Cranial nerves

  • IV - VI couples
  • VII - IX couples
  • X - XII couples
  • Cranial nerves twelve pairs of nerves in the brain; there is also an intermediate nerve that some authors consider XIII pair. Craniocerebral nerves are located at the base of the brain (Fig. 1). Part of the cranial nerves are predominantly motor functions (III, IV, VI, XI, XII pairs), others-sensitive (I, II, VIII pair), the rest are mixed (V, VII, IX, X, XIII pairs). In certain cranial nerves are parasympathetic and sympathetic fibers.

    12 pairs of cranial cerebral nerves
    Fig. 1. The base of the brain. The cranial nerves:
    a - olfactory bulb;
    b - the optic nerve;
    in - olfactory tract;
    g - oculomotor nerve;
    d - block nerve;
    e - trigeminal nerve;
    W - lateral nerve;
    C - front and intermediate nerves;
    and - predverno-cochlear nerve.
    K - language-pharyngeal and vagus nerves;
    l - hypoglossal nerve;
    m - extension nerve.

    I pair, olfactory nerve (n. olfactorius), originates from the nerve cells of the mucous membrane of the nose. Fine fibrils this nerve pass in the skull through the holes lattice plates ethmoid bone, come to the olfactory bulb, which then goes into the olfactory tract. Extending backwards, this tract forms olfactory triangle. At the level of the olfactory tract and of the triangle lies olfactory tubercle, in which end of the fiber coming from the olfactory bulb. In the olfactory cortex fiber distributed in the hippocampus. With the defeat of the olfactory nerve occurs complete loss of smell - anosmia or partial violation of hyposmia.
    II pair, optic nerve (n. opticus), starts from the ganglion cells of the layer of the retina. Extensions of these cells gather in the optic nerve, which, after the entry into the cavity of the skull forms on the base of the brain, optic chiasm - hiazmu. But this is not a complete intersection, it crossed only the fiber coming from the inner halves of the retina. After intersection of the optic nerve carries the name of the optic tract, which ends in the outer geniculate body. From the outside geniculate body starts Central visual path that ends in the occipital cortex of the brain. If any pathological processes in the brain, affecting the intersection of the optic nerve, optic tract or the way, there are various forms of loss of vision fields - hemianopsia.
    Optic nerve disorders can be inflammatory (neuritis), long (long nipple) and dystrophic (atrophy) of the character.
    Cause optic neuritis may be different disease (meningitis, encephalitis, arachnoiditis, multiple sclerosis, flu, inflammation sinusal nose , and others).
    Manifested by a sudden decrease in visual acuity and the narrowing of the field of view.
    Congestive nipple is the most important symptom of increasing intracranial pressure, which may be associated most often with a brain tumor, occasionally gummow, a solitary tuberculum, cyst and other Stagnant nipple for a long time does not lead to visual impairment is found when fundoscopy. When the disease is reduced visual acuity and may come blindness.
    Optic atrophy may be primary (when the spinal " dryness", syphilis of the brain, multiple sclerosis, injured optic nerve and others) or secondary, as the outcome neuritis or congestive nipple. In this disease there is a sharp decrease in visual acuity up to blindness, and the narrowing of the field of view.
    Treatment depends on the etiology of the disease.

    scheme of conducting the visual pathways
    Fig. 2. Scheme of conducting the visual pathways.

    III pair, oculomotor nerve (n. oculomotorius), formed fibers running from the same nuclei lying in the Central gray matter, under the running water of the brain (selview water supply). Out on the base of the brain between his legs through the top orbital cleft, penetrates into the eye socket and innervates all the muscles of the eyeball except the superior oblique and external direct muscles. Contained in the eye parasympathetic nerve fibers nerviruet smooth muscles of the eye. The defeat of the pair III is characterized by drooping of the upper eyelid (ptosis), divergent strabismus and mydriasis (pupil dilation).