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Neuro > Ear > Flashcards

Ear Flashcards

1
Q

What can the ear be divided into

A

External
Middle
Inner

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2
Q

What can the external ear be divided into

A

Both functionally and structurally

Auricle (pinna)
External acoustic meatus

Ends at the tympanic membrane

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3
Q

What is the auricle

A

Paired structure found on either side of the head

Function is to capture and direct sound waves towards external acoustic meatus

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4
Q

What type of structure is the auricle

A

Mostly cartilaginous

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5
Q

What is the only part of the auricle not supported by cartilage

A

Lobule

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6
Q

What does the cartilaginous part of the auricle form

A

Outer curvature - helix

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7
Q

What is the second innermost curvature running parallel with the helix

A

Antihelix

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8
Q

What does the antihelix divide into

A

Two crura

Inferoanterior crus

Superoposterior crus

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9
Q

What is the hollow depression in the middle of the auricle

A

Concha

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10
Q

What does the concha continue into

A

Into the skull as the external acoustic meatus

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11
Q

What shape is the external acoustic meatus

A

Sigmoid shape tube

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12
Q

Where does the external acoustic meatus run

A

Deep part of concha - tympanic membrane

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13
Q

What is the external 1/3 of the external acoustic meatus compromised of

A

Cartillage

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14
Q

What is the inner 2/3 of the external acoustic meatus compromised of

A

Temporal bone

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15
Q

What path does the external acoustic meatus take

A

S-shape

  1. superior anterior direction
  2. superior posteriorly
  3. inferior anterior
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16
Q

Describe the tympanic membrane

A

Lies at distal end of the external acoustic meatus

Connective tissue structure
- skin on outside
- mucous membrane on inside

Membrane connected to the surrounding temporal bone by a fibrocartilaginous ring

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17
Q

What is the vasculature of the external ear

A

Branches of the external carotid artery

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18
Q

What innervates the skin of auricle

A

Greater auricular nerve (branch of the cervical plexus)

Lesser occipital nerve (branch of the cervical plexus)

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19
Q

What innervates the skin of the auricle and external auditory meatus

A

Auriculotemporal nerve (branch of the mandibular nerve)

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20
Q

What innervates the deeper aspect of the auricle and external auditory meatus

A

Branches of the facial and vagus nerves

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21
Q

Where does the middle ear lie

A

Within the temporal bone

Extends from the tympanic membrane to the lateral wall of the inner ear

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22
Q

What are the main functions of the middle ear

A

Transmit vibrations from the tympanic membrane to the inner ear via the auditory ossicles

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23
Q

What can the middle ear be divided into

A

Tympanic cavity

Epitympanic recess

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24
Q

Describe the tympanic cavity

A

Located medially to tympanic membrane

Contains auditory ossicles
- malleus
- incus
- stapes

Transmit vibrations through to the middle ear

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25
Q

What are the bones of the auditory ossicles

A

Malleus
Incus
Stapes

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26
Q

What is the role of the auditory ossicle
s

A

Sound vibrations cause a movement in the tympanic membrane which then creates movement (ossification) in the auditory ossicles

Link tympanic membrane to the oval window of the internal ear

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27
Q

What is the largest and most lateral of the ear bones

A

Malleus

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28
Q

Describe incus

A

Consists of body and two limbs

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29
Q

What is the smallest bone in the human body

A

Stapes - joins the incus to the oval window

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30
Q

What is the role of mastoid air cells

A

Act as buffer system of air

Release air into the tympanic cavity when the pressure is too low

31
Q

What are the two muscles of the middle ear

A

Tensor tympani
Stapedius

32
Q

What is the role of the tensor tympani and stapedius

A

Protective function

Contract in response to loud noise - inhibit vibrations to the malleus, incus and stapes = reduce sound to the inner ear

Known as - acoustic reflex

33
Q

Describe tensor tympani

A

Originates from the auditory tube

Attaches to handle of malleus - pulling it medially when contracting

Innervated by tensor tympani nerve - branch of the mandibular nerve

34
Q

Describe the stapedius muscle

A

Attaches to the stapes

Innervated by facial nerve

35
Q

Describe the eustachian tube

A

Cartilaginous and bony tube

Connects the middle ear to the nasopharynx

Acts to equalise the pressure of the middle ear to that of the external auditory meatus

