Sensitive nerves. science technology technology
The nervous system regulates and coordinates the activity of all organs. It also ensures the interaction of the body with environment. The nervous system includes the brain and spinal cord (central nervous system), which process information and form commands to change the activity of organs, as well as nerves (peripheral nervous system), which connect the brain with organs.
What are nerves?
Nerves are bundles of fibers (outgrowths of nerve cells) surrounded by special sheaths. The number of nerve fibers in one nerve reaches tens and hundreds of thousands, so the diameter of the nerve ranges from fractions of a millimeter to a centimeter. The length of the nerves and the number of their branches are determined by the peculiarities of the structure and development of the organs to which the nerves are directed.
31 pairs of spinal nerves depart from the spinal cord (to the right and left sides of the body), which serve the organs, muscles and skin of the trunk and limbs. 12 pairs of cranial nerves depart from the brain, regulating the activity of mainly the organs of the head and neck. The longest of all cranial nerves - the vagus - is involved in the regulation of the work of the organs of the chest and abdominal cavities. The cranial nerves have serial numbers and their own names. They depart mainly from the brain stem - there are nuclei (nerve centers) of the cranial nerves. There are sensory, motor and mixed cranial nerves.
Sensory cranial nerves
Sensory nerves transmit information from the sense organs to the brain. These include the olfactory, optic, and vestibulocochlear nerves.
Olfactory nerve
Olfactory nerves transmit information to the brain from receptor cells located in the nasal mucosa. Thin threads of the nerve (15-20) penetrate the cranial cavity, the olfactory bulbs lying on the lower surface of the frontal lobes of the cerebral hemispheres. From here, the olfactory tracts begin, along which information is sent to the subcortical centers and to the cerebral cortex. If the frontal region is damaged, olfactory disorders are possible.
optic nerve
The optic nerve is formed by processes of nerve cells in the retina of the eye, emerging near the posterior pole of the eyeball. Inside the skull, the optic nerve fibers cross and pass into the optic tract, which ends in the subcortical centers. Further, the pathways go to the highest center in the cortex of the occipital lobe of the hemispheres. At the intersection of the optic nerves, only the nerve fibers coming from the inner halves of the retina cross, creating conditions for binocular vision (obtaining one image in both eyes). With damage to the optic nerve, optic chiasm or optic tract, visual impairment will vary, which makes it possible to diagnose their localization.
Vestibulocochlear nerve
The vestibulocochlear nerve consists of 2 parts: cochlear and vestibular. The first conducts impulses from the organ of hearing, the second - from the organ of balance. Hearing and balance receptors are located inside the temporal bone. Both parts of the nerve are connected in the internal auditory canal, from there they enter the cranial cavity. In the brain, the pathways for conducting auditory and vestibular information are different: the auditory center is located in the temporal lobe of the cerebral hemispheres, and the vestibular center is located in the cerebellum. If the temporal bone is damaged, not only hearing loss and balance disorder are possible, but also a violation of salivation and facial expressions, since next to the vestibulocochlear nerve in the internal auditory canal there is a nerve (facial) involved in innervation salivary glands and mimic muscles.
Motor cranial nerves
Motor cranial nerves conduct commands to the muscles of the eyeball, tongue, and some muscles of the neck.
Oculomotor, trochlear and abducens nerves
The oculomotor, trochlear and abducens nerves penetrate from the cranial cavity into the orbit and provide all the variety of movements of the eyeballs and the muscle that lifts the upper eyelid. With damage to the oculomotor nerve, divergent strabismus, eyelid drooping and pupil dilation are observed. Damage to the trochlear nerve gives the slanted position of the eyeballs and causes a doubling of the objects being viewed. If the abducens nerve is damaged, internal strabismus develops.
Accessory and hypoglossal nerves
The accessory nerve goes to the muscles involved in the movements of the head and neck. When it is damaged, torticollis is observed - a tilt of the head with a turn to the other side. The hypoglossal nerve conducts commands to the muscles of the tongue. With its defeat, there is a deviation of the tongue to the affected side, which affects the position of the larynx.
