1b Auditory Systems Flashcards by Zara Edwards

What does a vestibular organ capture?

Captures low frequency motion (movements)

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What does a hearing organ capture?

Captures high frequency motion (sound)

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What is meant by the frequency of a sound?

The number of cycles of the sound per second, perceived tone

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What is the frequency measured in?

Hertz

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What is the amplitude?

the sound pressure - therefore corresponding to loudness

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What is the human range of hearing?

20-20000 Hz
0-120 decibels

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What are the functions of the outer ear?

Capture sound and focus it onto the tympanic membrane

Modest amplification of the upper range of speech frequencies by resonance in the canal

To protect the ear from external threats

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By how much does the outer ear amplify the sound?

10 DB

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What is the middle ear?

All the structures from the tympanic membrane to the oval window

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What is the main function of the middle ear?

Mechanical amplification (Provides an additional 20-30DB)

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What happens to the tympanic membrane when a sound hits it?

It vibrates at the same frequency as the sound wave which just hit it

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What are the ossicles?

The three smallest bones in the body -

Malleus
Incus
Stapes

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What is the inner ear called?

Cochlea

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What is the function of the cochlea?

function is to transduce vibration into nervous impulses

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What two things does the cochlea capture?

Captures the pitch and intensity of the sound

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Where does the stapes connect to the cochlea?

The oval window

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Where does the sound go from the oval window of the cochlea?

Scala Vestibuli

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What does the scala vestibuli and the scala tympani contain?

Perilymph

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What does the scala media contain?

Endolymph

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What is the perilymph high in?

Sodium

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What is the endolymph high in?

Potassium

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Where is the hearing organ or Organ of Corti Located?

In the basilar membrane - separates the scala media and the scala tympani

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What type of structures are the scala vestibuli and the scala tymphani?

Bone structures

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What type of structure is the scala media?

Membranous Structure

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What structure does the Organ of Corti lie in?

The basilar Membrane

Which sound frequency moves the base of the basilar membrane?

high frequency sounds

Which sound frequency moves the apex of the basilar membrane of the cochlea?

Apex - Wide and loose Moved by lower frequency (Hz) sounds

How is the basilar membrane arranged?

Tonotopically

What are the two types of hair cells which the organ of corti contains?

Inner hair cells Outer hair cells

What is the difference in the way the inner and outer hair cells of the organ of corti are arranged?

Inner = one line Outer = three lines

What sits above the hair cells in the cochlea?

the tectoral membrane

What does the tectoral membrane allow?

Allows hair deflection, which in turn depolarises the cell

Inner hair cells carry which type of signal?

Afferent signals

Which nerve do the inner hair cells pass information to?

Auditory nerve

What is the function of the inner hair cells?

Transduction of the sound into nerve impulses

What do the outer hair cells do?

Carry efferents from the auditory nerve

What is the function of the Outer Hair cells?

Modulate the sensitivity of the response

What are the hairs of the hair cells called?

Stereocilium

What is the longest cilium called?

Kinocilium

What does deflection of the stereocilium towards the longest cilium cause?

Opening of K+ Channels

What happens inside the hair cell when the stereocilium are deflected towards the tallest one?

K+ Channels open, Causes depolarisation Opens Ca2+ channels leads to the release of an excitatory neurotransmitter (Glutamate) and therefore the simulation of the afferent nerve

How does louder sounds affect the sterocilium?

Louder sounds deflect the kinocilium more

What causes the movement of the sterocilium?

The sheer force of the tectoral membrane over the top of the sterocilium will move them

What happens when the cells are hyper-polarised?

K+ channels are closed

What happens to the nerves from the spiral ganglion?

Via the vesticulo-cochlear nerve, they travel to the ipsilateral cochlear nuclei in the pons

Which cranial nuclei come into the pons?

5,6,7,8

Where is the cochlear nuclei?

In the pons

Where does the auditory system nerve decussate?

In the brain stem - in the pons, at the superior olive level

AWhat area of the thalamus is related to hearing?

Medial geniculate body

Where is the auditory cortex>

The temporal lobe

After what point are the auditory connections bilateral?

After the superior olive level

What are the three types of hearing loss?

Conductive Sensorineural Central

What is conductive hearing loss?

Problem is located in the outer / middle ear

What is sensorineural hearing loss?

Damage to the sensory organ (cochlear) or the nerve (auditory nerve)

What is central hearing loss?

originates in he brain and the brainstem

What is the time fram for sudden hearing loss?

Minutes to days

What is the time frame for progressive hearing loss?

Months to years

What is cerumen impaction?

Wax in the ear

What is otisis

inflammation of the middle ear- bubbles can be seen through the ear drum, suggesting there is liquid inside

What is otosclerosis?

When you get breakdown of the middle ear bones

What are the causes of sensorineural hearing loss?

Inner ear - noise, presbycusis, ototoxicity Nerve - acoustic neuroma

What is presbycusis?

Deterioration of the hair cells due to old age

What is ototoxicity?

Chemotherapy causes inner ear nerve damage And Antibiotics - Gentomycin = aminoglycosides

What is a vestibular schwaanoma?

A unilateral tumour which causes damage to the nerve resulting in sensorineural hearing loss

What does a tuning fork?

two tests assess the presence of gross hearing

what are the two tests done with a tuning fork called?

Weber test Rinne test

What is the webber test?

Tuning fork placed on top of the head - sound should be heard in the middle

What is the Rinne test?

tuning fork placed behind the ear

If Rinne test is louder than webber, what does this suggest?

That your problem is an outer ear / conductive problem

What pattern on a audiogram would be seen in conductive hearing loss?

Difference between Bone and air conduction

What pattern on a audiogram would be seen in sensorineural hearing loss?

Same conduction between air and bone

What are the four treatments of hearing loss?

Fix underlying cause hearing Aids Cochlear Implants Brainstem Implants

What is Otoacoustic emissions?

They are the normal sounds produced by the cochlea produced specifially by the outer hair cells as they expand and contract

What special test is part of the newborn hearing screening and hearing loss monitoring?

Otoacoustic Emissions