Hearing Flashcards
what is the pathway sound must travel by to reach the oval window?
Tympanic Membrane - Malleus - Incus - Stapes - Oval Wndow
What is the ratio Tympanic Membrane : Oval Window
the first is 20x bigger thus there is an amplification of the wave
What are the subdivisions of the cochlea?
Scala Vestibuli
Scala Media
Scala Tympani
Where is the basilar membrane found?
between the scala media and scala tympani
What is tonotopia?
the coding of different information by the basilar membrane depending on the frequency of the sound
What area of the basilar membrane codes for higher frequencies?
the stiffer part: the base (close to the oval window)
What area of the basilar membrane codes for lower frequencies?
the less stiff part: the apex (away from oval window)
what type of cells code for sound and where are they found?
Hair Cells
on the basilar membrane
what is at the top of the hair cells?
Stereocillia
What type of hair cells can be damaged by aspirin or gentomycin or other ototoxic compunds? and what is the result of the damage?
Outer hair cells
Loss of hearing
Where does the efferent signal for the outer hair cells come from?
Superior Olivary Complex
What do inner hair cells do?
Sound coding
What are the stereocillia of the outer hair cells attaching to?
the tectorial membrane
What is the function of the outer hair cells?
increase movement of the basilar membrane when low intensity waves reach the cochlea
depolarisation causes contraction
What type of channels sit at the top of the inner hair cells? how are they activated?
K+ channels
Mechanically Activated
What is the Kinocillium?
tallest sterocillia at the top of the inner hair cell
Movement towards the Kinocillium causes 1
Movement away from the Kinocillium causes 2
1 Depolarisation (Always bigger) 2 Hyperpolarisation
activation of the inner hair cells causes the release of the neurotransmitter….
Glutamate
Which scala is filled with high [k+]
scala media
How is K recycled for activation of the inner hair cells?
thanks to K channels between the scala media and the scala tympani
what is the middle ear’s function?
impedance matching, without it all the sound would just bounce back
Where does the information of the auditory pathway is integrated?
Superior Olivary Complex
Where is the cell body of the CN8?
Spiral Ganglion within the chochlea
The nerve cells of CN8 are bipolar T/F
T
The information that reaches each Superior Olivary Complex comes from one ear only
F, information comes from both
Where is the nucleus of CN8?
Pons
in which lobe is the auditory cortex?
Temporal Lobe
Information from the Superior Olivary Complex travels via
the lateral lemniscus
what midbrain structure connects the lateral lemniscus of the pons with the Medial Geniculate Nucleus of the thalamus
the inferior colliculus
What is the Medial Geniculate Nucleus (MGN) related to
Hearing
in the cortex of the brain is there asymmetrical representation of complex sounds? if so how it it divided?
Speech-> left
Music -> Right
the auditory cortex is tonotropic (T/F) and receives information from one ear only (T/F)
T
F
What is the pathway for sound signalling?
Inner Hair Cells - CN8 (Spiral Ganglion) - Chochlear Nuclei - Superior Olive (x2) - Lateral Lemniscus - Inferior Colliculus - Medial Geniculate Nucleus - Auditory Cortex
At what site do we determine where is sound coming from?
Superior Olivary Complex
The medial superior olive localises time depending on… (1)… and this is the most relevant form for —-2–
1 Time Delay
2 Low frequencies
Time Delay analysis of sound depends on
more neurons are activated by the ear where the sound is closer to
Localising sound by intensity differences happens in
Lateral Superior Olive and Medial Nucleus of Trapezius Body
Localising sound by intensity differences is more relevant for
Higher Frequencies
What is the process of Localising sound by intensity differences
1 one nuclei gets activated more than the other
2 lateral superior olive sends excitatory signal to ipsilateral Medial Nucleus of Trapezius Body which then sends inhibitory signal to contralateral lateral superior olive
3 Both lateral superior olives send signals to the higher centres but one is going to be stronger than the other due to more inhibition from Medial Nucleus of Trapezius Body
