Cranial nerves. Cranial nerves 12 pairs of cranial nerves how to understand

Functional types of cranial nerves.

IV. PRESENTATION OF NEW MATERIAL.

III. CONTROL OF STUDENTS' KNOWLEDGE

II. MOTIVATION OF LEARNING ACTIVITIES

1. The knowledge gained in this lesson is necessary in your educational (when studying nervous diseases) and practical activities.

2. Based on the knowledge gained in this lesson, you will be able to build reflex arcs yourself various types reflexes, as well as navigate the topography of the I-VI pairs of cranial nerves.

A. Individual assignments for students for oral response at the board (25 minutes).

1. General characteristics of the telencephalon.

2. Furrows, convolutions, lobes of the telencephalon.

3. Internal structure telencephalon.

4. Brain cavity.

5. Meninges of the brain.

B. Answer the silent cards (written survey):

1. Cerebral hemisphere, superolateral surface.

2. Furrows and convolutions on the medial and lower (partial) surfaces of the cerebral hemispheres.

3. Furrows and convolutions on the lower surfaces of the cerebral hemispheres.

4. Brain; frontal section.

5. Brain; horizontal section.

6. Conducting pathways of reflex movements (diagrams).

Plan:

1. Functional types of cranial nerves.

2. Cranial nerves I-VI pairs.

There are 12 pairs of cranial nerves originating from the brain. Each pair of nerves has its own number and name; they are designated by Roman numerals in order of location.

The cranial nerves have different functions, because they consist only of motor or sensory, or of two types of nerve fibers (mixed).

Purely motor – III, IV, VI, XI, XII pairs of cranial nerves.

Purely sensitive – I, II, VIII pairs of cranial nerves.

Mixed – V, VII, IX, X pairs of cranial nerves.

I para-olfactory nerve(n.olfactorius)–– represents a set of thin filaments (olfactory filaments), which are processes of olfactory nerve cells located: in the mucous membrane of the nasal cavity, in the area of ​​the upper nasal passage, the superior turbinate, the upper part of the nasal septum.

They go through the holes of the cribriform plate into the cranial cavity into the olfactory bulb.

From here, impulses are transmitted along the olfactory brain and the tract to the cerebral cortex. Functionally purely sensitive.

II pair – optic nerve (n.opticus)- formed by processes of neurites of the retina of the eye, exits from the orbit into the cranial cavity through the optic canal. In front of the sella turcica, it forms an incomplete chiasma of the optic nerves and passes into the optic tract.

The optic tracts approach the external geniculate body, the thalamic pads and the superior colliculus of the midbrain, where the subcortical visual centers are located. Functionally purely sensitive.

III pair- oculomotor nerve(n.oculomotorius)– motor in function, with an admixture of parasympathetic fibers.

One part of the nerve originates from the motor nucleus, located at the bottom of the cerebral aqueduct.

The second part of the nerve comes from the parasympathetic nucleus of Yakubovich, located in the midbrain.

Passes into the orbit through the upper orbital fissure, where it is divided into 2 branches: upper and lower.

Innervates the muscles of the eye. Parasympathetic fibers innervate the smooth muscles of the eyeball - the muscle that constricts the pupil and the ciliary muscle.

IV pair – trochlear nerve (n. trochlearis)-motor. It starts from the nucleus, located at the bottom of the cerebral aqueduct at the level of the lower colliculi of the roof of the midbrain, passes into the orbit through the superior orbital fissure. Innervates the superior oblique muscle of the eye.

V para-trigeminal nerve(n.trigeminus)– mixed.

Sensitive fibers innervate the skin of the face, the front of the head, eyes, mucous membranes of the nasal and oral cavity, paranasal sinuses nose

In terms of the number of innervated areas, it is the main sensory nerve of the head.

Motor fibers - innervate the masticatory muscles; muscles of the floor of the mouth; muscle that stretches the soft palate and one of the muscles tympanic cavity.

The main nuclei of the V pair (sensitive and motor) are located in the tegmentum of the bridge in the upper half of the rhomboid fossa.

It leaves the brain through two roots: motor (smaller) and sensory (larger). Sensory fibers are processes of sensory neurons that form at the top of the pyramid node trigeminal nerve.

The peripheral processes of these cells form the 3rd branch of the trigeminal nerve:

1. The first is the optic nerve.

2. The second is the maxillary.

3. The third is the mandibular nerve.

The first branches are purely sensitive in their composition, and the third branch is mixed, because motor fibers are attached to it.

Optic nerve(n.ophthalmicus) - goes into the orbit through the superior orbital fissure, here it is divided into 3 main branches that innervate the contents of the orbit; eyeball; skin upper eyelid; conjunctiva of the eye; mucous membrane of the upper part of the nasal cavity, frontal, sphenoid sinuses and cells of the ethmoid bone.

The terminal branches, leaving the orbit, innervate the skin of the forehead.

Maxillary nerve(n.maxillaris) passes through the round opening into the pterygopalatine fossa, where it gives off branches going into the oral cavity, nasal cavity and eye socket.

Branches depart from the pterygopalatine node that innervate the mucous membrane of the soft and hard palate, nasal cavity.

From it depart: the infraorbital and zygomatic nerves, as well as nodal branches to the pterygopalatine ganglion.

Infraorbital nerve - gives off branches to innervate the teeth, gums of the upper jaw, innervates the skin of the lower eyelid, nose, upper lip.

Zygomatic nerve - gives off branches from parasympathetic fibers to the mucous gland, innervates the skin of the temporal, zygomatic and buccal areas.

Mandibular nerve(n.mandibularis) - exits the skull through the foramen ovale and is divided into a number of motor branches to all masticatory muscles: the mylohyoid muscle; the tensor venus muscle and the tensor tympani muscle.

The mandibular nerve gives off a number of sensory branches, including large ones: the lingual and inferior alveolar nerves; smaller nerves (lingual, auriculotemporal, meningeal).

Small nerves innervate the skin and mucous membrane of the cheeks, part auricle, external auditory canal, eardrum, skin temporal region, parotid salivary gland, lining of the brain.

The lingual nerve innervates 2/3 of the tongue and oral mucosa (perceives pain, touch, temperature).

The inferior alveolar nerve enters the mandibular canal, innervates the teeth and gums of the lower jaw, then passes through the mental foramen to innervate the skin of the chin and lower lip.

VI pair - abducens nerve (n.abducens) - lies in the posterior part of the bridge at the bottom of the IV ventricle. It starts from the brain stem and passes into the orbit through the superior orbital fissure.

The function is motor.

The brain (encephalon) is divided into brain stem, big brain And cerebellum. The brain stem contains structures related to the segmental apparatus of the brain and subcortical integration centers. Nerves arise from the brain stem, as well as from the spinal cord. They got the name cranial nerves.

There are 12 pairs of cranial nerves. They are designated by Roman numerals in order of their arrangement 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 pure motor: III - oculomotor, IV - trochlear, VI - abducens, XI - accessory, XII - sublingual. And four mixed: V - trigeminal, VII - facial, IX - glossopharyngeal, X - vagus. In addition, some cranial nerves contain autonomic nuclei and fibers.

Characteristics and description of individual cranial nerves:

I pair - olfactory nerves(nn.olfactorii). Sensitive. 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 pathway begins to the cortical end of the olfactory analyzer - the hippocampus.

If the olfactory nerve is damaged, the sense of smell is impaired.

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 and forms the optic chiasm in the diencephalon, from which the optic tracts begin. Function optic nerve is the transmission of light stimuli.

