Cranial nerves are nerves that do not stem from the spinal nerves but directly from specialized nerv cell clusters (nuclei) inside the brain stem.
All cranial nerves pass through the bony skull at characteristic sites.
The cranial nerves are numbered in roman numerals according to their chronological order of their exits from rostral to caudal.The classification though is not coherent.The olfactoric nerve fibres that come from the olfactory bulb are seen as the first cranial nerve. Different from that the Jacobson's organ is also seen as the first cranial nerve.The optic nerve is the second cranial nerve. Nowadays, it is generally agreed that the first and second cranial nerve are a tract of the brain and actually no specific nerves.1. The olfactoric nerve: Transmits signals from nose to brain.Sensory (special visceral afferent, taste perception) 2. The optic nerve: transmits signals from the retina to the brain.Sensory (special somatic afferent)3. The oculomotor: performs eye movement, innervates the levator palpebrae superioris and the iris. Somatomotor and vegetative (parasympathetic)4. The trochlear: controls the superior oblique muscle (somatomotor)5. The trigeminal: subdivides into opthalmic, maxillary and mandibular nerve. It transmits the sensory information of the face and innervates the masticatory muscles.6. The abducens: innervates the lateral eye muscle (somatomotor)7. The fascial: controls the muscles of fascial expression, the stapedius muscle, conveys the taste sensation of the anterior two-thirds of the tongue and innervates all glands in the head apart from the parotid gland. (brachiomotor, vegetative/parasympethatic and sensory qualities)8. The acoustic/vestibulocochlear: responsible for transmission of information from the cochlea and the balance system.Sensory.9. The glossopharyngeal: transmits the signals of the posterior tongue to the brain and innervates pharyngeal muscles. Important for swallowing. Also innervates the parotid gland. Sensory/sensitive, brachiomotor, vegetative/parasympathetic.10. The vagus: main nerve of the parasympathetic system and regulates viscera. Sensory/sensitive, vegetative/parasympathetic, brachiomotor.11. The accessory: motoric controll of trapezius and sternocleidomastoid muscle. The accessory actually comes from the spinal cord, though as it runs parallel to the spinal cord into the skull and also leaves the skullbase, it is seen as a cranial nerve.Somatomotor.12. The hypoglossi: controls tongue movement.Somatomotor.
