Physiology of Hearing and Balance

Question 1

What is the general function of the external ear

Answer 1

Collect sound

Question 2

What is the general function of the middle ear

Answer 2

Mechanical force amplifier

Question 3

What is the general function of the inner ear

Answer 3

Sound transducer / analyser

Question 4

What is sound

Answer 4

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

Question 5

What does frequency dictate

Answer 5

Pitch

Question 6

What does amplitude dictate

Answer 6

Intensity

Question 7

What frequency can humans perceive

Answer 7

20-20000Hz

Question 8

Why do mammals under water not need an external ear

Answer 8

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

Question 9

What is the overall pressure gain in the middle ear

Answer 9

x22

Question 10

What is the function of the angular ligament

Answer 10

It suspends the stapes in the oval window

Question 11

What happens if there is a very high frequency sound

Answer 11

There is rotation between the malleus and incus

Question 12

How do we get a pressure gain in the middle ear

Answer 12

We need to transfer sound from air to liquid

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

Question 13

What does the ossicular chain act as

Answer 13

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

Question 14

What is the function of the Eustachian tube

Answer 14

Ventilation pathway for the middle ear mucosa

Question 15

What is the eustachian tube made up of

Answer 15

Bony and cartilaginous portions

Question 16

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

Answer 16

Closed

Question 17

What opens the Eustachian tube

Answer 17

Tensor veli palatini and levator palatine muscles

Question 18

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

Answer 18

Babies with cleft palates

Question 19

Dysfunction of the Eustachian tube leads to what

Answer 19

Middle ear negative pressure

Question 20

What do the oval and round windows in the cochlea allow

Answer 20

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

Question 21

Where is the endolymph found

Answer 21

Scala media

Question 22

Where is perilymph found

Answer 22

Scala vestibuli

Question 23

Where is the scala media found

Answer 23

Suspended in between scala tympani and scala vestibuli

Question 24

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

Answer 24

Basilar membrane
outer hair cells
inner hair cells

Question 25

What can gentamicin cause damage to

Answer 25

The outer hair cells

Question 26

What is the function of the outer hair cells

Answer 26

They are involved in modulating sounds

Question 27

What is the function of the inner hair cells

Answer 27

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

Question 28

In one word, what is the function of hair cells

Answer 28

Transduction: conversion of mechanical "bending force" into electrical impulse

Question 29

When does depolarisation of the hair cells occur

Answer 29

When the hair cells are deflected towards the longest hair cells

Question 30

When does hyper polarisation occur

Answer 30

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

Question 31

What happens when hair cells bend

Answer 31

Generate Action potentials and generates a firing to the spiral ganglion

Question 32

How is a frequency picked up?

Answer 32

Cells depolarise and fire an action potential to the cochlear nerve

Question 33

How many electrodes are on a cochlear implant

Answer 33

20-24

Question 34

What does ECOLI stand for

Answer 34

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

Question 35

Where is the location of the primary auditory cortex

Answer 35

Supeiror temporal gyrus (Brodman areas 41/42)

Question 36

What systems are involves in balance

Answer 36

``` Ears Eyes Proprioception CNS Cardiac ```

Question 37

What pathology can affect balance

Answer 37

``` Meningitis Migraines Diabetes Arthritis Stress SOL MS Arrythmias Postural Hypotension ```

Question 38

What is the name of the structure involved with balance

Answer 38

Labyrinth

Question 39

What is meant by the vestibular end organs

Answer 39

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

Question 40

What is another name of the utricle and saccule

Answer 40

Otolith organs

Question 41

Describe the appearance of the maculae of the otolith organs

Answer 41

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

Question 42

How can we tell that movement has stopped

Answer 42

The firing of action potentials will stop

Question 43

What are otoconia made of

Answer 43

Calcium carbonate crystals

Question 44

Describe the orientation of otolith organs

Answer 44

360 orientation so all planes of motion can be detected | You can sense angular or linear acceleration

Question 45

What is the strola

Answer 45

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

Question 46

Describe the paring of the semi-circular canals

Answer 46

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

Question 47

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

Answer 47

The cupula sits inside the ampulla

Question 48

What causes deflection in the semi-circular canals

Answer 48

Movement of perilymph

Question 49

What does bending cause

Answer 49

Stereocilia to deflect

Question 50

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

Answer 50

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

Question 51

What can cause a mismatch of the vestibulo-ocular reflex

Answer 51

Labyrinthitis | tumour

Question 52

How can we test the vestibulo-coular reflex

Answer 52

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

Question 53

What is spontaneous nystagmus

Answer 53

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

Question 54

Why does the abnormal eye movements occur

Answer 54

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.

Question 55

What is a vestibular schwannoma and how does it cause imbalance

Answer 55

tumour of the VIII nerve sheath (schwann) cells | Causes imbalance due to slowly progressive loss of function

Question 56

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

Answer 56

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