When various parts of the visual analyzer are affected, disorders occur 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 connect to the muscle that changes the curvature of the lens, resulting in changes in the accommodation of the eye.

When the oculomotor nerves are damaged, strabismus occurs, accommodation is impaired, and 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 sensitive.

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

- pavement in the hindbrain,

- inferior nucleus of the trigeminal nerve medulla oblongata,

- mesencephalic in the midbrain.

By sensory neurons information comes from receptors on the skin of the 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 cavities, tongue, eyeball and from the meninges.

Motor core located in the bridge tire. Motor neurons innervate the muscles of mastication, the muscles of the velum palatine, and the muscles that contribute to the tension of the tympanic membrane.

When a nerve is damaged, paralysis occurs masticatory muscles, disturbance of sensitivity in the relevant areas up to its loss, 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 rectus, which moves the eyeball outward. When it is damaged, convergent strabismus is observed.

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

Motor core located in the bridge tire. Innervates the facial muscles, the orbicularis oculi muscle, the mouth muscle, the auricular muscle and the subcutaneous muscle of the neck.

Sensitive — nucleus of the solitary tract medulla oblongata. Information is received here from sensitive taste fibers starting from the taste buds located in the anterior 2/3 of the tongue.

Vegetative — superior salivary nucleus located in the bridge tire. From it, efferent parasympathetic salivary fibers begin to the sublingual and submandibular, as well as the parotid salivary and lacrimal glands.

When the facial nerve is damaged, the following disorders are observed: paralysis of the facial muscles occurs, the face becomes asymmetrical, speech becomes difficult, the swallowing process is disrupted, taste and tear production are impaired, etc.

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

When the vestibular nerve is damaged, dizziness, rhythmic twitching of the eyeballs, and staggering when walking often occur. Damage to the auditory nerve leads to hearing impairment, the appearance of sensations of noise, squeaking, and grinding.

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

Sensitive core — nucleus of the solitary tract medulla oblongata. This nucleus is common to the nucleus of the facial nerve. The perception of taste in the posterior third of the tongue depends on the glossopharyngeal nerve. The glossopharyngeal nerve also provides sensitivity to the mucous membranes of the pharynx, larynx, trachea, and soft palate.

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

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

When this cranial nerve is damaged, taste disturbance occurs in the back third of the tongue, dry mouth is observed, sensitivity of the pharynx is impaired, paralysis of the soft palate is observed, and choking when swallowing.

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

Sensitive core — nucleus of the solitary tract medulla oblongata. Sensitive fibers transmit irritations from hard tissue meninges, from the mucous membranes of the pharynx, larynx, trachea, bronchi, lungs, gastrointestinal tract and other internal organs. Most 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 neuronal processes compared to other cranial nerves. Innervates the smooth muscles of the trachea, bronchi, esophagus, stomach, small intestine, and 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 impaired in the back third of the tongue, 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 common nuclei in the brain stem.

XI pair - accessory nerve(n. accessorius). Motor nerve. It has two nuclei: in the medulla oblongata and in the 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, and raise the shoulders above the horizontal.

If the injury occurs, there is difficulty turning the head to the healthy side, a drooping shoulder, and limited raising of the arm above the horizontal line.

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

When damaged, either weakness of the tongue muscles (paresis) or their complete paralysis occurs. This leads to speech impairment, it becomes unclear and slurred.

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Cranial nerves

Cranial nerves make up 12 pairs. Each pair has its own name and serial number, designated by Roman numerals: olfactory nerves – I pair; optic nerve – II pair; oculomotor nerve – III pair; trochlear nerve – IV pair; trigeminal nerve - V pair; abducens nerve – VI pair; facial nerve – VII pair; vestibulocochlear nerve – VIII pair; glossopharyngeal nerve – IX pair; vagus nerve – X pair; accessory nerve – XI pair; hypoglossal nerve - XII pair.

Cranial nerves vary in function and therefore in nerve fiber composition. Some of them (I, II and VIII pairs) are sensitive, others (III, IV, VI, XI and XII pairs) are motor, and others (V, VII, IX and X pairs) are mixed. The olfactory and optic nerves differ from other nerves in that they are derivatives of the brain - they were formed by protrusion from the brain vesicles and, unlike other sensory and mixed nerves, do not have nodes. These nerves consist of processes of neurons located on the periphery - in the organ of smell and organ of vision. Mixed-function cranial nerves are similar in structure and composition of nerve fibers to spinal nerves. Their sensitive part has nodes (sensitive ganglia of the cranial nerves), similar to the spinal ganglia. The peripheral processes (dendrites) of the neurons of these nodes go to the periphery in the organs and end in receptors in them, and the central processes follow into the brain stem to sensitive nuclei, similar to the nuclei posterior horns spinal cord. The motor part of the mixed cranial nerves (and motor cranial nerves) consist of the axons of nerve cells of the motor nuclei of the brain stem, similar to the nuclei of the anterior horn of the spinal cord. As part of the III, VII, IX and X pairs of nerves, parasympathetic fibers pass along with other nerve fibers (they are axons of neurons of the autonomic nuclei of the brain stem, similar to the autonomic parasympathetic nuclei of the spinal cord).

The olfactory nerve is sensitive in function and consists of nerve fibers that are processes of the olfactory cells of the olfactory organ. These fibers form 15-20 olfactory filaments (nerves), which exit the olfactory organ and penetrate through the cribriform plate of the ethmoid bone into the cranial cavity, where they approach the neurons of the olfactory bulb and nerve impulses are transmitted through various formations peripheral part olfactory brain into its central section.

The optic nerve is sensitive in function and consists of nerve fibers that are processes of the so-called glanglionic cells of the retina of the eyeball. From the orbit, through the optic canal, the nerve passes into the cranial cavity, where it immediately forms a partial decussation with the nerve of the opposite side (optic chiasm) and continues into the optic tract. Due to the fact that only the medial half of the nerve passes to the opposite side, the right optic tract contains nerve fibers from the right halves, and the left tract contains nerve fibers from the left halves of the retina of both eyeballs. The visual tracts approach the subcortical visual centers - the nuclei of the superior colliculus of the midbrain roof, the lateral geniculate body and the thalamic cushions. The nuclei of the superior colliculus are connected with the nuclei of the oculomotor nerve (through which the pupillary reflex is carried out) and with the nuclei of the anterior horns of the spinal cord (orienting reflexes to sudden light stimuli are carried out). From the nuclei of the lateral geniculate body and the thalamic cushions, nerve fibers in the white matter of the hemispheres follow to the cortex occipital lobes(visual sensory zone bark).

Oculomotor nerve motor in function, consists of motor somatic and efferent parasympathetic nerve fibers. These fibers are the axons of the neurons that make up the nerve nuclei. There are motor nuclei and an accessory parasympathetic nucleus. They are located in the cerebral peduncle at the level of the superior colliculi of the midbrain roof. The nerve exits the cranial cavity through the superior orbital fissure into the orbit and divides into two branches: superior and inferior. The motor somatic fibers of these branches innervate the superior, medial, inferior rectus and inferior oblique muscles of the eyeball, as well as the levator muscle. upper eyelid(all of them are striated), and the parasympathetic fibers are the constrictor pupillary muscle and the ciliary muscle (both smooth). Parasympathetic fibers on the way to the muscles switch in the ciliary ganglion, which lies in the posterior part of the orbit.

Trochlear nerve motor function, consists of nerve fibers extending from the nucleus. The nucleus is located in the cerebral peduncles at the level of the inferior colliculi of the midbrain roof. The nerves exit the cranial cavity through the superior orbital fissure into the orbit and innervate the superior oblique muscle of the eyeball.

