Auditory System

Question 1

presbyacusis

Answer 1

age-related sensorineural hearing loss…

may be aused by the difference of thickness of basilar membrane at the base (near oval/round windows) and apex (near helicotrema)

base - high frequency
apex - low frequency

Question 2

two types of hair cells

Answer 2

inner - actually transmit signal to the brain (single row; correspond to 95% of all AFFERENTS)

outer - fine tine the signal (3 rows, few afferents, but all INHIBITORY EFFERENTS). also amplify and protect basilar membrane. changes sensitivity of inner hair cells

Question 3

primary auditory pathway

Answer 3

SLIM!

1. CN VIII nerve
2. dorsal/ventral cochlear nuclei

CROSS OVER!!!!

3. superior olivary nucleus
4. lateral lemniscus
5. inferior colliculus
6. medial geniculate nucleus

Question 4

Lesions in primary auditory pathways

Answer 4

1. anything BELOW cochlear nuclei = IPSIlateral sensorineural hearing loss
2. anything ABOVE cochlear nuclei (SLIM) = affects sound localization, NOT DEAFNESS, since there are repetitive crossed pathways

Question 5

Tool to test for auditory pathway lesion?

Answer 5

ABR (auditory brain-evoked response)

Question 6

3 mechanisms to help with sound localization

Answer 6

1. interaural time difference (ITD) - time it takes for a sound to go from one side of the head to the other, good for low frequency sounds, uses MSO (medial superior olive) bilateral projection into single MSO
2. interaural level/intensity difference (ILD) - great for high freqency sounds
3. head transfer function - how shape of your head and ear change the sound according to which direction it came from

Question 7

Wernicke’s area and damage

Answer 7

Wernicke - Area 22, speech COMPREHENSION

Wernicke’s aphasia (receptive aphasia) - people unable to understand language even though they can speak normally

Question 8

Broca’s area and damage

Answer 8

Area 44/45 - involves speech PRODUCTION (BROduction)

Broca’s aphasia (expressive aphasia) - can still comprehend language but cannot produce language (spoken/written)

Question 9

two diseases that can cause conductive hearing lossq

Answer 9

otitis media - middle ear infection, often due to Eustachian tube restriction

otosclerosis - tissue overgrowth restricting ossicle (stapes) movement

Question 10

Difference between peri and endolymph

Answer 10

perilymph - high Na, low K like CSF) - in scala VESTIBULI and scala tympani

endolymph - low Na, high K like intracellular fluid in scala media

Question 11

primary auditory pathway

Answer 11

SLIM!

1. CN VIII nerve
2. dorsal/ventral cochlear nuclei

CROSS OVER!!!!

3. superior olivary nucleus
4. lateral lemniscus
5. inferior colliculus
6. medial geniculate nucleus
7. auditory cortex

Question 12

3 mechanisms to help with sound localization

Answer 12

1. interaural time difference (ITD) - time it takes for a sound to go from one side of the head to the other, good for low frequency sounds, uses MSO (medial superior olive) bilateral projection into single MSO, creates DELAY LINES
2. interaural level/intensity difference (ILD) - great for high freqency sounds
3. head transfer function - how shape of your head and ear change the sound according to which direction it came from

Question 13

How are hair cells depolarized and hyperpolarized?

Answer 13

When hair bundle moves TOWARD kinocilium ((longest haircell), tip links are pulled, mechanically gated receptors open, more K influx (from endolymph)

when hair bundles moves AWAY from kinocilium, close channel and hyperpolarize cell

Question 14

characteristic frequency (CF) (aka best frequency)

Answer 14

each afferent responds with lowest threshold to the CF (VIII afferents are frequency selective)

Question 15

What are some things that can damage hair cells?

Answer 15

loud sounds, continuous exposure, ototoxic antibiotics, cancer treatment drugs

Question 16

How do cochlear implants work?

Answer 16

implanted through mastoid into scala tympani, works by directly contacting spiral ganglion cells