Defeat of the VIII pair of cranial nerves. V-IX pairs of cranial nerves 8 cranial nerve

The first two nerves have significant differences from the rest of the 10 topics, since in fact they are a continuation of the brain, which is formed by protrusion brain bubbles. In addition, they do not have nodes (nuclei) that other 10 have. The nuclei of the cranial nerves, like other ganglia of the central nervous system, are concentrations of neurons that perform certain functions.

10 pairs, with the exception of the first two, are not formed from two types of roots (anterior and posterior), as is the case with spinal cords, but represent only one root - anterior (in III, IV, VI, XI, XII) or posterior (in V, from VII to X).

The common term for this type of nerve is "cranial nerves", although Russian-language sources prefer to use "cranial nerves". This is not a mistake, but it is preferable to use the first term - in accordance with the international anatomical classification.

All cranial nerves are laid in the embryo already in the second month. At the 4th month of prenatal development, myelination of the vestibular nerve begins - the overlay of myelin fibers. Motor fibers go through this stage earlier than sensory ones. The state of nerves in the postnatal period is characterized by the fact that, as a result, the first two pairs are the most developed, the rest continue to become more complicated. Final myelination occurs at about one and a half years of age.

Classification

Before proceeding to a detailed consideration of each individual pair (anatomy and functioning), it is best to familiarize yourself with them with the help of brief characteristics.

Table 1: Characteristics of 12 pairs

Nerves with sensory fibers

Olfactory begins in the nerve cells of the nasal mucosa, then passes through the cribriform plate into the cranial cavity to the olfactory bulb and rushes into the olfactory tract, which, in turn, forms a triangle. At the level of this triangle and tract, in the olfactory tubercle, the nerve ends.

The ganglion cells of the retina give rise to the optic nerve. Entering the cranial cavity, it forms a cross and in the further passage begins to be called the "optic tract", which ends in the lateral geniculate body. From it originates the central part of the visual path, going to the occipital lobe.

Auditory (aka vestibulocochlear) is made up of two. The cochlear root, formed from the cells of the spiral ganglion (belonging to the cochlear lamina), is responsible for the transmission of auditory impulses. The vestibular, coming from the vestibular ganglion, carries the impulses of the vestibular labyrinth. Both roots articulate into one in the internal auditory canal and go inward in the middle of the pons and medulla oblongata(slightly lower is the VII pair). The fibers of the vestibule - a significant part of them - pass into the posterior longitudinal and vestibulospinal bundles, the cerebellum. Cochlear fibers stretch to the lower tubercles of the quadrigemina and the middle geniculate body. Here originates the central auditory pathway, ending in the temporal gyrus.

There is another sensory nerve that has received a zero number. At first, it was called "additional olfactory", but was later renamed terminal due to the location of the terminal plate nearby. Scientists have yet to reliably establish the functions of this pair.

Motor

The oculomotor, starting in the nuclei of the midbrain (below the aqueduct), appears on the brain base in the region of the pedicle. Before heading to the eye socket, it forms an extensive system. Its upper section is made up of two branches that go to the muscles - the upper straight line and the one that raises the eyelid. The lower part is represented by three branches, two of which innervate the rectus muscles - the median and lower, respectively, and the third goes to the inferior oblique muscle.

The nuclei lying in front of the aqueduct at the same level as the lower tubercles of the quadrupoloma, create the beginning of the trochlear nerve, which in the area of ​​​​the roof of the fourth ventricle appears on the surface, forms a decussation and stretches to the superior oblique muscle located in the orbit.

From the nuclei located in the tire of the bridge, fibers pass, forming the abducens nerve. It has an exit where the middle is located between the pyramid of the medulla oblongata and the bridge, after which it rushes into the orbit to the lateral rectus muscle.

Two components form the 11th, accessory, nerve. The upper one begins in the medulla oblongata - its cerebral nucleus, the lower one - in the dorsal (its upper part), and more specifically, the accessory nucleus, which is localized in the anterior horns. The roots of the lower part, passing through the large occipital foramen, are directed into the cranial cavity and connected to the upper section of the nerve, creating a single trunk. It, leaving the skull, is divided into two branches. The fibers of the upper develop into the fibers of the 10th nerve, and the lower goes to the sternocleidomastoid and trapezius muscles.

Nucleus hypoglossal nerve is located in the rhomboid fossa (its lower zone), and the roots pass to the surface of the medulla oblongata in the middle of the olive and pyramid, after which they are combined into a single whole. The nerve emerges from the cranial cavity, then goes to the muscles of the tongue, where it produces 5 terminal branches.

Nerves with mixed fibers

The anatomy of this group is complex due to the branched structure, which allows innervating many departments and organs.

ternary

The area between the middle cerebellar peduncle and the pons is its exit point. Nucleus temporal bone forms nerves: ophthalmic, maxillary and mandibular. They have sensory fibers, motor fibers are added to the latter. The orbital is located in the orbit (upper zone) and branches into the nasociliary, lacrimal and frontal. The maxillary has an exit to the surface of the face, after it penetrates through the infraorbital space.

