8 Auditory and vestibular system Auditory and vestibular system2 Auditory system Auditory and vestibular system3 • Transduction of sound waves to the receptor and the action potential • Transmission to CNS • Signal processing – Sound decoding – Interpretation Auditory system Auditory and vestibular system4 • Transduction of sound waves to the receptor and the action potential generation • Transmission to CNS • Signal processing – Sound decoding – Interpretation http://www.slideshare.net/drpsdeb/presentations Auditory system Auditory and vestibular system5 • Air/water vibration caused by solid object • 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 Sound Auditory and vestibular system6 • Pure tone – Determined by frequency • Complex sound – Sum of pure tones ➢ Harmonic (musical) • periodic ➢ Disharmonic (noise) • aperiodic http://www.earmaster.com/music-theory- online/ch03/chapter-3-2.html http://www.acoustics.salford.ac.uk/acoustics_info/sound_synthesis/ http://www.slideshare.net/drpsdeb/presentations Audible spectrum Auditory and vestibular system7 http://www.slideshare.net/drpsdeb/presentations The intensity and volume of sound Auditory and vestibular system8 • Intensity of sound – Amplitude ➢ Whisper – 20 dB ➢ Speaking - 65 dB ➢ Jet engine – 100 dB ➢ Pain treshold – 120 dB • Volume – Subjectively perceived intensity The intensity and volume of sound Auditory and vestibular system9 • Intensity of sound – Amplitude ➢ Whisper – 20 dB ➢ Speaking - 65 dB ➢ Jet engine – 100 dB ➢ Pain treshold – 120 dB • Volume – Subjectively perceived intensity External ear Auditory and vestibular system10 ✓ Transmission of acoustic signal from environment to the tympanic membrane http://www.slideshare.net/drpsdeb/presentations Middle ear Auditory and vestibular system11 ✓ Transmission of acoustic signal from the tympanic membrane to the oval window and endolymph/basilar membrane –ossicular vs bone conduction http://www.slideshare.net/drpsdeb/presentations Middle ear Auditory and vestibular system12 • A significant difference in acoustic impedance between air and endolymph • Signal amplification – Tympanic membrane area/oval window area – Ossicles • Protective function – m.stapedius and tensor tympani – Eustachian tube http://slideplayer.com/slide/3433153/ Inner ear Auditory and vestibular system13 ✓ Transduction of endolymph/basilar membrane vibrations to receptor and action potential http://www.slideshare.net/drpsdeb/presentations Tonotopic arrangement Auditory and vestibular system14 • Proximal part – high frequency • Distal part – low frequency http://www.slideshare.net/drpsdeb/presentations Basilar membrane Auditory and vestibular system15 • Basal part – Narrow and tight High frquencies • Apical part – Wide and loose Low frequencies http://lh6.ggpht.com/_RIjx_Mg4ZVM/TNeYbcwJOYI/AAAAAAAACmA/9S_7HaZu5DI/s1600-h/image%5B62%5D.png https://www.semanticscholar.org/paper/Mass-and-Stiffness-Impact-on-the-Middle-Ear-and-the-Kim- Koo/16a2a6b5ffd1c963efd906cea109277bfbf0d7e3/figure/3 Organ of Corti Auditory and vestibular system16 ➢Inner hair cells ➢ aprox. 3 500 ➢Outer hair cells ➢ aprox. 12 000 ➢Tectorial membrane http://www.slideshare.net/drpsdeb/presentations Inner hair cells Auditory and vestibular system17 ➢ Sensory function http://www.slideshare.net/drpsdeb/presentations Outer hair cells Auditory and vestibular system18 • Modulation of the signal ✓ Amplification of required frequencies • The number increases towards apex (low frequencies) http://www.slideshare.net/drpsdeb/presentations http://www.neurophys.wisc.edu/auditory/johc.html Inervation of the organ of Corti Auditory and vestibular system19 http://www.slideshare.net/drpsdeb/presentations Sound processing Auditory and vestibular system20 • 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 Nucleus olivaris superior medialis Auditory and vestibular system21 ✓ Time delay based sound localization http://www.slideshare.net/drpsdeb/presentations Nucleus olivaris superior lateralis Auditory and vestibular system22 ✓ Intensity analysis based sound localization http://www.slideshare.net/drpsdeb/presentations Colliculi inferiores in various animal species Auditory and vestibular system23 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 https://www.animalfactsencyclopedia .com/Tarsier-facts.html https://en.wikipedia.org/wiki/Nu bian_ibex https://www.thesun.co.uk/tech/3543919/hum ans-communicate-with-dolphins-by-2021/ https://www.earth.com/news/bats- mammal-longevity/ Auditory cortex Auditory and vestibular system24 http://www.slideshare.net/drpsdeb/presentations Vestibular system Auditory and vestibular system25 • Associated with auditory system – Anatomic localization – Hair cells • Information about ➢ Position ➢ Acceleration ✓Linear ✓Angular http://www.slideshare.net/CsillaEgri/presentations Vestibular system Auditory and vestibular system26 • Associated with auditory system – Anatomic localization – Hair cells • Information about ➢ Position ➢ Acceleration ✓Linear ✓Angular http://www.slideshare.net/CsillaEgri/presentations Information about position and linear acceleration Auditory and vestibular system27 • Macula – CaCO3 crystals • Utriculus – Horizontal macula • Sacculus – Vertical macula http://www.slideshare.net/CsillaEgri/presentations Mechanism of reception ➢Flexion towards stereocilia ̶ Mechanically activated K+ channels are opened –depolarization ➢Flexion away from stereocilia ̶ The channels are clsed - hyperpolariztion http://www.slideshare.net/CsillaEgri/presentations Auditory and vestibular system28 Information about angular acceleration Auditory and vestibular system29 • Ampulla • Semicircular canals – Upper – Horizontal – Posterior http://www.slideshare.net/CsillaEgri/presentations Vestibular nuclei Auditory and vestibular system30 ✓ Integration of vestibular, visual and somatosensoric information ✓ Projections • Cerebellum • Oculomotoric nuclei • Nucleus of n. Accessorius – the muscles of the neck • Spinal nuclei • Thalamus - cortex http://www.slideshare.net/CsillaEgri/presentations 76. The basic physiology of auditory and vestibular system – brief characterization of the modality, basic information about signal detection and processing Auditory and vestibular system31 • The auditory and vestibular systems are interconnected by similar mechanisms of reception (“hair cells” activated by mechanical stimuli) • Auditory system • Brief characteristic of sound • Overview of ear anatomy and physiology • Middle ear more in details • Inner ear in details (anatomy, hair cells categorization and function…) • Main structures involved in signal processing and source localization • Vestibular system • Overview of anatomy with respect to fucnction (detection of position, linear and angular acceleration) • Main projections from vestibular nuclei • Nystagmus (presentation Vision II)