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Robyn Flashcards > Auditory and vestibular system > Flashcards

Auditory and vestibular system Flashcards

1
Q

What is sound?

A

Sounds is a vibration of particles

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2
Q

Define Frequency and its unit of measurement

A

Number of compressed or rarefied patches of air that pass by our ears each second, expressed as Hertz (Hz)

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3
Q

Define Intensity (or amplitude) and its unit of measurement

A

Air pressure difference between peaks and troughs, expressed as decibels (dB)

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4
Q

Whats the human hearing range?

A

= 20 Hz to 20,000 Hz

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5
Q

What are the properties of the pinna? (only visible part of ear)

A
  • The function of the pinna is to act as a kind of funnel which assists in directing the sound further into the ear.
  • The folds in the pinna helps sound bounce off helping to localise when sound is above or below
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6
Q

What are the ossicles of the middle ear? define their properties

A
  • Three tiny bones of the middle ear: Malleus, Incus, stapes
  • Also known as hammer, anvil, stirrup
  • Malleus to incus has a rigid connection
  • Incus to stapes has a flexible connection
  • Malleus must move with it and Incus is flexible, important for transfer of sound waves in middle ear
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7
Q

How does the middle ear transfer sound?

A

Ossicles amplify sounds to exert ~20 times more pressure on the oval window than on the tympanic membrane – overcoming the greater impedance of cochlear fluid

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8
Q

In what situation would the oval window barely move?

A

The oval would barely move if it was moved directly by sound due to the air-fluid interface, as fluid has a greater inertia (impedance).

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9
Q

Impedance matching between Air and water

A

Air and water have different impedances i.e. the tendency of each medium to oppose movement brought about by a pressure wave.

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10
Q

Inward movement of the tympanic membrane

A

Tympanic membrane pushed by the compression phase of a sound wave

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11
Q

Outward movement of tympanic membrane

A

Tympanic membrane pulled by the rarefaction phase of a sound wave

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12
Q

What is the primary function of the middle ear?

A
  • Is to transfer vibrations of the tympanic membrane to the oval window.
  • The key to accomplishing this task is a chain of the three ossicles
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13
Q

Anatomy of the cochlea

A
  • Ressiner’s membrane and the basilar membrane divide the cochlea into three spiralling fluid-filled compartments: the Scala vestibuli, the Scala media and Scala tympani
  • Scala vestibuli and Scala tympani are filled with perilymph
    Scala media is filled with endolymph
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14
Q

Describe the concentrations of potassium, calcium and sodium relative with intracellular concentrations

A
  • Low potassium concentration relative to intracellular
  • High calcium concentration relative to intracellular
  • High sodium concentration relative to intracellular
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15
Q

What is the potassium concentration of the endolymph

A

High potassium concentration – high potential – give positive potential

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16
Q

Outer hair cells function

A
  • Amplify the signal
  • Outer hair cells are innervated from the brain, undergo length changes in response to stimulation, and in some way, control and amplify the sensitivity of the inner hair cells.
  • Outer hair cells amplify basilar membrane motion
  • in outer hair cells depolarisation causes prestin to contract
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17
Q

Inner hair cells function

A
  • Transduce sound
  • Inner hair cells are extremely sensitive transducers that convert the mechanical force applied to the hair bundle into an electrical signal.
  • Inner hair cells transduce basilar membrane vibration into electrical activity. Basilar membrane vibration causes stereocilia on the surface of inner hair cells to bend
  • In inner hair cells depolarisation causes enhanced transmitter release
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18
Q

Anatomy of the organ of Corti

A
  • The organ of Corti contains the hair cells and sits on the basilar membrane
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19
Q

Anatomy of the basilar membrane

A
  • The basilar membrane within the cochlea of the inner ear is a stiff structural element that separates two liquid-filled tubes that run along the coil of the cochlea, the scala media and the scala tympani
  • Has a Base and Apex
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20
Q

How does basilar membrane displacement affect hair cells?

A
  • Stapes moves outward
  • BM moves upwards
  • Hair cells depolarise
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21
Q

How does basilar membrane displacement affect hair cells: Upward bowing of Basilar membrane

A
  • Stapes moves outward
  • BM moves upwards
  • Hair cells depolarise

Upward movement of the Basilar membrane tilts the hair bundles toward the stereovili, opening transduction channels

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22
Q

How does basilar membrane displacement affect hair cells: Downward bowing of Basilar membrane

A
  • Stapes moves inward
  • BM moves downwards
  • Hair cells hyperpolarise

Downward movement of the Basilar membrane tilts the hair bundles away from the longer stereovili, closing transduction channels

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23
Q

What are hair bundles connected by?