Mixed cranial nerves
The mixed cranial nerves include the trigeminal, facial, glossopharyngeal, and vagus nerves.
Trigeminal nerve
The trigeminal nerve has three main branches: the ophthalmic, maxillary, and mandibular nerves.
The optic nerve passes into the orbit and innervates its contents, the upper eyelid, the skin of the forehead and crown, the mucous membrane of the upper part of the nasal cavity and paranasal sinuses. The maxillary nerve is sensitive to the gums and teeth upper jaw, mucous membrane of the palate, nasal cavity and maxillary (maxillary) sinus, skin of the nose and cheeks. Sensory fibers of the mandibular nerve are sent to the gums and teeth mandible, the mucous membrane of the tongue and cheeks, as well as to the skin of the chin and the lower part of the auricle. The motor branches of the mandibular nerve conduct commands to the masticatory muscles. When damaged trigeminal nerve there are violations of the sensitivity of the skin of the face and palate, paralysis of the masticatory muscles may develop.
facial nerve
The facial nerve got its name due to the fact that its motor branches regulate the work of facial muscles. Sensory fibers of the facial nerve conduct taste stimuli from the anterior 2/3 of the tongue. Commands transmitted along the fibers of the facial nerve increase salivation and the production of tear fluid.
Glossopharyngeal nerve
The glossopharyngeal nerve innervates the mucous membrane of the posterior 1/3 of the tongue, the upper part of the pharynx and the tympanic cavity. The nerve contains a branch that conducts information from the carotid arteries about the state of the brain to the brain. blood pressure And chemical composition blood. Branches of the glossopharyngeal nerve leading to the muscles of the pharynx and the parotid salivary gland cause increased salivation.
Nervus vagus
The vagus nerve is the longest of the cranial nerves. Its numerous branches go to the muscles of the pharynx and soft palate, the organs of the neck, the skin of the auricle, the heart, the organs of respiration, digestion, the kidneys, and the endocrine glands. The large length of the vagus nerve is explained by the fact that in the distant ancestors of man, the organs innervated by it lay near the head and only in the process of evolution gradually moved back, stretching the nerve fibers.
On the neck, the vagus nerve passes in the region of the carotid artery and internal jugular vein, then goes to the mucous membrane of the root of the tongue, larynx, pharynx and esophagus. Its motor fibers regulate the volume and pitch of the voice and the act of swallowing. A large number of branches of the vagus nerve to the heart. In the chest cavity, it passes along the wall of the esophagus and gives branches to the esophagus, trachea, bronchi, lungs and heart, forming nerve plexuses around these organs. Under the influence of the vagus nerve, the heart slows down and weakens contractions, and the bronchi narrow.
Together with the esophagus, the vagus nerve passes through the diaphragm into the abdominal cavity, where it innervates the stomach, liver, spleen, pancreas, kidneys, small intestine and part of the large intestine. Under the action of the vagus nerve, the secretion of the digestive glands and intestinal motility are activated; the adrenal glands reduce the production of hormones. The vagus nerve is involved in the implementation of vomiting. Damage to the vagus nerve, depending on the location, can lead to dysfunction of the gastrointestinal tract (spastic conditions), a disorder of cardiac activity, laryngeal function (loss of sonority of the voice) and the act of breathing.
Vagotomy
Vagotomy reduces the acidity of gastric juice, because it blocks conduction
to the gastric mucosa of nerve impulses that increase secretion
acids by the parietal cells of the mucosa. When stem
vagotomies cross the entire vagus nerve. With selective
vagotomies cross only certain branches of the 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 of the cerebral vesicles. 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
| Numbering | Name | Functions |
|---|---|---|
| I | Olfactory | Susceptibility to odors |
| II | Visual | Transmission of visual stimuli to the brain |
| III | Oculomotor | Eye movements, pupillary response to light exposure |
| IV | Blocky | Moving the eyes down, outward |
| V | ternary | Facial, oral, pharyngeal sensitivity; the activity of the muscles responsible for the act of chewing |
| VI | diverting | Eye movement outward |
| VII | Facial | Muscle movement (facial, stirrup); activity salivary gland, sensitivity of the anterior part of the tongue |
| VIII | Auditory | Transmission of sound signals and impulses from the inner ear |
| IX | Glossopharyngeal | The movement of the muscle-lifter of the pharynx; activity of paired 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, partly in the ear canal and eardrums, the dura mater; smooth muscle activity (gastrointestinal tract, lungs) and cardiac |
| XI | Additional | Leading the head into various directions, shrugging the shoulders and bringing the shoulder blades to the spine |
| XII | Sublingual | Movements and movements of the tongue, acts of swallowing and chewing |
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 (the VII pair is somewhat lower). 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.