The mandibular is divided into anterior (motor) and posterior (sensory) parts. They give the nervous network:

• the anterior is divided into chewing, deep temporal, lateral pterygoid and buccal nerves;
• posterior - into the median pterygoid, ear-temporal, inferior alveolar, mental and lingual, each of which is again divided into small branches (their number is 15 in total).

Mandibular department trigeminal nerve communicates with the auricular, submandibular and sublingual nuclei.

The name of this nerve is known more than the other 11 pairs: many are familiar, at least by hearsay, about

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VI pair - abducens nerves

Abducens nerve (p. abducens) - motor. Abducens nucleus(nucleus n. abducentis) located in the anterior part of the bottom of the IV ventricle. The nerve exits the brain at the posterior edge of the pons, between it and the pyramid of the medulla oblongata, and soon outside of the back of the Turkish saddle enters the cavernous sinus, where it is located along the outer surface of the internal carotid artery (Fig. 1). Further penetrates through the upper orbital fissure into the orbit and follows forward over the oculomotor nerve. Innervates the external rectus muscle of the eye.

Rice. 1. Nerves of the oculomotor apparatus (diagram):

1 - superior oblique muscle of the eye; 2 - the upper rectus muscle of the eye; 3 - block nerve; 4 - oculomotor nerve; 5 - lateral rectus muscle of the eye; 6 - lower rectus muscle of the eye; 7 - abducens nerve; 8 - lower oblique muscle of the eye; 9 - medial rectus muscle of the eye

VII pair - facial nerves

(p. facialis) develops in connection with the formations of the second gill arch, so it innervates all the muscles of the face (mimic). The nerve is mixed, including motor fibers from its efferent nucleus, as well as sensory and autonomic (gustatory and secretory) fibers belonging to a closely related facial intermediate nerve(n. intermedius).

Motor nucleus facial nerve (nucleus n. facialis) is located at the bottom of the IV ventricle, in the lateral region of the reticular formation. The facial nerve root emerges from the brain along with the intermediate nerve root anterior to the vestibulocochlear nerve, between the posterior margin of the pons and the olive of the medulla oblongata. Further, the facial and intermediate nerves enter the internal auditory opening and enter the canal of the facial nerve. Here, both nerves form a common trunk, making two turns corresponding to the bends of the canal (Fig. 2, 3).

Rice. 2. Facial nerve (diagram):

1 - internal carotid plexus; 2 - knee assembly; 3 - facial nerve; 4 - facial nerve in the internal auditory canal; 5 - intermediate nerve; 6 - the motor nucleus of the facial nerve; 7 - upper salivary nucleus; 8 - the core of a single path; 9 - occipital branch of the posterior ear nerve; 10 - branches to the ear muscles; 11 - posterior ear nerve; 12 — a nerve to a stresechkovy muscle; 13 - stylomastoid opening; 14 - tympanic plexus; 15 - tympanic nerve; 16 - glossopharyngeal nerve; 17 - posterior belly of the digastric muscle; 18 - stylohyoid muscle; 19 - drum string; 20 - lingual nerve (from the mandibular); 21 - submandibular salivary gland; 22 - sublingual salivary gland; 23 - submandibular node; 24 - pterygopalatine node; 25 - ear node; 26 - nerve of the pterygoid canal; 27 - small stony nerve; 28 - deep stony nerve; 29 - large stony nerve

Rice. 3

I - a large stony nerve; 2 - node knee of the facial nerve; 3 - front channel; 4 - tympanic cavity; 5 - drum string; 6 - hammer; 7 - anvil; 8 - semicircular tubules; 9 - spherical bag; 10 - elliptical bag; 11 - node vestibule; 12 - internal auditory meatus; 13 - nuclei of the cochlear nerve; 14 - lower cerebellar peduncle; 15 — kernels of a pre-door nerve; 16 - medulla oblongata; 17 - vestibulocochlear nerve; 18 - motor portion of the facial nerve and intermediate nerve; 19 - cochlear nerve; 20 - vestibular nerve; 21 - spiral ganglion

First, the common trunk is located horizontally, heading anteriorly and laterally above the tympanic cavity. Then, according to the bend of the facial canal, the trunk turns at a right angle back, forming a knee (geniculum n. facialis) and a knee node (ganglion geniculi), belonging to the intermediate nerve. Having passed over the tympanic cavity, the trunk makes a second downward turn, located behind the cavity of the middle ear. In this area, branches of the intermediate nerve depart from the common trunk, the facial nerve exits the canal through the stylomastoid foramen and soon enters the parotid salivary gland. The length of the trunk of the extracranial facial nerve ranges from 0.8 to 2.3 cm (usually 1.5 cm), and thickness - from 0.7 to 1.4 mm: the nerve contains 3500-9500 myelinated nerve fibers, among which thick ones predominate.

