Cranial Nerve Physiology Flashcards
What is the pathway of the olfactory nerve?
Receptors in olfactory epithelium of nasal cavity, olfactory nerve fibres pass through foraminifera in cribriform plate and enter the olfactory bulb in the anterior cranial fossa
What are the component parts of the olfactory nerve?
Special sensory- smell
What are the clinical applications of the olfactory nerve?
Fractured cribriform plate may tear olfactory nerve fibres causing anosmia
What is the pathway of the optic nerve?
Enters via optic canal, nerves join to form optic chiasm, fibres from medial (nasal) half of each retina cross to form optic tract
What are the component parts of the optic nerve?
Special sensory-vision
What are the clinical applications of the optic nerve?
Increase in CSF pressure can cause papilloedema
Section of right optic nerve causes blindness through right eye
Section of optic chiasm causes loss of peripheral vision (bitemporal hemianopsia)
Section of right optic tract causes blindness in left temporal and right nasal fields (left homonymous hemianopsia)
What is the pathway of the oculomotor nerve?
Emerges from midbrain and exits via superior orbital fissure
What are the component parts of the oculomotor nerve?
Somatic motor - extraocular muscles (superior, medial & inferior rectus and inferior oblique) and eyelid (levator palpebrae superioris)
Visceral motor - parasympathetic to pupil causing constriction and to ciliary muscle causing accommodation of the lens
What is the clinical application of the oculomotor nerve?
Drooping of upper eyelid (ptosis)
Eyeball abducted and pointing down
No pupillary reflex
No accommodation of the lens
What is the pathway of the trochlear nerve?
Emerges from dorsal surface of the mid brain and exits via the superior orbital fissure
What are the component parts of the trochlear nerve?
Somatic motor - extraocular muscle (superior oblique turns eye downwards)
What are the clinical applications of the trochlear nerve?
Diplopia when looking down
What is the pathway of the ophthalmic branch of the trigeminal nerve?
Emerges from the pons, travels through the trigeminal ganglion and exits via the superior orbital fissure
What is the pathway of the maxillary branch of the trigeminal nerve?
Emerges from the pons, travels through the trigeminal ganglion and exits via the foramen rotundum
What is the pathway of the mandibular branch of the trigeminal nerve?
Emerges from the pons, travels through the trigeminal ganglion and exits via the foramen ovale
What are the component parts of the ophthalmic branch of the trigeminal nerve?
General sensory - from cornea, forehead, scalp, eyelids, nose and mucosa of nasal cavity and sinuses