinthine vestibule- entrance to the labyrinth; in the vestibule (part of the inner ear) the semicircular canals and the cochlea connect. Three semicircular canals are located in three mutually perpendicular planes and are interconnected; each canal near the vestibule ends with an ampulla. Hollow bony semicircular canals, the vestibule and the cochlear duct connecting them are located in the pyramid of the temporal bone. They are filled with perilymph - cerebrospinal fluid ultrafiltrate. In the bone canals is formed from membrane tissue membranous labyrinth (labyrinthus membranaceus), composed of three membranes

semicircular ducts (ductus semicirculares), and from the components otolith apparatus elliptical and spherical pouches (sacculus et utriculus). The membranous labyrinth is surrounded by perilymph and filled with endolymph. probably secreted by the cells of the labyrinth itself.

The receptors of the vestibular (statokinetic) analyzer are located in the semicircular ducts and in the otolithic apparatus of the inner ear. All three semicircular ducts end in ampullae containing receptor hair cells that make up the ampullar ridges. These scallops are embedded in the gelatinous substance that forms the dome. The receptor hair cells of the scallops are sensitive to the movement of the endolymph in the semicircular ducts of the canals and respond primarily to changes in the speed of movement - acceleration and deceleration, therefore they are called kinetic receptors.

Receptors of the otolithic apparatus are concentrated in areas called spots. (maculae). In one of the bags, such a spot occupies a horizontal position, in the other - a vertical position. The receptor hair cells of each spot are embedded in the gelatinous tissue containing sodium carbonate crystals - otoliths, a change in the position of which causes irritation of the receptor cells, while nerve impulses appear in them, signaling the position of the head in space (static impulses).

From the peripheral receptor apparatus of the vestibular system, impulses follow the dendrites of the first neurons of the vestibular pathways to the vestibular ganglion (gangl. vestibularis), or a Scarpe node located in the internal auditory canal. It contains the bodies of the first neurons. From here, the impulses follow along the axons of the same nerve cells passing as part of the vestibular portion of the common trunk of the VIII cranial nerve. As already noted, the VIII cranial nerve leaves the temporal bone through the internal auditory meatus, crosses the lateral cistern of the pons, and enters the brainstem in the lateral part of the bulbar-pontine sulcus, which delimits the basal surfaces of the pons and medulla oblongata. Entering the brain stem, the vestibular portion of the VIII cranial nerve is divided into ascending and descending parts (Fig. 10.6). The ascending part ends at the cells of the vestibular nucleus of Bechterew (nucl. superior). Some ascending fibers, bypassing Bekhterev's nucleus, enter the cerebellar vermis through the inferior cerebellar peduncle and end in its nuclei. The descending fibers of the vestibular portion of the VIII cranial nerve end in the triangular vestibular nucleus of Schwalbe (nucl. medialis) and in the Deuters kernel (nucl. lateralis), as well as in the lower nucleus of the Roller, located below the other vestibular nuclei (nucl. inferior). The bodies of the second neurons of the vestibular analyzer are located in the vestibular nuclei, whose axons follow in various directions, providing the formation of numerous vestibular connections.

The axons of the cells of the lateral nucleus of Deiters go down, penetrate into the outer sections of the anterior cords of the spinal cord, where they form the descending pre-door-spinal cord (Leventhal's bundle), which ends at the cells of the anterior horns of the same side of the spinal cord. The axons of the cells of the lower Roller nucleus reach the cells of the anterior horns of the opposite side of the cervical spinal cord. The axons of the cells of the vestibular nuclei of Bekhterev (upper), Schwalbe (medial) and Roller (lower) have connections with the medial longitudinal bundle. Having taken an upward direction in it and partially moving to the opposite side, they end at the cells

Rice. 10.6.Conducting pathways of impulses of vestibular sensitivity. 1 - pre-door-spinal path; 2 - semicircular ducts; 3 - vestibular node; 4 - vestibular root; 5 - lower vestibular nucleus; 6 - medial vestibular nucleus; 7 - lateral vestibular nucleus; 8 - upper vestibular nucleus; 9 - the core of the tent of the cerebellum; 10 - dentate nucleus of the cerebellum; 11 - medial longitudinal bundle; 12 - the core of the abducens nerve; 13 - reticular formation; 14 - superior cerebellar peduncle; 15 - red core; 16 - the nucleus of the oculomotor nerve; 17 - Darkshevich core; 18 - lenticular core; 19 - thalamus; 20 - cortex of the parietal lobe; 21 - cortex of the temporal lobe hemisphere brain.

nuclei of the cranial nerves that provide movement of the eyeballs (III, IV and VI cranial nerves). The presence of pre-door-oculomotor connections and the provision through the medial longitudinal bundle of connections between the nervous structures that coordinate the function of the striated muscles of the eyeballs determine the friendliness of eyeball movements and the preservation of gaze fixation with changes in head position. Violation of the conduction of nerve impulses along these nerve connections can cause vestibular nystagmus.

