lecture 3 Flashcards
definitino of sound
change in air pressure
amplitude determines how loud it is
frequency determines pitch
complexity determines timbre
what is the main challenge of the auditory system
- detect and code the amplitude and relevant frequencies
- difficult to detect because environment is changing
- uses information for hearing and sound localization
3 basic divisions of human ear and functions
outer ear- function to channel sound, filters sound waves depending on elevation of source, amplify sound
middle ear- prevents reflection of sound due to resistance in air/water differences (size of ear drum and lever action)
inner ear-converts fluid pressure waves into neural impulses
ossciles of middle ear
stiffening bones doesnt allow loud sounds to go through and protects ear
malleus–> controlled by trigeminal nerve
stapes–> controlled by facial nerves
hyperacuisis
lesions affection trigeminal and facial motor nerves can lead to increased acuitiy and hypersensitivity to sound
composition of inner ear labyrinth
bone: perilympth (low K)
membranous: endolympth (high K)
3 fluid filled compartments of cochlea
scala vestibuli, scala tympani, scala media
what is cochlea partitioned by
reisners membrane and basilar membrane
vibration on tectorial membrane
moves hair bundles in hair cells that creates changes in potential and NT release onto afferants
Georg von Bekesky
discovered basilar membrane is not uniform- was tapered and changed in stiffness
- mechanical frequency tuning of basilar membrane
- high at base and low at peak
best frequency
lowest amplitude/ freqeuncy you can detect
spiral ganglion cells
found certain cells respond best to certain frequencies along basilar membrane
what is the most basic feature of an auditory neuron
tuning curve
place code
each neuron has a best frequency that depends on its place in the cochlea
cochlear implant
can retreive hearing by putting electrode and transducer into cochlea and send current pulses to different parts of membrane
