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CRANIAL NERVES OUTLINE • • Cranial nerve nuclei locations Cranial nerves I-XII – Origin and Location – Course – General arrangement – Function • • • • • Nerves that are formed from nuclei in the brain 12 Cranial nerves CN I and II are components from the forebrain CN III-XII are from the brainstem CN –Sensory, motor, mixed Overview • • • • • CN I, II, and VIII are devoted to special sensory input. CN III, IV, and VI control eye movements and pupillary constriction. CN XI and XII are pure motor (XI: sternocleidomastoid and trapezius; XII: muscles of tongue). CN V, VII, IX, and X are mixed. CN III, VII, IX, and X carry parasympathetic fibers Functional components • Somatic efferent • Brachial efferent • Visceral efferent • Visceral afferent • Somatic afferent • Special sensory OPTIC NERVE • Formation of image on retina • Retina encodes information and project it to the brain via the optic nerve • Optic nerve undergoes semi decussation in optic chiasm and project to the lateral geniculate body • Thalamocortical neurons project image to the primary visual cortex • Visual pathway is a typical sensory pathway in the sense that: – It consists of 3 neurons – 1st order-bipolar cells of the retina synapse with ganglion cells – 2nd order- optic nerve, optic chiasm and optic tract – 3rd order- from the lateral geniculate bodies (thalamus) to the visual cortex OCLOMOTOR NERVE • Emerges from the midbrain • Nerve runs anteriorly from midbrain. • Enters orbit through superior orbital fissure (SOF) • Contains somatic efferent & visceral efferent fibers. Nuclei & distribution • Somatic efferent- oculomotor nucleus-extraocular muscles & levator palpebrae superioris • Visceral efferent: Edinger-Westphal nucleus; ciliary ganglion- pupillary sphincter & ciliary muscle TROCHLEAR NERVE • Emerges from posterior aspect of brainstem near midline, courses anteriorly around cerebral peduncle, enters orbit through SOF • Only cranial nerve which all fibers cross to opposite side • Only nerve that emerges from the dorsal side of brainstem Nucleus & distribution • Located in midbrain. • Supply superior oblique m. TRIGEMINAL NERVE • Motor and sensory roots • Has three branches that supplies different areas of the face: – Opthalmic • Mainly sensory but also gives secrotomotor – Maxillary • Sensory – Mandibular • Sensory and motor • • • • Largest division V3 Sensory and motor Exits the cranium via foramen ovale Three sensory branches – Supply the area of skin around the embryonic mandibular prominence • – Auricotemporal (secretomotor to parotid gland), buccal, mental Motor fibres to muscles of mastication, anterior belly of digastric, tensor veli pallatini, tensor tympani and mylohyoid ABDUCENT • Contains only somatic efferent fibers • Follows long extradural path before entering SOF • Lies at the pontomedullary junction Nucleus & distribution • Located in pons • Supply lateral rectus Facial • • • • • • • Motor and sensory/parasympathetic root Exits cranial cavity via internal acoustic meatus Emerges in cerebellopontine angle between pons & olive. Passes through internal acoustic meatus into petrous part of temporal bone, where it divides into its branches Visceral efferent fibres pass through the styloidmastoid foramen----parotid plexus Parasympatheic, visceral efferent & visceral afferent fibres pass through the petrotympanic fissure to base of skull While still in petrous bone, facial nerve gives off greater petrosal, stapedial & chorda tympani Nuclei, ganglia & distribution • Special visceral efferent: efferent from facial nucleus supply following muscles -facial expression -stylohyoid -posterior belly of diagastric -Stapedius • Visceral efferent (parasympathetic): PS preganglionic fibers arising from superior salivatory nucleus synapse with neurons in pterygopalatine ganglion or submandibular ganglion to innervate: lacrimal, submandibular & sublingual glands • Chorda tympani branch special sensory for taste to anterior 2/3rds • Of tongue (nucleus of solitary tract) REVIEW TABLE 8:1 FROM ONLINE TEXT CN VIII-XII will be done in class.