In the parotid salivary gland, at a depth of 0.5-1.0 cm from its outer surface, the facial nerve divides into 2-5 primary branches, which are divided into secondary ones, forming parotid plexus(plexus intraparotidus)(Fig. 4).

Rice. four.

a - the main branches of the facial nerve, right side view: 1 - temporal branches; 2 - zygomatic branches; 3 - parotid duct; 4 - buccal branches; 5 - marginal branch mandible; 6 - cervical branch; 7 - digastric and stylohyoid branches; 8 - the main trunk of the facial nerve at the exit of the stylomastoid foramen; 9 - posterior ear nerve; 10 - parotid salivary gland;

b - facial nerve and parotid gland in a horizontal section: 1 - medial pterygoid muscle; 2 - branch of the lower jaw; 3 - chewing muscle; 4 - parotid salivary gland; 5 - mastoid process; 6 - the main trunk of the facial nerve;

c - three-dimensional diagram of the relationship between the facial nerve and the parotid salivary gland: 1 - temporal branches; 2 - zygomatic branches; 3 - buccal branches; 4 - marginal branch of the lower jaw; 5 - cervical branch; 6 - the lower branch of the facial nerve; 7 - digastric and stylohyoid branches of the facial nerve; 8 - the main trunk of the facial nerve; 9 - posterior ear nerve; ten - upper branch facial nerve

There are two forms external structure parotid plexus: reticular and main. At network form the nerve trunk is short (0.8-1.5 cm), in the thickness of the gland it is divided into many branches that have multiple connections with each other, as a result of which a narrow-loop plexus is formed. There are multiple connections with the branches of the trigeminal nerve. At trunk form the nerve trunk is relatively long (1.5-2.3 cm), divided into two branches (upper and lower), which give rise to several secondary branches; there are few connections between the secondary branches, the plexus is broadly looped (Fig. 5).

Rice. 5.

a - network structure; b - main structure;

1 - facial nerve; 2 - chewing muscle

On its way, the facial nerve gives off branches when passing through the canal, as well as when leaving it. Inside the channel, a number of branches depart from it:

1. Greater stony nerve(n. petrosus major) originates near the node of the knee, leaves the canal of the facial nerve through the cleft of the canal of the large stony nerve and passes along the sulcus of the same name to the ragged foramen. Having penetrated through the cartilage to the outer base of the skull, the nerve connects to the deep petrosal nerve, forming pterygoid canal nerve(p. canalis pterygoidei), entering the pterygoid canal and reaching the pterygopalatine node.

The large stony nerve contains parasympathetic fibers to the pterygopalatine ganglion, as well as sensory fibers from the cells of the geniculate ganglion.

2. Stapes nerve (p. stapedius) - a thin trunk, branches off in the canal of the facial nerve at the second turn, penetrates into tympanic cavity where it innervates the stapedius muscle.

3. drum string(chorda tympani) is a continuation of the intermediate nerve, separates from the facial nerve in the lower part of the canal above the stylomastoid opening and enters through the tubule of the tympanic string into the tympanic cavity, where it lies under the mucous membrane between the long leg of the anvil and the handle of the malleus. Through the stony-tympanic fissure, the tympanic string enters the outer base of the skull and merges with the lingual nerve in the infratemporal fossa.

At the point of intersection with the lower alveolar nerve, the drum string gives a connecting branch with the ear node. The string tympani consists of preganglionic parasympathetic fibers to the submandibular ganglion and taste-sensitive fibers to the anterior two-thirds of the tongue.

4. Connecting branch with tympanic plexus (r. communicans cum plexus tympanico) is a thin branch; starts from the node of the knee or from the large stony nerve, passes through the roof of the tympanic cavity to the tympanic plexus.

Upon exiting the canal, the following branches depart from the facial nerve.

1. Posterior ear nerve(p. auricularis posterior) departs from the facial nerve immediately after exiting the stylomastoid opening, goes back and up the anterior surface of the mastoid process, dividing into two branches: ear (r. auricularis), innervating the posterior ear muscle, and occipital (r. occipitalis), which innervates the occipital belly of the supracranial muscle.

2. digastric branch(r. digasricus) arises slightly below the ear nerve and, going down, innervates the posterior belly of the digastric muscle and the stylohyoid muscle.

3. Connecting branch with glossopharyngeal nerve (r. communicans cum nervo glossopharyngeo) branches off near the stylomastoid opening and extends anteriorly and down the stylo-pharyngeal muscle, connecting with the branches of the glossopharyngeal nerve.

Branches of the parotid plexus:

1. Temporal branches (rr. temporales) (2-4 in number) go up and are divided into 3 groups: anterior, innervating the upper part of the circular muscle of the eye, and the muscle wrinkling the eyebrow; medium, innervating the frontal muscle; posterior, innervating vestigial muscles auricle.

2. Zygomatic branches (rr. zygomatici) (3-4 in number) extend forward and upward to the lower and lateral parts of the circular muscle of the eye and the zygomatic muscle, which innervate.

