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ENT SM > Physiology of Hearing and Balance > Flashcards

Physiology of Hearing and Balance Flashcards

1
Q

What is the general function of the external ear

A

Collect sound

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2
Q

What is the general function of the middle ear

A

Mechanical force amplifier

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3
Q

What is the general function of the inner ear

A

Sound transducer / analyser

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4
Q

What is sound

A

A pressure wave caused by oscillating molecules set in motion by a vibration

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5
Q

What does frequency dictate

A

Pitch

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6
Q

What does amplitude dictate

A

Intensity

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7
Q

What frequency can humans perceive

A

20-20000Hz

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8
Q

Why do mammals under water not need an external ear

A

Sound is different in water and does not need to be channeled like us

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9
Q

What is the overall pressure gain in the middle ear

A

x22

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10
Q

What is the function of the angular ligament

A

It suspends the stapes in the oval window

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11
Q

What happens if there is a very high frequency sound

A

There is rotation between the malleus and incus

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12
Q

How do we get a pressure gain in the middle ear

A

We need to transfer sound from air to liquid

To generate the power to do this, we require movement from the ossicles

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13
Q

What does the ossicular chain act as

A

Pistor or lever arm with varying efficiency depending on frequency of sound transmitted

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14
Q

What is the function of the Eustachian tube

A

Ventilation pathway for the middle ear mucosa

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15
Q

What is the eustachian tube made up of

A

Bony and cartilaginous portions

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16
Q

What is the resting state of the cartilaginous tube? Open or closed

A

Closed

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17
Q

What opens the Eustachian tube

A

Tensor veli palatini and levator palatine muscles

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18
Q

When might the Eustachian tube not open and close as it should?

A

Babies with cleft palates

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19
Q

Dysfunction of the Eustachian tube leads to what

A

Middle ear negative pressure

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20
Q

What do the oval and round windows in the cochlea allow

A

The transmission of pressure wave in enclosed canal and vibration of the basilar membrane

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21
Q

Where is the endolymph found

A

Scala media

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22
Q

Where is perilymph found

A

Scala vestibuli

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23
Q

Where is the scala media found

A

Suspended in between scala tympani and scala vestibuli

24
Q

What are some of the important structures found on the organ of corgi

A

Basilar membrane
outer hair cells
inner hair cells

25
Q

What can gentamicin cause damage to

A

The outer hair cells

26
Q

What is the function of the outer hair cells

A

They are involved in modulating sounds

27
Q

What is the function of the inner hair cells

A

Main ones involved in receiving information and sending it back towards the brain

28
Q

In one word, what is the function of hair cells

A

Transduction: conversion of mechanical “bending force” into electrical impulse

29
Q

When does depolarisation of the hair cells occur

A

When the hair cells are deflected towards the longest hair cells

30
Q

When does hyper polarisation occur

A

When the hair cells are deflected away from the longest cilia (

31
Q

What happens when hair cells bend

A

Generate Action potentials and generates a firing to the spiral ganglion

32
Q

How is a frequency picked up?

A

Cells depolarise and fire an action potential to the cochlear nerve

33
Q

How many electrodes are on a cochlear implant

A

20-24

34
Q

What does ECOLI stand for

A 
mneumonic for the central pathway
Eight cranial nerve
Cochlear nucleus
Olivary complex
Lateral lemniscus
Inferior colliculus
35
Q

Where is the location of the primary auditory cortex

A

Supeiror temporal gyrus (Brodman areas 41/42)

36
Q

What systems are involves in balance

A 
Ears
Eyes
Proprioception
CNS 
Cardiac
37
Q

What pathology can affect balance

A 
Meningitis 
Migraines
Diabetes 
Arthritis 
Stress 
SOL 
MS 
Arrythmias 
Postural Hypotension
38
Q

What is the name of the structure involved with balance

A

Labyrinth

39
Q

What is meant by the vestibular end organs

A

The posterior and superior semicircular canals
ampullae of lateral
maculae of the utricle and saccule

40
Q

What is another name of the utricle and saccule

A

Otolith organs

41
Q

Describe the appearance of the maculae of the otolith organs

A

Big gel membrane (gelatinous matrix) with crystals (otoconia) imbedded in it - the crystals give weight to the organ so you can perceive gravity
Crystals are pushed and pulled in the gel membrane

42
Q

How can we tell that movement has stopped

A

The firing of action potentials will stop

43
Q

What are otoconia made of

A

Calcium carbonate crystals

44
Q

Describe the orientation of otolith organs

A

360 orientation so all planes of motion can be detected

You can sense angular or linear acceleration

45
Q

What is the strola

A

a curvilinear landmark in the middle ear to which the hairs (hair cells) in the macula are oriented.

46
Q

Describe the paring of the semi-circular canals

A

Orientated at 90 degrees to each other so paired, equal and opposite

47
Q

In a semi-circular canal, where does the cupula and ampulla sit

A

The cupula sits inside the ampulla

48
Q

What causes deflection in the semi-circular canals

A

Movement of perilymph

49
Q

What does bending cause

A

Stereocilia to deflect

50
Q

Describe the movement of liquid in the ear as you move your head

A

As you move your head to the right, the liquid moves and hits off of the left side
The side that you are turning to gets excited and the side you are turning away from has inhibition

51
Q

What can cause a mismatch of the vestibulo-ocular reflex

A

Labyrinthitis

tumour

52
Q

How can we test the vestibulo-coular reflex

A

Get the patient to put their thumb up out in front of them and focus their eyes on it. Ask them to shake their head from side to side. If the patient is very slow to do this, they may have a failure in the reflex

53
Q

What is spontaneous nystagmus

A

Nystagmus is defined as involuntary movement of the eyes. Most frequently it is composed of a mixture of slow and fast movements of the eyes

54
Q

Why does the abnormal eye movements occur

A

The eyes are being pushed the way that the brain thinks it is spinning and the eyes will flick back because they want to focus on one part.

55
Q

What is a vestibular schwannoma and how does it cause imbalance

A

tumour of the VIII nerve sheath (schwann) cells

Causes imbalance due to slowly progressive loss of function

56
Q

What does the central connections of the vestibular system have links to

A

Motor output to eyes
Motor output to the neck back and leg muscles
Vomiting centres

ENT SM (19 decks)

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