The trigeminal nerve is mixed in function, consisting of sensory and motor nerve fibers. Sensitive nerve fibers are peripheral processes (dendrites) of neurons of the trigeminal ganglion, which is located on the anterior surface of the pyramid temporal bone at its apex, between the layers of the dura mater of the brain, and consists of sensitive nerve cells. These nerve fibers form three branches of the nerve: the first branch is the ophthalmic nerve, the second branch is the maxillary nerve and the third branch is the mandibular nerve. The central processes (axons) of the neurons of the trigeminal ganglion constitute the sensory root of the trigeminal nerve, which goes into the brain to the sensory nuclei. The trigeminal nerve has several sensory nuclei (located in the pons, cerebral peduncles, medulla oblongata and upper cervical segments of the spinal cord). From the sensory nuclei of the trigeminal nerve, nerve fibers go to the thalamus. The corresponding neurons of the thalamic nuclei are connected through fibers extending from them to the lower part of the postcentral gyrus (its cortex).

The motor fibers of the trigeminal nerve are processes of the neurons of its motor nucleus, located in the pons. These fibers, upon exiting the brain, form the motor root of the trigeminal nerve, which joins its third branch, the mandibular nerve.

The ophthalmic nerve, or the first branch of the trigeminal nerve, is sensitive in function. Moving away from the trigeminal ganglion, it goes to the superior orbital fissure and through it penetrates into the orbit, where it divides into several branches. They innervate the skin of the forehead and upper eyelid, the conjunctiva of the upper eyelid and the membranes of the eyeball (including the cornea), the mucous membrane of the frontal and sphenoid sinuses and parts of the cells of the ethmoid bone, as well as part of the dura mater of the brain. The largest branch of the optic nerve is called the frontal nerve.

The maxillary nerve, or the second branch of the trigeminal nerve, is sensory in function, follows from the cranial cavity through the round foramen into the pterygopalatine fossa, where it is divided into several branches. The largest branch is called the infraorbital nerve, passes through the canal of the same name in the upper jaw and enters the face in the area of ​​the canine fossa through the infraorbital foramen. Area of ​​innervation of the branches of the maxillary nerve: skin of the middle part of the face (upper lip, lower eyelid, zygomatic region, nasal cavity, palate, maxillary sinus, parts of the cells of the ethmoid bone, upper teeth and part of the dura mater of the brain).

The mandibular nerve, or the third branch of the trigeminal nerve, has a mixed function. From the cranial cavity it passes through the foramen ovale into the infratemporal fossa, where it divides into a number of branches. Sensitive branches innervate the skin of the lower lip, chin and temporal region, the mucous membrane of the lower lip, and the dura mater of the brain. The motor branches of the mandibular nerve innervate all the masticatory muscles, the tensor palati muscle, the mylohyoid muscle and the anterior belly of the digastric muscle. The largest branches of the mandibular nerve are: the lingual nerve (sensitive, goes to the tongue) and the inferior alveolar nerve (sensitive, runs in the canal of the lower jaw, gives branches to the lower teeth, under the name of the mental nerve, through the opening of the same name, it exits to the chin).

Abducens nerve According to its function, the motor consists of nerve fibers extending from the neurons of the nerve nucleus located in the pons. It exits the skull through the superior orbital fissure into the orbit and innervates the lateral (external) rectus muscle of the eyeball.

The facial nerve, or interfacial nerve, is mixed in function and includes motor somatic fibers, secretory parasympathetic fibers and sensory taste fibers. Motor fibers arise from the nucleus of the facial nerve located in the pons. Secretory parasympathetic and sensory taste fibers are part of the intermedius nerve, which has parasympathetic and sensory nuclei in the pons and exits the brain near the facial nerve. Both nerves (facial and intermediate) follow into the internal auditory canal, in which the intermediate nerve exits into the facial one. After this, the facial nerve penetrates the canal of the same name, located in the pyramid of the temporal bone. In the canal it gives off several branches: the greater petrosal nerve, the chorda tympani, etc. The greater petrosal nerve contains secretory parasympathetic fibers to the lacrimal gland. The chorda tympani passes through the tympanic cavity and, leaving it, joins the lingual nerve from the third branch of the trigeminal nerve; it contains taste fibers for the taste buds of the body and tip of the tongue and secretory parasympathetic fibers in the submandibular and sublingual salivary glands.

Having given off its branches in the canal, the facial nerve leaves it through the stylomastoid foramen and enters the thickness of the parotid salivary gland, where it is divided into terminal branches, motor according to function. They innervate everything facial muscles face and part of the neck muscles: subcutaneous neck muscle, posterior belly of digastric muscle, etc.

The vestibular-cochlear nerve is sensitive in function and includes two parts: the cochlear - for the sound-receiving organ (spiral organ) and the vestibular - for vestibular apparatus(organ of balance). Each part has ganglion of sensory neurons, located in the pyramid of the temporal bone near inner ear.

The cochlear part (cochlear nerve) consists of the central processes of the cells of the cochlear ganglion (spiral ganglion of the cochlea).

The peripheral processes of these cells approach the receptor cells of the spiral organ in the cochlea of ​​the inner ear.

The vestibular part (vestibular nerve) is a bundle of central processes of the cells of the vestibular ganglion. The peripheral processes of these cells end on the receptor cells of the vestibular apparatus in the sac, uterus and ampoules of the semicircular ducts of the inner ear.

Both parts - the cochlea and the vestibule - from the inner ear follow side by side along the internal auditory canal into the bridge (of the brain), where the nuclei are located. The nuclei of the cochlear part of the nerve are connected with the subcortical auditory centers - the nuclei of the lower colliculi of the midbrain roof and the medial geniculate bodies. From the neurons of these nuclei, nerve fibers go to the middle part of the superior temporal gyrus (auditory cortex). The nuclei of the inferior colliculi are also connected with the nuclei of the anterior horns of the spinal cord (orienting reflexes to sudden sound stimulation are carried out). The nuclei of the vestibular part of the VIII pair of cranial nerves are connected to the cerebellum.

The glossopharyngeal nerve is mixed in function and includes sensory general and taste fibers, motor somatic fibers and secretory parasympathetic fibers. Sensitive fibers innervate the mucous membrane of the root of the tongue, pharynx and tympanic cavity, taste fibers - the taste buds of the root of the tongue. The motor fibers of this nerve innervate the stylopharyngeal muscle, and the secretory parasympathetic fibers innervate the parotid salivary gland.

The nuclei of the glossopharyngeal nerve (sensory, motor and parasympathetic) are located in the medulla oblongata, some of them are common with the vagus nerve. The nerve leaves the skull through the jugular foramen, descends down and anteriorly towards the root of the tongue and divides into its branches to the corresponding organs (tongue, pharynx, tympanic cavity).

The vagus nerve is mixed in function, consisting of sensory, motor somatic and efferent parasympathetic nerve fibers. Sensitive fibers branch in various internal organs, where they have sensitive nerve endings - visceroreceptors. One of the sensory branches - the depressor nerve - ends with receptors in the aortic arch and plays important role in regulation blood pressure. Relatively thin sensory branches of the vagus nerve innervate part of the dura mater of the brain and a small area of ​​skin in the external auditory canal. The sensitive part of the nerve has two nodes (superior and inferior) located in the jugular foramen of the skull.

