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Cranial Nerves

Cranial Nerves. Cranial Nerves. Cranial Nerves. Cranial Nerves. Cranial Nerves. Indicated by Roman numerals I-XII from anterior to posterior May have one or more of 3 functions Sensory (special or general) Somatic motor (skeletal muscles)

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Cranial Nerves

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  1. CranialNerves

  2. CranialNerves

  3. CranialNerves

  4. CranialNerves

  5. CranialNerves • Indicated by Roman numerals I-XII from anterior to posterior • May have one or more of 3 functions • Sensory (special or general) • Somatic motor (skeletal muscles) • Parasympathetic (regulation of glands, smooth muscles, cardiac muscle) • Proprioception • Positional information of body parts

  6. Modalities- Sensory • GSS:General Somatic Sensory: • General senses from ectoderm (skin) • Pain, temperature, pressure, vibration, and proprioception • SSS:Special Somatic Sensory: • Special senses derived from ectoderm: • Sight, sound, balance. • GVS:General Visceral Sensory: • General sensation from viscera • SVS:Special Visceral Sensory: • Special senses derived from endoderm: • Taste and smell

  7. Modalities- Motor • GSM:General Somatic Motor: • Skeletal muscles. • GVM:General Visceral Motor: • To smooth muscles of gut tract, glands, vessels, and all other internal organs • General visceral motor is autonomic motor. • SVM:Special Visceral Motor: • Muscles derived from pharyngeal arches. • Masticatory muscles • Muscles of facial expression • Pharyngeal muscles • Laryngeal muscles • Tongue muscles

  8. Generalizations • Cranial nerves have same basic structure as spinal nerves. Dorsal root and ventral root. Dorsal root ganglion. • Motor components of cranial nerves begin within brain within motor nuclei. Comparable to spinal cord anterior horns. • Cell bodies of sensory fibers are located in dorsal root (cranial) ganglia.

  9. Generalizations • Special sensory cranial nerves: Are actually tracts. No motor nuclei and no sensory ganglia. • Motor cranial nerves: Begin in cranial motor nuclei. Have no sensory roots and no sensory root ganglia. • Mixed cranial nerves: Have both cranial motor nuclei and sensory ganglia. Sensory ganglia are usually given specific names.

  10. Generalizations • For each cranial nerve know: Modality (modalities). Function (functions). Sensory areas and/or muscles innervated. Foramen through which it passes. Specific ganglion (if applicable). Specific information included in this slide presentation.

  11. CranialNerves • Special Sense Nerves • I,II,VIII • Somatic Motor Nerves • Eye—III,IV,VI • Tongue--XII • “Rest of body” nerves • IX,X,XI • Face and jaws • VII, V

  12. SENSORY SpecialGeneral Smell skin Vision teeth Hearing eye tongue oral cavity nasal cavity middle ear throat meninges MOTOR Muscles Glands eyes salivary extrinsic sweat intrinsic lacrimal jaws mucous larynx tongue throat ear facial expression Nerve “Targets” in Head

  13. NERVE TARGET ENTER to CRANIAL CAVITY I. Olfactory Olfactory epithelium Cribiform plate (ethmoid) II. Optic Retina Optic canal (sphenoid) VIII. Auditory Inner ear Internal auditory meatus (temporal) Special Sense Nerves

  14. Olfactory Nerve

  15. Cranial nerve I Function: smell Clinical test for damage: determine whether a person can smell something aromatic CN I: OLFACTORY

  16. Olfactory Nerve (CN I) • Olfactory nerve fibers pass from: Olfactory receptor cells. Through: Cribriform plate. To: Olfactory bulbs. • Modality: SVS

  17. Optic Nerve (CN II) • Begins in ganglionic layer of retina (not rods and cones). • Exits orbit through optic canal. • 50% decussation in optic chiasma: • Near pituitary gland • Near internal carotid • Modality: • SSS

  18. Optic Nerve

  19. Cranial nerve II Function: vision Clinical test for damage: tests peripheral vision and visual acuity Effects of damage: blindness in part or all of the visual field CN II: OPTIC

  20. Vestibulocochlear Nerve

  21. Vestibulocochlear Nerve (CN VIII) • Leaves cranial cavity via internal acoustic meatus: Accompanied by facial nerve. • Modality: SSS • Auditory (cochlear) component: Cell bodies in spiral ganglion of cochlea. Function: Hearing.

  22. Vestibulocochlear Nerve (CN VIII) • Vestibular component: Cell bodies in vestibular ganglion. From receptors for balance and equilibrium. Function: Balance.

