The Auditory System Flashcards

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1
Q

What is the external ear made up of

A

Pinna (auricle)
External auditory meatus
Tympanic membrane

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2
Q

What does the external ear do

A

Conducts sound waves to middle ear

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3
Q

What is the middle ear made up of

A

Tympanic cavity
Ossicles (malleus, incus, stapes) -small bones

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4
Q

What does the middle ear do

A

Conducts sound waves to inner ear

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5
Q

What is the inner ear made up of

A

Cochlear and vestibular system
Vestibulocochlear nerve

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6
Q

What does the inner ear do

A

Hearing and equilibrium (balance)

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7
Q

How is the pinna Innervated

A

Mandibular trivision of the trigeminal nerve and cervical nerve 2+3

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8
Q

What is the pinna

A

External ear
Elastic cartilage covered with skin
Sound waves pass into the eternal auditory meatus

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9
Q

What 3 parts of the external ear helps to funnel sounds into the ear canal

A

Tragus, helix and concha

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10
Q

How is the external auditory meatus (ear canal) Innervated

A

Auriculotemporal nerve and the vagus nerve

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11
Q

External auditory meatus

A

-canal that conducts sounds to the tympanic membrane
-2-3cm long
-cartilaginous lateral third
-skin continuous with skin of pinna
-skin is continuous with external layer of tympanic membrane which is at the distal end of external auditory meatus

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12
Q

Does the external auditory meatus have a slight s bend true or false

A

True and it needs to be straightened in order to use an otoscope

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13
Q

What produces cérumen (earwax)

A

Sebaceous and ceruminous glands

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14
Q

What is the tympanic membrane

A

External ear
Ear drum

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15
Q

What is the tympanic membrane (eardrum)

A

-oval thin and semi transparent membrane
-1cm diameter
-mucous membrane internally (columnar epithelium)
-laterally concave

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16
Q

What does the tympanic membrane seperate

A

External auditory meatus form the tympanic cavity

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17
Q

Where does the tympanic membrane conduct sound waves to

A

Auditory ossicles

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18
Q

The tympanic membrane is covered with skin externally. What kind of tissue is this

A

Stratified squamous epithelium

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19
Q

How is the central Umbro formed

A

Handle of malleus

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20
Q

What kinds of fibres does the Tense part inferior to lateral handle of malleus have

A

Has radial and circular fibres

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21
Q

What kind of fibres does the flaccid part superior to handle of malleus (eardrum) have

A

Thin and lacks fibres

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22
Q

How is the tympanic membrane Innervated

A

Glossopharyngeal nerve

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23
Q

What are the two parts of the tympanic cavity

A
  • tympanic cavity proper medial to the tympanic membrane
    -epitympanic recess supero- medial to the tympanic membrane
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24
Q

What does the tympanic cavity contain

A

-the auditory ossicles (malleus, incus, stapes)
-tensor tympani and stapedius muscles
-chords tympani (branch of the facial nerve)
-tympanic nerve plexus

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25
Q

What is the tympanic cavity in communication with

A

The nasopharynx via the Eustachian tube
The mastoid air cells vis the aditus and mastoid antrum

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26
Q

What part of the ear is the tympanic cavity

A

Middle ear

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27
Q

Tympanic cavity walls

A

-tegmetal wall
-jugular wall
-membranous wall
-labryinthine wall
-mastoid wall
-carotid wall

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28
Q

Tegmetal wall

A

Roof
-formed by Tegan tympani, a thin plate of bone
-seperates tympanic cavity from middle cranial fossa and brain

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29
Q

Jugular wall

A

Floor
-formed from bone
-seperates tympanic cavity from superior bulb of internal jugular vein

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30
Q

Membranous wall

A

Lateral wall
-formed from tympanic membrane and lateral bony wall of epitympanic recess
-seperates tymapnic cavity from external ear

