function and structure of auditory system

• What are all sounds made of?

  Different frequencies and tones unique to each thing
• What are the conductive parts of the ear?

  Outer and middle ear
• What is the function of the inner ear?

  Sensory processing
• What is the role of the middle ear in sound transmission?

  Impedance matching
• What is the surface area ratio from the eardrum to the oval window?

  Approximately 20:1
• How much pressure amplification occurs in the middle ear?

  Approximately 26 times
• What would happen without impedance matching in the ear?

  Only 0.1% of energy transfer would occur
• What is the ossicular reflex in the middle ear?

  It is an attenuation mechanism
• What happens when the muscles in the middle ear contract?

  The levers are stiffened to protect against loud sounds
• At what sound level does the ossicular reflex activate?

  Above 80 dB
• Why is the ossicular reflex ineffective for impulse noises?

  There is a delay for the reflex to kick in
• How does the ossicular reflex help with sound perception?

  It helps discriminate between high and low frequencies
• What is the role of the organ of Corti?

  It is involved in sensory processing in the cochlea
• Where does the organ of Corti sit?

  On the basilar membrane
• What types of cells are found in the organ of Corti?

  Sensory inner and outer hair cells
• What is the function of hair cells in the cochlea?

  They convert mechanical movement into electrical signals
• What is the structure of hair bundles in hair cells?

  Made up of many stereocilia arranged in rank of height
• What is the role of the transduction channel in hair cells?

  It links tip links to ion channels
• What are tip links in hair cells made of?

  Cadherins (CDH23 and PCDH15)
• What is the significance of the height rank of stereocilia?

  It is important for the function of hair cells
• What are the ionic components of perilymph?

  High sodium and low potassium
• What is the composition of endolymph?

  High potassium and low sodium
• Why must cochlear fluids be kept apart?

  They have different ionic components
• How are sound waves transformed in the cochlea?

  Sound waves are turned into fluid waves
• What determines the position of maximal displacement on the basilar membrane?

  It depends on the frequency of sound
• What happens to hair bundles during sound-induced basilar membrane movement?

  Hair bundles move and stimulate ion channels
• What is the role of the tectorial membrane in relation to hair bundles?

  It sits on top of stereocilia and interacts with hair bundles
• What is the basic input and output process in hair cells?

  Hair cells convert mechanical signals into electrical signals