3. Buccal branches (rr. buccales) (3-5 in number) run horizontally anteriorly along the outer surface of the masticatory muscle and supply the muscles around the nose and mouth with branches.

4. Marginal branch of the lower jaw(r. marginalis mandibularis) runs along the edge of the lower jaw and innervates the muscles that lower the corner of the mouth and lower lip, the chin muscle and the laughter muscle.

5. Cervical branch (r. colli) descends to the neck, connects to the transverse nerve of the neck and innervates t. platysma.

Intermediate nerve(p. intermedins) consists of preganglionic parasympathetic and sensory fibers. Sensitive unipolar cells are located in the knee node. The central processes of the cells ascend as part of the nerve root and terminate in the nucleus of the solitary pathway. Peripheral processes of sensory cells go through the tympanic string and the large stony nerve to the mucous membrane of the tongue and soft palate.

Secretory parasympathetic fibers originate in the superior salivary nucleus in the medulla oblongata. The root of the intermediate nerve emerges from the brain between the facial and vestibulocochlear nerves, joins the facial nerve and goes in the canal of the facial nerve. The fibers of the intermediate nerve leave the trunk of the facial, passing into the tympanic string and the large stony nerve, reach the submandibular, hyoid and pterygopalatine nodes.

VIII pair - vestibulocochlear nerves

(n. vestibulocochlearis) - sensitive, consists of two functionally different parts: vestibular and cochlear (see Fig. 3).

Vestibular nerve (n. vestibularis) conducts impulses from the static apparatus of the vestibule and semicircular canals of the labyrinth of the inner ear. Cochlear nerve (n. cochlearis) provides the transmission of sound stimuli from the spiral organ of the cochlea. Each part of the nerve has its own sensory nodes containing bipolar nerve cells: the vestibulum - vestibular ganglion (ganglion vestibulare) located at the bottom of the internal auditory canal; cochlear part - cochlear node (cochlear node), ganglion cochleare (ganglion spirale cochleare), which is in the snail.

The vestibular node is elongated, it distinguishes two parts: upper (pars superior) and lower (pars inferior). The peripheral processes of the cells of the upper part form the following nerves:

1) elliptic saccular nerve(n. utricularis), to the cells of the elliptical sac of the vestibule of the cochlea;

2) anterior ampullar nerve(n. ampularis anterior), to the cells of the sensitive strips of the anterior membranous ampulla of the anterior semicircular canal;

3) lateral ampullar nerve(p. ampularis lateralis), to the lateral membranous ampulla.

From the lower part of the vestibular node, peripheral processes of cells go in the composition spherical saccular nerve(n. saccularis) to the auditory spot of the sac and in the composition posterior ampullar nerve(n. ampularis posterior) to the posterior membranous ampulla.

The central processes of the cells of the vestibular ganglion form vestibular (upper) root, which exits through the internal auditory opening behind the facial and intermediate nerves and enters the brain near the exit of the facial nerve, reaching 4 vestibular nuclei in the bridge: medial, lateral, superior and inferior.

From the cochlear node, the peripheral processes of its bipolar nerve cells go to the sensitive epithelial cells spiral organ of the cochlea, forming together the cochlear part of the nerve. The central processes of the cochlear ganglion cells form the cochlear (lower) root, which goes along with the upper root into the brain to the dorsal and ventral cochlear nuclei.

IX pair - glossopharyngeal nerves

(p. glossopharyngeus) - the nerve of the third branchial arch, mixed. It innervates the mucous membrane of the posterior third of the tongue, the palatine arches, the pharynx and the tympanic cavity, the parotid salivary gland and the stylo-pharyngeal muscle (Fig. 6, 7). There are 3 types of nerve fibers in the composition of the nerve:

1) sensitive;

2) motor;

3) parasympathetic.

Rice. 6.

1 - elliptical-saccular nerve; 2 - anterior ampullar nerve; 3 - posterior ampullar nerve; 4 - spherical-saccular nerve; 5 - the lower branch of the vestibular nerve; 6 - the upper branch of the vestibular nerve; 7 - vestibular node; 8 - root of the vestibular nerve; 9 - cochlear nerve

Rice. 7.