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.
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. The nucleus of the temporal bone forms the 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).
The mandibular division of the trigeminal nerve communicates with the auricular, submandibular, and hypoglossal nuclei.
The name of this nerve is known more than the other 11 pairs: many are familiar, at least by hearsay, about
Mechanical stimuli are transformed into a nervous process in the tactile receptors themselves, among which the tactile Meissner bodies occupy a special place in humans. The excitation that has arisen in them is transmitted along the nerve fibers, which are sensitive conductors, to the central nervous system. The paths of sensitive conductors are very diverse. What they have in common is that they enter the peripheral nerve, which is the nerve trunk. In this nerve trunk, both sensory and motor fibers are created. Before entering the spinal cord, the sensory (afferent) and motor (efferent) nerves separate: all motor nerves make up the anterior pair of spinal cord roots, and the sensory nerves make up the posterior pair of spinal cord roots.
Most of the nerves human body are mixed, and therefore, when they are affected, sensory disorders are almost always combined with motor disorders. However, in some cases, due to the unequal vulnerability of the fibers, the latter are affected selectively (for example, diphtheria toxin affects motor fibers more strongly, and the influenza virus affects sensitive ones). But this provision applies to the peripheral nerves before the divergence of sensory and motor fibers in the spinal cord.
Here, the anterior (motor) roots leave the spinal cord and go again to the periphery, making up a common nerve trunk with sensory fibers. The path from the periphery to the spinal cord and back to the periphery is the nervous
the path of spinal motor reflexes, the most elementary in their organization.
Otherwise, the path of sensory or sensory nerves that conduct mechanical irritation develops. These nerves pass through the posterior spinal ganglion and divide into ascending and descending branches that branch off to various cells in the spinal cord. The descending branches end in the same segment of the spinal cord, and the ascending ones rise to the medulla oblongata, where they end in the nuclei, from which the nerve fibers go to the optic tubercle and further to the cerebral cortex. On this path, the sensory nerves have, as it were, two switching stations: one in the spinal ganglion, the other in the medulla oblongata.
For diseases nervous system the change in the localization of the sensory nerves along this path is clearly distinguished. Sensitive fibers belonging to one posterior root or one segment supply a certain continuous area on the skin, called the radicular zone of sensitivity. Therefore, it is easy for a neuropathologist to distinguish a disorder of skin sensitivity of spinal origin from disorders of tactile sensitivity of peripheral origin.
The further course of the sensory nerves that conduct stimulation of tactile receptors can be judged by sensitivity disorders in lesions of the thalamus. In this case, tactile sensitivity is most strongly upset only on one half of the body, and the skin sensitivity of the hand suffers more than the skin sensitivity of the leg. With this lesion, the boundary between tactile and pain sensitivity disappears. A simple touch causes pain. Such painfully increased sensitivity is called hyperesthesia (as opposed to loss of sensation, anesthesia). This type of disorder indicates that the circular localization of skin sensations at the level of the spinal "station" of the sensory nerves has been replaced by a one-sided localization of these sensations at the level of the thalamus.
An electrophysiological study of the action currents of tactile sensory nerves showed that the impulse that occurs when a weak mechanical stimulus (touch) is applied has a high frequency (up to 200 m in 1 sec), speed, discontinuity (up to 80 m in 1 sec) and the rapid onset of adaptation to the stimulus. The speed of conducting impulses of tactile stimuli into the cortex exceeds the conduction of pain impulses by about 8 times.