Part of the axons of the second neurons, whose bodies are embedded in the vestibular nuclei, come into contact with vegetative structures, in particular with the posterior nucleus of the vagus nerve and with nuclei of the hypothalamic region diencephalon. The presence of these connections explains the appearance in the pathology of the vestibular analyzer, in particular when it is overexcited, pronounced vegetative, predominantly parasympathetic reactions in the form of nausea, vomiting, blanching of integumentary tissues, sweating, increased intestinal peristalsis, lowering blood pressure, bradycardia, etc.

The vestibular system has bilateral connections with the cerebellum, which is probably due to a certain proximity of the functions of these parts of the nervous system. The fibers that go from the vestibular nuclei to the cerebellum are mainly axons of cells whose bodies are located in the superior and medial nuclei (in the Bekhterev and Schwalbe nuclei). These connections pass through the lower cerebellar peduncle and end mainly in the nuclei of its vermis.

In addition, the vestibular apparatus of the brain stem has connection with reticular formation, with formations of the extrapyramidal system, in particular with red nuclei and with subcortical nodes, as well as with cerebral cortex brain. The connections of the vestibular nuclei with the cortex have not yet been fully traced. The cortical end of the vestibular analyzer is located in the temporal lobe of the brain, somewhere near the cortical end of the auditory analyzer. It is possible that the cortical cells that receive information from the vestibular analyzer are located in the temporal lobe of the brain and in the parietal and frontal lobes adjacent to it.

Irritation of the receptors of the semicircular canals can be provoked by rotation or infusion of hot or cold water into the external auditory meatus. As a result, dizziness and vestibular nystagmus occur in the plane of the semicircular canal, in which the maximum movement of the endolymph occurs.

Numerous connections of the vestibular apparatus explain the abundance of pathological symptoms that occur when it is damaged. Among the vestibular symptoms, there are sensory (dizziness), oculomotor (nystagmus), tonic (decrease in muscle tone, deviation of outstretched arms and torso), statokinetic (imbalance, gait, forced head position, etc.).

The most informative results of the study of hearing and vestibular functions can be obtained during the neuro-otiatric examination of the patient, which is carried out by the relevant specialists.

10.2.2. Facial (VII) nerve (n. facialis)

The facial nerve is mainly motor, but it also contains sensory (taste and general types sensitivity) and secretor-

nye (parasympathetic) fibers that form so-called intermediate nerve (nervus intermedius), or wrisberg nerve, also known as XIII cranial nerve, which passes a significant part of the path together with the VII cranial nerve (Fig. 10.7). In this regard, the facial nerve, together with the intermediate nerve, is sometimes called the intermediate facial nerve. (nervus intermedio-facialis).

Own The (motor) part of the facial nerve in the brainstem is represented by the motor nucleus, located in the lower part of the pontine tire. This nucleus consists of several cell groups, each of which provides innervation of certain facial muscles. In him it is customary to distinguish between the upper part, which has a connection with the cortex of both hemispheres of the brain, since the cortical-nuclear fibers going to it make an incomplete supranuclear decussation, and the lower part, which has a connection only with the cortex of the opposite hemisphere of the brain. The upper and lower parts of the nucleus of the facial nerve provide innervation of the mimic muscles of the upper and lower parts of the face, respectively.

The nuclei of the intermediate nerve are located mainly in the medulla oblongata and are common with the nuclei of the IX cranial nerve. These are the upper parts of the taste nucleus of the solitary tract and the parasympathetic salivary nucleus (nucleus salvatorius). The intermediate nerve also includes parasympathetic cells diffusely located near the motor nucleus of the seventh cranial nerve, which provide the function of the lacrimal gland.

The main, motor, root of the VII nerve exits the brainstem in the transverse bulbar-pontine groove between the medulla oblongata and the pons. Lateral to it, the intermediate nerve emerges from the same groove. Soon they join into a common trunk (VII and XIII nerves), which passes through the lateral cistern of the bridge (cerebellopontine space). Subsequently, the 7th cranial nerve along with VIII cranial nerve penetrates into the canal of the internal auditory canal, and then separated from him and included in own channel - canal of the facial nerve, or fallopian canal. Passing through this canal, the facial nerve makes a distinct bend (the outer knee of the facial nerve); at this bend the knee node is located (ganglion geniculi, refers to the system of the intermediate nerve), containing pseudo-unipolar sensory cells, which are the bodies of the first neurons of the sensitive taste pathway and the pathway of general types of sensitivity, providing general types of sensitivity on the outer surface of the tympanic membrane and in the area of ​​​​the external auditory canal. The axons of the first neuron of taste sensitivity, passing in the centripetal direction as part of the intermediate nerve, transmit the corresponding impulses to the upper part of the taste nucleus (the nucleus of a single bundle) located in the tegmentum of the brain stem. The axons of pseudo-unipolar cells of general types of sensitivity coming from the knee node, entering the brain stem, complete their journey in the nuclei of the trigeminal nerve.

