Topic 6: Auditory System

Question 1

What cranial nerve carries both auditory & vestibular information?

Answer 1

CN VIII

Question 2

How are sound characterized?

Answer 2

by frequency (pitch/Hertz)

amplitude (loudness/ decibel)

Question 3

What are the three bones of middle ear? What do they do?

Answer 3

malleus, incus and stapes

transfer sound waves into inner ear & amplify it

Question 4

tympanic membrane

Answer 4

seperate external ear from middle ear

Question 5

What is frequency of sound characterized with?

Answer 5

the number of sound waves/ second

Question 6

How are the anatomy of hearing & balance similar?

Answer 6

the cochlea & vestibular apparatus are closely connected

sensory receptors in both are hair cells

Question 7

what is the amplitude of sound characterized with?

Answer 7

height of waves

Question 8

What does eustachian tube do?

Answer 8

connects the middle ear and pharynx

help maintain equal pressure on both sides of eardrum by allowing outside air to enter the middle ear

Question 9

What is the funciton of external ear?

Answer 9

directing the soundwaves to middle & inner ear

amplify sound waves at the frequencies of human speech

Question 10

perilymph

How is the perilymph different from the inside of cell? (amount of K+, Na+)

Answer 10

space btw bony & membranous labyrinth

low K+, high Na+

Question 11

what part of inner ear is responsible for sound processing?

Answer 11

cochlea

Question 12

where does the stapes of middle ear push in when sound pressure is high?

Answer 12

oval window

Question 13

What part of inner ear are associated with vestibular system?

Answer 13

semicircular canals, saccule, & utricle

Question 14

what happen when stapes push in the oval window?

Answer 14

the pressure fluid (endolymph) increases & the round window bulge outward

Question 15

how are the receptors in semicircular canal, ultricle & saccule activated?

Answer 15

by head movements

Question 16

endolymph

How does endolymph similar to the inside of cell?

Answer 16

the fluid inside the membranous labyrinth

high in potassium & low sodium

Question 17

Structure of inner ear?

Answer 17

bony and membraneous labyrinth

Question 18

Where are the sounds receptors activated?

Answer 18

cochlea

Question 19

vestibule

Answer 19

connect cochlea & semicircular canals

Question 20

What does cochlea transduces? What does cochlea consists of?

Answer 20

sound waves into neural impulses

3 parallel canals: scala vestibuli, scala media & scala tympani

Question 21

scala tympani

What window (oval or round) does scala tympani meet with?

what does it contain with?

Answer 21

one of the canal of cochlea

round window

perilymph

Question 22

where does the bony labyrinth locate? membranous labyrinth?

Answer 22

within the temporal bone

suspended within the bony labyrinth

Question 23

what receptors does the inner ear have?

Answer 23

auditory & vestibular receptors

Question 24

Where does the organ of Corti locate?

What does it have?

Answer 24

on top of basilar membrane

auditory receptors- hair cells

Question 25

stereocilia kinocilium

Answer 25

group of hair cells single hair cell

Question 26

Reissner's membrane

Answer 26

seperate scala vestibuli & scala media

Question 27

At the apex of cochlea, what happen?

Answer 27

the scala media closed off scala vestibuli & scala tympani connect via helicotrema

Question 28

What does scala media contain?

Answer 28

endolymph

Question 29

Where do hair cells actually locate? When there is a sound wave, what happen to hair cells?

Answer 29

btw basilar memmbrane and tectorial membrane they bend and become depolarization or hyperpolarization

Question 30

where does tectorial membrane locate?

Answer 30

hang over the Organ of Corti

Question 31

scala vestibuli what window (oval or round) does it meet with? what does it contain?

Answer 31

one of the canal of cochlea oval window perilymph

Question 32

Basilar membrane How does it help auditory system generate action potentials?

Answer 32

seperate scala media & scala tympani when there is sound wave, basilar membrane moves, causing hair cells move to generate action potentials

Question 33

How does the basilar membrane structure change from apex to base? How does this structure affect to its ability to analyze the frequency?

