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YR2: Neuroscience and Mental Health > Sound Conduction and Transduction > Flashcards

Sound Conduction and Transduction Flashcards

1
Q

What scale is used to measure how loud a sound is?

A

Decibels (logarithmic scale)

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2
Q

What is pitch? What is the audible range for humans in terms of frequency?

A

Perception of frequency

20-20,000 Hz

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3
Q

What is the name given to the wing shaped flap of skin and cartilage that makes up the outer ear?

A

Pinna

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4
Q

Describe the shape of the outer ear and its importance.

A

Conical: starts off wide at the external auditory meatus + narrows to the tympanic membrane
This focuses the noise + increases the pressure on the tympanic membrane

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5
Q

Is the tympanic cavity fluid-filled or air-filled? What is its function?

A

Air-filled
Transmits vibrations of tympanic membrane across the cavity to the internal ear; accomplished by 3 interconnected but moveable bones (ossicles)

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6
Q

How do the ossicles increase the pressure of vibration of the tympanic membrane to match the impedance and reduce energy loss?

A

Incus has a flexible joint with the stapes, the resulting lever action increases force on the oval window
Stapes vibrates against superior oval window to induce pressure wave in inner ear fluid
Round window acts as a pressure release window- moves outwards to equalise pressure when stapes pushes oval window into cochlea

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7
Q

What is the point of the middle ear? Why isn’t the tympanic membrane continuous with the cochlea?

A

Cochlea contains fluid, in which you are trying to induce a pressure wave
If tympanic membrane was continuous with the cochlea, you would go straight from air to fluid + most of the energy will bounce back due to impedance
Sound waves require more energy to travel through fluid than air so the increase in pressure of vibration is crucial for this conduction

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8
Q

What 2 muscles are involved in making sure that the ossicles aren’t damaged by excessive vibration due to loud noise? What is the name given to this reflex?

A

Reflex contraction of Tensor Tympani + Stapedius reduce amplitude of vibrations passing through ossicles
Auditory reflex

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9
Q

What does displacement of stereocillia cause?

A

Opening of ion channels, depolarisation/ hyper polarisation of the nerve synapsing the hair cells
Bending of stereocillia towards the tallest stereocillium changes the internal voltage of the cell producing an electrical signal that goes to the brain (mechanotransduction)

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10
Q

What is the latency period of the auditory reflex?

A

50-100 ms

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11
Q

What is hyperacusis?

A

Painful sensitivity to low intensity sounds – can occur in conditions that lead to flaccid paralysis of the auditory reflex muscles (e.g. Bell’s Palsy)

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12
Q

Which test is used to determine the site of damage to the auditory system, that is causing hearing loss?

A

Weber Test

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13
Q

What are the 2 specialised membranes of the cochlea?

A

Oval Window

Round Window

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14
Q

What are the 3 chambers of the cochlea? What type of fluid does each contain?

A

Scala Vestibuli- Perilymph
Scala Media- Endolymph
Scala Tympani- Perilymph

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15
Q

What is the difference in composition of perilymph and endolymph?

A

Perilymph: Low K+, High Na+
Endolymph: High K+, Low Na+

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16
Q

What structure connects the 2 perilymph chambers?

A

Helicotrema

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17
Q

Describe the mechanism of sound transduction

A

Vibration of tympanic membrane moves malleus + incus laterally, pushing the stapes medially onto the oval window, generating a wave in the fluid filled cochlea
The wave moves through the cochlea causing 2ndary tympanic membrane to bulge leading to vibration of the basilar membrane + stimulation of receptor cells

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18
Q

Describe the difference in sensitivity of different parts of the basilar membrane.

A

Higher frequency sounds = base

Lower frequency sounds = apex

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19
Q

What is the Organ of Corti?

A

Sense organ of the cochlea, which converts sound signals into nerve impulses that are transmitted to the brain via the cochlear nerve

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20
Q

Where is the Organ of Corti found?

A

It lies on top of the basilar membrane + beneath the tectorial membrane

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21
Q

What are the 2 types of cell in the organ of corti?

A

Inner + outer hair cells

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22
Q

Describe 6 features and the function of inner hair cells.

A

Found alone
Not in contact with tectorial membrane
Send afferents to brain- provide sensory transduction
~3500 per cochlea
Function:
Have stereocilia that move in response to the movement of endolymph in the scala media
Transmit auditory stimulus

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23
Q

Describe 5 features and the functions of outer hair cells.

A 
Found in groups of 3 
In contact with tectorial membrane  
Receive efferents from brain 
Vulnerable to damage (can result in sensorineural hearing loss)
~11,000 per cochlea 
Function: 
Electromotile so can expand + contract to amplify the amount of vibration
Control of inner hair cells
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24
Q

Which compartment of the cochlea does the stereocilia of the hair cells project into?

A

Endolymph (base is in the perilymph)

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25
Q

What internally generated sounds are the outer hair cells responsible for?

A

Otoacoustic emissions

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26
Q

What are stereocilia connected by? What do these act as? What is activated by stretching these?

A

Tip links
Act as small springs stretched by stereocillia sliding
Stretching results in opening of ion channels + response currents

27
Q

What bony conical structure is found at the middle of the cochlea?

A

Modiolus

28
Q

Describe what happens when the basilar membrane is displaced upwards.

A

Depolarisation
Stereocilia move away from the modiolus
K+ channels open
K+ enters from endolymph

29
Q

Describe what happens when the basilar membrane is displaced downwards.

