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Conduction deafness: ossification of ossicle articulations

Learn about the intricate workings of the ear, from tympanum and otitis media to hair cells and tonotopy in the cochlea. Discover how sound is perceived and processed, including topics on equilibrium, cochlear implants, and hearing aids.

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Conduction deafness: ossification of ossicle articulations

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  1. Fluid behind tympanum Otitis media =middle ear infection “tube” to relieve pressure and allow drainage. “Popping ears” and equalization of pressure across tympanic membrane. Conduction deafness: ossification of ossicle articulations Attenuation reflex protects cochlea from large vibrations = loud sounds

  2. Scala vestibuli Scala media Scala tympani

  3. Endolymph Organ of Corti

  4. Mechanosensitive K+ channels in Stereocilia Composition of endolymph

  5. Stereocilia with mechanically-gated K+ channels • Open K+ channels • Depolarize • Open Voltage-gated Ca++ channels • Release of NT from synaptic vesicles

  6. Activity of Hair Cells • Depolarization leads to more NT release • Hyperpolarization leads to less NT release

  7. All hair cells nearly identical • Basilar membrane thickens toward the apex

  8. Tonotopy in Cochlea Base Apex

  9. Coding for Pitch = frequency = tone & Intensity • Base .... high pitch (treble) • Apex .... low pitch (bass) • Pitch coded by location of vibrations of Organ of Corti : Which hair cells are stimulated…which set of sensory axons have action potentials • Intensity coded by degree of displacement of stereocilia of hair cells and ultimately the frequency of action potentials in those axons that are active

  10. Auditory Range • Humans: 20- 20,000 Hz; optimal 1000-4000 Hz Demo of auditory range and presbycusia

  11. Audiogram Decibel = unit for expressing relative loudness on a log scale “Nerve deafness” cause by damage to hair cells.

  12. Pure sine waves Fourier Analysis of Complex Waves Complex wave

  13. Pathway to Temporal Lobe In Brainstem Organ of Corti Hair Cells Cochlear Ganglion = Spiral Ganglion Superior Olive Cochlear Nuclei • VIII cranial nerve • Medial geniculate nucleus of thalamus MG of Thalamus Auditory Cortex

  14. Sound Localization • Low frequency by delay in arrival of soundwave between ears • High frequency by attenuation of intensity • Processed in Superior Olive • Practical Applications? L or R speaker w/ hi and lo frequency tone

  15. Tonotopy in Auditory Cortex

  16. Organs of Equilibrium

  17. Semicircular Canal • Angular acceleration • Three semicircular canals per ear in 3 planes

  18. Utricle and Saccule For static equilibrium (orentation to gravity)

  19. Vestibular Apparatus • Hair cells • NT release dependent upon degree of bending of kinocilium and microvilli • For ampula of semi-circular canals: cupula • For utricle and saccule: otolith membrane • Stereocilia in Endolymph (Hi K+, low Na+)

  20. Additional Topics • Information on cochlear implants • Hearing Aids • Understanding Speaker Frequency Response by Polk Audio’s Marketing Manager • Noise cancelling technology

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