Motor somatic fibers innervate the muscles of the pharynx, the muscles of the soft palate (with the exception of the muscle that strains the velum palatine) and the muscles of the larynx. Parasympathetic fibers of the vagus nerve innervate the cardiac muscle, smooth muscles and glands of all internal organs of the thoracic cavity and abdominal cavity, with the exception of the sigmoid colon and pelvic organs. Parasympathetic efferent fibers can be divided into parasympathetic motor and parasympathetic secretory fibers.

The vagus nerve is the largest of the cranial nerves and gives off numerous branches. The nerve nuclei (sensory, motor and autonomic - parasympathetic) are located in the medulla oblongata.

Neurology of motor cranial nerves

The nerve leaves the cranial cavity through the jugular foramen, lies on the neck next to the internal jugular vein and with the internal, and then with the common carotid artery; in the chest cavity it approaches the esophagus (the left nerve passes along the anterior surface, and the right nerve passes along its posterior surface) and together with it penetrates the abdominal cavity through the diaphragm. According to the location in the vagus nerve, the head, cervical, thoracic and abdominal sections are distinguished.

Branches extend from the head to the dura mater of the brain and to the skin of the external auditory canal.

The pharyngeal branches (to the pharynx and muscles of the soft palate), the superior laryngeal and recurrent nerve(innervate the muscles and mucous membrane of the larynx), upper cervical cardiac branches, etc.

From the thoracic region depart the thoracic cardiac branches, bronchial branches (to the bronchi and lungs) and branches to the esophagus.

From the abdominal region there are branches involved in the formation of nerve plexuses that innervate the stomach, small intestine, large intestine from the beginning to the sigmoid colon, liver, pancreas, spleen, kidneys and testicles (in women - ovaries). These plexuses are located around the arteries of the abdominal cavity.

The vagus nerve is the main parasympathetic nerve in terms of fiber composition and area of ​​innervation.

Accessory nerve motor function, consists of nerve fibers extending from the neurons of the motor nuclei. These nuclei are located in the medulla oblongata and in the first cervical segment of the spinal cord. The nerve exits the skull through the jugular foramen to the neck and innervates the sternomastoid and trapezius muscles.

Hypoglossal nerve motor function, includes nerve fibers extending from the neurons of the motor nucleus located in the medulla oblongata. It leaves the cranial cavity through the canal of the hypoglossal nerve in the occipital bone, follows, describing an arc, to the tongue from below and is divided into branches that innervate all the muscles of the tongue and the geniohyoid muscle. One of the branches of the hypoglossal nerve (descending) forms, together with the branches of the I-III cervical nerves, the so-called cervical loop. The branches of this loop (due to fibers from the cervical spinal nerves) innervate the neck muscles lying below the hyoid bone.

All cranial nerves are presented in the table (Appendix No. 1). Their type, the organ innervated by it and its functions are also discussed there.

So, motor nerves begin in the motor nuclei of the brainstem. The predominantly motor nerves include the following group of nerves: oculomotor (3rd), trochlear (4th), abducens (6th), accessory (11th), sublingual (12th).

Oculomotor nerve (3rd)

The oculomotor nerve innervates the medial rectus muscle, the inferior rectus muscle, the superior rectus muscle, the inferior oblique muscle, the levator palpebrae superioris muscle, and the pupillary sphincter.

Innervates the external muscles of the eye (with the exception of the external rectus and superior oblique), the muscle that lifts the upper eyelid, the muscle that constricts the pupil, the ciliary muscle, which regulates the configuration of the lens, which allows the eye to adapt to near and far vision.

System III pair consists of two neurons. The central one is represented by the cells of the cortex of the precentral gyrus, the axons of which, as part of the corticonuclear tract, approach the nuclei of the oculomotor nerve on both its own and the opposite side.

A wide variety of functions performed by the third pair is carried out using 5 nuclei for the innervation of the right and left eyes. They are located in the cerebral peduncles at the level of the superior colliculi of the midbrain roof and are peripheral neurons of the oculomotor nerve. From the two magnocellular nuclei, the fibers go to the external muscles of the eye on their own and partially the opposite side. The fibers innervating the muscle that lifts the upper eyelid come from the nucleus of the same and opposite side. From two small cell accessory nuclei, parasympathetic fibers are directed to the muscle constrictor pupil, on its own and the opposite side. This ensures a friendly reaction of the pupils to light, as well as a reaction to convergence: constriction of the pupil while simultaneously contracting the rectus intrinsic muscles of both eyes. From the posterior central unpaired nucleus, which is also parasympathetic, the fibers are directed to the ciliary muscle, which regulates the degree of convexity of the lens. When looking at objects located near the eye, the convexity of the lens increases and at the same time the pupil narrows, which ensures a clear image on the retina. If accommodation is impaired, a person loses the ability to see clear outlines of objects at different distances from the eye.

The fibers of the peripheral motor neuron of the oculomotor nerve begin from the cells of the above nuclei and emerge from the cerebral peduncles on their medial surface, then pierce the dura mater and then follow in the outer wall of the cavernous sinus. From the skull, the oculomotor nerve exits through the superior orbital fissure and enters the orbit.

Trochlear nerve(4th)

The nuclei of the trochlear nerves are located at the level of the inferior colliculi of the midbrain roof anterior to the central gray matter, below the nuclei of the oculomotor nerve. The internal nerve roots wrap around the outer part of the central gray matter and intersect at the superior medullary velum, which is a thin plate that forms the roof of the rostral part of the fourth ventricle. After the decussation, the nerves leave the midbrain downward from the inferior colliculus. The trochlear nerve is the only nerve emerging from the dorsal surface of the brainstem. On their way in the central direction to the cavernous sinus, the nerves first pass through the coracoid cerebellopontine fissure, then through the notch of the tentorium of the cerebellum, and then along the outer wall of the cavernous sinus, and from there, together with the oculomotor nerve, they enter the orbit through the superior orbital fissure.

The trochlear nerve innervates the superior oblique muscle, which rotates the eyeball outward and downward. Paralysis of the muscle causes the affected eyeball to deviate upward and somewhat inward. This deviation is especially noticeable when the affected eye looks down and towards the healthy side. There is double vision when looking down; it clearly manifests itself if the patient looks at his feet, in particular when walking up the stairs.

Abducens nerve(6th)

The abducens nerve innervates the lateral rectus muscle. The nucleus of the abducens nerve also contains neurons that, through the medial longitudinal fasciculus, are connected to the nucleus of the oculomotor nerve, which innervates the medial rectus muscle on the opposite side; therefore, the symptoms of damage to the nuclei and the nerve itself are different.

The VI (abducens) nerve has a single motor (GSE) nucleus. It lies in the pons and is responsible for the innervation of the rectus oculi muscle, which abducts the eye to the side.

Accessory nerve (11th)

The accessory (11th cranial nerve) innervates the sternocleidomastoid and trapezius muscles.

The XI (accessory) nerve combines information from two nuclei. The first motor (GSE) nucleus lies in cervical spine spinal cord, and is responsible for the innervation of the trapezius and sternocleidomastoid muscles (neck muscles). The second nucleus, information from which goes to three nerves (IX, X, XI), the double nucleus (nucleus ambigous), motor (SVE - specific visceral efferent) - located in the medulla oblongata just below the olives and lateral to the nucleus of the hypoglossal nerve, innervates the larynx.

Hypoglossal nerve (12th)

The sublingual (12th cranial nerve) innervates the muscles of the tongue. The hypoglossal nerve innervates the muscles of the ipsilateral half of the tongue, as well as the geniohyoid, thyrohyoid, omohyoid and sternothyroid muscles.

