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Case 5 > Hearing and the Ear > Flashcards

Hearing and the Ear Flashcards

1
Q

Why is Hearing Important

A

Speech and language development
Social Development
Education
Employment
Social Isolation
Health Implications

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2
Q

The frequency of sound is measured in?

A

The frequency of sound is measured in cycles per second (Hertz = Hz)

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3
Q

for every octave interval, what happens to the frequency?

A

Middle C has a frequency of 261Hz.

For every octave interval, the frequency doubles so the C above is 523Hz and the C below is 131Hz

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4
Q

what is sound

A

Sound is a vibration that propagates as an acoustic wave through a transmission medium such as a gas, liquid or solid.

Sound is a type of energy made by vibrations. When an object vibrates, it causes movement in surrounding air molecules. These molecules bump into the molecules close to them, causing them to vibrate as well. This makes them bump into more nearby air molecules.

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5
Q

what about an audiogram

A

Audiogram – test up to 4KHz. Not that much effect to 4KHz as only need up to this to understand speech. Lack of contact with others. Upper ranges lost at older ages

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6
Q

what is Presbycusis

A

Sensitivity, particularly at the high frequency end declines with normal ageing

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7
Q

what does Eustachian tube do

A

equalises pressure

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8
Q

what is wax important for

A

prevents infection

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9
Q

what is important to look for when viewing the eardrum using otoscope/auroscope

A

Look at the health of the tympanic membrane (eardrum).
Could have layers of skin cells – pressed against it is the first of the ear ossicles, the malleus or hammer.
Blood vessels in periphery.
Rupture – bleeding at the edges.

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10
Q

what keeps the tympanic membrane under pressure

A

Tensor tympanum

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11
Q

The tympanic membrane has a large surface area but the force generated by sound vibrations in air is weak. So, how is this sound generated?

A

Ossicles concentrate the force onto the smaller area of the oval window, increasing the efficiency of transmission of the vibrations to the fluid filled inner ear.

This increases the sensitivity of the ear

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12
Q

Anything interfering with free movement of the ossicles affects?

A

hearing

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13
Q

cochlea - curled tube, with 3 different tubes inside. innermost tube is?

A

scala media

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14
Q

which of the 3 tubes in cochlea is most important in sound detection?

A

basilar membrane – splitting noise into different frequencies

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15
Q

what sits on top of the basilar membrane?

A

the organ of corti

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16
Q

what do the hair cells sitting on the organ of corti do?

A

Hair cells sitting on this vibrate whilst the tectorial membrane remains stationary. Opens potassium channels which delivers action potentials to the nerve cells

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17
Q

Scala vestibuli and tympani contains?

A

Scala vestibuli and tympani contains normal perilymph (extracellular fluid) – high in Na+ low in K+

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18
Q

Scala media contains?

A

Scala media has endolymph – high in K+ and low in Na+
It’s the high level of K+ that enables depolarisation

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19
Q

Stria vascularis can be damaged, which causes?

A

loss of hearing

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20
Q

what is endocochlear potential

A

endolymph is +80mV compared to perilymph = endocochlear potential

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21
Q

what happens when the stereocilia are deflected?

A

When the stereocilia are deflected, K+ channels on the surface open and K+ flows into the hair cell due to the driving force of the endocochlear potential. This depolarizes the hair cell which leads to transmittter release

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22
Q

how many rows of hair cells in the cochlear?

A

3

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23
Q

role of inner hair cells of the inner row in cochlea?

A

pitch detection and determination

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24
Q

role of outer hair cells in cochlea?