The existence of structures that provide sensitivity in the common trunk of the VII and XIII cranial nerves explains the possible pain syndrome in case of neuropathy of the VII cranial nerve, as well as pain and herpetic eruptions in Head's syndrome, which is based on ganglioneuritis with a lesion of the knee node caused by a virus herpes zoster.

Passing through the temporal bone, the trunk of the facial nerve and its constituent intermediate (XIII) cranial nerve, it gives off 3 branches (Fig. 9.8). The first to depart from it contains parasympathetic fibers great stony nerve (n. petrosus major). The preganglionic fibers included in it, which are the axons of the cells of the lacrimal nucleus located in the trunk

10.7. Facial (VII) nerve.

1 - the core of a single beam; 2 - upper salivary nucleus; 3 - the nucleus of the facial nerve; 4 - knee (internal) of the facial nerve; 5 - intermediate nerve; 6 - knee assembly; 7 - deep stony nerve; 8 - internal carotid artery; 9 - pterygopalatine node; 10 - ear knot; 11 - lingual nerve; 12 - drum string; 13 - stapedial nerve and stapedial muscle; 14 - tympanic plexus; 15 - crankshaft nerve; 16 - knee (external) of the facial nerve; 17 - temporal branches; 18 - frontal belly of the occipital-frontal muscle; 19 - muscle wrinkling the eyebrow; 20 - circular muscle of the eyes; 21 - muscle of the proud; 22 - large zygomatic muscle; 23 - small zygomatic muscle, 24 - muscle that raises the upper lip; 25 - muscle that lifts the upper lip and wing of the nose; 26, 27 - nasal muscle; 28 - muscle that raises the corner of the mouth; 29 - muscle that lowers the nasal septum; 30 - upper incisor muscle; 31 - circular muscle of the mouth; 32 - lower incisor muscle; 33 - buccal muscle; 34 - muscle lowering the lower lip; 35 - chin muscle; 36 - muscle that lowers the corner of the mouth; 37 - muscle of laughter; 38 - subcutaneous muscle of the neck; 39 - zygomatic branches; 40 - sublingual gland; 41 - cervical branch; 42 - submandibular node; 43 - posterior ear nerve; 44 - stylohyoid muscle; 45 - posterior belly of the digastric muscle; 46 - stylomastoid opening; 47 - occipital belly of the occipital-frontal muscle. Motor nerves are marked in red, sensory nerves in blue, and parasympathetic nerves in green.

Rice. 10.8.Facial nerve and its components nerve fibers, variants of their defeat in case of damage to different levels. a - in the region of the cerebellopontine angle; b, c, d - levels of damage in the canal of the facial nerve; e - damage to the facial nerve after exiting the stylomastoid foramen; 1 - internal auditory meatus; 2, 3 - cochlear and vestibular parts of the vestibulocochlear (VIII) nerve; 4 - intermediate (XIII) cranial nerve, or posterior root of the facial nerve; 5 - secretory fibers to the salivary glands; 6 - secretory fibers to the salivary glands; 7 - large stony nerve; 8 - stirrup nerve; 9 - drum string; 10 - stylomastoid opening.

of the brain near the main, motor, nucleus of the VII cranial nerve, exit the pyramid of the temporal bone through the cleft of the canal of the large stony nerve and pass along the sulcus of the same name to the torn hole. Through it, a large stony nerve enters the base of the skull, where it connects with a deep stony nerve. (n. petrosus profundus). Their fusion leads to the formation of the nerve of the pterygoid canal. (n. canalis pterygoidei), passing through the pterygoid canal to the pterygopalatine ganglion (ganglion pterygopalatinum).

Postganglionic fibers originating from the neurons of the pterygopalatine ganglion innervate the lacrimal gland and the mucous glands of the nasal and oral cavities. If the facial nerve is damaged above the origin of the large stony nerve, which is involved in the formation of the nerve of the pterygoid canal, dry eyes occur - xerophthalmia, what can be the cause of keratitis, episcleritis, ophthalmitis; insufficient moisture content of the homolateral part of the nasal cavity is also possible.

The next branch, extending from the trunk of the facial nerve, in the area passing through its own canal, is stapedial nerve (n. stapedius), innervating the same-named muscle (m. stapedius), tensile eardrum. Violation of the function of this nerve leads to the development in the patient of a perversion of the timbre of perceived sounds. Sounds take on an unpleasant, harsh character, a phenomenon known as hyperacusis.