Answer 33

It is wider & flexible at apex -\> low frequency It is stiffer & smaller at base -\> high frequency

Question 34

how does tonotopic map in auditory system different from in cortex?

Answer 34

in cortex, low frequency is analyzed in rostral side high frequency is analyzed in caudal side In auditory system, low frequency is at apex (caudal side) high frequency is at base (rostral side)

Question 35

helicotrema Why is this structure important?

Answer 35

the perilymph flow (connection) btw scala vestibuli & scala tympani the pathway of pressure waves move from oval window -\> round window

Question 36

What are two ways that loudness is encoded in? Explain each

Answer 36

firing rate - more intense stimulus -\> more vibration on basilar membrane -\> polarizing hair cells more number of active neurons - more intense stimuli -\> larger response of the basilar membrane -\> activating more hair cells

Question 37

Where is the base of cochlea? Where is the apex of cochlea?

Answer 37

at the oval window at the top of cochlea where scala media closes off

Question 38

What is the fluid that inside of membranous labyrinth?

Answer 38

endolymph

Question 39

What are the auditory informations that being sent to auditory cortex?

Answer 39

timing of sounds directionality of sound frequency contents of sound

Question 40

where is the 1st order neurons of auditory pathway? 2nd order neurons ?

Answer 40

spiral ganglion dorsal & ventral cochlear nucleus in rostral medulla

Question 41

In where of the auditory pathway producing topography map of auditory space?

Answer 41

inferior colliculus

Question 42

Where is the 1st place that the auditory information start to project bilaterally to the cortex?

Answer 42

superior olive

Question 43

Where is the 1st stage of selectivity for combination of frequencies?

Answer 43

medial geniculate nucleus

Question 44

what do we have when auditory information reach auditory cortex?

Answer 44

conscious sound perception

Question 45

in where of the auditory pathway, directionality of sound is determined?

Answer 45

superior olive

Question 46

How is the directionality of sound determined?

Answer 46

by difference in time & amplitude to each ear

Question 47

Where is the convergence of all binaural inputs?

Answer 47

inferior colliculus

Question 48

What is the space that btw membranous & bony labyrinth?

Answer 48

perilymph

Question 49

If we have a lesion on the left side of dorsal cochlear nucleus, what will hapen?

Answer 49

you can't determine the frequency contents of sound on left ear

Question 50

If you have a lesion on one side of superior olive, will you still hear normally?

Answer 50

yes, you still hear normally because the auditory information bilateral projects at superior olive to auditory cortex

Question 51

Damage to what can result in the deafness?

Answer 51

middle ear cochlea CN VIII

Question 52

what does circuitry in localization of low frequency (\<3kHz) sound depend on?

Answer 52

depend on time difference reaching btw each ear

Question 53

What side of superior olive (medial/ lateral) is in synaptic connects with ventral cochlear nucleus for localization of low frequency (\<3kHz) sounds?

Answer 53

medial superior olive

Question 54

Why is medial superior olive significant in localization of low frequency sounds?

Answer 54

MSO acts as coincidence detector that will fire action potentials only when sound information in both ears reach MSO

Question 55

what does circuitry in localization of high frequency (\>3kHz) sound depend on?

Answer 55

difference in loudness of the sound in each ear

Question 56

How does circuitry in localization of low frequency (\<3kHz) sound pathway work? What is the result of this pathway?

Answer 56

ventral cochlear nucleus excites lateral superior olive (LSO) -\> activate medial nucleus of trapezoid body (MNTB) -\> inhibit LSO in other side of different ear strong stimulus to the ipsilateral ear

Question 57

What part of the ear amplify the soundwaves at frequencies of human speech?

Answer 57

external ear

Question 58

binaural inputs

Answer 58

the fusion of all auditory informations ( timing of sound, directionality & frequency contents of signal)