1 - tympanic nerve; 2 - knee of the facial nerve; 3 - lower salivary nucleus; 4 - double core; 5 - the core of a single path; 6 - the core of the spinal cord; 7, 11 - glossopharyngeal nerve; 8 - jugular hole; 9 - connecting branch to the ear branch vagus nerve; 10 - upper and lower nodes of the glossopharyngeal nerve; 12 - vagus nerve; 13 - the upper cervical node of the sympathetic trunk; 14 - sympathetic trunk; 15 - sinus branch of the glossopharyngeal nerve; 16 - internal carotid artery; 17 - common carotid artery; 18 - external carotid artery; 19 - tonsil, pharyngeal and lingual branches of the glossopharyngeal nerve (pharyngeal plexus); 20 - stylopharyngeal muscle and nerve to it from the glossopharyngeal nerve; 21 - auditory tube; 22 - tubal branch of the tympanic plexus; 23 - parotid salivary gland; 24 - ear-temporal nerve; 25 - ear node; 26 - mandibular nerve; 27 - pterygopalatine node; 28 - small stony nerve; 29 - nerve of the pterygoid canal; 30 - deep stony nerve; 31 - a large stony nerve; 32 - carotid-tympanic nerves; 33 - stylomastoid opening; 34 - tympanic cavity and tympanic plexus

Sensitive fibers- processes of afferent cells of the upper and lower nodes (ganglia superior et inferior). The peripheral processes follow as part of the nerve to the organs where they form receptors, the central ones go to the medulla oblongata, to the sensitive solitary tract nucleus (nucleus tractus solitarii).

motor fibers originate from nerve cells in common with the vagus nerve double nucleus (nucleus ambiguous) and pass as part of the nerve to the stylo-pharyngeal muscle.

Parasympathetic fibers originate in the autonomic parasympathetic lower salivary nucleus (nucleus salivatorius superior) which is located in the medulla oblongata.

The glossopharyngeal nerve root exits the medulla oblongata behind the exit site of the vestibulocochlear nerve and, together with the vagus nerve, leaves the skull through the jugular foramen. In this hole, the nerve has the first extension - upper node (ganglion superior), and at the exit from the hole - the second extension - lower node (ganglion inferior).

Outside the skull, the glossopharyngeal nerve lies first between the internal carotid artery and the internal jugular vein, and then in a gentle arc it goes around the back and outside of the stylo-pharyngeal muscle and comes from the inside of the hyoid-lingual muscle to the root of the tongue, dividing into terminal branches.

Branches of the glossopharyngeal nerve.

1. Tympanic nerve (p. tympanicus) branches off from the lower node and passes through the tympanic canaliculus into the tympanic cavity, where it forms together with the carotid-tympanic nerves tympanic plexus(plexus tympanicus). The tympanic plexus innervates the mucous membrane of the tympanic cavity and the auditory tube. The tympanic nerve leaves the tympanic cavity through its upper wall how small stony nerve(p. petrosus minor) and goes to the ear node. The preganglionic parasympathetic secretory fibers, suitable as part of the small stony nerve, are interrupted in the ear node, and the postganglionic secretory fibers enter the ear-temporal nerve and reach the parotid salivary gland in its composition.

2. Branch of the stylo-pharyngeal muscle(r. t. stylopharyngei) goes to the muscle of the same name and the mucous membrane of the pharynx.

3. Sinus branch (r. sinus carotid), sensitive, branches in the carotid glomus.

4. almond branches(rr. tonsillares) are sent to the mucous membrane of the palatine tonsil and arches.

5. Pharyngeal branches (rr. pharyngei) (3-4 in number) approach the pharynx and, together with the pharyngeal branches of the vagus nerve and sympathetic trunk, form on the outer surface of the pharynx pharyngeal plexus(plexus pharyngealis). Branches depart from it to the muscles of the pharynx and to the mucous membrane, which, in turn, form intramural nerve plexuses.

6. Lingual branches (rr. linguales) - the final branches of the glossopharyngeal nerve: contain sensitive taste fibers to the mucous membrane of the posterior third of the tongue.

Human Anatomy S.S. Mikhailov, A.V. Chukbar, A.G. Tsybulkin

The brain (encephalon) is divided into brain stem , big brain and cerebellum. In the brain stem there are structures related to the segmental apparatus of the brain, and subcortical integration centers. From the brain stem, as well as from the spinal cord, nerves depart. They got the name cranial nerves.

There are 12 pairs of cranial nerves. They are designated by Roman numerals in the order of their location from bottom to top. Unlike spinal nerves, always mixed (both sensory and motor), cranial nerves can be sensory, motor and mixed. Sensory cranial nerves: I - olfactory, II - visual, VIII - auditory. There are also five purely motor: III - oculomotor, IV - block, VI - efferent, XI - accessory, XII - sublingual. And four mixed: V - trigeminal, VII - facial, IX - glossopharyngeal, X - wandering. In addition, some cranial nerves contain autonomic nuclei and fibers.

Characterization and description of individual cranial nerves:

I couple - olfactory nerves(nn.olfactorii). Sensitive. It is formed by 15-20 olfactory filaments, consisting of axons of olfactory cells located in the mucous membrane of the nasal cavity. The filaments enter the skull and end in the olfactory bulb, from where the olfactory path begins to the cortical end of the olfactory analyzer - the hippocampus.

When the olfactory nerve is damaged, the sense of smell is disturbed.

II pair - optic nerve(n. opticus). Sensitive. Consists of nerve fibers formed by processes of nerve cells in the retina. The nerve enters the cranial cavity, forms the optic chiasm in the diencephalon, from which the visual tracts begin. Function optic nerve is the transmission of light stimuli.

