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Semester 3 > PBL 4 > Flashcards

PBL 4 Flashcards

1
Q

Name the two perilymph chambers present within the cochlea, and how they are both separated from the cochlear duct, as well as which window they are connected to.

A

Scala vestibuli - connected to the oval window, separated from the cochlear duct by reissners membrane

Scala tympani - connected to the round window, separated from the cochlear duct by the basilar membrane

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2
Q

What is the tip of the cochlear spiral known as where the two scala chambers are interconnected?

A

Helicotrema

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3
Q

Name the two structural properties of the basilar membrane that determine its response to sound

A

Width - wider at the apex and narrow at base

Flexibility - more stiff at base and flexible at apex

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4
Q

What is the difference between outer and inner hair cells in the organ of corti?

A

Outer hair cells - tips end in the tectorial membrane

Inner hair cells - tips end just below the tectorial membrane

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5
Q

What is the decibal level at which sound becomes harmful

A

80Db

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6
Q

What differences are there in high and low frequencies on their impact on the basilar membrane?

A

High frequency sound - shorter wavelength, vibrates the basilar membrane nearer to the oval window (base/stiff part)

Low frequency sound - longer wavelength, vibrates the basilar membrane nearer to the round window (apex/flexible part)

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7
Q

What differences are there in loud and quiet sounds on their impact on the basilar membrane?

A

Loud sounds - distort the basilar membrane more

Quiet sounds - distort the basilar membrane less

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8
Q

How does the movement of hair cell receptors in the organ corti allow sound transduction in the spiral ganglion cells

A

TRPA1 channels are opened when hair cells bend, allowing an influx of Na+ and K+
Entry of K+ causes the hair cells to become depolarised, which activates Ca2+ channels
Entry of Ca2+ triggers release of glutamate, which then activates spiral ganglion fibres lying post synaptic to the hair cell

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9
Q

Desribe the auditory pathway to the cortex?

A
  • Information is carried from hair cells by CN VIII
  • CN VIII synapses at the cochlear nucleus on the ipsilateral medulla oblongata
  • medulla oblongata sends axons to the contralateral inferior colliculi in midbrain
  • inferior colliculi mediate reflex responses
  • inferior colliculi send axons to medial geniculate nucleus of thalamus
  • medial geniculate nucleus of thalamus projects information to auditory cortex in temporal lobe
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10
Q

What is the difference in the ventral and dorsal cochlear nucleus and how they communicate with the inferior colliculi?

A

Ventral cochlear nuclei cells - send axons to superior olive, which then communicates with inferior colliculi at each side

Dorsal cochlear nuclei - send axons directly to contralateral inferior colliculi

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11
Q

Which are the muscles involved in the auditory reflex and what nerves are they innervated by?

How does contraction of these muscles help to diminish sound conduction?

A

Tensor tympani - mandibular nerve (V3)
Stapedius - facial nerve (VII)

Diminishes sound conduction by causing the ossicles of the middle ear to become more rigid

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12
Q

What is the name of the sensory receptors of the vestibular complex?

A

Maculae

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13
Q

What are the different forms of acceleration that the otoliths organs detect?

A

Saccule - vertical acceleration

Utricle - horizontal acceleration

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14
Q

What are the different types of plane that your semicircular canals are sensitive to?

A

Superior/Anterior - pitch (looking up and down)
Posterior - roll (tilting head side to side)
Lateral - yaw (looking side to side)

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15
Q

Regarding hair cells in the semicircular ducts, what is a cupula?

A

A gelatinous structure that extends the full width of the ampulla (the area above the hair cells, which is pushed to one side during endolymph movement)

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16
Q

What are the different types of cilium present on a hair cell?

A

Stereocolia (80-100)

Kinocilium (one large one at the end)

17
Q

How does the direction of endolymph within a semicircular canal result in the firing or inhibition of the vestibular nerve?

A

Endolymph pushing fluid towards the kinocilium - increases firing
Endolymph pushing fluid away from the kinocilium - decreases firing

18
Q

Where are the cell bodies for the vestibular nerve located?

A

Scarpa’s ganglion

19
Q

How are acceleration sensations detected by the macula of the oolith organs?