This nerve includes nerve fibers that arise from neurons of the motor nucleus located in the medulla oblongata. It leaves the cranial cavity through the canal of the hypoglossal nerve in the occipital bone, follows, describing an arc, to the tongue from below and is divided into branches that innervate all the muscles of the tongue and the geniohyoid muscle. One of the branches of the hypoglossal nerve (descending) forms, together with the branches of the I-III cervical nerves, the so-called cervical loop. The branches of this loop (due to fibers from the cervical spinal nerves) innervate the neck muscles lying below the hyoid bone.

Lecture 5 Cranial nerves

Functions of twelve pairs of cranial nerves

In ordinary life, a person very rarely thinks about how many nerves are in his body. Only after illness or injury does he begin to realize how important a role nerves play in normal functioning. various organs and the whole organism as a whole.

Sense organs play a huge role in people's lives. Without sight, smell, touch, hearing and the ability to experience different tastes, life loses some of its attractiveness and becomes complex and dangerous. Most of the human senses are controlled by 12 pairs of cranial nerves.

Classification of cranial nerves

12 pairs of cranial nerves depart from the brain stem, more often referred to as cranial nerves in the international classification. Each pair has its own name and is designated by Roman letters. Some sources consider the intermediate nerve to be the thirteenth pair, but this concept has not been approved by world experts.

• | pair – olfactory nerve.
• || pair – optic nerve.
• ||| pair – oculomotor nerve.
• |V pair – trochlear nerve.
• V pair – trigeminal nerve.
• V| pair – abducens nerve.
• V|| pair - facial nerve.
• V||| pair – vestibulocochlear nerve.
• |X pair – glossopharyngeal nerve.
• X pair – vagus nerve.
• X| para – accessory nerve.
• X|| pair - hypoglossal nerve.

Functions of the cranial nerves

Each of the 12 pairs of cranial nerves is responsible for performing certain actions that provide different stages of a person’s perception of the surrounding reality.

Each of the 12 pairs of cranial nerves, controlling its own narrow area of ​​​​work, generally provides a person with the opportunity to see, hear, smell, taste, and also react to what is happening. This complex system can be compared to an orchestra, where each instrument plays its own part, all together creating a harmonious and beautiful melody.

Cranial nerves and their nuclei

12 pairs of cranial nerves depart from the brain:

I. Olfactory nerve - n. (nervus) olfactorius;

II. Optic nerve - n. opticus;

III. Oculomotor nerve - n. oculomotorius;

IV. Trochlear nerve - n. trochlearis;

V. Trigeminal nerve - n. trigeminus;

VI. Abducens nerve - n. abducens;

VII. Facial nerve - n.facialis;

VII. Vestibulo-auditory nerve - n. vestibulocochlearis;

IX. Glossopharyngeal nerve - n. glossopharyngeus;

X. Vagus nerve - n. vagus;

XI. Accessory nerve - n. accessorius;

XII. Hypoglossal nerve - n. hypoglossus.

In contrast to mixed (consisting of afferent sensory and efferent motor and autonomic fibers) spinal nerves, among the cranial nerves there are both mixed and only afferent or only efferent.

Only afferent (sensory) nerves are the I, II and VIII pairs. Only efferent nerves - III, IV, VI, XI and XII pairs. The remaining four pairs (V, VII, IX and X) are mixed. The first two pairs (olfactory and optic nerves) are fundamentally different in nature and origin from the other nerves. They are outgrowths of the forebrain.

Let us characterize the remaining ten pairs of cranial nerves. They all arise from the brain stem. III and IV - from the midbrain; V - from the pons; VI, VII and VIII - from the groove between the pons and the medulla oblongata; IX, X, XI and XII - from the medulla oblongata. All nerves, with the exception of IV, exit the brain on the ventral (front) side. The IV nerve exits on the dorsal side, but immediately bends around the brainstem and passes to the ventral side.

The neurons whose processes form the cranial nerves are similar to the neurons that form the spinal nerves. Next to the GM lie the cranial ganglia, similar to the spinal ganglia. They contain sensory neurons. Their peripheral processes form sensory fibers of mixed nerves. The central processes enter the brainstem and end on the nuclei in the brainstem. Such kernels are called sensory nuclei of the cranial nerves. Their cells are similar to the interneurons of the dorsal horns of the SC. Also in the brain stem there are nuclei from which neurons extend axons that form efferent fibers. They come in two types. If fibers from these nuclei go to skeletal (voluntary) muscles, this somatic-motor kernels. They belong to the somatic NS. Their neurons are similar to the motor neurons of the anterior horns of the SC. If the fibers from these nuclei end on the autonomic ganglia, such nuclei are called vegetative. Their neurons are similar to the central autonomic neurons lying in the intermediate substance of the SC. All autonomic neurons brain stem belong to the parasympathetic part of the ANS (see Chapter 8).

So, depending on which fibers form the nerve, the latter may have one, two or more nuclei (Fig. 22). Most of these nuclei (nuclei of the V - XII nerves) lie in the thickness of the medulla oblongata and the pons. In drawings, they are usually projected onto the bottom of the IV ventricle - the rhomboid fossa (see 4.2). The nuclei of the III and IV nerves are located in the midbrain.

Rice. 22. Nuclei of cranial nerves and exit of nerves from the brainstem:

1 - motor and 2- autonomic nucleus of the oculomotor

nerve;.3 - red core; 4- motor core trochlear nerve;

5 - trigeminal nerve nuclei (marked with dots); b- motor

abducens nerve nucleus; 7- motor nucleus of the facial nerve;

8 - autonomic nuclei of the facial and glossopharyngeal nerves; 9- double

core; 10- autonomic nucleus of the vagus nerve; eleven- motor

accessory nerve nucleus; 12- motor nucleus of the hypoglossus

nerve; 13- olive kernel. Nucleus of the solitary tract and sensory

the nuclei of the vestibulo-auditory nerve are not shown in this figure

Efferent cranial nerves. Oculomotor (III pair), block(IV pair) and abducting(VI pair) nerves control eye movements. Each of these nerves has a somatic motor nucleus, the fibers from which go to the muscles of the eye. The oculomotor nerve innervates the superior, inferior and internal rectus muscles, as well as the inferior oblique muscle of the eye; trochlear - superior oblique muscle of the eye; abductor - external rectus muscle of the eye. The nuclei of the III and IV nerves are located in the midbrain, the nucleus of the VI nerve is in the bridge under the facial tubercle in the rhomboid fossa (see 7.2.4). The oculomotor nerve has another nucleus - the autonomic one. It produces parasympathetic fibers that carry impulses that reduce the diameter of the pupil and regulate the curvature of the lens. There are close mutual connections between the nuclei of these three pairs of nerves, due to which combined eye movements and image stabilization on the retina are achieved.

Accessory nerve(XI pair) controls the muscles of the larynx, as well as the sternocleidomastoid muscle of the neck and the trapezius muscle shoulder girdle. The nucleus is located in the medulla oblongata, part of it extends into the SC.

Hypoglossal nerve(XII pair). Innervates the muscles of the tongue and controls its movements. The nucleus of this nerve extends almost throughout the entire medulla oblongata.

Mixed cranial nerves.Trigeminal nerve(V pair) contains afferent and efferent somatic motor fibers. Sensitive fibers innervate the skin of the face, teeth, mucous membranes of the oral and nasal cavities, carrying out pain, temperature, skin and muscle sensitivity.

Cranial nerve examination

Motor fibers control the muscles of mastication and some muscles of the middle ear.