The third branch, extending from the trunk of the facial nerve, - drum string (chorda tympani), represents a direct continuation of the intermediate nerve. It contains taste fibers, which are dendrites of cells whose bodies are located in the knee node, and secretory autonomic fibers (axons of autonomic neurons whose bodies are located in the nucleus of a single bundle). Through the channel of the same name, the drum string penetrates into the tympanic cavity, passes through it under the mucous membrane between the anvil and the handle of the malleus. After that, the drum string through the stony-tympanic fissure (glazer fissure) goes to the outer side of the base of the skull, after which it joins the lingual nerve, which belongs to the V cranial nerve system. As a result, taste fibers reach the two anterior thirds of the tongue, and secretory fibers reach the sublingual and submandibular vegetative nodes (Fig. 10.9). Postganglionic fibers extending from these nodes innervate the sublingual and submandibular salivary glands, respectively. If the function of the drum string is disturbed, the taste sensations in the anterior 2/3 of the tongue are disturbed, while the perception of sour and sweet mainly falls out. Due to the fact that the drum string is involved in the innervation of the salivary glands, its defeat can lead to a decrease in the secretion of saliva, which can only be detected by resorting to a special, rather complex examination. There is an opinion (Nomura S., Mizino N., 1983),

Rice. 10.9.Taste system. 1 - crank assembly; 2 - intermediate (XIII) nerve; 3 - the lower node of the IX nerve; 4 - lower node X of the nerve; 5 - taste nucleus (nucleus of a single bundle);

6 - bulbotalamic tract;

7 - nuclei of the thalamus; 8 - hippocampal gyrus; 9 - semilunar node; 10 - epiglottis.

that the tympanic string anastomoses with the system of the glossopharyngeal and superior laryngeal nerves.

After departing from the VII cranial nerve, the tympanic string, this nerve leaves the bone canal of the same name through the stylomastoid foramen (foramen stylomostoideum) to the outer side of the base of the skull.

The presence of these three branches of the facial nerve allows you to quite accurately determine the location of its lesion. If the nerve damage is located above the place of origin of the large stony nerve, then along with paresis of the facial muscles, the functions of all three of these branches of the facial nerve are impaired. If the pathological process is above the place where the second branch, the stapedial nerve, originates from the main nerve trunk, the function of the lacrimal gland will be preserved, but hyperacusis and taste disorder will appear. If the nerve is affected between the place where the stapedial nerve and the knee node originate from it, then the paresis of the facial muscles will be combined only with a taste disorder and, possibly, a violation of superficial sensitivity in the area of ​​​​the external auditory canal. In case of damage to the trunk of the facial nerve below the discharge of the tympanic string, only peripheral paresis or paralysis of the muscles innervated by it on the side of the pathological process will appear in the clinical picture.

After the exit of the VII cranial nerve from the temporal bone through the stylomastoid foramen, it departs from it posterior auricular nerve (n. auriculus posterior), innervates the muscles of the auricle and the occipital muscle. Somewhat distally from the facial nerve, the digastric branch is separated (ramus digastricus), innervates the posterior belly of the digastric muscle and the stylohyoid muscle. In addition, connecting branches are separated from the trunk of the facial nerve - anastomoses to the glossopharyngeal and vagus nerves.

Then the trunk of the facial nerve passes through the parotid gland and in front of the external auditory meatus divides into branches, forming the so-called big goose paw (pes anserinus major) and thus forming parotid plexus (Plexus parotideus). Branches depart from here, providing innervation of facial muscles. The largest of them are as follows: temporal (rr. temporales), buccal (rr. buccales), zygomatic (rr. zygommatici) and marginal branch of the lower jaw (r. marginalis mandibulae). In addition, the cervical branch descends to the neck (ramus colli) for innervation of the subcutaneous muscle of the neck.

Damage to the facial nerve (nucleus or any part of the trunk) leads to peripheral paralysis or paresis of the muscles innervated by the facial nerve, at the same time, asymmetry of the face develops, noticeable at rest and sharply intensifying with mimic movements. With paralysis of facial muscles on the side of the lesion, the face is motionless, the palpebral fissure is wide, blinking movements are absent or rare (flash test). When you try to wrinkle your forehead, skin folds on this side do not form. ("polished" forehead). The patient fails to close the eye: when trying to close the eye, the eyeball on the side of the lesion turns up (Bell sign) and through the gaping palpebral fissure under the upward iris, the sclera is visible ("hare eye", lagophthalmos) (Fig. 10.10). If there is not paralysis, but paresis of the circular muscle of the eye, then when you try to close your eyes tightly, the eyelids do not close tightly, while on the side of the lesion the eyelashes do not sink into the skin folds (symptom of eyelashes). In the case of moderate paresis of the circular muscle of the eye, the patient can close the eyelids on both sides, but cannot close them only on the side of the lesion, while leaving the other eye open (eyelid dyskinesia, or sim-

Rice. 10.10.Signs of damage to the left facial nerve, detected when the patient tries to close his eyes and bare his teeth (schematic image).

pt. Revillo). When the cheeks are inflated, air comes out of the corner of the mouth on the side of the lesion, cheek when breathing on the same side "sails". Passively raising the corners of the patient's mouth, the examiner notes that with an identical effort on both sides, there is a decrease in muscle tone on the side of the lesion, in connection with this, the corner of the mouth rises higher than on the healthy one. (symptom of Rusetsky). When the teeth are bared on the side of the lesion of the circular muscle of the mouth, they are exposed less than on the healthy side, and the oral fissure becomes like a tennis racket, the handle of which shows the side of the lesion (racket symptom). The patient usually has difficulty eating, as it falls under the paretic cheek and sometimes has to be removed from there with the help of the tongue. Liquid food and saliva may flow from an insufficiently covered corner of the mouth on the side of the lesion. In this corner of the mouth, with paresis of the circular muscle of the mouth, the patient cannot hold a strip of paper. (test of the circular muscle of the mouth), he cannot or find it difficult to whistle, blow out the candle.

