neuro 8.5 hearing

Question 1

what is the primary function of the auditory system

Answer 1

to provide the sense of hearing (conscious experience)

Question 2

what are some uses of hearing in daily life

Answer 2

-identify
-localize
-communicate

Question 3

what happens if the auditory system is dysfunctional

Answer 3

results in deafness

Question 4

what type of physical stimulus is sensed by the auditory system

Answer 4

rapid vibration which we perceive as sound

Question 5

what is the audible frequency range in humans

Answer 5

20Hz-20000Hz

Question 6

how long is the cochlea and how is it shaped

Answer 6

-about 35mm long and coiled 2.5 times

Question 7

what is the Scala vestibuli and what does it do

Answer 7

It receives vibrations from the oval window and is separated from the Scala media by reissners membrane

Question 8

what is the Scala tympani and its function

Answer 8

-it reaches the round window and is separated from the Scala media by the basilar membrane

Question 9

what is the Scala media

Answer 9

-the middle compartment of the cochlea that contains the organ of corti

Question 10

what kind of hair cells are in the cochlea

Answer 10

they only have stereocilia, no kinocilia

Question 11

what type of waves is sound made of

Answer 11

periodic, longitudinal waves of high frequency

Question 12

what is the speed of sound in air

Answer 12

330-340m/s

Question 13

is sound faster in air or in water/metal

Answer 13

faster in water/metal

Question 14

what is a pure tone and how is it characterised

Answer 14

a sound with just amplitude (intensity) and frequency

Question 15

what is real sound

Answer 15

a fundamental frequncy (pitch) plus overtones, which define the sounds unique characteristics

Question 16

what is a note

Answer 16

a random pressure change With norecognisable frequency

Question 17

how is sound intensity measured

Answer 17

in decibals (dB) using the formula
dB = 20 x log (Po/pref)

Question 18

at what frequency is 0 dB defined for humans

Answer 18

2000HZ

Question 19

what is a phon scale

Answer 19

a normalised scale for comparing perceived loudness at different frequencies

Question 20

what does the outer ear do

Answer 20

acts as a funnel to direct sound waves to the tympanic membrane

Question 21

what does the middle ear do

Answer 21

-transfers sound from tympanic membrane to oval window
-air-filled and contains ossicles (malleus, incus, stapes)

Question 22

where is the stapes located

Answer 22

on top of the oval window

Question 23

what do ossicles do functionally

Answer 23

convert air-phase sound into fluid phase sound

Question 24

what causes amplification of sound in middle ear

Answer 24

1-area difference between tympanic membrane and oval window
2-lever action of malleus and incus
together provide 20x amplification

Question 25

which muscles dampens sound and how

Answer 25

-tensory tympani and stapedius -their contraction increases rigidity, dampens propagation, and serves as protection from loud sounds

Question 26

what initiates movement in the cochlea

Answer 26

-oval window and stapes move outward causing pressure changes in Scala vestibuli

Question 27

what happens to the pressure in the Scala tympani due to this movement

Answer 27

pressure increases due to the pressure difference between Scala vestibule and tympani

Question 28

what does the pressure change cause in the cochlea

Answer 28

the basilar membrane moves upward

Question 29

what happens to the organ of corti with basilar membrane movement

Answer 29

it shears upward toward the tectorial membrane

Question 30

what happens to the stereocilia of outer hair cells during this movement

Answer 30

they tilt toward the longer stereocilia, triggering activation

Question 31

what does tilting cause in outer hair cells

Answer 31

depolarisation, leading to receptor potential

Question 32

what protein is responsible for outer hair cell contraction

Answer 32

prestin -membrane protein that detects depolarisation and contracts without ATP or Ca2+

Question 33

what outer hair cell contraction mechanism called

Answer 33

electromechanical transduction, depolarisation triggers contraction

Question 34

what does outer hair cell contraction do to the basilar membrane

Answer 34

-it causes further upward movement, works as cochlear amplifier

Question 35

what happens if Prestin is missing

Answer 35

results in complete deafness

Question 36

what reduces the distance between the tectorial and basilar membranes

Answer 36

amplified upward movement of the basilar membrane

Question 37

what happens when inner hair cell sulcus space is reduced

Answer 37

endolymph flows out, causing deflection of inner hair cell stereocilia

Question 38

what happens when inner hair cell sterocilia are deflected

Answer 38

-inner hair cells are activtaed -voltage gated Ca2+ channels open, so Ca2+ influx -neurotransmitter is released

Question 39

what happens after neurotransmitter release from inner hair cells

Answer 39

afferent nerves generate action potentials that travel to the CNS

Question 40

what coding system is used for intensity detection

Answer 40

rate coding --> based on the frequency of action potentials

Question 41

what do standing waves develop in the cochlea

Answer 41

on the basilar membrane, depending on sound frequency

Question 42

what increases with greater sound intensity

Answer 42

-basilar movement -endolymph flow neurotransmitter relaase -AP frequency

Question 43

what coding system is used for intensity detection

Answer 43

rate coding- based on frequency of action potentials

Question 44

where do high-frequency sounds produce standing waves

Answer 44

close to the stapes (base of cochlea)

Question 45

where do low-frequency sounds produce standing waves

Answer 45

far from the stapes (toward the apex)

Question 46

why does wave location depend on frequency

Answer 46

-the basilar membrane is not uniform, its thickness varies along its length

Question 47

how is sound source distance detected

Answer 47

-through phase difference between the ears

Question 48

how do the ears contribute to spatial localisation

Answer 48

-each ear detects sound slightly differently -the CNS compares the phase difference between ears -determines localisation of the sound source

Question 49

where do 95% of the afferent fibers in the cochlea come from

Answer 49

inner hair cells - they are the actual receptors

Question 50

what forms the spiral ganglion

Answer 50

the bodies of the neurons

Question 51

what forms the cochlear nerve

Answer 51

-the axons of the neurons in the spiral ganglion

Question 52

what is the auditory afferent pathway

Answer 52

1-cochlear nucleus 2-both superior olivary nuclei 3-auditory cortex (Br 40,41)

Question 53

which muscles are involved in auditory efferentation

Answer 53

tensor tympani and stapedius (protective function)

Question 54

what neurotransmitter affects outer hair cells in efferentation

Answer 54

acetylcholine (ACh)

Question 55

what happens when ACh is released onto outer hair cells

Answer 55

-ACh binds to nAChRs (cation channels) -depolarization -activation of voltage-gated Ca2+ channels -increased [Ca2+]I -activates Ca2+-dependent K+ channels -hyperpolarization -decrease electromechanical transduction

Question 56

what is otoacoustic emission used for

Answer 56

to test if outer hair cells function properly

Question 57

how does otoacoustic emission work

Answer 57

auditory system is stimulated with sharp sound, and noise generated by outer hair cells is recorded

Question 58

why is this test used in babies or unconscious patients

Answer 58

it is objective and doesnt require a response from the patient

Question 59

how is OAE related to intracranial pressure

Answer 59

contraction noise of outer hair cells is somehow related, so the method can also investigate intracranial pressure