The trigeminal nerve has three sensory nuclei, two of which are located in the medulla oblongata and pons, and one in the midbrain. The only motor nucleus of this nerve is located in the pons.

The name “trigeminal” is due to the fact that it consists of three branches carrying information from three “floors” of the face - the forehead; nose, cheeks and upper jaw; lower jaw. Motor fibers pass in the inferior branch of the trigeminal nerve.

Facial nerve(VII pair) contains three types of fibers:

1) afferent sensory fibers bring impulses from the taste buds of the anterior two-thirds of the tongue. These fibers end in the nucleus of the solitary tract - the common sensory nucleus of the facial, glossopharyngeal and vagus nerves. It extends from the medulla oblongata into the pons;

2) somatic motor fibers innervate the facial muscles, as well as the muscles of the eyelids, and some muscles of the ear. These fibers come from the motor nucleus located in the pons;

3) autonomic parasympathetic fibers of the facial nerve innervate the submandibular and sublingual salivary glands, lacrimal glands, and glands of the nasal mucosa. They begin from the parasympathetic superior salivary nucleus, also located in the pons

Glossopharyngeal nerve(IX pair) is similar in composition to the facial nerve, i.e. also contains three types of fibers:

1) afferent fibers bring information from the receptors of the posterior third of the tongue and end on the neurons of the nucleus of the solitary tract;

2) efferent somatic motor fibers innervate some muscles of the pharynx and larynx. The fibers begin in the nucleus ambiguus - the common motor nucleus for the glossopharyngeal and vagus nerves, located in the medulla oblongata;

3) efferent parasympathetic fibers begin in the inferior salivary nucleus and innervate the near-ear salivary gland.

Nervus vagus(X pair) is so called because of the extensive distribution of its fibers. It is the longest of the cranial nerves; with its branches it innervates respiratory organs, a significant part of the digestive tract, heart. Latin name this nerve n. vagus, therefore it is often called the vagus.

Just like the VII and IX nerves, the vagus contains three types of fibers:

1) afferents carry information from the receptors of the previously mentioned internal organs and vessels of the chest and abdominal cavities, as well as from the dura mater of the brain and the external auditory canal with the auricle. These fibers carry information about the depth of breathing, pressure in blood vessels, stretching of organ walls, etc. They end in the nucleus of the solitary tract;

2) efferent somatic motor innervates the muscles of the pharynx, soft palate, and larynx (including those that control the tension of the vocal cords). The fibers begin in the double core;

3) efferent parasympathetic fibers begin from the parasympathetic nucleus of the vagus nerve in the medulla oblongata. The parasympathetic part of the vagus nerve is very large, so it is predominantly an autonomic nerve.

From sensory cranial nerves Only the vestibulo-auditory nerve (VIII pair) departs from the brain stem. It brings impulses from the auditory and vestibular receptors of the inner ear to the central nervous system. The sensory nuclei of this nerve - two auditory (ventral and dorsal) and four vestibular (lateral, medial, superior and inferior) - are located on the border of the medulla oblongata and the pons in the area of ​​the vestibular field (see 7.2.2).

The VIII nerve originates in the inner ear and consists of two separate nerves - the cochlear (auditory) nerve and the vestibular nerve.

In conclusion, it should be noted that the nuclei of the cranial nerves have many afferents and efferents. Thus, all sensory nuclei send efferents to the thalamus (diencephalon), and from there information enters the cerebral cortex. In addition, sensory nuclei transmit signals to the reticular formation of the brain stem (see 7.2.6). All motor nuclei receive afferents from the cerebral cortex as part of the corticonuclear tract (see 6.4). Finally, there are numerous connections between the cranial nerve nuclei themselves, which facilitates the coordinated activity of various organs. In particular, thanks to the connections between the sensory and motor nuclei, the arcs of the stem unconditioned reflexes (for example, gag, blinking, salivation, etc.), similar to the spinal unconditioned reflexes, are closed.

The brain (encephalon) is divided into brain stem, big brain And cerebellum. The brain stem contains structures related to the segmental apparatus of the brain and subcortical integration centers. Nerves arise from the brain stem, as well as from the spinal cord. They got the name cranial nerves.

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

Characteristics and description of individual cranial nerves:

I pair - olfactory nerves(nn.olfactorii). Sensitive. 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 pathway begins to the cortical end of the olfactory analyzer - the hippocampus.

If the olfactory nerve is damaged, the sense of smell is impaired.

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 and forms the optic chiasm in the diencephalon, from which the optic tracts begin. The function of the optic nerve is the transmission of light stimuli.

When various parts of the visual analyzer are affected, disorders occur 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 connect to the muscle that changes the curvature of the lens, resulting in changes in the accommodation of the eye.

When the oculomotor nerves are damaged, strabismus occurs, accommodation is impaired, and 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 sensitive.

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

Pavement in the hindbrain,

Inferior nucleus of the trigeminal nerve in the medulla oblongata,

Midbrain in the midbrain.

Sensitive neurons receive information from receptors on the skin of the 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 cavities, tongue, eyeball and from the meninges.

Motor core located in the bridge tire. Motor neurons innervate the muscles of mastication, the muscles of the velum palatine, and the muscles that contribute to the tension of the tympanic membrane.

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

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

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

Motor core located in the bridge tire. Innervates the facial muscles, the orbicularis oculi muscle, the mouth muscle, the auricular muscle and the subcutaneous muscle of the neck.

Sensitive - nucleus of the solitary tract medulla oblongata. This receives information from sensitive taste fibers starting from the taste buds located in the anterior 2/3 of the tongue.

Vegetative - superior salivary nucleus located in the bridge tire. From it, efferent parasympathetic salivary fibers begin to the sublingual and submandibular, as well as the parotid salivary and lacrimal glands.

When the facial nerve is damaged, the following disorders are observed: paralysis of the facial muscles occurs, the face becomes asymmetrical, speech becomes difficult, the swallowing process is disrupted, taste and tear production are impaired, etc.

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

When the vestibular nerve is damaged, dizziness, rhythmic twitching of the eyeballs, and staggering when walking often occur. Damage to the auditory nerve leads to hearing impairment, the appearance of sensations of noise, squeaking, and grinding.

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

Sensitive core - nucleus of the solitary tract medulla oblongata. This nucleus is common to the nucleus of the facial nerve. The perception of taste in the posterior third of the tongue depends on the glossopharyngeal nerve. The glossopharyngeal nerve also provides sensitivity to the mucous membranes of the pharynx, larynx, trachea, and soft palate.

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

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

When this cranial nerve is damaged, taste disturbance occurs in the back third of the tongue, dry mouth is observed, sensitivity of the pharynx is impaired, paralysis of the soft palate is observed, and choking when swallowing.

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

Sensitive core - nucleus of the solitary tract medulla oblongata. Sensitive fibers transmit irritations from the dura mater, from the mucous membranes of the pharynx, larynx, trachea, bronchi, lungs, gastrointestinal tract and other internal organs. Most 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 neuronal processes compared to other cranial nerves. Innervates the smooth muscles of the trachea, bronchi, esophagus, stomach, small intestine, and 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 impaired in the back third of the tongue, 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 common nuclei in the brain stem.

XI pair - accessory nerve(n. accessorius). Motor nerve. It has two nuclei: in the medulla oblongata and in the 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, and raise the shoulders above the horizontal.

If the injury occurs, there is difficulty turning the head to the healthy side, a drooping shoulder, and limited raising of the arm above the horizontal line.