36
Q

What are the two main functions of the inner ear

A

Convert mechanical signals from the middle ear into electrical signals - which can transfer information to the auditory pathways in the brain

Maintain balance by detecting position and motion

37
Q

Where is the inner ear located

A

Within petrous part of temporal bone

Lies between middle ear and internal acoustic meatus

38
Q

What are the two components of the inner ear

A

Bony labyrinth

Membranous labyrinth

39
Q

Describe the bony labyrinth

A

Composed of cochlea, vestibule and three semi-circular canals

Structures lined internally with periosteum and contain perilymph (a fluid)

40
Q

Describe membranous labyrinth

A

Lies within the body labyrinth

Consists of cochlear duct, semi-circular ducts, utricle and saccule

Fille with endolymph (fluid)

41
Q

Describe oval window

A

Lies between the middle ear and vestibule

42
Q

Describe the round window

A

Separates the middle ear from the scala tympani (part of the cochlear duct)

43
Q

Describe vestibule

A

Central part of the bony labyrinth

Separated from middle ear by oval window

Communicates anteriorly with cochlea
Posteriorly with semi-circular canals

Saccule and utricle - located within

44
Q

Describe the cochlea

A

Auditory part of the inner ear

Twists upon itself around a central portion of the bone = modiolus

Cone shape which points in anterolateral direction

45
Q

Where are branches of the cochlear portion of the vestibulocochlear nerve found

A

Base of the modiolus

46
Q

Describe semi-circular canals

A

Three
- anterior
- lateral
- posterior

Contain semi-circular ducts = responsible for balance (along with utricle and saccule)

Right angles to each other

Swelling at one end = ampulla

47
Q

What is the range of human hearing

A

20Hz-20kHz

48
Q

Is the outer ear air or fluid

A

Air

49
Q

Is the middle ear air or fluid

A

Air

50
Q

Is the inner ear air or fluid

A

Fluid

51
Q

When does the pinna form

A

Between 10th - 18th week in utero

52
Q

What is the size of the tympanic membrane

A

8x10mm diameter

14mg

84mm2 - 55mm2

53
Q

How much energy is lost from transferring air to fluid

A

99.9%

54
Q

What is the role of the middle ear

A

Amplification of the airborne vibration e.g. make it louder

55
Q

What type of control is the tensor tympani

A

Voluntary and involuntary control

56
Q

What is the role of the eustachian tube

A

Ventilation to middle ear space

Drainage of secretions

57
Q

What is the vestibulocochlear apparatus

A

Set of fluid filled sacs, encased in bone

58
Q

What is the cochlear responsible for

A

Hearing

59
Q

What is the labyrinth responsible for

A

Balance

60
Q

What is the innervation of the vestibulocochlear apparatus

A

Vestibulocochlear nerve

61
Q

Describe the cochlea

A

2.5 turns fluid filled bony tube

2 openings - round and oval window

3 compartments - scala tympani, scala media and scala vestibuli

2 ionic fluids

62
Q

Cochlear fluids

What ions are in

Endolymph

A

High K+

63
Q

Cochlear fluids

What ions are in

Perilymph

A

Like ECF and CSF

Na+ rich

64
Q

What are the cochlear fluids gradients maintained by

A

Na, K-ATPase

NKCC1 CIC-K chlorine channels

65
Q

What would ion channel abnormalities in the cochlear result in

A

Deafness

66
Q

Where are frequencies detected in the cochlear - basilar membrane

A

High frequencies - at base (narrow)

Low frequencies - at apex (wide)

67
Q

What is the role of inner hair cells in the basilar membrane

A

Mechanical transduction

68
Q

What is the role of outer hair cells in the basilar membrane

A

Fine tuning

Can alter stiffness of the basilar membrane to ensure maximal stimulation at one site and dampened at another = increased resolution

69
Q

What does displacement of the basilar membrane cause

A

Movement of the specialised mechanical transducing cells

70
Q

How is frequency (pitch) encoded

A

In nerves by location along the basilar membrane

71
Q

How is intensity (loudness) encoded

A

In nerves by numbers responding and firing rate

72
Q

How is sound transduction encoded

A

Inner hair cells (and OHCs)

73
Q

How is amplification encoded

A

Outer hair cells

74
Q

What is the central auditory pathway

A

8th nerve

Cochlear nucleus

Olive

Lateral lemniscus

Inferior colliculus

Neuro (15 decks)

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