With the defeat of various parts of the visual analyzer, there are disorders associated with a decrease in visual acuity up to complete blindness, as well as disturbances in light perception and visual fields.

III pair - oculomotor nerve(n. oculomotorius). Mixed: motor, vegetative. It starts from the motor and autonomic nuclei located in the midbrain.

The oculomotor nerve (motor part) innervates the muscles of the eyeball and upper eyelid.

Parasympathetic fibers the oculomotor nerve is innervated by smooth muscles that constrict the pupil; they also approach the muscle that changes the curvature of the lens, as a result of which the accommodation of the eye changes.

When damaged oculomotor nerves strabismus occurs, accommodation is disturbed, the size of the pupil changes.

IV pair - trochlear nerve(n. trochlearis). Motor. It starts from the motor nucleus located in the midbrain. Innervates the superior oblique muscle of the eye.

V pair - trigeminal nerve(n. trigeminus). Mixed: motor and sensory.

It has three sensitive cores where the fibers coming from the trigeminal ganglion end:

Bridge in the hindbrain

Inferior nucleus of the trigeminal nerve in the medulla oblongata

Midbrain in the midbrain.

Sensory neurons receive information from receptors skin face, from the skin of the lower eyelid, nose, upper lip, teeth, upper and lower gums, from the mucous membranes of the nasal and oral cavity, tongue, eyeball and from the meninges.

Motor nucleus located in the cover of the bridge. Motor neurons innervate the muscles of mastication, muscles of the palatine curtain, as well as muscles that contribute to the tension of the tympanic membrane.

When a nerve is damaged, paralysis of the masticatory muscles occurs, a violation of sensitivity in the corresponding areas up to its loss, and pain occurs.

VI pair - abducens nerve(n. abducens). Motor. The core is located in the bridge tire. Innervates only one muscle of the eyeball - the external straight line, which moves the eyeball outward. When it is damaged, convergent strabismus is observed.

VII pair - facial nerve(n. facialis). Mixed: motor, sensory, vegetative.

Motor nucleus located in the cover of the bridge. It innervates the mimic muscles, the circular muscle of the eye, mouth, the muscle of the auricle and the subcutaneous muscle of the neck.

sensitive - single track core medulla oblongata. This receives information on sensitive taste fibers, starting from the taste buds located in the anterior 2/3 of the tongue.

Vegetative - superior salivary nucleus located in the cover of the bridge. Efferent parasympathetic salivary fibers begin from it to the sublingual and submandibular, as well as the parotid salivary and lacrimal glands.

If the facial nerve is damaged, the following disorders are observed: paralysis of the facial muscles occurs, the face becomes asymmetrical, speech becomes difficult, swallowing is disturbed, taste and tearing are disturbed, etc.

VIII pair - vestibulocochlear nerve(n. vestibulocochlearis). Sensitive. Allocate snails and vestibular nuclei located in the lateral divisions of the rhomboid fossa in the medulla oblongata and the pontine tegmentum. Sensory nerves (auditory and vestibular) are formed by sensory nerve fibers coming from the organs of hearing and balance.

Damage to the vestibular nerve often causes dizziness, rhythmic twitches eyeballs, staggering when walking. Damage to the auditory nerve leads to hearing loss, the appearance of sensations of noise, squeak, rattle.

IX pair - glossopharyngeal nerve(n. glosspharyngeus). Mixed: motor, sensory, vegetative.

sensitive core - single track core medulla oblongata. This nucleus is common with the nucleus of the facial nerve. From the glossopharyngeal nerve depends on the perception of taste in the back third of the tongue. Thanks to the glossopharyngeal nerve, the sensitivity of the mucous membranes of the pharynx, larynx, trachea, and soft palate is also provided.

Motor nucleus- double core, located in the medulla oblongata, innervates the muscles of the soft palate, epiglottis, pharynx, larynx.

Vegetative nucleus- parasympathetic inferior salivary nucleus medulla oblongata, which innervates the parotid, submandibular and sublingual salivary glands.

If this cranial nerve is damaged, there is a violation of taste in the posterior third of the tongue, dry mouth is observed, a violation of the sensitivity of the pharynx occurs, paralysis of the soft palate is observed, choking when swallowing.

X pair - nervus vagus(n. vagus). Mixed nerve: motor, sensory, autonomic.

sensitive core - single track core medulla oblongata. Sensitive fibers transmit irritation from the dura mater, from the mucous membranes of the pharynx, larynx, trachea, bronchi, lungs, gastrointestinal tract and others. internal organs. Most of the interoreceptive sensations are associated with the vagus nerve.

Motor - double core medulla oblongata, fibers from it go to the striated muscles of the pharynx, soft palate, larynx and epiglottis.

Autonomic nucleus - dorsal nucleus of the vagus nerve(medulla oblongata) forms the longest processes of neurons in comparison with other cranial nerves. Innervates the smooth muscles of the trachea, bronchi, esophagus, stomach, small intestine, upper part of the large intestine. This nerve also innervates the heart and blood vessels.