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

When damaged, either weakness of the tongue muscles (paresis) or their complete paralysis occurs. This leads to speech impairment, it becomes unclear and slurred.

nervous tissue. One part of them performs sensitive functions, the other – motor functions, the third combines both. They have afferent and efferent fibers (or only one of these types), responsible for receiving or transmitting information, respectively.

The first two nerves have significant differences from the rest from the 10, since they are essentially a continuation of the brain, formed through the protrusion of the brain vesicles. In addition, they do not have nodes (nuclei) that are present in the other 10. The nuclei of the cranial nerves, like other ganglia of the central nervous system, are concentrations of neurons that perform specific functions.

10 pairs, with the exception of the first two, are not formed from two types of roots (anterior and posterior), as happens with spinal roots, 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 an error, but it is preferable to use the first term - in accordance with the international anatomical classification.

All cranial nerves are formed in the fetus already in the second month. At the 4th month of prenatal development, myelination of the vestibular nerve begins - the coating of fibers with myelin. Motor fibers go through this stage earlier than sensory fibers. 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 complex. Final myelination occurs around the age of one and a half years.

Classification

Before proceeding to a detailed examination of each individual pair (anatomy and functioning), it is most convenient to familiarize yourself with them using brief characteristics.

Table 1: Characteristics of 12 pairs

Numbering	Name	Functions
I	Olfactory	Sensitivity to odors
II	Visual	Transmission of visual stimuli to the brain
III	Oculomotor	Eye movements, pupillary response to light exposure
IV	Block	Moving the eyes downwards, outwards
V	Trigeminal	Facial, oral, pharyngeal sensitivity; activity of the muscles responsible for the act of chewing
VI	Abductor	Moving the eyes outward
VII	Facial	Movement of muscles (facial muscles, stapedius); activity of the salivary gland, sensitivity of the anterior part of the tongue
VIII	Auditory	Transmission of sound signals and impulses from the inner ear
IX	Glossopharyngeal	Movement of the levator pharyngeal muscle; pair activities salivary glands, sensitivity of the throat, middle ear cavity and auditory tube
X	Wandering	Motor processes in the muscles of the throat and some parts of the esophagus; providing sensitivity in the lower part of the throat, partially in the ear canal and eardrums, dura mater of the brain; activity of smooth muscles (gastrointestinal tract, lungs) and cardiac
XI	Additional	Abduction of the head in various directions, shrugging of the shoulders and adduction of the shoulder blades to the spine
XII	Sublingual	Movements and movements of the tongue, acts of swallowing and chewing

Nerves with sensory fibers

The olfactory begins in the nerve cells of the nasal mucous membranes, 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.

Retinal ganglion cells give rise to the optic nerve. Having entered the cranial cavity, it forms a decussation and, as it passes further, it begins to bear the name “optic tract,” which ends in the lateral geniculate body. The central part of the visual pathway originates from it, going to the occipital lobe.

Auditory (also known as vestibulocochlear) consists of two. The cochlear root, formed from the cells of the spiral ganglion (belonging to the plate of the bony cochlea), is responsible for the transmission of auditory impulses. The vestibule, coming from the vestibular ganglion, carries impulses from the vestibular labyrinth. Both roots articulate into one in the internal auditory canal and are directed inward in the middle of the pons and medulla oblongata (the VII pair is located somewhat lower). The fibers of the vestibule - a significant part of them - pass into the posterior longitudinal and vestibulospinal fascicles and the cerebellum. The fibers of the cochlea extend to the lower tubercles of the quadrigeminal and the medial geniculate body. The central auditory pathway originates here and ends in the temporal gyrus.

There is another sensory nerve that has received the number zero. At first it was called “accessory olfactory”, but was later renamed terminal due to the presence of a 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 peduncle. Before heading into the orbit, it forms a branched system. Its upper section consists of two branches going to the muscles - the superior rectus and the one that raises the eyelid. Bottom part is represented by three branches, two of which innervate the rectus muscles - the middle and inferior muscles, 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 quadruple create the beginning of the trochlear nerve, which appears on the surface in the roof area of ​​the fourth ventricle, forms a cross and stretches to the superior oblique muscle located in the orbit.

From the nuclei located in the tegmentum of the bridge, fibers pass that form 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.

The two components form the 11th accessory nerve. The upper one begins in the medulla oblongata - its cerebral nucleus, the lower one - in the spinal cord (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 foramen magnum, are directed into the cranial cavity and connect with the upper part of the nerve, creating a single trunk. Coming out of the skull, it divides into two branches. The fibers of the upper one grow into the fibers of the 10th nerve, and the lower one goes to the sternocleidomastoid and trapezius muscles.

Core 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.

Mixed fiber nerves

The anatomy of this group is complex due to its branched structure, which allows it to innervate many sections and organs.

Trigeminal

The area between the middle cerebellar peduncle and the pons is its exit point. The nucleus of the temporal bone forms the nerves: orbital, maxillary and mandibular. They have sensory fibers, and 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 access to the surface of the face after it penetrates through the infraorbital space.

The mandibular bifurcates into an anterior (motor) and posterior (sensitive) part. They provide a nerve network:

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

The mandibular division of the trigeminal nerve communicates with the auricular, submandibular and sublingual nuclei.

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

Cranial nerves make our lives easier every day, as they ensure the functioning of our body and the connection of the brain with the senses.

What it is?

How many are there in total and what functions does each of them perform? How are they usually classified?

General information

The cranial nerve is a collection of nerves that begin or end in the brainstem. There are 12 nerve pairs in total. Their numbering is based on the order of exit:

• I – responsible for the sense of smell
• II – responsible for vision
• III – allows the eyes to move
• IV – directs the eyeball down and out;
• V – is responsible for the measure of sensitivity of facial tissues.
• VI – abducts the eyeball
• VII – connects facial muscles and lacrimal glands with the CNS (central nervous system);
• VIII – transmits auditory impulses, as well as impulses emitted by the vestibular part of the inner ear;
• IX - moves the stylopharyngeal muscle, which lifts the pharynx and connects with the central nervous system parotid gland, makes the tonsils, pharynx, soft palate, etc. sensitive;
• X - innervates the chest and abdominal cavities, cervical organs and head organs;
• XI - provides nerve cells with muscle tissue that turns the head and raises the shoulder;
• XII - responsible for the movements of the lingual muscles.

Leaving the brain area, the cranial nerves go to the skull, which has characteristic openings for them. They exit through them, and then branching occurs.

Each of the nerves of the skull is different in composition and functionality.

How does it differ from, for example, a spinal cord nerve: the spinal nerves are predominantly mixed, and diverge only in the peripheral region, where they are divided into 2 types. FMNs represent either one or the other type and in most cases are not mixed. Pairs I, II, VIII are sensitive, and III, IV, VI, XI, XII are motor. The rest are mixed.

Classification

There are 2 fundamental classifications of nerve pairs: by location and functionality:
At exit point:

• extending above the brain stem: I, II;
• the exit site is the midbrain: III, IV;
• the exit point is Varoliev Bridge: VIII,VII,VI,V;
• the exit site is the medulla oblongata, or rather its bulb: IX, X, XII and XI.

