1. Cranial nerves

3. Classification of cranial nerves Sensory cranial nerves: contain only afferent (sensory) fibers  Ⅰ Olfactory nerve  Ⅱ Optic nerve  Ⅷ Vestibulocochlear nerve Motor cranial nerves: contain only efferent (motor) fibers  Ⅲ Oculomotor nerve  Ⅳ Trochlear nerve  Ⅵ Abducent nerve  Ⅺ Accessory nerv  Ⅻ Hypoglossal nerve Mixed nerves: contain both sensory and motor fibers---  Ⅴ Trigeminal nerve,  Ⅶ Facial nerve,  Ⅸ Glossopharyngeal nerve  Ⅹ Vagus nerve

4. Cranial Nerve I: Olfactory Arises from the olfactory epithelium Passes through the cribriform plate of the ethmoid bone Fibers run through the olfactory bulb and terminate in the primary olfactory cortex Functions solely by carrying afferent impulses for the sense of smell

6. Cranial Nerve II: Optic Arises from the retina of the eye Optic nerves pass through the optic canals and converge at the optic chiasm They continue to the thalamus where they synapse From there, the optic radiation fibers run to the visual cortex Functions solely by carrying afferent impulses for vision

8. Cranial Nerve VIII: Vestibulocochlear Fibers arise from the hearing and equilibrium apparatus of the inner ear, pass through the internal acoustic meatus, and enter the brainstem at the pons- medulla border Two divisions – cochlear (hearing) and vestibular (balance) Functions are solely sensory – equilibrium and hearing

9. Dysfunctions:  Vestibular vertigo and balance disturbances  Cochlear unilateral deafness and loss of sound appreciation

10. Cranial Nerve III: oculomotor  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 accommodation )

11. Damage causes drooping eyelid, dilated pupil, double vision, difficulty focusing and inability to move eye in certain directions.

12. Cranial Nerve IV: Trochlear Fibers emerge from the dorsal midbrain and enter the orbits via the superior orbital fissures; innervate the superior oblique muscle Primarily a motor nerve that directs the eyeball

13. Dysfunction: loss of downward, inner movement of eye

14. Cranial Nerve VI: Abdcuens  Fibers leave the inferior pons and enter the orbit via the superior orbital fissure.  Primarily a motor nerve innervating the lateral rectus muscle.  Dysfunction: loss of lateral eye movement

15. Cranial Nerve XI: Accessory Primarily a motor nerve –Supplies fibers to the larynx, pharynx, and soft palate –Innervates the trapezius and sternocleidomastoid, which move the head and neck Dysfunction: impaired head, neck, shoulder movement

16. Cranial Nerve XII: Hypoglossal Fibers arise from the medulla and exit the skull via the hypoglossal canal Innervates both extrinsic and intrinsic muscles of the tongue, which contribute to swallowing and speech

17. Dysfunction:  Unilateral lesions can cause paresis, atrophy, furrowing, fibrillation and fasciculation on the affected half  On protrusion tongue deviates towards the affected side due to unopposed action of the contralateral genioglossus

18. Cranial Nerve V: Trigeminal Composed of three divisions: ophthalmic (V 1 ), maxillary (V 2 ), and mandibular (V 3 ) Fibers run from the face to the pons via the superior orbital fissure (V 1 ), the foramen rotundum (V 2 ), and the foramen ovale (V 3 ) Conveys sensory impulses from various areas of the face (V 1 ) and (V 2 ), and supplies motor fibers (V 3 ) for mastication

21. Motor: muscles of facial expression & some others Parasympathetic: stimulation of lacrimal, submandibular, sublingual glands, nasal/palatal mucosa Special sense: taste to anterior 2/3 of tongue and palate Somatic sense: small part of ear area Branches travel throughout the head Complexity provides basis for clinical testing Cranial Nerve VII: Facial

23. Dysfunctions:  Motor paralysis of the muscles of facial expression  Parasympathetic loss or excessive tearing or salivation  Sensory loss of taste from anterior 2/3

24. Cranial 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. Glossopharyngeal

25.  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 Cranial Nerve X: vagus

26. Damage causes hoarseness or loss of voice, impaired swallowing. Gl dysfunction, blood pressure anomalies.