The peripheral nervous system includes 31 pairs of spinal nerves and 12 pairs of cranial nerves that travel from the spinal cord and brain to the periphery.
Olfactory nerve (n. olfactorius) (I pair) refers to the nerves of special sensitivity. It starts from the olfactory receptors of the nasal mucosa in the superior nasal concha. Represents 15-20 thin nerve threads formed by non-fleshy fibers. The threads do not form a common trunk, but penetrate into the cranial cavity through the ethmoid plate of the ethmoid bone, where they are attached to the cells of the olfactory bulb (bullus olfactorius), which is a collection of mitral cells. Intertwined with the dendrites of the bulb cells, the fibers of the filaments form the olfactory tract (tractus olfactorius). The fibers of the olfactory pathway conduct an impulse to the subcortical, or primary, centers of smell, from where some of the fibers go to the cerebral cortex (vaulted gyrus).
Optic nerve (n. opticus) (II pair) also refers to nerves of special sensitivity. Its fibers originate from the ganglion cells of the retina. The nerve formed by them penetrates into the eye sockets, and from there into the cranial cavity through the optic canal of the sphenoid bone. In the region of the sphenoid bone, the nerve fibers partially cross, that is, they cross the fibers coming from the medial halves of the retina. Moving to the opposite side, the medial fibers are connected to the fibers of the lateral part, as a result, the optic tract (tractus opticus) (Fig. 254, 255) begins from the intersection, which ends in the subcortical centers of vision, consisting of the lateral geniculate body, the optic tubercle and the upper mounds of the plate of the roof of the midbrain. From the subcortical centers of vision, impulses enter the visual analyzer located in the cortex of the occipital lobe of the brain, on both sides of the spur groove.
Oculomotor nerve (n. oculomotorius) (III pair) is mixed. The nucleus of the oculomotor nerve lies at the level of the superior colliculus of the midbrain, in the tegmentum of the cerebral peduncles, from the medial side of which the nerve exits. From the skull through the superior orbital fissure, the oculomotor nerve passes into the orbit and divides into two branches - superior and inferior. The branches of the oculomotor nerve approach the levator levator lid muscle, the superior, internal, and inferior rectus muscles, and the inferior oblique muscle of the eyeball.
Block nerve (n. trochlearis) (IV pair) related to motor nerves. The nucleus of the trochlear nerve is located in the midbrain. Rounding the brain stem from the lateral side, the nerve exits to the base of the brain, passing between the brain stem and the temporal lobe. Then, together with the oculomotor nerve, it passes from the skull to the orbit and innervates the superior oblique muscle of the eyeball.
Trigeminal nerve (n. trigeminus) (V pair) is mixed. In it, a motor nucleus is isolated, located in the tire of the bridge and giving rise to fibers that form the motor root (radix motoria), and a sensitive nucleus.
Sensitive fibers start from the cells of the trigeminal ganglion (ganglion trigeminale) and form a sensitive root (radix sensoria). Both roots exit the brain at the border of the pons and middle cerebellar peduncles and divide into orbital, maxillary, and mandibular branches. The ophthalmic nerve (n. ophthalmicus) is sensitive, exits the skull into the orbit through the superior orbital fissure and is divided into three branches:
Frontal nerve (n. frontalis), which gives several branches going to the skin of the forehead and back of the nose;
Lacrimal nerve (n. lacrimalis), passing along the outer wall of the orbit and ending in the lacrimal gland and the upper eyelid;
Nasociliary nerve (n. nasociliaris), heading to the eyeball, eyelids, lacrimal sac, mucous membrane of the lattice cells of the sphenoid sinus, nasal cavity and skin of the back of the nose.
The maxillary nerve (n. maxillaris) is also sensitive. It exits the skull into the pterygopalatine fossa through a round hole and goes to the orbit through the infraorbital fissure. Then it passes through the infraorbital groove and infraorbital canal. In this area, the maxillary nerve is called the infraorbital nerve (n. infraorbitalis). It exits through the infraorbital foramen and penetrates the skin of the face.
