BIOL 2420 - EXAM 3 STUDY QUESTIONS AND CORRECT ANSWERS
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Course
BIO 2420
Institution
BIO 2420
What structures in the middle ear are responsible for sound amplification? the tympanic membrane that vibrates through 3 ear bones that end at oval window. tympanic membrane is bigger compared to oval window
What is the function of and clinical complication associated with the Eustachian tube? lin...
BIOL 2420 - EXAM 3 STUDY QUESTIONS
AND CORRECT ANSWERS
What structures in the middle ear are responsible for sound amplification? ✅the
tympanic membrane that vibrates through 3 ear bones that end at oval window.
tympanic membrane is bigger compared to oval window
What is the function of and clinical complication associated with the Eustachian tube?
✅links the middle ear to the back of the nose
Drains into the mouth to equilibrate pressure
Route of bacterial entry for most ear infections
What inner ear structure converts sounds waves into APs? ✅cochlea
What is the function of the round window on the cochlea? ✅to allow fluid movement
but avoid pressure buildup in cochlea, pressure is relieved by outward displacement of
the round window
How does the cochlea differentiate between different pitches (notes) and loudness?
✅sound loudness is determined by how forceful the cochlear member is defected
a shorter wavelength doesn't go all the way into cochlea and displace hair cells nearby
a louder wavelength can go further into cochlea. loud (high amplitude) sound causes
the membranes to vibrate more vigorously than soft (low amplitude) sound
as sound becomes louder, the AP frequency increases
How is sound, a mechanical stimulus, converted into an electrical signal? ✅stereocilia
affected has mechanoreceptors which can open the K+ gated ion channels
Why is K+ used instead of Na+ to depolarize hair cells in the ear? ✅if Na+ was used,
you would need ATPases and more blood vessels needed to supply oxygen and
nutrients for ATP, increased blood flow would cause more excessive vibrations
K+ from high [K+] in endolymph (center chamber) enters sterocilia passively when
mechanically-gated K+ channels open, K+ then efflux through leak channels at the hair
cell base into high [Na+] / low [K+] perilymph, K+ moves in and out passively
What negative impact does extremely loud noise or aging have on stereocilia? ✅can
defect stereocilia strongly enough to break them off, stereo cilia do not regenerate
, Other hearing problems include otosclerosis and tinnitus. What is the cause of each?
✅OTOSCLEROSIS
calcification of the ossicles, lose ability to tympanic membrane to go to oval window and
lose amplification of sound
TINNITUS
(phantom sensation of ringing in the ears)
due to damaged or misfiring neurons between the cochlea and the brain, most common
cause is loud noise-inducing hearing loss other causes: ear infections, emotional stress,
and vascular disease "CURE"- white noise
Explain how the semicircular canals are able to determine orientation in 3 different
planes? ✅each semicircular canal has one ampulla containing hair cells with short-to-
long stereocilia, fluid that is moved makes the stereocilia to deflect, which then detects
and sends signals afferent neurons
proprioceptors deal with body orientation (x,y,z planes)
oriented perpendicular to each other, and detect head rotational changes (up, down,
and side to side)
-The canals are in the three planes and helps determine orientation in the head
-Mix of hyperpolarizing and depolarizing in both ears help
How does the labelled-line model explain why taste buds are able to separate different
tastants? ✅each taste receptor is connected to an afferent neuron, each afferent
neuron tracts to a specific spot in the gustatory cortex located towards the back of the
frontal lobe
all receptors for a particular taste within all tastes buds synapse to same regions of
brain, makes possible for the brain to decipher each tastant (referred to as the labeled
lines model)
Explain how sweet, bitter, salty and sour taste receptors work? ✅SWEET
stimulated by mono or disaccharides binding to a receptor and using G proteins
BITTER
stimulated by alkaloids by two different ways: blocks an ionotropic receptor K+ channel
and triggers a sour taste, bitter molecule bind to a G protein coupled receptor
SALTY
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