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AUDITORY PHYSIOLOGY

AUDITORY PHYSIOLOGY. Mr. Arjun Maitra Assistant Professor Dept. of Physiology PCMS&RC. TO MY STUDENTS HERE I HAVE TRIED TO SIMPLIFY THE HUGE SUBJECT WITH ANIMATIONS, DIAGRAMS, FLOW CHARTS & RELEVENT MCQs. DIFFERENT TEXT BOOKS AND REFERENCE BOOKS HAVE BEEN USED FOR

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AUDITORY PHYSIOLOGY

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  1. AUDITORY PHYSIOLOGY Mr. Arjun Maitra Assistant Professor Dept. of Physiology PCMS&RC

  2. TO MY STUDENTS HERE I HAVE TRIED TO SIMPLIFY THE HUGE SUBJECT WITH ANIMATIONS, DIAGRAMS, FLOW CHARTS & RELEVENT MCQs. DIFFERENT TEXT BOOKS AND REFERENCE BOOKS HAVE BEEN USED FOR PREPARING THE CONTENTS. REMEMBERTHESE SLIDES ARE NOT THE SUBSTITUTE OF YOUR TEXT BOOKS ANIMATIONS AND DIAGRAMS ARE COLLECTED FROM DIFFERENT WEBSITE SOLELY FOR EDUCATION PURPOSE.

  3. ACOUSTICS • f= c/l l = wave length • f = frequency • c = velocity • FREQUENCY = PITCH • PEAK SENSITIVITY OF HUMAN EAR • 250 = 4000Hz SOUND PRESSURE LEVEL = DECIBEL SPL = 20 log10P / Pref P= AMPLITUDE Pref =2 X10(-5)Pa 10 FOLD SPL= 20dB LOUDNESS = PHON BY THE AGE OF 50 UPPER RANGE NARROWS TO 12000Hz AUDITORY RANGE = 20 Hz – 20,000Hz ACUITY AT THE RANGE 1000 – 4000Hz, FREQUENCY DISCRIMINATION 2 - 6Hz

  4. HUMAN EAR

  5. MIDDLE EAR

  6. EAR DRUM IS CRITICALLY DAMPED AT HEARING THRESHOLD VIBRATE WITH AN AMPLITUDE OF ABOUT 0.01nm (1/10 OF DIAMETER OF HYDROGEN ATOM) WOW!!! EFFICIENCY OUTPUT TO INNER EAR 30% (OVERALL) 60% (BELOW 3000Hz) SOUND AMPLIFICATION = 1.3 X 17=22.1 TIMES TYMPANIC REFLEX : REDUCES SOUND BY 20dB REACTION TIME = 40 – 60 ms

  7. WELCOME TO INNER EAR WELCOME TO INNER EAR

  8. COCHLEA 35mm LONG MAKES 2 ¾ TURNS

  9. HELICOTREMA

  10. ORGAN OF CORTI

  11. ARRANGEMENTS OF HAIR CELLS 20,000 3500

  12. OUTER HAIR CELLS TIPS ARE EMBEDDED IN TECTORIAL MEMBRANE INNERVATED BY UNMYELINATED AXONS OF SMALL BIPOLAR CELLS(TYPE II) 10:1 CONVERGENCE

  13. INNER HAIR CELLS TIPS ARE FLOATING FORM RIBBON SYNAPSE INNERVATED BY MYELINATED AXONS OF LARGE BIPOLAR CELLS (TYPE I) 1:10 DIVERGENCE

  14. TIP LINK

  15. ACTUALLY WHAT HAPPENS WHEN A SOUND WAVE COMES

  16. PERILYMPH & ENDOLYMPH Chemical Composition of the Cochlear fluids ST SV Perilymph Perilymph Endolymph CSF Sodium (mM) 148 141 1.3 149 Potassium (mM) 4.2 6.0 157 3.1 Chloride (mM) 119 121 132 129 Bicarbonate (mM) 21 18 31 19 Calcium (mM) 1.3 0.6 0.023 - Protein (mg/dl) 178 242 38 24 pH 7.3 7.3 7.4 7.3 Potential (mV) 0 <3 85 0 ST = scala tympani, SV = scala vestibuli, CSF = cerebrospinal fluid

  17. K+SECRETED BY MARGINAL CELLS OF STRIA VASCULARIS

  18. AUDITORY ACTION POTENTIAL RMP = - 60mV EFFECTIVE POTENTIAL =140mV EVENTS BASILAR MEMBRANE MOVEMENT K+ENTRY THROUGH TIPLINK CHANNELS DEPOLARIZATION OPENING OF Ca++CHANNELS AT BASOLATERAL SURFACE ACTION POTENTIAL GLUTAMATE SECRETION

  19. PERIPHERAL AUDITORY PROCESSING PRIMARY AFFERENTS HAVE CELL BODIES IN SPIRAL GANGLION 30,000 TYPE I AFFERENTS FROM INNER HAIR CELLS 3000 TYPE II AFFERENTS FROM OUTER HAIR CELLS PLACE PRINCIPLE / TONOTOPIC MAPPING (FREQUENCY CODING)

  20. PHASE LOCKING & VOLLEY EFFECT • PHASE LOCKING • UPTO 1000Hz • ARP OF HAIR CELLS 1ms VOLLEY EFFECT ABOVE 1000Hz

  21. INTENSITY CODING FIRING RATE NUMBER OF NEURONS

  22. CENTRAL AUDITORY PROCESSING

  23. COCHLEAR NUCLEI DCN – QUALITY VCN – TIME SENSITIVE CELL TYPE BUSHY CELLS HIGH FIDELITY FIRING MSO STELLATE CELLS DYNAMIC FIRING COCHLEAR NUCLEI ONWARDS PATHWAY “S-L-I-M”

  24. AUDITORY CORTEX AREA 41,42

  25. LOCALISATION OF SOUND INTRA AURAL TIME DELAY MSO IS RESPONSIBLE

  26. INTRA AURAL INTENSITY DIFFERENCE LSO IS RESPONSIBLE

  27. I HOPE NOW YOU CAN HEAR BETTER I HOPE NOW YOU CAN HEAR THE WORLD BETTER... SO HAPPY LISTENING

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