Throughout the maxillary nerve, the following branches depart:
The zygomatic nerve (n. zygomaticus) goes to the skin of the neck and the anterior parts of the temporal region;
Upper alveolar nerves (nn. alveolaris superiores) perforate the thickness of the upper jaw, forming the upper dental plexus, the branches of which innervate the gums and teeth of the upper jaw;
Palatine nerves (nn. palatini) pass through the large and small palatine canals and enter the oral cavity through the large and small palatine openings, heading to the mucous membrane of the hard and soft palate;
Posterior nasal branches (rr. nasales posterior) go to the mucous membrane of the nasal cavity through the sphenopalatine opening.
The mandibular nerve (n. mandibularis) is mixed, exits the skull through the oval hole in the greater wing of the sphenoid bone and branches into sensory, motor and mixed branches.
Sensitive branches include:
Ear-temporal nerve (n. auriculotemporalis), heading to the anterior part of the auricle, the external auditory meatus and the skin of the temple;
Buccal nerve (n. buccalis), which innervates the buccal mucosa;
Lingual nerve (n. lingualis), giving branches that lie in the first two thirds of the back of the tongue.
Motor branches include:
Chewing nerve (n. massetericus), which innervates the masticatory muscle;
Deep temporal nerves (nn. temporales profundi), heading to the temporal muscle;
Medial and lateral pterygoid nerves (nn. pterygoidei medialis et lateralis), suitable for the muscles of the same name;
The nerve of the muscle that strains the palatine curtain (n. tensoris veli palatini), which innervates the muscle of the same name and the soft palate;
The nerve of the muscle that strains the eardrum (n. tensoris timpani), which innervates the muscle of the same name.
The mixed branch is the lower alveolar nerve (n. alveolaris inferior). Its motor branch goes to the maxillohyoid muscle and the anterior belly of the digastric muscle. Then, leaving through the opening of the lower jaw into the canal of the same name, it gives branches that form the lower dental plexus, thus innervating the gums and teeth of the lower jaw. The terminal branch of the lower alveolar nerve is called the mental nerve (n. mentalis), passes through the mental opening of the lower jaw and goes to the lower lip and skin of the chin.
Abducens nerve (n. abducens) (VI pair) related to motor nerves. Its core lies in the region of the bridge, from where the nerve exits to the base of the brain, passing between the pyramid and the bridge. From the skull, the abducens nerve exits through the superior orbital fissure into the orbit, where it innervates the lateral rectus muscle of the eyeball.
Facial nerve (n. facialis) (VII pair) is also a motor nerve, the nucleus of which is located in the region of the bridge. Passing between the bridge and the olive, the nerve is at the base of the brain, and then through the internal auditory opening enters the temporal bone. Moving along the internal auditory meatus and the canal of the facial nerve, the facial nerve exits through the stylomastoid foramen to the outer surface of the base of the skull. Passing through the thickness of the parotid gland and branching into terminal branches, the nerve forms the so-called large crow's foot on the face. The terminal branches of the facial nerve are divided into temporal, zygomatic, buccal. The cervical branch of the facial nerve and the marginal branch of the lower jaw are also distinguished. The terminal branches innervate the posterior belly of the digastric muscle, the mimic muscles of the face, and partly the subcutaneous muscle of the neck.
The vestibulocochlearis nerve (n. vestibulocochlearis) (VIII pair) refers to the nerves of special sensitivity and consists of two parts: the vestibular root (radix vestibularis) and the cochlear root (radix cochlearis), starting inside the pyramid of the temporal bone in the inner ear. The vestibular nerve conducts impulses from a static apparatus located in the vestibule and semicircular canals of the inner ear. The cochlear nerve is the conductor of impulses of the organ of Corti, located in the cochlea of the inner ear and responding to sound stimuli. Both nerves leave the pyramid of the temporal bone to the brain through the internal auditory opening, passing through the internal auditory meatus. The place of their exit is located lateral to the facial nerve. Nerve fibers terminate at the nuclei of these nerves, which lie in the lateral corners of the rhomboid fossa.
Glossopharyngeal nerve (n. glossopharyngeus) (IX pair) is mixed, with a predominance of the sensitive part. Sensory fibers start from sensory nodes located in the region of the jugular foramen, through which the glossopharyngeal nerve exits the skull, and motor fibers, like the vagus nerve, from the cells of the double nucleus, which lies in the rhomboid fossa.
