Flashcards in Hearing Deck (31)
What does each wave component determine in sound
wavelength = frequency = pitch
amplitude = loudness
waveform = how smooth the sound
What is the function of the pinna
localise and collect sound
what is the function of ossicles?
without it, sound wave from air will just reflect off the fluid medium
how do we overcome the impedance?
by providing a 200x the pressure.
How is the 200x pressure generated?
by the relative size of tympanic membrane and the lever action of the ossicles
What are the three chambers of the cochlea?
What's the difference between scala vestibuli and scala tympani?
Nothing really, they are continuous at the apex, but otherwise separated by the cochlear duct
They both carry perilymph
The apex is _______ and ______, which is able to detect ______ frequency sound.
The base is _______ and ______, which is able to detect ______ frequency sound
broad and floppy
narrow and frigid
T/F the tonotopic encoding of sound only occurs at the level of the cortex
False, tonotopic organisation begins at the basilar membrane
What does the organ of corti consist?
inner and outer hair cells
What is found on top of the hair cells?
What is the name of the tallest stereocilia
How is sound transduced into a neural signal?
sound wave causes movement of basilar membrane, which generates a shearing force along with tectorial membrane. The physical pulling on the hair cell channels leads to K+ dependent Ca+ influx, and neurotransmitter release
T/F K+ Channels are usually closed
False, they are partially open to create resting membrane potential
T/F the alternating pattern of depolarisation and hyperpolarisation is asymmetric
True, hyperpolarisation is much smaller. Hair cells tend to want to depolarise in the direction of kinocilium
What is the function of stria vascularis
it creates the K+ gradient between endolymph and perilymph
What is the function of inner hair cell?
they depolarise 95% of the afferent nerves going to the brainstem
What is the function of outer hair cell?
they provide efferent signals from superior olivary complex and amplify the movement of basilar membrane
Depolarisation causes OHC to ________
Hyperpolarisation causes OHC to _______
what happens if we don't have functional OHC?
basilar membrane movement can be 100x less
T/F Aminoglycoside can affect the function of OHC
True, gentamicin is ototoxic, so we need to always monitor the amount of drug taken
the primary auditory neuron is a bipolar neuron. Which two locations does it project to?
dorsal cochlear nucleus, which then projects upward
ventral cochlear nucleus, which then projects to superior olive
What is the name of the auditory ascending tract? Which structure does it pass? which structure does this secondary neuron terminate at?
medial geniculate nucleus
Which area in the brainstem is responsible for localisation of sound? What does this complex consist?
the superior olivary complex
lateral and medial superior olives
What is the function of medial superior olive?
localisation of sound by time delay
What is the function of lateral superior olive?
localisation of sound by intensity difference
How do we localise sound by time delay
sound wave travels to the two ears at different time. The ear that's closer to the sound origin will fire AP before the other ear. Both sides fire AP towards a series of neurons in MSO. At one point, one neuron will receive both signals at the same time, and this neuron may have deviated from the centre, hence direction of sound can be determined
In localisation by intensity, one neuron will project to two areas of superior olive. What are the two areas?
ipsilateral LSO and contralateral medial nucleus of trapezoid body (MNTB)
How does intensity of sound help sound localisation?
the relative amount of excitation from LSO and inhibition from MNTB will determine where the sound is
There is more excitation on the neuron that's stimulated first
What is the auditory cortex also known as?