When the vagus nerve is damaged, the following symptoms occur: taste is disturbed in the posterior third of the tongue, the sensitivity of the pharynx and larynx is lost, paralysis of the soft palate occurs, sagging of the vocal cords, etc. Some similarity in the symptoms of damage to the IX and X pairs of cranial nerves is due to the presence of nuclei in the brain stem that they have in common.

XI pair - accessory nerve(n. accessorius). motor nerve. It has two nuclei: in the oblong and in spinal cord. Innervates the sternocleidomastoid muscle and the trapezius muscle. The function of these muscles is to turn the head in the opposite direction, raise the shoulder blades, raise the shoulders above the horizontal.

In case of damage, there is difficulty in turning the head to the healthy side, a lowered shoulder, limited raising of the arm above the horizontal line.

XII pair - hypoglossal nerve(n. hypoglossus). This is the motor nerve. The nucleus is located in the medulla oblongata. The fibers of the hypoglossal nerve innervate the muscles of the tongue and partly the muscles of the neck.

When damaged, either weakness of the muscles of the tongue (paresis) or their complete paralysis occurs. This leads to a violation of speech, it becomes indistinct, weaving.

The structure of the nerve includes two roots: the cochlear, which is the lower, and the vestibule, which is the upper root.

The cochlear part of the nerve is sensitive, auditory. It starts from the cells of the spiral node, in the cochlea of ​​the labyrinth. The dendrites of the cells of the spiral ganglion go to the auditory receptors - the hair cells of the organ of Corti.

The axons of the cells of the spiral ganglion are located in the internal auditory canal. The nerve passes in the pyramid of the temporal bone, then enters the brainstem at the level of the upper part of the medulla oblongata, ending in the nuclei of the cochlear part (anterior and posterior). Most of the axons from the nerve cells of the anterior cochlear nucleus cross over to the other side of the pons. A minority of axons do not participate in the decussation.

Axons end on the cells of the trapezoid body and the upper olive on both sides. Axons from these brain structures form a lateral loop ending in the quadrigemina and on the cells of the medial geniculate body. The axons of the posterior cochlear nucleus cross in the area of ​​the median line of the bottom of the IV ventricle.

On the opposite side, the fibers connect with the axons of the lateral loop. The axons of the posterior cochlear nucleus terminate in the inferior colliculi of the quadrigemina. The part of the axons of the posterior nucleus that is not involved in the decussation connects to the fibers of the lateral loop on its side.

Damage symptoms. When the fibers of the auditory cochlear nuclei are damaged, there is no impairment of hearing function. When a nerve is damaged various levels auditory hallucinations, symptoms of irritation, hearing loss, deafness may appear. Decrease in hearing acuity or deafness on the one hand occurs when the nerve is damaged at the receptor level, when the cochlear part of the nerve and its anterior or posterior nuclei are damaged.

Symptoms of irritation in the form of a sensation of whistling, noise, cod may also join. This is due to irritation of the cortex of the middle part of the superior temporal gyrus by a variety of pathological processes in this area, such as tumors.

Front part. In the internal auditory meatus, there is a vestibular node formed by the first neurons of the pathway of the vestibular analyzer. Dendrites of neurons form receptors of the labyrinth of the inner ear, located in the membranous sacs and in the ampullae of the semicircular canals.

The axons of the first neurons make up the vestibular part of the VIII pair of cranial nerves, located in the temporal bone and entering through the internal auditory opening into the substance of the brain in the region of the cerebellopontine angle. The nerve fibers of the vestibular part end on the neurons of the vestibular nuclei, which are the second neurons of the pathway of the vestibular analyzer. The nuclei of the vestibular part are located at the bottom of the V ventricle, in its lateral part, and are represented by lateral, medial, upper, lower.

The neurons of the lateral nucleus of the vestibule give rise to the vestibulo-spinal pathway, which is part of the spinal cord and ends in the neurons of the anterior horns.

The axons of the neurons of this nucleus form a medial longitudinal bundle, located in the spinal cord on both sides. The course of the fibers in the bundle has two directions: descending and ascending. descending nerve fibers participate in the formation of part of the anterior cord. Ascending fibers are located to the nucleus of the oculomotor nerve. Fibers of the medial longitudinal beam have a connection with the nuclei of III, IV, VI pairs of cranial nerves, due to which impulses from the semicircular canals are transmitted to the nuclei of the oculomotor nerves, causing the movement of the eyeballs when changing the position of the body in space. There are also bilateral connections with the cerebellum, the reticular formation, the posterior nucleus of the vagus nerve.

