CRANIAL NERVES Dr. Amani A. Elfaki Associate Professor Department of Anatomy
LEARNING OBJECTIVES Named the cranial nerves Identify the funcunal component of each cranial nerve Identify the effect of each cranial nerve damage
The cranial nerves named as follows:- 1. Olfactory 2. Optic 3. Ocluomotor 4. Trochlear 5. Trigeminal 6. Abducent 7. Facial 8. Vestibulocochlear 9. Glossopharyngeal 10. Vagus 11. Accessory 12. Hypoglossal
FUNCUNAL COMPONENTS
Sensory means afferent to CNS Motor means efferent from the CNS
Sensory means afferent to CNS General sensation from somatic organ (muscle, skin) = GSA General sensation from viscera = GVA Special sensation of taste & smell = SVA Special sensation of vision and audition = SSA
Motor means efferent from the CNS Motor to skeletal muscles = GSE Autonomic secretomotor to viscera =GVE Motor to muscles of a special origin = SVE
Olfactory Nerve I Sense of smell Damage causes impaired sense of smell
Optic Nerve II Provides vision Damage causes blindness in visual field
Oculomotor Nerve III Somatic and Autonomic motor function Eye movement (Superior, inferior, medial rectus muscles and inferior oblique muscle), opening of eyelid (levator palpebrae superioris), constriction of pupil (circular muscle), focusing (ciliary muscle and accomodation) Damage causes drooping eyelid, dilated pupil, double vision, difficulty focusing and inability to move eye in certain directions
Trochlear Nerve IV Eye movement (superior oblique muscle) Damage causes double vision and inability to rotate eye inferolaterally
Trigeminal Nerve V Ophthalmic branch sensations from nasal cavity, skin of forehead, upper eyelid, eyebrow, nose Maxillary branch sensations from lower eyelid, upper lips and gums, teeth of the maxilla, cheek, nose, palate, pharynx Mandibular branch sensations from teeth of the mandible, lower gums and lips, palate, tongue. Motor function of temporalis and masseter muscles. Damage produces loss of sensation and impaired chewing
Abducens Nerve VI Provides eye movement (lateral rectus m.) Damage results in inability to rotate eye laterally and at rest eye rotates medially
Facial Nerve VII Somatic Motor - facial expressions Autonomic Motor - salivary and lacrimal glands, mucous membranes of nasal and palatine mucosa Special Sensory - taste on anterior 2/3 s of tongue Damage produces sagging facial muscles and disturbed sense of taste (no sweet and salty)
Branches of Facial Nerve Clinical test: Test anterior 2/3 s of tongue with substances such as sugar, salt, vinegar, and quinine; test response of tear glands to ammonia fumes; test motor functions by asking subject to close eyes, smile, whistle, frown, raise eyebrows, etc.
Vestibulocochlear Nerve VIII Special Sensory Provides hearing (cochlear branch) and sense of balance (vestibular branch) Damage produces deafness, dizziness, nausea, loss of balance and nystagmus
Glossopharyngeal Nerve IX Somatic motor Swallowing and voice production via pharyngeal muscles Autonomic motor - salivation, gagging, control of BP and respiration Sensations from posterior 1/3 of tongue including taste Sensations from baroreceptors and chemoreceptors Damage results in loss of bitter and sour taste and impaired swallowing, blood pressure anomalies (with CN X).
Vagus Nerve X Sensations from skin at back of ear, external acoustic meatus, part of tympanic membrane, larynx, trachea, espophagus, thoracic and abdominal viscera Sensations from bararoceptors and chemoreceptors Special sensory taste from epiglottis and pharynx Somatic motor Swallowing and voice production via pharyngeal muscles Autonomic motor smooth muscle of abdominal viscera, visceral glands secretions, relaxation of airways, and normal or decreased heart rate. Damage causes hoarseness or loss of voice, impaired swallowing, GI dysfunction, blood pressure anomalies (with CN IX), fatal if both are cut
Accessory Nerve IX Swallowing, head, neck and shoulder movement via trapezius and sternocleidomastoid and pharyngeal muscles Damage causes impaired head, neck, shoulder movement
Hypoglossal Nerve XII Tongue movements for speech, food manipulation and swallowing If both are damaged can t protrude tongue If one side is damaged tongue deviates towards injured side
Cranial Nerve Disorders Trigeminal neuralgia (tic douloureux) recurring episodes of intense stabbing pain in trigeminal nerve area (near mouth or nose) pain triggered by touch, drinking, washing face treatment may require cutting nerve Bell s palsy disorder of facial nerve causes paralysis of facial muscles on one side may appear abruptly with full recovery within 3-5 weeks