NPB 110B, W 19 Homework #8 auditory system
Name
AUDITORY
1. The surface area of the tympanic membrane is than the surface area of the
oval window. This is necessary to translate pressure waves into pressure waves. The
window is there to accommodate the movement of the fluid, because fluids are non-
.
larger; air; fluid; round; compressible
2. What effect does fluid movement in the cochlear have on the basilar membrane?
It creates a traveling wave that moves along the basilar membrane.
3. In the figure below, indicate at which site on the basilar membrane (1-7) highest
frequency sound amplitudes would peak and which site lowest frequency sounds would
peak.
high frequencies: 1; low frequencies: 7
Purves et al., 2008, Fig. 13.5
4. The basilar membrane is constructed such that it responds differentially to different sound
frequencies. List the two properties of the basilar membrane that vary along its length to help
in frequency discrimination.
stiffness; width
1
, NPB 110B, W 19 Homework #8 auditory system
Name
5. The cochlear hair cells that transduce sound are mechanoreceptors. Their cilia touch against
a fairly rigid tectorial membrane, such that when the basilar membrane is displaced upward,
the cilia are sheared. What happens to the membrane potential? Why? (1 sentence):
Opening of mechanically-gated ion channels (tip links) at the tips of the cilia allow positive
charge to move into the cochlear hair cell, depolarizing it.
6. The apical ends of the cochlear hair cells are bathed in a special medium called endolymph
contained within the scala media. Endolymph has unusual ion concentrations. Which ion(s)
are different? Are they higher or lower concentration than normal?
K+; higher concentration than normal
2
Name
AUDITORY
1. The surface area of the tympanic membrane is than the surface area of the
oval window. This is necessary to translate pressure waves into pressure waves. The
window is there to accommodate the movement of the fluid, because fluids are non-
.
larger; air; fluid; round; compressible
2. What effect does fluid movement in the cochlear have on the basilar membrane?
It creates a traveling wave that moves along the basilar membrane.
3. In the figure below, indicate at which site on the basilar membrane (1-7) highest
frequency sound amplitudes would peak and which site lowest frequency sounds would
peak.
high frequencies: 1; low frequencies: 7
Purves et al., 2008, Fig. 13.5
4. The basilar membrane is constructed such that it responds differentially to different sound
frequencies. List the two properties of the basilar membrane that vary along its length to help
in frequency discrimination.
stiffness; width
1
, NPB 110B, W 19 Homework #8 auditory system
Name
5. The cochlear hair cells that transduce sound are mechanoreceptors. Their cilia touch against
a fairly rigid tectorial membrane, such that when the basilar membrane is displaced upward,
the cilia are sheared. What happens to the membrane potential? Why? (1 sentence):
Opening of mechanically-gated ion channels (tip links) at the tips of the cilia allow positive
charge to move into the cochlear hair cell, depolarizing it.
6. The apical ends of the cochlear hair cells are bathed in a special medium called endolymph
contained within the scala media. Endolymph has unusual ion concentrations. Which ion(s)
are different? Are they higher or lower concentration than normal?
K+; higher concentration than normal
2