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31
Q

Labryinthine wall

A

Medial wall
-formed from lateral wall of vestibule (including oval window) and initial turn (including round window) of the cochlear
-seperates tympanic cavity from inner ear

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32
Q

Mastoid wall

A

Posterior wall
-aditus links tympanic cavity to the antrum which in turn communicates with the mastoid air cells
-facial nerve canal is between the antrum and the posterior wall of the tympanic cavity
-mastoid antrum and air cells are within the mastoid process
-lined with mucous membrane that is continuous with lining of tympanic cavity
-tegmen tympani seperates antrum from middle cranial fossa

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33
Q

Carotid wall

A

Anterior wall
-contains openings of the pharyngotympanic tube and the canal for the tensor tympani
-seperates tympanic cavity from the carotid canal (and internal carotid artery)

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34
Q

Ossicles

A

-middle ear
-three bones, incus, malleus and stapes
-transmit sounds from the tympanic membrane to the cochlear
-increase the force of sound waves
-maintain the frequency of the sound waves

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35
Q

Malleus

A

(Part of the ossicles in the middle ear)
-handle of malleus is embedded in the tympanic membrane
-neck lies against the flaccid part of the tympanic membrane
-head in epitympanic recess and is in contact with incus

36
Q

Incus

A

(Part of the ossicles in the middle ear)
-body of incus (anvil) is in epitympanic recess and articulates with the malleus
-long limb articulates with stapes
-short limb is connected by a ligament to the posterior of the tympanic cavity

37
Q

Stapes

A

(Part of the ossicles in the middle ear)
-stapes (stirrup) is the smallest ossicle
-has two limbs and a base
-base fits into the oval window of the medial wall
-transmits sound waves to cochlear

38
Q

What are the 2 muscles in the tympanic cavity

A

Tensor tympania and stapedius
Reduce vibrations when contracted to protect against loud noises

39
Q

Tensor tympani muscle origin

A

-has origin on cartilaginous part of eustachin tube, greater wind of sphenoid and temporal bone

40
Q

Tensor tympani muscle insertion

A

Handle of malleus and tenses tympanic membrane

41
Q

How is the tensor tympani muscle Innervated

A

By a mandibule nerve

42
Q

Origin of the stapedius muscle

A

Inside pyramidal eminence of posterior wall

43
Q

Insertion of the stapedius muscle

A

Inserts onto neck of stapes and pulls it posteriorly and tilts its base in the oval window

44
Q

How is the stapedius muscle Innervated

A

By a branch of the facial nerve VIII

45
Q

Hyperacusis

A

Distorted and aching sounds due to stapedius paralysis

46
Q

What is the pharyngotympanic also known as

A

Eustachian tube

47
Q

What does the pharyngotympanic tube communicate with

A

Nasopharynx

48
Q

What does the pharyngotympanic tube do

A

Equalises pressure between middle and external ears

49
Q

Pharyngotympanic tube

A

-posters latéral third is bony and the remainder is cartilaginous
-exits through foramen lacerum
-Lined with mucous membrane
-walls normally in contact but can be open by contracting tensor veil palatini lavator veil palatini eg yawning or swallowing

50
Q

What does the vestibulocochlear organ do

A

-involved in the reception of sound and the maintenance of equilibrium (balance)
-vestibulocochlear organ is contained within the otic cavity in the inner ear

51
Q

Where is the octic cavity

A

-in a region of dense bone located in the petrous part of the temporal bone
-therefore inferior to the middle cranial fossa

52
Q

What are the tunnels called that the octic cavity contains

A

The bony labyrinth

53
Q

What is the bony labyrinth

A

-fluid filled space
-the fluid is called perilymph

54
Q

What is suspended inside the bony labyrinth

A

Membranous labyrinth
This also contains fluid: endolymph (lots of potassium but less sodium)