A
  • during acceleration, the statoconia ‘lag behind’ the gelatinous material, distorting the hair cells below
  • hair cells are depolarised and a signal is sent through the vestibular nerve
20
Q

Where are the vestibular nuclei located on the brainstem?

A

Between the pons and medulla oblongata

21
Q

How does the rotational VOR cause your eyes to rotate right, when your head rotates to the left?

A
  • left horizontal semicircular canal senses rotation towards the left sending a signal to left vestibular nucleus
  • excitatory fibres to right abducens nuclei (excite lateral rectus of right eye)
  • excitatory fibres to left occulomotor nuceli (excite medial rectus of left eye)
22
Q

How does alcohol effect the VOR?

A

Alcohol has an effect on the cerebellum, which is essential in controlling the VOR. Therefore the VOR tends to breakdown with alcohol consumption

23
Q

What is nystagmus?

A
  • Where the vestibular system thinks the head is moving, when it actually isn’t.
  • Slow and fast phase of VOR are triggered
  • Trouble controlling eye movements
24
Q

What are the two phases of the VOR?

A

Slow phase - eyes slowly rotate in opposite direction

Fast phase - eyes rapidly reset to centre of vision

25
Q

What is the caloric reflex test and how can it induce nystagmus?

A

Introducing warm or cold water into the external auditory meatus - this causes a convection current in the endolymph which stimulates hair cells as if the head was rotating.

This induces the VOR response

26
Q

What is the vestibulo-cervical reflex (VCR)?

A
  • stimulation of semicircular canals
  • axons are sent from the medial vestibular nucleus in the medial longitudinal fasciculus to upper cervical spinal cord
  • signals are sent to regulate head position by reflex activity of the neck muscles in response to movement
27
Q

What is otitis media?

A

Infection of the middle ear causing inflammation

Due to a blockage in the Eustachian tube

28
Q

What is otitis media with Effusion?

A

Where fluid is present in the middle ear an extended period
This fluid is usually sterile but may become infected by bacteria or viruses
It can cause temporary hearing loss

29
Q

What are grommets?

A

Used to treat glue ear (otitis media with effusion)
Small temporary tubes that are placed into the tympanic membrane during surgery.
They take over the function of the Eustachian tube and aim to keep the eardrum open and drain away excess fluid

30
Q

What is benign paroxysmal positional vertigo (BBPV)?

A
  • Where dislodged bits of otoliths stimulate the cupula in the posterior semicircular canal
  • creates the illusion of movement
31
Q

What is Meiniere’s Disease?

A

An increase in endolymph pressure within the middle ear - this disrupts signal transduction resulting in tinnitus, nausea and spontaneous nystagmus
Results in reoccurring episodic rotatory vertigo

32
Q

What are the two types of hearing loss and what is the difference between them?

A

Conductive - where there is a mechanical problem conducting sound waves along the external or middle ear

Sensorineural - where there is damage to hair cells of the inner ear or damage to the vestibulocochlear nerve

33
Q

What is the difference between Weber’s and Rinne’s

A

Webers - place tuning fork in middle of the forehead, see which ear the noise is loudest
Rinnes - place tuning fork on mastoid process and then in front of ear once patient can no longer hear sound, see if sound was louder through bone or air

34
Q

If a patient shows the following results:
Webers test - noise appears greater in left ear
Rinnes rest (on left ear) - patient says noise is greater in air than bone

What kind of hearing loss do they have?

A

Sensorineural hearing loss in the right ear

35
Q

If a patient shows the following results:
Webers test - noise appears louder in right ear
Rinne’s test (on right ear) - noise appears louder through bone

What kind of hearing loss do they have?

A

Conductive hearing loss in right ear

36
Q

What is tympanomtery?

A

Test of middle ear compliance - tests the stiffness of the eardrum and estimates the middle ear pressure and volume of external canal

37
Q

What are the difference in ionic concentrations between perilymph and endolymph?

A

Perilymph - rich in sodium, and poor in potassium

Endolymph - rich in potassium, and poor in sodium

38
Q

What structure produces endolymph and secretes it into the cochlea?

A

Stria vascularis

39
Q

Successful adaption to a cochlear implant is least likely in which group of patients

A

Pre-lingually deaf adults

Semester 3 (13 decks)

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