Hearing

Question 1

Sound properties - pitch/frequency

Answer 1

Measured in Hertz (Hz)

Question 2

Sound properties - loudness

Answer 2

Amplitude; size of the waves

Question 3

What frequency range can humans normally hear?

Answer 3

20-20,000 Hz

Question 4

What frequency range is human speech?

Answer 4

250-8000 Hz

Question 5

Hearing changes with age

Answer 5

Frequency range that can be heard decreases with age
High frequency sounds lost first

Question 6

Sound wave properties

Answer 6

Condensation (peak)
Rarefaction (trough)

Question 7

3 broad ear parts

Answer 7

External
Middle
***

Question 8

Parts of the external ear - Pinna/Auricle

Question 10

Parts of the external ear - Tympanic membrane/ear drum

Question 11

Parts of the middle ear - ***those three tiny bones

Answer 11

Tiny join capsules *

Question 12

Parts of the middle ear - Eustachian tube

Answer 12

Auditory tube
“Ears popping” -> equalising pressure

Question 13

Parts of the middle ear - mastoid air cells

Answer 13

Involved I keeping pressure

Question 14

Parts of the inner ear - fluid

Answer 14

Perilymph

Question 15

Parts of the inner ear - cochlear

Question 16

Most common cause of hearing loss presentation at the GP

Answer 16

Over-presence of wax

Question 17

Function of middle ear (broad)

Answer 17

Amplification of sound

Question 18

Function of inner ear (broad)

Answer 18

Conversion of vibrations into electric signals

Question 19

Middle ear - impedance matching

Answer 19

Greater area of tympanic membrane than oval window
Level action of teh major ossicles
Buckling of the tympanic membrane

Question 20

Acoustic impedance

Answer 20

Ratio of pressure to velocity - high impedance means that you need to apply a high pressure to a structure in order to move it
***

Question 21

Impedance mismatch

Question 22

Impedance matching mechanisms

Answer 22

Area ratio
Lever ratio

Question 23

Area ration

Answer 23

tympanic membrane is larger in this area than in the stapes footplate, like a drawing pin increasing pressure at the sharp end

Question 24

Lever ratio

Answer 24

processes of the malleus and incus are unequal in length. This increases the force (but decreases the velocity) at the stapes, just as it is easier to let a load in a wheelbarrow when the load is closer to the wheel than the handles are

Question 25

Names of the three bones in the middle ear

Answer 25

Malleus (hammer) Incus (anvil) Stapes (stirrup)

Question 26

Transmission fo vibrations by bones in the middle ear

Answer 26

Malleus attached to tympanic membrane Vibration of the membrane & thus the malleus Malleus attached to incus Incus attached to stapes Foot of stapes fits into the oval window

Question 27

Modification & protection

Answer 27

2 skeletal muscles attach to the ossicles They reflexively dampen excessive loud sounds Sound attenuation reflex (works for loud sounds not for high frequency)

Question 28

Sound attenuation reflex

Answer 28

Responds effectively to low frequency sounds Will decrease up to 100 fold the energy that reached the eardrum It’s a slow reflex (useless against gunshots; only lasts ~10 minutes)

Question 29

*** for making notes -> Paget’s disease as a case study

Question 30

*** for making notes -> secretory otis media as a case study

Question 31

Broad roles of the inner ear

Answer 31

Hearing Balance

Question 32

Inner ear broad structure notes

Answer 32

Interconnecting fluid filled tunnels and chambers within the petrous portion of the temporal bone

Question 33

Inner ear - boney labyrinth

Answer 33

Cochlea - hearing Vestibule - balance Semicircular canals - balance

Question 34

Cells in the cochlea

Answer 34

Highly modified Forming the spiral organ (organ of corti) Epithelial cells + specialised sensory hair cells

Question 35

Cochlea

Answer 35

Specialised sensory hair cells No axons Basilar regions covered with synaptic terminals of sensory neurons Embedded in the tectoral membrane

Question 36

Organ of corti

Answer 36

12,000 outer hair cells in 3 rows 3,500 inner hair cells in a single row; form synapses with afferent nerve terminals -> axons -> cochlear clues of the brainstem

Question 37

Hair celll - steocilium

Answer 37

Sterocilium look kinda ike villi & are connected by tip links ***

Question 38

Tip Links

Answer 38

Tiny links between stereocilia The bending action of tip links (caused by sound vibrations I think**) causes mechanical transduction

Question 39

Genetic causes of deafness CAN be linked to

Answer 39

Stereocilia & involved proteins

Question 40

Transduction

Answer 40

Displacement of hair cells causes high potassium and low sodium levels in cells

Question 41

Process of transduction

Answer 41

Stereocilia bent Receptor potential varies with oscillation of sound stimuli Overall net depolarisation Electrical potential of the perilymph Signal is called the cochlear microphonic No latency, no threshold

Question 42

How is the cochlear organised?

Answer 42

Tonotopically -> High frequency at start and low frequency at end

Question 43

Tuned hairs

Answer 43

Each inner hair cell responds to specific frequency band Each afferent axon connects to only one hair cell Each hair cell thus displays sharp defined tuning curve Each hair cell has a low threshold to simulation at its characteristic frequency

Question 44

Auditory pathways

Answer 44

Travelling from the cochlear to the auditory nerve, the there are 2 pathways: up the dorsal cochlear nucleus or the *** Either way arrives at the ***

Question 45

Conductive deafness

Answer 45

Anything that blocks out ear or middle ear

Question 46

Sensorineural deafness

Answer 46

Cochlear -> noise trauma, drugs, infection, congenital presbycusis Auditory nerve -> tumour (acoustic neuroma, very rare)

Question 47

Tinnitus

Answer 47

Common complaint Associated with a number of conditions Can be accompanied by vertigo and/or partial deafness

Question 48

Tests for deafness

Answer 48

Weber’s test Rinne’s test

Question 49

Weber’s test

Answer 49

Bone conduction Tuning fork in the middle of the skull

Question 50

Rine’s test

Answer 50

Air conduction Tuning fork on mastoid process, when no longer heard then use sound conduction