With the localization of the pathological process in the motor zone of the cortex or along the cortical-nuclear pathway in a patient on the side opposite to the pathological process, usually occurs brachiofacial syndrome or hemiparesis, while developing a central paresis of the facial muscles. Due to the almost complete decussation of the cortico-nuclear pathways, suitable for the lower part of the nucleus of the facial nerve, manifestations of paresis of facial muscles occur in the lower part of the face, although some decrease in the strength of facial muscles, in particular, a weakening of the closing of the eyelids, can also be detected in the upper part of the face.

With a limited cortical pathological focus in the lower part of the precentral gyrus on the opposite side of the pathological focus, a combination of paresis in the central type of muscles of the face and tongue may occur - faciolingual syndrome. With the development in the same zone of epileptogenic

the focus is possible local Jacksonian convulsive paroxysms, manifested on the side contralateral to the pathological process by clonic convulsions in the muscles of the face and tongue, sometimes in combination with paresthesia. As noted by D. Jackson (J. Jackson, 1835-1911), a local convulsive seizure, starting with spasms of the facial muscles, often transforms into secondary generalized tonic-clonic epileptic seizure.

10.2.3. Abducens (VI) nerve (n. abducens)

The abducens nerve is motor. It consists of axons of peripheral motor neurons, the bodies of which are located in the motor nucleus located in the pons operculum. The dendrites of these cells through the system of the medial longitudinal bundle are in connection with other cell formations of the brain stem, including the nuclei of the oculomotor nerve of their own and opposite sides. VI cranial nerve penetrates the entire thickness of the bridge and emerges from the transverse groove on the ventral surface of the brain stem, on the border between the bridge and the medulla oblongata, medial to the roots of the VII cranial nerve, above the pyramids of the medulla oblongata. After that, the VI cranial nerve, creeping along the base of the skull, reaches the cavernous venous sinus and passes in its outer wall. Coming out of the cranial cavity through the superior orbital fissure, it enters the orbit.

VI cranial nerve innervates only one striated muscle - the direct external muscle of the eye (m. Rectus lateralis oculi). Damage to the VI cranial nerve leads to a limitation of the mobility of the eyeball outward (Fig. 10.11), there may be a tendency to turn it inward (strabismus convergens) due to the fact that the direct internal muscle of the eye, being an antagonist of the paralyzed muscle, pulls the eyeball in its direction. Damage to the VI cranial nerve results in diplopia (double vision), especially pronounced when you try to turn your gaze towards the pathological process. The images of objects visible in such cases are bifurcated in the horizontal plane, while the severity of doubling increases as the desire to turn the gaze towards the paralyzed muscle increases. Diplopia may be accompanied by dizziness, gait uncertainty and spatial disorientation. Patients often tend to cover one eye (diplopia usually disappears).

Insufficiency of function of the VI cranial nerve is often observed in combination with another neurological symptom.

Rice. 10.11.The manifestation of paralysis of the left external rectus muscle of the eye when you try to turn your gaze towards the affected muscle (schematic image).

matics and can be a manifestation of polyneuropathy, meningitis, thrombosis of the cavernous sinus, fracture and tumors of the base of the skull, etc. Bilateral damage to the VI cranial nerve and the resulting convergent strabismus can occur with a pronounced increase in intracranial pressure and, in this case, both VI cranial nerves are pressed against the bones of the base skulls.

10.2.4. Trigeminal (V) nerve (n. trigeminus)

Trigeminal nerve (Fig. 10.12) is mixed. Its main, sensitive portion provides all kinds of sensitivity of the skin of the face and scalp to the coronal suture, cornea, conjunctiva, mucous membranes of the nose and its accessory cavities, oral cavity, teeth, and dura mater. The motor portion innervates the masticatory muscles. In addition, the trigeminal nerve contains both sympathetic and parasympathetic fibers.