A

cochlear amplifier

25
how many rows of outer hair cells
3
26
how many rows of inner hair cells
1
27
how does the cochlear amplifier work?
when the waves pass along the basilar membrane -> this excites the outer hair cells, causing them to contract effectively, these outer hair cells bounce on the basilar membrane in phase with the wave (just like someone bouncing on a trampoline) -> this bouncing increases the size of the wave on the basilar membrane
28
how do cochlear microphonics work
When the ear is damaged, the hairs may oscillate in the absence of external sound. This can cause the basilar membrane to vibrate and act as a loudspeaker that emits sound
29
the distance the wave travels along the basilar membrane depends on?
depends on the frequency of the wave
30
what is tonotopy
Tonotopy – splitting of the sound into its various frequencies.
31
there are higher frequencies of the waves along the basilar membrane where the cochlear is ____, and lower frequencies of these waves where the cochlear is ____ ?
different sections of the cochlea are designed to detect different frequencies higher frequencies where the cochlear is narrower lower frequencies where the cochlear is wider
32
what are cochlear implants used for?
Cochlear implants can be used to restore some hearing to people who have lost cochlear hair cell function, but in whom the sensory neurones of the spiral ganglion are still functional
33
The principal under which the cochlear implants work is:
tonotopy
34
how do cochlear implants work
1) A processor breaks down sound into its frequency components 2) The different frequency channels are transmitted to the implant receiver 3) The signal is conducted along wires that end in electrodes in the cochlea 4) The electrodes stimulate the nerve cells underneath the appropriate region of the basilar membrane
35
The tonopic relationship of frequency to position is seen where?
The tonopic relationship of frequency to position is seen not only on the basilar membrane but at all levels within the auditory pathways – it is the principal on which cochlear implants work
36
Tonotopy is preserved all the way from?
Tonotopy is preserved all the way from the ear to the auditory cortex. Input from the different ears is compared in the medulla (helps with locating a sound).
37
what about the primary auditory cortex (Heschl’s gyrus)?
The primary auditory cortex (Heschl’s gyrus) is tucked into the superior-medial surface of the temporal lobe. It has a tonotopic map of frequency
38
both Broca's area and Wernicke's area are involved in language processing and are present only on?
present only on the left (dominant) hemisphere
39
The secondary auditory cortex that surrounds Heschl’s gyrus includes?
Wernicke's area
40
wernicke's aphasia
Wernicke’s aphasia – language fluent and grammatical but often meaningless, including nonsense words that sound similar to real ones [“You know that smoodle pinkered and that I want to get him round and take care of him like you want before.” ]
41
Broca's aphasia
Broca’s aphasia – language halting and non-grammatical (lack of pronouns, articles, and conjunctions) [here a patient describes a picture – “picnic …flying kite… swimming… house..tree….pouring water..boat… trees…. okay… car”]
42
how is the ear protected from sound/harmful higher frequencies?
when there's harmful, higher frequencies,The stapedius muscle limits the movement of the stapes to protect the cochlea from loud noise
43
what about the stapedius muscle regarding external sounds?
The stapedius muscle is activated by loud external sounds, to protect the cochlea (DELAY)
44
what about the stapedius muscle regarding our own voice?
Before we start to speak, the stapedius muscle activates so that low frequency sound from our own voice (transmitted via soft tissue and bone) is attenuated (reduced in force/loudness). (no DELAY)
45
when can you get temporary deafness/noise-induced hearing loss?
Temporary deafness may be experienced after exposure to high intensity sound, e.g. after a period of time at a rock concert
46
symptoms of noise-induced hearing loss (name 2)
Ear discomfort after exposure Sounds appear muffled Difficulty in interpreting speech, particularly if there is a background noise Ringing or buzzing sensation in the ears
47
Noise induced hearing loss typically first appears as a reduction in sensitivity at about?
4kHz
48
in noise-induced hearing loss, speech becomes harder to interpret because?
consonants produce sound in this high frequency band of 2-4kHz
49
why is this band (of 2-4kHz) lost in noise-induced hearing loss?
the 2-4kHz range is vulnerable in noise-induced hearing loss because it aligns closely with the resonant frequency of the external auditory canal (which is around 2.5 to 3 kHz in most adults). [The external auditory canal naturally amplifies sounds in this frequency range due to its resonant properties, meaning sounds in this band are transmitted more efficiently to the eardrum and middle ear.]
50
what is tinnitus?
Tinnitus = “ringing or buzzing sensation in the ears” [tinnitus is A symptom not a specific condition - may be described as a ringing, whistling or buzzing. This sensation is virtual (not real) sound and originates within the brain.]
51
name 1 possible cause of tinnitus
Conditions that reduce the perception of external sounds e.g. ear wax build up, ear infections, glue ear, otosclerosis Hair cell damage due to high intensity noise exposure, or drug side effects (e.g. aspirin, quinine, antibiotics) Lesions of the auditory nerve e.g. acoustic neuroma (benign tumour)
52
what is pulsatile tinnitus
tinnitus should NOT be confused with pulsatile tinnitus, which is a different phenomenon pulsatile tinnitus - real sounds from blood flow in the ear, muscle activity or grinding of the temporo-mandiblar (jaw) joint.
53
treatment of tinnitus
Treatment; masking (using white noise or music), Tinnitus Retraining Therapy (helping the patient to habituation to, and therefore ignore, the tinnitus).
54
What happens when the ear is exposed to damaging noise levels
1)The first sign of damage is disruption of the hairs on the hair cells 2)Longer exposure to intense sound leads to rounding up and shortening of the hairs 3)In the final stages, the remaining parts of the hairs fuse into a single mass
55
Eustachian tube is the link between?
the link b/w pharynx and ear
56
say the order of the 3 tubes of the cochlea
3 different tubes of the cochlea: Scala vestibuli at top, scala tympani at bottom Scala media in the middle, in b/w scala vestibuli and scala tympani
57
Not being able to produce endolymph is what causes?
causes deafness in children
58
as the hair cells on the basilar membrane move, they cause what channels to open?
causes K+ channels to open. [when the hairs on basilar membrane move, the tectorial membrane remains stationary] [basilar membrane moves up and down]
59
stapedius muscle is supplied by what nerve
CN VII

Case 5 (9 decks)

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