8 Auditory and vestibular system 1 Auditory system • Transduction of sound waves to the receptor and the action potential • Transmission to CNS • Signal processing – Sound decoding – Interpretation 2 Auditory system • Transduction of sound waves to the receptor and the action potential • Transmission to CNS • Signal processing – Sound decoding – Interpretation 3 Sound • Produced by vibration of solid object in the air or water • Sound characteristics – Frequency – pitch – Amplitude – intensity – Timbre – given by representation of harmonic frequencies of the oscillation • Pure tone • Complex sound http://www.slideshare.net/drpsdeb/presentations 4 Sound • Pure tone • Complex sound – Harmonic (musical) • periodic – Disharmonic (noise) • aperiodic http://www.earmaster.com/music-theory- online/ch03/chapter-3-2.html http://physics.bowlerderby.com/soundwaves.html 5 Audible spectrum http://www.slideshare.net/drpsdeb/presentations 6 The intensity and volume of sound • Intensity of sound – Amplitude ➢ Whisper – 20 dB ➢ Speaking - 65 dB ➢ Jet engine – 100 dB ➢ Pain treshold – 120 dB https://www.boundless.com/physics/textbooks/boundless-physicstextbook/sound-16/sound-intensity-and-level-129/intensity-458-6077/ 7 The intensity and volume of sound • Intensity of sound – Amplitude ➢ Whisper – 20 dB ➢ Speaking - 65 dB ➢ Jet engine – 100 dB ➢ Pain treshold – 120 dB • Volume – subjectively perceived intensity https://www.boundless.com/physics/textbooks/boundless-physicstextbook/sound-16/sound-intensity-and-level-129/intensity-458-6077/ 8 External ear Transmission of acoustic signal from environment to the tympanic membrane http://www.slideshare.net/drpsdeb/presentations 9 Middle ear Transmission of acoustic signal from the tympanic membrane to the oval window and perilymph http://www.slideshare.net/drpsdeb/presentations 10 Middle ear • A significant difference in acoustic impedance between air and perilymph • Signal amplification – Tympanic membrane area/oval window area – Ossicles • Protective function – m.stapedius and tensor tympani – Eustachian tube http://slideplayer.com/slide/3433153/ 11 Inner ear Transduction of endolymph vibrations to receptor and action potential http://www.slideshare.net/drpsdeb/presentations 12 Tonotopic arrangement • Proximal part – high frequency • Distal part – low frequency http://www.slideshare.net/drpsdeb/presentations 13 Organ of Corti ➢Inner hair cells ➢ aprox. 3 500 ➢Outer hair cells ➢ aprox. 12 000 http://www.slideshare.net/drpsdeb/presentations 14 Inner hair cells ➢ Sensory function http://www.slideshare.net/drpsdeb/presentations 15 Outer hair cells • Modulation of the signal ✓ Amplification of required frequencies • The number increases towards apex (low frequencies) http://www.neurophys.wisc.edu/auditory/johc.htmlhttp://www.slideshare.net/drpsdeb/presentations 16 Outer hair cells • Modulation of the signal ✓ Amplification of required frequencies • The number increases towards apex (low frequencies) http://www.neurophys.wisc.edu/auditory/johc.htmlhttp://www.slideshare.net/drpsdeb/presentations 17 Inervation of the organ of Corti http://www.slideshare.net/drpsdeb/presentations 18 • Nucleus spiralis cochleae • Nucleus cochlearis ventralis – Information about intensity – Time delay – the sound direction • Nucleus cochlearis dorsalis – Information about frequency • Olivary nuclei – Analysis of direction – Modulation (increase) of the outer hair cells sensitivity • Colliculi inferiores – Integration of information from the lower structures – Centre of acoustic reflexes • N. corporis geniculati medialis – Thalamus • Auditory cortex http://www.slideshare.net/drpsdeb/presentations 19 Nucleus olivaris superior medialis Time delay based sound localization http://www.slideshare.net/drpsdeb/presentations 20 Nucleus olivaris superior lateralis Intensity analysis based sound localization http://www.slideshare.net/drpsdeb/presentations MNTB – medial nucleus trapezoid body 21 Colliculi inferiores in various animal species Gerald Schneider. 9.14 Brain Structure and Its Origins, Spring 2014. (Massachusetts Institute of Technology: MIT OpenCourseWare), http://ocw.mit.edu (Accessed). License:Creative Commons BY-NC-SA 22 Auditory cortex http://www.slideshare.net/drpsdeb/presentations 23 Vestibular system • Anatomic localization • Hair cells • Information about ➢ Position ➢ Acceleration ✓Linear ✓Angular http://www.slideshare.net/CsillaEgri/presentations 24 Vestibular system • Anatomic localization • Hair cells • Information about ➢ Position ➢ Acceleration ✓Linear ✓Angular http://www.slideshare.net/CsillaEgri/presentations 25 Information about position and linear acceleration • Macula – CaCO3 crystals • Utriculus – Horizontal macula • Sacculus – Vertical macula http://www.slideshare.net/CsillaEgri/presentations 26 Mechanism • Flexion towards stereocilia – Opening of mechanically activated K+ channels –depolarization • Flexion away from stereocilia – Closing of the channels - hyperpolariztion http://www.slideshare.net/CsillaEgri/presentations 27 Information about angular acceleration • Ampulla • Semicircular canals – Upper – Horizontal – Posterior http://www.slideshare.net/CsillaEgri/presentations 28 Vestibular nuclei Integration of vestibular, visual and somatosensoric information Projections – Cerebellum – Oculomotoric nuclei – Nucleus of n. Aaccessorius – the muscles of the neck – Thalamus - cortex http://www.slideshare.net/CsillaEgri/presentations 29