Symptoms of the lesion are characterized by a triad of symptoms: dizziness, nystagmus, impaired coordination of movement. There is a vestibular ataxia, manifested by a shaky gait, deviation of the patient in the direction of the lesion. Dizziness is characterized by attacks lasting up to several hours, which may be accompanied by nausea and vomiting. The attack is accompanied by horizontal or horizontal-rotary nystagmus. When a nerve is damaged on one side, nystagmus develops in the direction opposite to the lesion. With irritation of the vestibular part, nystagmus develops in the direction of the lesion.

Peripheral lesions of the vestibulocochlear nerve can be of two types: labyrinthine and radicular syndromes. In both cases, there is a simultaneous violation of the functioning of the auditory and vestibular analyzer. The radicular syndrome of peripheral lesions of the vestibulocochlear nerve is characterized by the absence of dizziness, and may manifest as an imbalance.

8. VIII pair of cranial nerves - vestibulocochlear nerve

The structure of the nerve includes two roots: the cochlear, which is the lower, and the vestibule, which is the upper root.

The cochlear part of the nerve is sensitive, auditory. It starts from the cells of the spiral node, in the cochlea of ​​the labyrinth. The dendrites of the cells of the spiral ganglion go to the auditory receptors - the hair cells of the organ of Corti.

The axons of the cells of the spiral ganglion are located in the internal auditory canal. The nerve passes in the pyramid of the temporal bone, then enters the brainstem at the level of the upper part of the medulla oblongata, ending in the nuclei of the cochlear part (anterior and posterior). Most of the axons from the nerve cells of the anterior cochlear nucleus cross over to the other side of the pons. A minority of axons do not participate in the decussation.

Axons end on the cells of the trapezoid body and the upper olive on both sides. Axons from these brain structures form a lateral loop ending in the quadrigemina and on the cells of the medial geniculate body. The axons of the posterior cochlear nucleus cross in the area of ​​the median line of the bottom of the IV ventricle.

On the opposite side, the fibers connect with the axons of the lateral loop. The axons of the posterior cochlear nucleus terminate in the inferior colliculi of the quadrigemina. The part of the axons of the posterior nucleus that is not involved in the decussation connects to the fibers of the lateral loop on its side.

Damage symptoms. When the fibers of the auditory cochlear nuclei are damaged, there is no impairment of hearing function. With damage to the nerve at various levels, auditory hallucinations, symptoms of irritation, hearing loss, deafness may appear. Decrease in hearing acuity or deafness on the one hand occurs when the nerve is damaged at the receptor level, when the cochlear part of the nerve and its anterior or posterior nuclei are damaged.

Symptoms of irritation in the form of a sensation of whistling, noise, cod may also join. This is due to irritation of the cortex of the middle part of the superior temporal gyrus by a variety of pathological processes in this area, such as tumors.

Front part. In the internal auditory meatus, there is a vestibular node formed by the first neurons of the pathway of the vestibular analyzer. Dendrites of neurons form receptors of the labyrinth of the inner ear, located in the membranous sacs and in the ampullae of the semicircular canals.

The axons of the first neurons make up the vestibular part of the VIII pair of cranial nerves, located in the temporal bone and entering through the internal auditory opening into the substance of the brain in the region of the cerebellopontine angle. The nerve fibers of the vestibular part end on the neurons of the vestibular nuclei, which are the second neurons of the pathway of the vestibular analyzer. The nuclei of the vestibular part are located at the bottom of the V ventricle, in its lateral part, and are represented by lateral, medial, upper, lower.

The neurons of the lateral nucleus of the vestibule give rise to the vestibulo-spinal pathway, which is part of the spinal cord and ends in the neurons of the anterior horns.

The axons of the neurons of this nucleus form a medial longitudinal bundle, located in the spinal cord on both sides. The course of the fibers in the bundle has two directions: descending and ascending. Descending nerve fibers are involved in the formation of part of the anterior cord. Ascending fibers are located to the nucleus of the oculomotor nerve. The fibers of the medial longitudinal bundle have a connection with the nuclei of III, IV, VI pairs of cranial nerves, due to which impulses from the semicircular canals are transmitted to the nuclei of the oculomotor nerves, causing the movement of the eyeballs when the body position changes in space. There are also bilateral connections with the cerebellum, the reticular formation, the posterior nucleus of the vagus nerve.

Symptoms of the lesion are characterized by a triad of symptoms: dizziness, nystagmus, impaired coordination of movement. There is a vestibular ataxia, manifested by a shaky gait, deviation of the patient in the direction of the lesion. Dizziness is characterized by attacks lasting up to several hours, which may be accompanied by nausea and vomiting. The attack is accompanied by horizontal or horizontal-rotary nystagmus. When a nerve is damaged on one side, nystagmus develops in the direction opposite to the lesion. With irritation of the vestibular part, nystagmus develops in the direction of the lesion.

Peripheral lesions of the vestibulocochlear nerve can be of two types: labyrinthine and radicular syndromes. In both cases, there is a simultaneous violation of the functioning of the auditory and vestibular analyzer. The radicular syndrome of peripheral lesions of the vestibulocochlear nerve is characterized by the absence of dizziness, and may manifest as an imbalance.