A

Tip links

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24
Q

Tip links

A
  • Hair bundles are surrounded by endolymph within the Scala media
  • Mechanoelectrical transducer channel
  • Tip links enable us to hear – very importable, lose ability to hear if tip links damaged
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25
What receptors are IHCs?
Primary sensory receptors
26
Inner hair cells being sensory receptors
Endolympth: high K, +80mV Perilymph: low K, 0mV Glutamate synapse Voltage gated Ca channel
27
What are OHCs?
``` Are electromotile and act as the cochlear amplifier In a: • BM moves upwards • Hair bundles move towards taller stereocilia • OHC depolarises • OHC contracts • OHC becomes shorter • Amplifies upwards movement of BM ```
28
What must the middle ear do?
The middle ear must amplify sound to overcome the increased impedance of fluid within the cochlea
29
What does mechanical energy of sound so?
The mechanical energy of sound causes displacement of the basilar membrane within the cochlea
30
What is the function of hair cells?
Hair cells transduce mechanical stimuli into receptor potentials using their stereocilia and the mechanoelectrical transducer channel
31
How is the cochlea organised?
The cochlea is tonotopically organised to encode sound frequency.
32
What is the point of the vestibular system?
• Answers two basic questions: – ‘Which way is up?’ – ‘Where am I going?’
33
• What does the vestibular system contributes to?
– Keeping our eyes still as we move – Maintaining our upright posture – Our ability to perceive our own movement within space
34
Gross anatomy of the vestibular system
d
35
What is the vestibular labyrinth filled with?
with endolymph
36
what are the sensory receptors of the vestibular system?
Hair cells
37
What are the principles for vestibular sensory receptor hair cells same as?
as hair cells of the auditory system but they respond to lower frequencies (0 to ~20 Hz)
38
What is the outcome of a graded receptor potential in the vestibular system?
- Produce an action potential - Glutamate released exciting glutamate receptors on afferent nerve - Depolarization of sensory cell
39
How is the vestibular hair bundle structured?
* Vestibular hair cells keep their kinocilium throughout life * Vestibular Saccular Hair Cell – cant move to a higher frequency like cochlear inner hair as cannot move as much * Cochlear Inner Hair Cell
40
What are the two types of vestibular hair cell?
Type I and type II
41
What's the difference between type I and type II vestibular hair cells
- Difference it the type of connection with afferent fibre | - Type 1 has calyx which surrounds bottom of cell
42
What does the saccule and the utricle detect?
- Detect head tilt and linear acceleration
43
Anatomy of the ampulla of the semicircular canals
The ampullary cupula, or cupula, is a structure in the vestibular system, providing the sense of spatial orientation. The cupula is located within the ampullae of each of the three semicircular canals.
44
Describe the structure of the cupula
gelatinous structure penetrated by hair bundles
45
What do the semicircular canals detect?
angular acceleration (rotation)
46
What does the inertia of endolymph do during rotation?
• The inertia of endolymph during rotation displaces the cupula as we turn one way, endolymph will turn the opposite direction
47
how do the Semicircular canals on either side of the head work?
work in pairs
48
Where do the Horizontal canals on both sides lie?
lie in roughly the same plane so can act as a functional pair.
49
Where does the anterior canal lie?
on one side lies in parallel with the posterior canal on the other side so acts as a functional pair.
50
Out of the vestibular system and visual system, which is quicker?
Vestibular system quicker than visual
51
What channels do Photoreceptors have?
g-protein coupled receptors
52
What channels do Mechanoreceptors in Vestibular system have?
Ion channels
53
pulling left eye back
Ipsilaterally to oculomotor nucleus
54
pulling right eye back
Contralaterally to abducens nucleus
55
Vestibular nystagmus enables what? and how?
The resetting of eye position during sustained head rotation • Experiment: subject seated and rotated towards the right at a constant rate in the dark • Slow phase: Eyes rotate in the opposite direction to head movement • Quick phase: Rapid resetting movement back to the centre of the gaze • Right quick phase movement = right beating nystagmus
56
Menière’s Disease affects What? and How?
The vestibular labyrinth • Poorly understood, spontaneous condition – No definitive cause – Potentially due to excessive endolymph • Intermittent, relapsing vertigo (spinning feeling) • Can be accompanied by tinnitus and distorted hearing • Treatment: diuretics, sedatives, steroids – Varied success
57
What does the utricle and saccule detect?
detects head tilt and linear acceleration
58
Where are hair cells in vestibular system found?
sensory patch called the macula
59
What sensory receptor are Vestibular hair cells?
are mechanoreceptors
60
What do the semicircular canals detect?
detect angular acceleration
61
How does the vestibulo-ocular reflex work?
uses sensory vestibular information and provides motor output to the eyes to keep eyes fixed during rotation of the head
62
Function of Vestibular nystagmus
resets eye position during sustained head rotation

Robyn Flashcards (11 decks)

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