Anatomy and Physiology of Hearing: From Sound Waves to Auditory Hallucinations - Prof. Dou, Study notes of Biology

Download Anatomy and Physiology of Hearing: From Sound Waves to Auditory Hallucinations - Prof. Dou and more Study notes Biology in PDF only on Docsity! 7 February Figure 7.33 Tuning fork bends, compresses the air in front of it Sound waves Amplitude – loudness Period (T) – time between one peak and the next Frequency – pitch = 1/T Hertz (Hz) = cycles/second Human range – 20-20,000 Hz 30 dB – empty room 100 dB – enough to damage ears Speed of sound is a constant 340 m/sec (1,100 ft/sec) in air Figure 7.34 Pinna Outside of ear Capture sound waves Direct inward Auditory canal → eardrum (tympanic membrane) → malleus: connected to eardrum, incus, stapes: connected to cochlea Eustachian tubes open to relieve pressure between inner ear and rest of body Sound waves move tympanic membrane back and forth Therefore bones move Air pressure waves converted to mechanical movements of bone Converted to fluid pressure Figure 7.35 Stapes connected to oval window → scala vestibuli → turns corner at helicotrema → scala tympani → round window bulges Cochlear duct separated from scala vestibule and scala tympani by basilar membrane Figure 7.37 On basilar membrane is organ of Corti Connects to cochlear nerve Hair cells embedded Have projections – stereocilia Stick into tectorial membrane Fluid causes basilar membrane to move, hair cells to rub against tectorial membrane Bent one direction – hyperpolarization Other direction – depolarization Alters release of neurotransmitter, firing of nerve End of basilar membrane near stapes Stiffer Detect treble, high frequency Other end Less stiff, more flexible Detect bass, low frequency Lose hair cells on treble end Aging Difficulty with high frequency