The bodies of the first neurons (pseudo-unipolar cells) of the sensitive portion of the V cranial nerve are located in the trigeminal (lunate or gasser) node (gangl. trigeminale), located in the mycelium fossa - a depression in the dura mater on the upper anterior surface of the pyramid of the temporal bone. The axons of the cells located in this node form sensory root of cranial nerve V heading through the side tank of the bridge to its surface. Entering the bridge sensitive spine is divided into two parts. One of them contains fibers of deep sensitivity and part of the fibers of tactile sensitivity, it ends in the pontine nucleus of the trigeminal nerve located in the cover of the bridge (nucl. pontinus nervi trigemini), or superior sensory nucleus of cranial nerve V (nucl. sensorius superior nervi trigemini) - nucleus of proprioceptive sensitivity. The second part, consisting of fibers of pain and temperature sensitivity, as well as of the fibers of tactile sensitivity accompanying them, forms the descending root of the V cranial nerve, which goes down, passes through the medulla oblongata and descends to the II cervical segment of the spinal cord. The descending root of the trigeminal nerve is surrounded by cells that form the nucleus of the spinal cord of the trigeminal nerve (nucleus spinalis nervi trigemini), also known as the inferior sensory nucleus of the trigeminal nerve (nucleus sensorius inferior nervi trigemini). The cells of the nucleus of the spinal tract of the trigeminal nerve are the bodies of the second neurons of the pathways of superficial, mainly pain and temperature, as well as tactile sensitivity. The axons of these cells, as well as the axons of the second neurons located in the pontine nucleus of the trigeminal nerve, join the medial sensory loop and at the same time pass to the opposite side, following along with the fibers of the spinothalamic pathway. Next they rise up as part of the tegmentum of the brainstem and reach the bodies of third neurons located in the ventrolateral nuclei of the thalamus. From here, along the axons of third neurons, impulses carrying information about the state of sensitivity on the face enter the lower sections of the postcentral gyrus (head projection zone) of the predominantly opposite hemisphere.

The dendrites of the cells of the semilunar node go to the periphery, forming three main branches of the V cranial nerve: I - ophthalmic nerve (n. ophtalmicus), II - upper

Rice. 10.12.Trigeminal (V) nerve.

1 - the nucleus of the spinal tract of the trigeminal nerve; 2 - the motor nucleus of the trigeminal nerve; 3 - pontine nucleus of the trigeminal nerve; 4 - the nucleus of the mesencephalic pathway of the trigeminal nerve; 5 - trigeminal nerve; 6 - eye branch; 7 - frontal branch; 8 - nasociliary nerve; 9 - posterior ethmoid nerve; 10 - anterior ethmoid nerve; 11 - lacrimal gland; 12 - supraorbital nerve (lateral branch); 13 - supraorbital nerve (medial branch); 14 - supratrochlear nerve; 15 - subblock nerve; 16 - internal nasal branches; 17 - external nasal branch; 18 - ciliary knot; 19 - lacrimal nerve; 20 - maxillary nerve; 21 - infraorbital nerve; 22 - nasal and upper labial branches of the infraorbital nerve; 23 - anterior upper alveolar branches; 24 - pterygopalatine node; 25 - mandibular nerve; 26 - buccal nerve; 27 - lingual nerve; 28 - submandibular node; 29 - submandibular and sublingual glands; 30 - lower alveolar nerve; 31 - mental nerve; 32 - anterior belly of the digastric muscle; 33 - maxillofacial muscle; 34 - maxillofacial nerve; 35 - chewing muscle; 36 - medial pterygoid muscle; 37 - branches of the drum string; 38 - lateral pterygoid muscle; 39 - ear-temporal nerve; 40 - ear knot; 41 - deep temporal nerves; 42 - temporal muscle; 43 - muscle straining the palatine curtain; 44 - muscle straining the eardrum; 45 - parotid gland. Sensory nerves are indicated in blue, motor nerves in red, and parasympathetic nerves in green.

jaw nerve (n. maxillaris) and III - mandibular nerve (n. mandibularis). The composition of the mandibular branch also includes the motor portion of the V cranial nerve, consisting of axons of cells located in its motor nucleus (nucl. motorius n. trigemini) in the tire of the bridge. Nerve fibers coming from this nucleus exit the bridge as part of the motor root passing by the semilunar node, adjoin the III branch of the trigeminal nerve and, following in its composition, reach the masticatory muscles and provide their innervation.

From the initial part of each of the three main branches of the trigeminal nerve, a branch departs into the cranial cavity to the dura mater (r. meningeus).

ophthalmic nerve - sensitive, passes in the lateral wall of the cavernous sinus, and then through the superior orbital fissure penetrates into the orbit, where it is divided into 3 parts: lacrimal nerve (n. lacrimalis), frontal nerve (n. frontalis) And but-ciliary nerve (n. nasociliaris). These nerves provide innervation of the skin of the upper face and anterior scalp from the level of the palpebral fissures to the region of the coronal suture, as well as the cornea, conjunctiva of the sclera and eyelids, the main and frontal paranasal sinuses, and the upper sections of the nasal mucosa. When the optic nerve is damaged, the corneal reflex usually decreases or disappears.

maxillary nerve - sensitive, exits the cranial cavity through a round hole and gives the following branches: zygomatic nerve (n. zygomaticus), infraorbital nerve (n. infraorbitalis), whose branches are, in particular, upper alveolar nerves (nn. alveolares superiores). They innervate the skin of the middle part of the face, the mucous membrane of the lower part of the nasal cavity, the maxillary (maxillary) sinus, hard palate, gums, as well as the periosteum and teeth of the upper jaw.

