Exam 3 Flashcards
what is the external part of the ear called?
the pinna
what does the outer ear consist of?
pinna, ear canal, and the eardrum
what does the middle ear consist of?
from ear drum to the oval window: contains three small bones malleus, incus, and stapes
passage through the middle ear does what to the sound?
amplifies it
what does the inner ear consist of?
semicircular canal and cochlea
what happens in the cochlea?
mechanical sound waves are converted to electrical nerve impulses
for an unwound cochlea, there is a thicker and thinner end which is which? (Apical or Basal end)
thicker is the Apical end, thinner is the Basal end
for an unwound cochlea which frequencies do the Apical and Basal ends move more for?
the Apical end moves more for lower frequencies because thicker = lower resonant frequency
the Basal end moves more for high frequencies because thin = higher resonant frequency
the basilar membrane has a thick and thin end which are which (Apical and Basal)
Apical is thick and Basal is thin
the basilar membrane is tonotopically organized - what does that mean?
different locations on the membrane correspond to different frequencies
Denes and Pinson 1993 : 90
- shows how far the basilar membrane is pushed out of place by different frequencies
What was the conclusion found?
lower frequencies (25 Hz) are higher farther (30 mm) from the stapes than higher frequencies (1600 Hz –> 17 mm)
explain how hair cells work - what is their role?
they are attached to the basilar membrane, the hair cell fires if movement of the basilar membrane pushes the cell out of position sufficiently
what is the response curve of a hair cell?
shows the lowest intensity at which a pure tone at a given frequency triggers a firing of the cell - the low point shows the freq. the hair cell responds to most readily - the closer to the apical end (thick) the lower the resonant frequency
Moore 1997 : 33
- shows the response curves for different hair cells
What does the lowest point show?
the lowest point is the characteristic freq. where it will fire at the lowest amplitude
what is the most important factor of a hair cell?
the location of it - they are all the same otherwise
what causes hair loss at certain frequencies?
the hair cells are pushed too far and sheared off
the outer hair cells are different from inner how?
when the outer hair cells fire they change length to push back on the basilar membrane and amplify the signal
Denes and Pinson 1993 : 95
- shows human’s hearing range
What does this show about our speech sounds as humans?
What is the peak sensitivity?
speech sounds evolved to be where our hearing is particularly good - the peak sensitivity is between 1000 and 10,000 Hz
tonotopically organized signals from the ear are passed to the brain through what?
the auditory nerve, through various bodies in the brainstem and to the cerebrum (uppermost and outermost part of the brain)
signals from the right ear are passed to where? what is this called?
the left hemisphere of the brain - decussation
where is the auditory cortex located and what does it border?
in each hemisphere of the temporal lobe of the cerebral cortex on the superior temporal gyrus (STG) - borders the lateral (Sylvian) fissure
what is the primary auditory cortex?
entryway into the cerebral cortex for signals from the ears
how is the primary auditory cortex organized?
tonotopically - different locations correspond to different frequency bands
the frequency-based locations in the primary auditory cortex correspond to what?
frequency-sensitive locations on the basilar membrane