By functional purpose:

• perception functions: I, II, VI, VIII;
• motor activity of the eyes and eyelids: III, IV, VI;
• motor activity of the cervical and lingual muscles: XI and XII
• parasympathetic functions: III, VII, IX, X

Let's take a closer look at the functionality:

ChMN functionality

Sensitive group

I – olfactory nerve.
Consists of receptors, which are thin processes that thicken towards the end. There are special hairs on the ends of the processes that capture odors.
II – nerve of vision.
It runs through the entire eye, ending in the visual canal. At the exit from it, the nerves cross, after which they continue their movement to the central part of the brain. The visual nerve delivers signals received from the outside world to the necessary sections of the brain.
VIII – vestibulocochlear nerve.
Belongs to the sensory type. Consists of 2 components, different in functionality. The first conducts impulses emanating from the vestibule of the inner ear, and the second transmits hearing impulses that emanate from the cochlea. In addition, the vestibular component is involved in regulating the position of the body, arms, legs and head and, in general, coordinates movements.

Motor group

III – oculomotor nerve.

These are processes of nuclei. Runs from the midbrain to the orbit. Its function is to engage the muscles of the eyelashes, which carry out accommodation, and the muscle that constricts the pupil.

IV - trochlear nerve.

It is of the motor type, located in the orbit, entering there through a gap from above (on the side of the previous nerve). Ends at the eyeball, or rather it superior muscle, which it provides to nerve cells.

VI – abducens nerve.

Like the block one, it is motor. It is formed by processes. It is located in the eye, where it penetrates from above, and provides nerve cells to the external eye muscle.

XI – accessory nerve.

Representative of the motor type. Dual-core. The nuclei are located in the spinal cord and medulla oblongata.

XII – hypoglossal nerve.

Type - motor. Nucleus in the medulla oblongata. Provides nerve cells to the muscles and muscles of the tongue and some parts of the neck.

Mixed group

V – trigeminal.

Leader in thickness. It got its name because it has several branches: ophthalmic, mandibular and maxillary.

VII – facial nerve.

It has a front and an intermediate component. The facial nerve forms 3 branches and provides normal movement of the facial muscles.

IX – glossopharyngeal nerve.

Belongs to the mixed type. Consists of three types of fibers.

X – vagus nerve.

Another representative of the mixed type. Its length exceeds that of the others. Consists of three types of fibers. One branch is the depressor nerve, ending in the aortic arch, regulating blood pressure. The remaining branches, which have a higher susceptibility, provide the membrane of the brain with nerve cells and skin ears.

It can be divided (conditionally) into 4 parts: the head section, the neck section, the chest section and the abdominal section. The branches extending from the head go to the brain and are called meningeal. And those that suit the ears are ear-friendly. The pharyngeal branches come from the neck, and the cardiac branches and thoracic branches depart from the chest, respectively. The branches directed to the plexus of the esophagus are called esophageal.

What can failure lead to?

The symptoms of the lesions depend on which nerve was damaged:

Olfactory nerve

Symptoms appear more or less pronounced, depending on the severity of the nerve damage. Basically, the defeat manifests itself in the fact that a person either senses odors more acutely, or does not distinguish between them, or does not feel them at all. A special place can be given to cases when symptoms appear only on one side, since their bilateral manifestation usually means that a person has chronic rhinitis

Optic nerve

If it is affected, vision deteriorates to the point of blindness on the side where it occurred. If part of the retinal neurons is affected or during the formation of a scotoma, there is a risk of local vision loss in a certain area of ​​the eye. If blindness develops bilaterally, it means that the optic fibers have been affected at the crosshairs. If damage occurs to the middle visual fibers, which completely intersect, then half of the visual field may fall out.

However, there are also cases when the visual field is lost in only one eye. This usually occurs due to damage to the optic tract itself.

Oculomotor nerve

When the nerve trunk is damaged, the eyes stop moving. If only part of the nucleus is affected, then the external eye muscle becomes immobilized or very weak. If, however, complete paralysis occurs, then the patient has no way to open his eyes. If the muscle responsible for raising the eyelid is very weak, but still functions, the patient will be able to open the eye, but only partially. The muscle that raises the eyelid is usually the last to be damaged. But if the damage reaches it, it can cause divergent strabismus or external ophthalmoplegia.

Trochlear nerve

Defeats for this couple are quite rare. It is expressed in the fact that the eyeball loses the ability to move freely outward and downward. This happens due to a violation of innervation. The eyeball seems to freeze in a position turned inward and upward. A characteristic feature of such damage will be double vision or diplopia, when the patient tries to glance down, to the right, or to the left.

Trigeminal nerve

The main symptom is segmental disturbance of perception. Sometimes sensitivity to pain or temperature may be completely lost. At the same time, the sensation from changes in pressure or other deeper changes are perceived adequately.

If the facial nerve is inflamed, then the half of the face that was affected hurts. The pain is localized in the ear area. Sometimes the pain can spread to the lips, forehead or lower jaw. If the optic nerve is affected, the corneal and brow reflexes disappear.

In cases of damage to the mandibular nerve, the tongue almost completely (2/3 of its area) loses the ability to distinguish tastes, and if its motor fiber is damaged, it can paralyze the masticatory muscles.

Abducens nerve

The main symptom is convergent strabismus. Most often, patients complain that they have double vision, and objects that are located horizontally appear double.

However, defeat of this particular pair separately from others rarely occurs. Most often, 3 pairs of nerves (III, IV and VI) are affected at once, due to the proximity of their fibers. But if the lesion has already occurred at the exit from the skull, then most likely the lesion will reach the abducens nerve, due to its greater length compared to the others.

Facial nerve

If the motor fibers are damaged, it can paralyze the face. Facial paralysis occurs on the affected half, which manifests itself in facial asymmetry. This is supplemented by Bell's syndrome - when trying to close the affected half - eyeball turns up.

Since one half of the face is paralyzed, the eye does not blink and begins to water - this is called paralytic lacrimation. Facial muscles can also be immobilized if the motor nucleus of the nerve is damaged. If the lesion also affects the radicular fibers, then this is fraught with the manifestation of Millard-Hubler syndrome, which manifests itself in blocking the movement of the arms and legs on the unaffected half.

vestibulocochlear nerve

When nerve fibers are damaged, hearing is not lost at all.
However, various hearing problems, irritation and hearing loss, even deafness, can easily occur if the nerve itself is damaged. Hearing acuity decreases if the lesion is of a receptor nature or if the anterior or posterior nucleus of the cochlear component of the nerve is damaged.

Glossopharyngeal nerve

If he is affected, the back of the tongue ceases to distinguish tastes, the top of the pharynx loses its receptivity, and the person confuses tastes. Loss of taste is most likely when the projection cortical areas are damaged. If the nerve itself is irritated, the patient feels burning pain ragged intensity near the tonsils and tongue, at intervals of 1-2 minutes. Pain can also occur in the ear and throat. When palpated, most often between attacks, the pain sensation is strongest behind the lower jaw.

Nervus vagus

If it is affected, the esophageal and swallowing muscles are paralyzed. Swallowing becomes impossible, and liquid food enters the nasal cavity. The patient speaks through his nose and wheezes, since the vocal cords are also paralyzed. If the nerve is affected on both sides, a suffocating effect may occur. Bari- and tachycardia begins, breathing becomes impaired and the heart may malfunction.

Accessory nerve

If the lesion is one-sided, it becomes difficult for the patient to raise his shoulders, and his head does not turn in the direction opposite to the affected area. But it leans towards the affected area willingly. If the lesion is bilateral, then the head cannot turn in either direction and falls back.

Hypoglossal nerve

If it is affected, the tongue will be completely or partially paralyzed. Paralysis of the periphery of the tongue is most likely if the nucleus or nerve fibers are affected. If the lesion is one-sided, the functionality of the tongue is slightly reduced, but if it is bilateral, the tongue paralyzes, and it can also paralyze the limbs.