Mandibular nerve - mixed in composition, leaves the cranial cavity, exiting through the foramen ovale, and is divided into branches: chewing nerve (n. masstericus), mainly motor, but also contains a sensitive portion that provides innervation of the mandibular joint, deep temporal nerves (nn. temporales profundi)- motor, external and internal pterygoid nerves (nn. pterygoidei lateralis et medialis)- mostly motor buccal nerve (n. buccalis)- sensitive, ear-temporal nerve (n. auriculotemporalis)- sensitive, lingual nerve (n. lingualis)- sensitive, inferior alveolar nerve (n. alveolaris inferior)- mixed, passes through the mandibular canal, giving numerous branches to the tissues of the lower jaw, its distal part exits this canal through the mental foramen (foramen mentalis).

The mandibular nerve provides sensory innervation to the skin in front of the auricle and in the lower third of the face, the buccal mucosa. Its motor portion innervates the masticatory muscles (m. temporalis, m. masseter, mm. pterigoidei lateralis et medialis), as well as the anterior belly of the digastric muscle, the muscles of the diaphragm of the mouth, the muscle that strains the palatine curtain (m. tensor veli palatii), the muscle that strains eardrum (m. tensor tympani).

With damage to the trigeminal nerve disturbances of sensitivity are characteristic first of all (fig. 10.13). Possible paroxysmal pain in the face of the type of trigeminal neuralgia (see Chapter 28) or permanent pain in a particular area innervated by its branches.

If conduction along the branch of the trigeminal nerve is impaired, then anesthesia or hypoesthesia occurs in the zone of its innervation. There it turns out broken like

Rice. 10.13.Innervation of the skin of the face and head.

a - peripheral innervation: I, II, III - zones of innervation, respectively, I, II and III branches of the trigeminal (V) nerve; 1 - large occipital nerve; 2 - large ear nerve; 3 - small occipital nerve; 4 - cutaneous cervical nerve; 6 - segmental innervation: 1-5 - Zelder zones; C2 and C3 - zones of the upper cervical segments of the spinal cord; 6 - brain stem, nucleus of the spinal cord of the trigeminal nerve.

superficial and deep sensitivity. In such cases, it is sensory disturbance on the face of the peripheral type (Fig. 10.13a).

It should be borne in mind that the boundaries of the zones of innervation of the branches of the trigeminal nerve overlap each other and therefore, if one of them is damaged, the skin area on which sensitivity disorders are detected may be smaller than the zone of innervation.

Sensitivity disorders can also occur with damage to the sensory nuclei of the trigeminal nerve located in the brain stem. With the defeat of one of the two sensitive nuclei of the V cranial nerve, sensory disturbances of the dissociated type occur on the face (Fig. 10.13b).

More often this is a violation of pain and temperature sensitivity with the preservation of proprioceptive in cases of damage to the nucleus of the spinal cord (descending root) of the trigeminal nerve. Since this nucleus has a large extent, the function of its part is more often disturbed. If only its upper part is affected, then sensitivity disorders are detected on the side of the lesion in the oral part of half of the face (nose and lips), if the pathological process spreads along the core, then sensory disorders are gradually noted over an increasing area of ​​the face and, as a result, can cover its entire half. If the lower part is affected, the sensitivity will be impaired in the lateral parts of the corresponding half of the face. Thus, each “floor” of the nucleus on the face corresponds to a certain area in the form of a bracket, known as Zelder zone, or bulbous zone. With damage to the nucleus of the spinal tract of the trigeminal nerve in certain areas of Zelder, only pain and temperature sensitivity drops out, while deep and tactile sensitivity remain intact. In such cases we are talking about a sensitivity disorder of the segmental type.

The defeat of the motor nucleus, motor root or III branch of the trigeminal nerve is accompanied by the development of peripheral paralysis or paresis of the masticatory muscles. Due to their atrophy on the side of the lesion, asymmetry of these muscles may occur over time. Hypotrophy of the temporal muscle (m. temporalis). With paralysis m. masseter there is an asymmetry of the oval of the face.

The tension of the chewing muscles during chewing movements is weakened. This can be determined by placing your hands on the chewing muscles on both sides and comparing their tension. With a unilateral lesion of the masticatory muscles, it is also possible to reveal the asymmetry of the bite force. If paralysis or paresis of the external and internal pterygoid muscles occurs, then the slightly lowered lower jaw deviates from the midline towards the pathological process. With bilateral damage to the masticatory muscles, bilateral weakening of the bite, and sometimes drooping of the lower jaw, may occur. Decreased or absent mandibular reflex is also characteristic.

10.3. SOME SYNDROMES OF DAMAGE TO THE BRIDGE AND ITS CRANIAL NERVE

Localization of the pathological process in one half of the brain bridge can lead to the development of the following alternating syndromes.