A

Hyperpolarisation
Stereocilia move towards the modiolus
K+ channels close

30
Q

What separates scala vestibuli + scala media? What separates scala media + scala tympani?

A

Scala Vestibuli-Scala Media: Reissner’s (vestibular) membrane
Scala Media-Scala Tympani: Basilar membrane

31
Q

Describe the central auditory pathway to the primary auditory cortex.

A 
Hair cells depolarise 
Synapse with neurones in spiral ganglion
Cochlear division of CNVIII synapses with the ipsilateral cochlea nucleus in medulla (dorsally + ventrally) - transmission onwards is bilateral 
Superior olivary nucleus 
Inferior colliculus
Medial geniculate nucleus
Auditory cortex
32
Q

Up to what point is the auditory pathway from one ear ipsilateral?

A

Cochlear nuclei

Beyond this point there is bilateral representation

33
Q

The inferior colliculus receives input from both cochlea. What is the inferior colliculus responsible for?

A

Reflex associations: turning your head towards loud noise

34
Q

Describe a phenomenon that is involved in sharpening the signal coming from the cochlea.

A

Lateral inhibition

35
Q

To which parts of the CNS do collaterals from the auditory pathway go?

A

Reticular formation

Cerebellum

36
Q

In which lobe is the primary auditory cortex?

A

Temporal

37
Q

What is the secondary auditory cortex responsible for?

A

Responding to sounds coming off/on

Responding to the duration of sound

38
Q

What is the name given to the axons that project from the medial geniculate nucleus to the primary auditory cortex?

A

Acoustic radiations (travel via the internal capsule)

39
Q

How do you localise short sound burst?

How do you localise continuous sound?

A

Short: Interaural time delay
Continuous: Interaural intensity difference

40
Q

What is conductive hearing loss?

A

Middle ear damaged
Ear not capable of transmitting vibration of sound waves onto cochlea
Amplification system is eliminated

41
Q

What is sensorineural hearing loss and what can it be caused by?

A

Cochlea/ cochlear nerve damaged

Signal transmitted to the primary auditory cortex is reduced/ lost

42
Q

What is the term used to describe loss of hearing due to the death of hair cells in normal ageing?

A

Presbyacusis

43
Q

What is Timbre?

A

What distinguishes 2 sounds at the same frequency + intensity

44
Q

What is the hair bundle?

A

A cluster of modified microvilli called Stereocillia

45
Q

What does impedance measure?

A

Reluctance of a system in receiving energy from a source

46
Q

What is resonant frequency?

A

Frequency at which the impedance of the system is minimal

47
Q

What is effected in conductive hearing loss? List 4 causes

A

Outer + middle ear
Ear is not capable of transmitting the vibration of sound waves onto the cochlea
Fluid accumulation in inner ear, perforated tympanic membrane, ostosclerosis + barotrauma

48
Q

What generates a difference in pressure between the 2 liquid filled chambers of the cochlea? What is the consequence of this?

A

Motion of the Stapes

Causes vibration of basilar membrane

49
Q

What is the Organ of Corti comprised of?

A

Basilar + Tectorial membranes
Hair cells
Supporting cells

50
Q

Define intensity and volume

A

Intensity: Amplitude of sound waves
Volume: Perception of amplitude

51
Q

What is the external ear composed of?

A

Pinna (Auricle)
External acoustic meatus (auditory canal)
Tympanic membrane (ear drum)

52
Q

Name the auditory ossicles and describe their connections

A

Malleus: connected to tympanic membrane
Incus: connected to malleus by synovial joint
Stapeus: connected to Incus by synovial joint + attached to lateral wall of the internal ear at oval window

53
Q

What is the internal ear composed of?

A 
Bony labyrinth (3 parts- vestibule, semi-circular canals, cochlea)
Membranous labyrinth (Membraneous ducts + sacs within bony cavities)
54
Q

What is the bony labyrinth lined and filled with?

A 
Lined with periosteum
Fluid filled (perilymph)
55
Q

List the components of the membraneous labyrinth and their functions. What are these spaces filled with?

A

Semi-circular ducts: balance
Cochlear duct: Hearing
2 sacs: Utricle + Saccule: Balance
All filled with endolymph

56
Q

How is sound amplified by the structure of the tympanic membrane and oval window?

A

Focussing the vibrations from large SA of tympanic membrane to small SA of oval window
Decrease in SA results in pressure increase

57
Q

What maintains the concentration gradient of Na+ and K+ between the different cochlea compartments?

A

Stria vascularis

58
Q

Describe the difference in fibres on the basilar membrane

A 
Base= Short + stiff - vibrate in response to high frequency
End= Long + loose - vibrate in response to low frequency
59
Q

What is meant by tonotopic mapping?

A

Different parts of auditory cortex for different pitches
Low frequencies = ventral neurones
High frequencies = dorsal neurones

60
Q

What can cause conductive hearing loss?

A 
Wax
Infection
Otoscleorisis of ossicles
Perforated tympanic membrane
Barotrauma
Fluid accumulation
61
Q

State 3 causes of pre-lingual hearing loss

A

Perinatal/ bacterial meningitis
Congenital infection e.g. rubella
Head injury

62
Q

State 6 common causes of hearing loss in adults

A 
Genetics
Ototoxicity (chemotherapy)
Infection
Tumour
Head injury
Loud noises
63
Q

Name 1 solution to address the loss of hair cells causing hearing loss

A

Bypass dead cells + stimulate nerve fibres directly with cochlear implants

YR2: Neuroscience and Mental Health (20 decks)

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