Sensory nerves include:
Tympanic nerve (n. tympanicus), following into the tympanic cavity, where it forms a nerve plexus, the branches of which are directed to the mucous membrane of the tympanic cavity and the auditory tube;
Lingual branches (rr. linguales), which innervate the posterior third of the tongue;
Pharyngeal branches (rr. pharyngei), heading to the mucous membrane of the pharynx;
Branches of the tonsils (rr. tonsillares), which are suitable for the mucous membrane of the palatine tonsils and arches.
Motor nerves include:
The branch of the stylo-pharyngeal muscle (r. musculi stylopharyngei), which innervates the stylo-pharyngeal muscle;
Pharyngeal branches (rr. pharyngei), which, uniting with the vagus nerve, are sent to the muscles of the pharynx.
Vagus nerve (n. vagus) (X pair)(Fig. 266, 267) is mixed. Its motor fibers start from the cells of the motor nucleus, and the sensory ones - from the cells of the sensory ganglia, which lie in the region of the jugular foramen. From the brain, the vagus nerve exits behind the olive, and from the skull through the jugular foramen and is divided into many branches that go to the organs of the head, neck, chest and abdominal cavities.
Head office includes:
Branch of the brain (r. meningeus), heading to the dura mater of the posterior cranial fossa;
Ear branch (r. auricularis), which innervates the skin of the auricle and external auditory canal.
Neck section includes:
Pharyngeal branches (rr. pharyngei), which take part in the formation of the pharyngeal plexus, combine with the branches of the glossopharyngeal nerve and innervate the muscles of the pharynx and palatine arches, and the sensory nerves innervate the mucous membrane of the pharynx;
Superior laryngeal nerve (n. laryngeus superior), which innervates the region of the mucous membrane of the larynx, located above the vocal cords, as well as some muscles of the larynx;
The upper and lower cardiac branches (rr. cardiaci cervicales superiores et inferiores), which take part in the formation of the cardiac plexuses that innervate the heart.
The thoracic region includes:
Recurrent laryngeal nerve (n. laryngeus recurrens) (Fig. 266), which, branching, innervates the trachea and esophagus, and its final branch, called the lower laryngeal nerve (n. laryngeus inferior), goes to the mucous membrane and muscles of the larynx;
Thoracic cardiac branches (rr. cardiaci thoracici) involved in the formation of the cardiac plexus;
Bronchial and tracheal branches (rr. bronchiales et tracheales), going to the mucous membrane, smooth muscles and glands of the bronchi and trachea;
Esophageal branches (rr. esophagei), innervating the walls of the esophagus.
The abdominal region includes:
Anterior and posterior gastric branches (rr. gastrici anteriores et posteriores), which descend from the esophagus to the stomach, forming the anterior and posterior gastric plexuses and innervating the mucous membrane and glands of the stomach;
The celiac branches (rr. celiaci) are a continuation of the gastric nerves and through the blood vessels, together with the sympathetic plexuses, are sent to the pancreas, liver, spleen, kidneys, small and large intestine, up to the sigmoid colon.
Accessory nerve (n. accessorius) (XI pair)(Fig. 266, 267) refers to the motor nerves and consists of two parts. wandering part accessory nerve is represented by cranial roots (radices craniales), starting from the motor nucleus, which lies in the region of the medulla oblongata, and emerging from the brain behind the olive, below the vagus nerve. The spinal part includes the spinal roots (radices spinales), heading up from the spinal cord and exiting into the cranial cavity through the foramen magnum. After exit, both parts are combined and exit the skull through the jugular foramen, where they are again divided into internal and external branches. The inner branch goes to the vagus nerve, and the outer one goes to the trapezius and sternocleidomastoid muscles.