Miylard-Gubler syndrome - occurs with a unilateral pathological focus in the lower part of the brain bridge and damage to the nucleus of the facial nerve or its root and the cortical-spinal tract. On the side of the lesion, peripheral paresis or paralysis of facial muscles occurs, on the opposite side - central hemiparesis or hemiplegia. Described in 1856 by the French doctor A. Millard (1830-1915) and in 1896 by the German doctor A. Gubler (1821-1897).

Fauville syndrome- occurs with a unilateral pathological focus in the lower part of the brain bridge, due to damage to the nuclei or roots of the facial and abducens nerves, as well as the pyramidal tract and sometimes the medial loop. On the side of the lesion, it manifests itself as peripheral paresis or paralysis of the facial muscles and the direct external muscle of the eye; on the opposite side - central hemiparesis or hemiplegia and, possibly, a disorder in the hemitype of pain and temperature sensitivity. Described in 1858 by the French neurologist A. Foville (1799-1879).

Raymond-Sestan syndrome - occurs with a unilateral pathological focus in the bridge due to a combined lesion of the pontine center of gaze, middle cerebellar peduncle, medial loop and pyramidal pathway. Paresis of gaze towards the pathological focus is noted, on the side of the focus - hemiataxia; on the opposite side - central hemiparesis or hemiplegia, hemitype disorders of pain and temperature sensitivity. Described in 1903 by French neuropathologists F. Raymond (1844-1910) and E. Cestan (1873-1932).

Gasperini syndrome - arises as a result of a pathological focus in the cover of the bridge. Manifested by signs of dysfunction of the auditory, facial, abducens and trigeminal nerves on the side of the lesion and a disorder of pain and temperature sensitivity according to the gemitype on the opposite side. Described by the Italian neurologist M. Gasperini.

With extracerebral localization of the pathological focus in the cranial cavity, the following syndromes are possible.

Syndrome of the lateral cistern of the bridge, or cerebellopontine angle, - a combination of signs of damage to the auditory, facial and trigeminal nerves passing through the lateral cistern of the bridge. It usually develops during the formation of a pathological process in it, more often with acoustic neuroma.

Gradenigo syndrome - hearing loss caused by a combined lesion of the sound-conducting and sound-perceiving apparatus of the auditory nerve, in combination with dysfunction of the facial, abducent and trigeminal nerves. Manifested by paresis of mimic and chewing muscles, converging strabismus, diplopia and pain in the face. Usually it is a consequence of purulent otitis media, in which the infection penetrates into the cranial cavity through the top of the pyramid of the temporal bone, which leads to the formation of limited leptomeningitis with the involvement of these cranial nerves in the process. Described in 1904 by the Italian otorhinolaryngologist G. Gradenigo (1859-1925).

With a unilateral lesion of the bridge of the so-called bridge center of gaze located in the tire, paresis of the gaze develops in the direction of the pathological process.

With bilateral damage to the bridge of the brain, the following syndromes are possible.

pontine myelinolysis syndrome - bilateral demyelination of mainly efferent pathways at the level of the brain bridge: corticospinal (pyramidal), frontopontocerebellar and corticonuclear. Manifested by central tetraparesis, signs of pseudobulbar syndrome and cerebellar insufficiency. Ophthalmoparesis, pupillary disorders, tremor, tonic convulsions, decreased activity of mental processes are characteristic. Over time, the development of sopor, coma is possible. It occurs in connection with metabolic disorders during starvation, chronic intoxication (with alcoholism, infectious diseases, severe somatic pathology). There is an opinion that pontine myelinolysis can be provoked by excessive hydration, leading to severe hyponatremia with cerebral edema, which occurs more often in patients with alcoholism, since in them abstinence from alcohol leads to an increase in the blood level of antidiuretic hormone and the likelihood of developing hyponatremia with intravenous infusion of fluids and treatment with diuretics is particularly great. On CT and MRI, low-density foci are found in the central part of the pons and in the adjacent parts of the brain stem. The selectivity of the defeat of the base of the bridge is explained by the peculiarities of its myeloarchitectonics.

Dancing eye syndrome (ocular myoclonus) - hyperkinesis of the eyeballs in the form of friendly fast, irregular, uneven in amplitude of their movements, performed in the horizontal plane and especially pronounced in the initial stage of fixing the gaze on the object. Possible with damage to the tire of the bridge or midbrain.

Roth-Bilshovsky syndrome (Pseudoophthalmoplegia Bilshovsky) - loss of the ability to voluntary movements of the eyeballs to the sides with the preservation of their reactions to stimulation of the labyrinth, while convergence of the eyes is possible and their movements in the vertical plane are preserved. It occurs due to the growth of a tumor or circulatory disorders in the trunk cover, it may also be a manifestation of multiple sclerosis. Described in 1901 by the domestic neuropathologist V.K. Roth (1848-1916), in 1903 the German neuropathologist M. Bielschowsky (1869-1940).