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How we Hear Biology 2121

Chapter 15. How we Hear Biology 2121. Nature of Sound. What is sound? Pressure disturbances (high and low pressure) Produced by vibrating object (molecule vibration) Compression of air molecules (high pressure) and rarefacation (low pressure)

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How we Hear Biology 2121

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  1. Chapter 15 How we HearBiology 2121

  2. Nature of Sound • What is sound? Pressure disturbances (high and low pressure) • Produced by vibrating object (molecule vibration) • Compression of air molecules (high pressure) and rarefacation(low pressure) • Compression and rarefactions are called sound waves.

  3. Nature of Sound • 6. Frequency: number of waves pass a point / time • Wavelength: distance between two crests • Frequency range of hearing : 20-20,000 Hz. • Most sensitive- 1500 to 4000 Hz • Ultrasonic Sound • 9. Pitch, Loudness and decibels

  4. Parts of the ear- Outer ear • OuterEar • (1). Helix and Lobule • (2). ExternalAcousticMeatus (Auditory Canal) • (3). CeruminousGlands • (4). TympanicMembrane • TheTympanicCavity – Middle Ear • (1). AuditoryOssicles • Malleus • Incus • Stapes • Skeletal Muscles

  5. Middle Ear TheTympanicCavity – Middle Ear (1). Pharyngotympanic (auditory) Tube (2). Skeletal Muscles **OtitisMedia

  6. inner ear • Entrance - Inner Ear • (1). Vestibular and CochlearWindows • The Inner Ear • (1). OsseousLabyrinth • Vestibule, Cochlea and Semicircular Canals • Filled with perilymph

  7. Inner Ear • (2). MembranousLaybrinth • Sacs and ducts inside the osseous labyrinth • Filled with endolymph

  8. Inner ear – Vestibule • The Vestibule • (1). Perilymph surrounds sacs • Saccule and Utricle • Maculae – Equilibrium Receptors • The Semicircular Canals • (1). Contains: • Semicircularduct • Ampulla – CristaAmpullaris

  9. cochleA • TheCochlea • (1). Cochlearduct • Organ of Corti • Modiolus • (2). SpiralLamina divides bony cochlea into 3-area • Scalavestibuli • Scala media • Scala Tympani • (3). Helicotrema

  10. Organ of corti • (1). ScalaVestibuliand Tympani– perilymph • (2). ScalaMedia– contains Organ of Corti (Endolymph) • Cochlear Duct • (3). ScalaMedia • StriaVascularis – external wall (endolymph) • Floor – basilar membrane (supports organ of corti) – where CN VIII originates

  11. Formation of cN VIII (Auditory nerve) • CN VIII • (1). CochlearNerve • Afferent fibers coiled around hair cells in the Organ of Corti • (2). VestibularNerve • Wound around hair cells in the Maculae

  12. Basilar membrane SoundWavestoaNerveTransduction (1). Soundwaves and vibrations through the outer and inner ear (2). Ossiclesvibrate – oval window sets fluids in motion (3). Perilymph in motion (4). Activation of the basilarmembrane and Organ of Corti Frequencies (1). Low <20 Hz (2). Highest Sensitivity– 1500 to 4000 Hz

  13. Video Link • Process of Hearing • Transduction • Deafness

  14. Activation of the Basilar Membrane – Excitement of Hair Cells • (1). Pressure waves through the cochlear duct sets the basilar membrane into vibration • (2). Inner and Outer Hair Cells • Stereocilia and Kinocilium • Bending of the Cilia – Nerve Transduction

  15. Pathway to the brain

  16. Equilibrium PathWay to Brain

  17. deafness • Types • (1). Conduction • (2). Sensorineural • Profound vs. Hard of Hearing • Cochlear Implants

  18. Equilibrium – Maculae • (1). Vestibule • Maculae – Static Equilibrium • (2). Structure • Hair Cells and Otoliths • Vestibular Nerve VIII • (3). Response • Vertical movements

  19. Equilibrium - Semicircular Canal • (1). CristaAmpularis • Ampulla • (2). Rotational and Angular movements • Acceleration and deceleration • (3). Structure • Cells – supporting and hair • Cupula

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