Hearing Flashcards
Wavelength refers to
pitch; short wavelength = high pitch (high frequency)
Amplitude refers to
loudness; large amplitude = loud sound
Waveform refers to
tone/timbre
What is the function of the pinna?
Localization of sound and funnelling of waves into the middle ear
Which ossicle is attached to the tympanic membrane?
Malleus
Which ossicle is attached to the oval window?
Stapes
What is the general role of the cochlea?
transforms physical motion of the oval window into a neural response
What is the function of the middle ear?
match impedance of the air to the impedance of the fluid within the inner ear
What are the 3 chambers of the cochlea?
Scala vestibuli
Scala media
Scala tympani
What is the organisation of the basilar membrane with regards to frequency of sound?
stiffer at base (oval window) for high frequency sounds; wider and more floppy (like a flipper) at the apex for low frequency sounds
What is the tonotopic organisation of hair cells of the basilar membrane?
towards the apex the hair cells will respond to low frequencies; as you move inwards toward the base each hair cell encodes increasing frequency of sound
Where is the organ of corti?
Lies on the basilar membrane with the scala media above and the scala tympani below
What is the function of the stereocilia?
project from the top of the hair cells to the tectorial membrane above; bending occurs as the basilar membrane moves, causes neuronal signaling
What is the function of the tectorial membrane?
As the basilar membrane moves up and down in response to movement of the oval window, shear force movement of the tectorial membrane across the hair cells bends the stereocilia which signals to neurons
Movement of inner hair cell stereocilia towards the kinocilium results in
full opening of K+ channels and tf K+ influx and depolarization of the cell; this opens VD-Ca channels (Ca in) leading to release of glutamate (NT)
Movement of inner hair cell stereocilia away from the kinocilium results in
full closure of K+ channels and hyperpolarization of the cell, closing VDCCs and stopping glutamate release
Displacement relative to the kinocilium favours
depolarization; ie depolarizations (moving towards) are much larger than hyperpolarizations (moving away)
Depolarization and repolarization of hair cells is dependent on
K+
The scala media contains
endolymph
The scala tympani contains
perilymph
The concentration of K+ in endolymph is
high (80mV)
The concentration of K+ in perilymph is
low (0mV)
What is the significance of high [K+] in the scala media?
Without it, K+ will not flow into hair cells and cause depolarization when K+ channels open
What is unique about neuronal firing in hearing?
normally K+ is released in response to depolarization; in the inner ear depolarization depends on K+ influx due to the high [K+] around the hair cells
Inner hair cells are
major transducers of sound waves to neural signals
Outer hair cells
amplify movement of the basilar membrane through contraction in response to depolarization and elongation to hyperpolarization
How do drugs impact on hearing?
inhibit movement of the outer hair cells which decreases movement and therefore amplification of the basilar membrane 100x
The superior olivary complex is comprised of
medial and lateral superior olives and the trapezoid body
How does the MSO localize sound?
measures the time that sound arrives at each ear, especially low frequencies
Low frequency sounds are lateralized by the
MSO
High frequency sounds are lateralized by the
LSO and inhibition of excitation of the contralateral LSO via the medial nuclei of the trapezoid body
How does the LSO localize sound?
Sound inputs via the cochlear nuclei in the brainstem activate excitatory signals from LSO up to the brain, as well as an inhibitory signal via the MNTB to the contralateral LSO, inhibiting excitatory input from the opposite ear
The auditory cortex is located
in Herschls gyrus on the superiolateral temporal lobes
Speech sounds are heard in the
left hemisphere
Environmental sounds are heard in
both hemispheres
Music is heard in the
right hemisphere
