T2 L12 Physiology of hearing

Question 1

What are the functions of hearing?

Answer 1

Altering to dangers
Localisation of objects
Recognition
Communication via speech

Question 2

What are sounds?

Answer 2

Pressure waves that propagate through air at 340m/s

Question 3

What is the equation for intensity?

Answer 3

dB = 10 x log (sound intensity / reference intensity) or 20 x log (sound pressure / reference pressure)

Question 4

What is the range of frequencies of ideal human hearing?

Answer 4

20-20,000Hz

Question 5

Above what intensity can lead to permanent hearing damage?

Answer 5

90dB

Question 6

What forms the peripheral auditory system?

Answer 6

Outer ear
Middle ear
Cochlea
Auditory nerve

Question 7

What is the function of the middle ear?

Answer 7

Transmit sound from outer to inner ear.

Transmits vibrations from tympani to oval window of cochlea & increases pressure by 45X

Question 8

What is Ottis media?

Answer 8

Known as glue ear

Infection or inflammation of middle ear

Question 9

What can Ottis media be caused by?

Answer 9

Upper respiratory tract infection

Question 10

What happens if glue ear is chronic?

Answer 10

It can lead to conductive hearing loss

Question 11

What is the treatment for glue ear?

Answer 11

Grommets to drain

Question 12

What is otoscleorsis?

Answer 12

Fusion of the stapes with the oval window

Question 13

What is the cochlea?

Answer 13

Long, coiled, fluid-filled tube

Question 14

What sounds does the basal end of the cochlea detect?

Answer 14

High frequency sounds

Question 15

What sounds does the apical end of the cochlea detect?

Answer 15

Low frequency sounds

Question 16

How do scala vestibule and scala tympani communicate?

Answer 16

Via helicotrema at apex of cochlear

Question 17

What areas contain perilymph?

Answer 17

Scala vestibular

Scala tympani

Question 18

What is the composition of perilymph?

Answer 18

High Na+

Low K+

Question 19

What areas contain endolymph?

Answer 19

Scala media

Question 20

What is the composition of endolymph?

Answer 20

High K+

Low Na+

Question 21

What is the function of the organ or corti?

Answer 21

Detect sound-induced motions of basilar membrane and convert them into electrical signals

Question 22

What are the 2 types of sensory hair cells?

Answer 22

Inner hair cells

Outer hair cells

Question 23

What are the inner hair cells innervated by?

Answer 23

Afferent nerve fibres

Question 24

What are the outer hair cells innervated by?

Answer 24

Efferent nerve fibres

Question 25

What membrane of the hair cells is bathed in endolymph?

Answer 25

Apical membrane

Question 26

What membrane of the hair cells is bathed in perilymph?

Answer 26

Basolateral membrane

Question 27

How many hair cells in each human cochlea?

Answer 27

15,000 | Don't regenerate

Question 28

Describe mechanotransduction in hair cells

Answer 28

Deflection of hair bundle --> opens nonselective cation channels K+ is the major cation in endolymph so it enters & depolarises hair cells. Ca2+ enters & causes adaption Ca2+ triggers release of vesicles

Question 29

What is the movement of K+ in endolymph driven by?

Answer 29

Electro-gradient

Question 30

What do outer hair cells do to the basilar membrane motion?

Answer 30

Amplify it

Question 31

What is Prestin?

Answer 31

Modified anion exchanger in basolateral membrane | Outer hair cell motor

Question 32

What type of axons innervate an inner hair cell?

Answer 32

10-20 type I spiral neurons

Question 33

What is the function of type I spiral neurons?

Answer 33

Signal reception of sound over a wide range of intensities to the brain

Question 34

What type of axons innervate outer hair cell?

Answer 34

Type II spiral neurons

Question 35

What is the function of type II spiral neurons?

Answer 35

Signal reception of painfully loud sound that causes cochlear damage to the brain

Question 36

What do efferent fibres from medial olive innervate?

Answer 36

Outer hair cells

Question 37

What do efferent fibres from lateral olive synapse on?

Answer 37

Type I afferent fibres

Question 38

What can cause sensorineural hearing loss?

Answer 38

Noise Ageing Oxotoxic drugs Genetic mutations

Question 39

How can noise cause sensorineural hearing loss?

Answer 39

Physical effects on hair bundle structure Mitochondrial damage, cytotoxic free radicals Glutamate excitotoxicity

Question 40

How can ageing cause sensorineural hearing loss?

Answer 40

Hair cells Stria vascularis Cochlear ganglion

Question 41

What drugs are ototoxic?

Answer 41

``` Aminoglycoside antibiotics Cisplatin Loop diuretics Salicylate Solvents ```

Question 42

What are some targets of deafness genes in the cochlea?

Answer 42

``` Tight junctions Gap junctions Afferent synapse Tectorial membrane Stria vascularis Transduction complex ```

Question 43

What are cochlear implants?

Answer 43

``` Surgically implanted electronic device that provides sound to person who is profoundly deaf Expensive Maximum of 24 channels Speech sounds robotic music sounds awful ```

Question 44

Where does parallel processing start?

Answer 44

In cochlear nucleus

Question 45

What is the superior olivary complex?

Answer 45

2 binaural cues to localise sound in space

Question 46

Where are interaural intensity differences detected?

Answer 46

In lateral superior olive

Question 47

Where are interaural time differences detected?

Answer 47

Medial superior olive

Question 48

What is the inferior colliculus?

Answer 48

Obligatory synaptic station for all afferents Laminar organisation, iso-frequency sheets Combines complex frequency & amplitude analysis of DCN with information on sound localisation from SOC Encode complexity & localisation of sounds Auditory reflex centre, reflexive orientation to stimuli

Question 49

Where is the primary auditory cortex located?

Answer 49

Upper surface of temporal lobe

Question 50

What do lesions in auditory cortex cause?

Answer 50

Defects in sound localisation Discrimination of temporal pattern Intelligibility of speech

Question 51

What do lesions in Broca's & Wernicke's area cause?

Answer 51

Impair production & comprehension of speech