Hypoglossal nerve (n. hypoglossus) (XII pair)(Fig. 265, 266, 267) also refers to the motor nerves. It starts from the nucleus, which lies in the rhomboid fossa, and, passing between the pyramid and the olive, exits the brain into the skull, and from there it goes through the hypoglossal nerve canal to the muscles of the tongue. One of its branches, descending, connects with the branch of the cervical plexus and participates in the formation of a cervical loop that innervates the neck muscles located below the hyoid bone.
Motor and sensory nerves.
What are motor and sensory nerves?
The nervous system ensures the vital activity of the body due to the ability to respond to external and internal stimuli. The nervous system is divided into central and peripheral. The divisions of the nervous system differ in their functions. The functions of the somatic nervous system can be controlled by consciousness, meanwhile, the functions of the autonomic nervous system are not controlled by our consciousness - it regulates vital important processes in organism. Nerves are made up of parallel nerve fibers. According to their functions, the fibers of the nervous system are divided into motor, sensory and autonomic.
ON A NOTE
Sometimes it is extremely difficult to find out the cause of pain. It is necessary to check whether the pain is caused by psychological causes.
Information about sensations, recorded by sensitive nerve fibers, enters the brain. Sensations experienced on the left side of the body are transmitted to the right hemisphere of the brain and vice versa.
motor fibres.
Motor nerve fibers transmit excitation from the central nervous system to the striated muscles. Thanks to them, we can tense our muscles, breathe, etc.
sensitive fibres.
Along sensitive nerve fibers, impulses propagate from peripheral receptors to the central nervous system. Thanks to sensitive fibers, we feel pain, cold and heat, determine the mass and shape of objects.
vegetative fibers.
They form the autonomic or autonomic nervous system, which coordinates the activity of smooth muscles, various glands, and the heart. The autonomic nervous system is divided into two sections: sympathetic and parasympathetic, which regulate activity in different ways. internal organs. For example, with increased functioning of the parasympathetic nervous system, diarrhea appears. If the sympathetic nervous system dominates, then reverse processes occur.
Major motor and sensory nerve fibers.
The peripheral nervous system includes the cranial and spinal nerves, as well as the nerves of the autonomic nervous system.
cranial nerves.
Humans have 12 pairs of cranial nerves. Nerves consist of motor or sensory fibers, or they can be mixed, i.e. consist of both. The cranial nerves originate in the brain stem or medulla oblongata and innervate the tissues of the head and neck. Let's name all the cranial nerves: Olfactory nerve (lat. P. olfactorius; sensitive). The optic nerve (lat. p. opticus; sensitive).
Oculomotor nerve (lat. P. oculomotorius; motor, autonomic).
Block nerve (lat. P. trochlearis; motor).
Trigeminal nerve (lat. p. trigeminus; motor, sensitive).
Facial nerve (lat. p. facialis; motor, sensory, autonomic).
Vestibulocochlear nerve (lat. P. vestibulocochlea-ris; sensitive).
Abducens nerve (lat. p. abducens; motor). Glossopharyngeal nerve (lat. p. glossophaiyngeus; sensitive, motor, autonomic).
Vagus nerve (lat. p. vagus; sensitive, motor, autonomic). Accessory nerve (Latin accesorius; motor). Hypoglossal nerve (lat. p. hypoglossus; motor)
The structure of nerves.
Basic structural unit nervous system is a neuron. A nerve is made up of bundles of nerve fibers. An axon departs from the body of the neuron. Most axons have a myelin sheath.
Regeneration
Damaged fibers of the peripheral nervous system may grow together. Operations on nerve fibers (suturing or transplantation) are performed only by microsurgeons. Damaged nerve fibers of the central nervous system are not restored.
Spinal nerves.
31 pairs of spinal nerves leave the spinal cord:
Neck nerves, 8 pairs. Roots extend from the cervical part of the spinal cord.
Thoracic nerves, 12 pairs. Roots extend from the thoracic part of the spinal cord.
Lumbar nerves, 5 pairs. The roots depart from the lumbar part of the spinal cord.
II. Sacral nerves, 5 pairs. The roots originate from the sacral part of the spinal cord. Coccygeal nerves, 1 pair. Roots extend from the terminal part of the spinal cord.
The spinal nerves innervate the muscles of the trunk, as well as the muscles of the lower and upper extremities.
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