Auditory/Vestibular Anatomy Flashcards
2 Nerves of Ext Ear
Mostly V3, some X
2 Main Sections of Tympanic Membrane
Pars flaccida and tensa (larger, vibrates)
2 Windows
Oval which stapes pushes against and round as relief valve
Vestibular N VIII
Bipolar cells that go to vestibular nuclei (or some project to cerebellum)
3 Adjacent Ducts in Cochlear System
Scala vestibuli and tympani - perilymph filled
Scala media - endolymph filled
Helicotrema
End of cochlea where scala vestibuli and tympani meet
Propagation to Hair Cells
Sit on organ of Corti (in scala media) which is on basilar membrane b/w media and tympani. As perilymph in tympani moves, moves basilar membrane, pushing organ of Corti and hair cells against tectorial membrane, opening them
Cochlear Pitch Differentiation
Different Hz/wavelengths vibrate different parts of cochlear ducts. High pitches near round window and low pitches near helicotrema
Cochlear Nervous Pathway
Bipolar axons from cochlea, vestibulocochlear n. VIII w/ cell bodies in spiral ganglia, dorsal and ventral cochlear nuclei, 2nd order form dorsal and ventral cochlear nuclei, some cross at trapezoid body (goes up bilaterally), some synapse in superior olivary nuclei, ascend in lateral lemniscus to inferior colliculus (synapse), brachium of inferior colliculus to medial geniculate nucleus for thalamic relay, then auditory cortex
Left/Right Sound Descrimination
Each side bilaterally goes to each superior olive. It takes longer for signal from opposite side to reach, so it calculates which side the sound is on
Lesion in Internal Acoustic Meatus Effects
Hearing/vestibular/VII - taste ant 2/3, parasymp to non-parotid glands, etc gone
Acoustic Neuroma
Tumor in inner ear that bulges out, but puts pressure on VII and VIII
