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NMSK > EAR > Flashcards

EAR Flashcards

1
Q

What are the three parts of the ear

A

Outer ear
Inner ear
Middle ear

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2
Q

What is the outer ear comprised of and its function

A
  • Pinna- hearing O
    collects sound waves and channels them into the ear canal
  • External acoustic meatus
  • tympanic membrane
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3
Q

What is the middle ear comprised of and its function

A

air-filled tympanic cavity, three auditory ossicles, and tympanic membrane

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4
Q

What is the inner ear and its function

A

cochlea (the organ of hearing) and the vestibular system (the organ of balance).

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5
Q

How does mechanically gated transduction work

A

Movements affect stretch-sensitive ion channels at the tip of the sensory hairs

Tip links connecting cilia open the K+ channels

Leads to depolarisation

Voltage-gated Ca2+ channels open

Influx of Ca2+ causes release of neurotransmitter by exocytosis

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6
Q

How do you know if have vestibular problem

A

Head tilt towards lesion

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7
Q

What are the two parts of the vestibular organ

A

Semicircular canals- give dynamic information, fluid filled and say how head it moving
Otolith organs- static information.

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8
Q

What are the two otolith organs

A

Utricle
Saccule

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9
Q

What does the saccule sense

A

gathers sensory information to orient the body in space. It primarily gathers information about linear movement in the vertical plane, including the force due to gravity.
Stationary

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10
Q

How do the otolith organs

A

Each organ has a sheet of hair cells, the macula, whose cilia are embedded in a gelatinous mass, just like the semicircular canals. Unlike the canals, however, this gel has small crystals of calcium carbonate embedded in it, called otoliths. The otoliths provide the inertia, so that when movement to one side occurs, the otolith–gel mass causes the hair cells to deviate

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11
Q

What does the utricle do

A

linear accelerations and head-tilts in the horizontal plane
Detects horizontal movement

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12
Q

What are the semicircular canals filled with

A

Endolymph

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13
Q

How do the canals determine head movement

A

There are 3 canals, each one is in a different plane
Flow within the endolymph matches head rotation in the same plane as the canal.
Movement of endolymph causes cilla to move, which results in release of neurotransmitters

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14
Q

Why do you get a head and body tilt with vestibular problems

A

On side of lesion:
The excitatory impulse to the extensor muscles is failed
So you just get flexor
Also muscle isn’t functioning as anti gravity

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15
Q

What is the floccunolodular lobe

A

Part of the cerebellum

receives input from, and functions in conjunction with, the vestibular system to regulate equilibrium/balance and posture

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16
Q

What does the floccunolodular lobe structure look like

A

Ipselateral projection

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17
Q

What is hearing

A

Hearing is the neural perception of sound energy

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18
Q

How is sound generated

A

All objects vibrating in air or water generate sound

Causes compression and rarefaction of molecules in the environment, creating areas of increased and decreased pressure

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19
Q

What is the wavelength of sound

A

Distance between areas with maximal pressure

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20
Q

What is sound frequency

A

Pitch

21
Q

What is sound pressure

A

Volume/ amplitude

22
Q

What is the pinna made from

A

Elastic cartilage and skin

23
Q

What CN innervates the muscle of the pinna

A

CN 7

24
Q

What is the structure of the external acoustic meatus like

A

L shapes tube ending in tympanic membrane
Contains sebaceous glands that produce earwax, and hairs to act as a barrier to dust, insects etc.

25
Q

What is the structure of the tympanic membrane lie,

A

Covered by epithelium on the outside
Covered by mucus membrane on the inside

26
Q

What is the function of the pinna and external acoustic meatus

A

Pinna and external auditory meatus act as funnel to collect sound wave vibrations and direct to the eardrum

27
Q

What is the function of the tympanic membrane

A

When sound waves reach your eardrum, they cause the membrane to vibrate, which then travels to the middle ear
Also acts as barrier to bacteria getting into the inner ear

28
Q

What is the function of the middle ear

A

The middle ear is an air-filled cavity in the temporal bone containing ossicles transferring tympanic membrane vibrations to the inner ear

29
Q

What are the three ossicles

A

malleus, incus, and stapes

30
Q

What is the function of ossicles

A

Acts as a series of levers to transmit sound wave vibrations
The stapes is attached to the membrane covering the oval window of the cochlear

31
Q

What does the middle ear consist of

A

Ossicles
Tympanic bulla

32
Q

What is the Eustachian tube/ guttural pouch and its function

A

Auditory tube
Connects middle ear to pharynx
Narrow and normally closed
Purpose is to equalise the air pressure on the two sides of the tympanic membrane

33
Q

How is sound waves transmitted to inner ear

A

To achieve this, it increases pressure and reduces amplitude of vibrations through the ossicles
Stapes pushes on fluid in inner ear

34
Q

How many canals are there in the cochlear and what are they called

A

3
Outer, middle, inner

35
Q

What is each canal filled with

A

Upper and lower canals- perilymph
Middle canal- endolymph

36
Q

What is the difference between peri lymph and endolymph

A

Endolymph is higher in K+ and more positive electro potential

37
Q

Where are the sensory cells on the cochlear

A

Basilar membrane

38
Q

How does the cochlear work

A

When the oval window is compressed by the ossicles it creates wave that travel through the fluid of the cochlear
These waves cause the basilar membrane to move too
Causes hair cells and stereocilia to move for transduction of stimulus

39
Q

How is frequency of sound discriminated

A

High frequency waves have maximum amplitudes near round window

Low frequency cause membrane to vibrate with maximum amplitude near tip of cochlear

40
Q

How is the vestibular cochlear nerve connected to organ

A

Communicates with hair cells and enters brainstem just under cerebellum
Afferent from organ of Corti
Efferent to organ of Corti (tensions membrane)

41
Q

What is the caudal colliculus

A

4 bumps that form of the root of the midbrain

42
Q

What does the caudal colliculus do

A

Auditory information co-ordinates head/ear/neck muscles to orientate the animal’s head towards sound source

43
Q

How does the brain determine the direction of sound

A

based on differences in arrival time between both ears
Lower sound pressure at furthest ear (sound shadow)
Mobile external ears help with location of sound from behind/infront

44
Q

What are the two different types of hearing loss

A

Conduction
Sensation

45
Q

What are the causes of conduction hearing loss

A

Otitis externa (wax in ear canal)- sound waves can’t get down
Otitis media (pus/ fluid in ear)- oscilles cant vibrate
Rupture of tympanic membrane

46
Q

What are some problems with sensation hearing loss

A

Damaged hair cells – loud or continuous sound
Ototoxic drugs (e.g. streptomycin)
Inherited conditions

47
Q

Where does conduction hearing loss occur

A

External to internal acoustic meatus

48
Q

Where does sensation hearing loss occur

A

Inner ear

49
Q

How does BAER work

A

Each ear is stimulated separately by a click stimuli
Accumulated action potential from the cochlea via the cochlear nerve can be measured as auditory evoked potential
Sedation or anaesthesia required to avoid artefacts
Can be used to determine brain health in a coma

NMSK (47 decks)

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