The nervous system includes the spinal cord and brain, nerves branching from them and their branches. All nerve branches connect to the peripheral nervous system. There are 12 pairs of cranial nerves and 31 pairs of spinal nerves. Each pair has its own name and number, which is indicated by a Roman numeral. The cranial nerves are located at the base of the brain. According to the composition of nerve fibers, three of their functions are distinguished: motor, sensitive and mixed.
Sensitive cranial nerves are formed from fibers of neurons that lie outside the brain. These include the olfactory, optic and auditory nerves. They provide vestibular function, hearing, vision and smell. The first pair starts from nerve cells that are located in the nasal mucosa. With the defeat of this nerve, there is a complete loss of the ability to smell. The second pair is the optic nerve, which originates in the cells of the retina. Its atrophy leads to a sharp decrease in visual acuity, sometimes to complete blindness. The eighth auditory pair of nerves is responsible for the hearing and activity of the vestibular apparatus. If his work is disturbed, dizziness, hearing loss, ataxia, vestibular dysfunction occur.
Motor function combines five pairs of nerves. They originate in the motor nuclei of the trunk. The third, fourth and sixth pair of nerves are associated with the device and movement of the eyes. The oculomotor nerve is the third pair. It is formed by fibers starting from the nuclei of the same name. The parasympathetic fibers contained in this nerve innervate the muscles of the eye. The affected cranial nerves of the third pair are characterized by prolapse of the upper eyelid, divergent strabismus and dilated pupil. With the defeat of the IV block nerve in vision, doubling of objects is noted. When the gaze is lowered, a slight squint appears. If the activity of the abduction nerve VI is disrupted , the movement of the eyeball outside changes, this leads to a convergent strabismus and double vision.
The facial nerve (VII) controls the facial muscles. Additionally, it contains fibers of taste sensitivity and has vegetative fibers that regulate the function of the salivary and lacrimal glands. The incremental XI nerve regulates the function of certain types of muscle. With its defeat, muscle paresis or paralysis appears. The last, sublingual XII nerve is connected to the muscles of the tongue. If the activity of this nerve is impaired, there is a limitation of the mobility of the tongue forward and its deviation to the sick side. Atrophy of the muscles, pains of the root of the tongue, fibrillar twitching is manifested.
Mixed functions of the cranial nerves are performed by V, IX, and X pairs. The fifth, trigeminal nerve controls the chewing muscles and provides facial sensitivity. The glossopharyngeal (IX) nerve is responsible for salivation, palatability, and the state of the pharynx and tongue. The vagus (X) nerve provides sensitivity to the posterior portions of the oral cavity, larynx, and pharynx. He is responsible for the functioning of their muscles. Cranial nerves of the X pair provide a parasympathetic interconnection of internal organs.
With the defeat of the trigeminal nerve, there are attacks of sharp pains of a neuralgic nature in the corresponding areas of the face. They are accompanied by redness and lacrimation. With pathology of the IX pair, pain in the pharynx is felt, difficulty swallowing occurs, a taste disorder is noticed, salivation is impaired. When the vagus nerve is damaged, deviations in the activity of internal organs occur. With bilateral damage, there is an upset swallowing, nasal tone of speech, pain in the auricle. Such violations are always accompanied by a difficult prognosis.