  23. CN VIII: VESTIBULOCOCHLEAR • Cranial Nerve VIII • Function: hearing and equilibrium • Clinical tests: test hearing, balance, and ability to walk a straight line • Effects of damage: deafness, dizziness, nausea, loss of balance, and nystagmus

  24. NERVE TARGET EXIT CR. CAVITY IV. Trochlear Superior oblique m. (with trochlea) Sup. orbital fissure (sphenoid) VI. Abducens Lateral rectus “ III. Oculomotor (Also parasympathetic to ciliary mm, constrictor pupillae) • Sup.,med.,inf.rectus • Inferior Oblique • Levator palpebrae • superioris “ XII. Hypoglossal Intrinsic, extrinsic mm. of tongue Hypoglossal canal (occipital) Somatic Motor Nerves(Eye Muscles and Tongue)

  25. Trochlear Nerve

  26. CNIV: TROCHLEAR • Cranial nerve IV • Function: eye movements and proprioception • Clinical test for injury: ability to rotate eye inferolaterally • Effects of damage – double vision, patient tilts head toward affected side

  27. Trochlear Nerve (CN IV) • Enters orbit through superior orbital fissure. • Innervates superior oblique muscle of the eye. • Modality: GSM. • Only crossed cranial nerve. • Only cranial nerve that emerges dorsally.

  28. Abducens Nerve

  29. Abducens Nerve (CN VI) • Enters orbit through superior orbital fissure. • Lies on medial aspect of lateral rectus muscle. • Innervates lateral rectus muscle of the eye. • Modality: GSM.

  30. Cranial Nerve VI Function: Eye movements Clinical test: lateral eye movement Effects of damage: inability to rotate eye laterally; at rest – eye rotates medially because of action of antagonistic muscles CN VI: ABDUCENS

  31. Oculomotor Nerve

  32. Oculomotor Nerve (CN III) • Supplies four of the six extrinsic muscles of the eye. • Has a parasympathetic component. • Will be discussed in a group with other parasympathetic nerves.

  33. CNIII: OCULOMOTOR • Cranial nerve III • Function: • eye movements, opening of eyelid, constriction of pupil, focusing, proprioception • Clinical tests for injury: • differences in pupil size; pupillary response to light; eye tracking • Effects of damage • dropping eyelid, dilated pupil, double vision

  34. Hypoglossal Nerve

  35. Hypoglossal Nerve (CN XII) • Exits cranial cavity via hypoglossal foramen. • Descends anteriorly in neck between internal carotid and internal jugular. • In neck gives rise to superior root of ansa cervicalis and a nerve to thyrohyoid muscle. • Supplies extrinsic and intrinsic muscles of tongue. • Modality: GSM.

  36. Cranial Nerve XII Function: tongue movements of speech, food manipulation, and swallowing Clinical test: tongue function Effects of damage: difficulty in speech and swallowing; atrophy of tongue; inability to stick out (protrude) tongue CN XII: HYPOGLOSSAL

  37. “Rest of Body” Nerves(all exit from jugular foramen)

  38. Glossoharyngeal Nerve

  39. Cranial Nerve IX Function: swallowing, salivation, gagging; touch, pressure, taste, and pain sensations from tongue, pharynx, and outer ear Clinical tests: gag reflex, swallowing, and coughing Effects of damage: difficulty swallowing CN IX: GLOSSOPHARANGEAL

  40. Vagus Nerve

  41. Cranial Nerve X Function: swallowing; taste; speech; respiratory, CV, and GI regulation; sensations of hunger, fullness, and intestinal discomfort Clinical tests: test with cranial nerve IX Effects of damage: hoarseness or loss of voice; impaired swallowing and GI motility CN IX: GLOSSOPHARANGEAL AND CN X: VAGUS

  42. Accessory Nerve

  43. Spinal Accessory Nerve (CN XI) • Arises from C1-3 (4). • Single trunk enters cranial cavity through foramen magnum. • Temporarily joins cranial root. Cranial roots leave with vagus nerve.

  44. Spinal Accessory Nerve (CN XI) • Spinal accessory trunk exits cranial cavity via jugular foramen. • Supplies: Sternocleidomastoid and trapezius. • Modality: SVM.

  45. Cranial Nerve XI Function: swallowing; head, neck, and shoulder movements Clinical tests: rotate head and shrug shoulders against resistance Effects of damage: impaired movement of head, neck, and shoulders; paralysis of sternocleidomastoid CN XI: ACCESSORY

  46. Facial Nerve(exits cranial cavity with VIII--internal auditory meatus) • Facial muscles (five branches fan out over face from stylomastoid foramen) • Temporal • Zygomatic • Buccal • Mandibular • Cervical • “chorda tympani” (crosses interior ear drum to join V3 ) • Taste to anterior 2/3 of tongue • Submandibular, sublingual salivary glands • Lacrimal glands

  47. Facial Nerve

  48. Facial Nerve

  49. Cranial Nerve VII Function: facial expression; sense of taste Clinical test: motor functions – close eyes, smile, whistle, frown, raise eyebrows; taste Effects of damage: inability to control facial muscles; distorted sense of taste CN VII: FACIAL

  50. Trigeminal Nerve (3 nerves in 1!) • V1. Ophthalmic • Exits with eye muscle group (superior orbital fissure, through orbit to superior orbital notch/foramina) • Sensory to forehead, nasal cavity • V2. Maxillary • Exits foramen rotundum through wall of maxillary sinus to inferior orbital foramina) • Sensory to cheek, upper lip, teeth, nasal cavity • V3. Mandibular • Exits foramen ovale to mandibular foramen to mental foramen • Motor to jaw muscles--Masseter, temporalis, pterygoids, digastric • Sensory to chin • Sensory to tongue

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