55
Q

Branches of bony labyrinth are called…

A

Canals

56
Q

Branches of membranous labyrinth are…

A

Ducts

57
Q

What is the bony labryinth comprised of

A

Vestibule, cochlea, semicircular canals

58
Q

What is the membranous labyrinth comprised of

A

Utricle and saccule, semicircular ducts, scala media

59
Q

What does the spiral ligament in the octic cavity do

A

Secures scala media within the cochlear canal
Otherwise secured by filaments through the perilymph

60
Q

Cochlea

A

-shell shaped
-first (basal) turn produces the medial (labryinthine) wall of the tympanic cavity
-first turn is punctured by the round window
-round window is covered by the secondary tympanic membrane
-cochlear canal starts at vestibule and make 2.5 turns around the modiolus
-cochlear canal contrains scala media

61
Q

Scala media (cochlear duct)

A

-spiral tube, blind at one end
-triangular in cross section
-also called cochlear duct
-supported by spiral ligament superficially and bony spiral lamina deeply

62
Q

What are the 2 compartments that the bony labyrinth of cochlear are separated into

A

Scala vestibule and Scala tympani

63
Q

What is the roof of the Scala media formed by

A

Vestibular membrane

64
Q

What is the floor of Scala media formed by

A

Basilar membrane

65
Q

Transmission of sound waves

A
  • Pressure waves in perilymph pass from oval to round windows
  • Ascend to apex via scala vestibuli.
  • Pass back to first turn via scala tympani
  • Reach round window and secondary tympanic membrane.
  • Waves dissipated into air of middle ear.
  • Sounds that we can hear take a short cut
  • They move vestibular membrane
  • Then the endolymph
  • Then the basilar membrane
66
Q

Where is the organ of corti

A
  • situated on basilar membrane
    -lies under gelatinous tectorial membrane
67
Q

What happens in the organ of corti

A
  • Sound waves move basilar membrane
  • This in turn bends the hairs (receptor) cells in relation to tectorial membrane where their ends are embedded
  • Hairs move up and down.
  • Mechanically gated ion channels open and close
  • Therefore, movement of hairs converted into receptor potential.
  • Movement of hairs: mechanically gated ion channels open and close
  • Receptor potential converted into an action potential in cochlear nerd neurons.
  • Nerve impulses transmitted to brain via spiral ganglion and cochlear division of CN VIII
68
Q

How are frequencies determined

A
  • Volume determined from amplitude of basilar membrane oscillation.
  • Low frequency (pitch) sounds travel further than those of higher frequencies
  • <50 Hz cause movements of entire basilar membrane
  • Excites hair cells near apex
  • Basilar membrane varies in thickness and width along its length
  • This is where high frequency sounds are detected (20000Hz) (base of cochlear)
  • It Is thin and wide at the apex this is where low frequency sounds are detected
  • Two ears- stereoscopic sound
69
Q

Where are high frequencies detected

A

Base of the cochlear

70
Q

Where are low frequency sounds detected

A

Apex Where it is thin and wide

71
Q

What does the internal acoustic meatus do

A

-the internal acoustic meatus transmits the vestibulocochlear nerve (CNVIII) from the cranial cavity to the middle ear
-it also transmits blood vessels and the facial nerve (CN VII)

72
Q

Neural pathways of hearing

A
  • Fibres of cochlear divisor of CN VIII pass to cochlear nucleus of medulla
  • Synapse with neurones that pass to the inferior colliculi of midbrain.
  • These neurones project to the thalamus
  • This sense axons to auditory cortex of temporal lobe: perceived as sound.
73
Q

What are the two kinds of hearing loss

A

Conductive or sensorineural

74
Q

Conductive hearing loss

A
  • Conductive hearing loss results from problems in the external and middle ears:
  • External auditory meatus (stenosis)
  • Tympanic membrane (perforation)
  • Tympanic cavity (fluid retention)
  • Auditory ossicles (inflammation, scarring)
75
Q

Sensorineural hearing loss

A
  • Sensorineural hearing loss results form problems with the inner ear or neurological pathway:
  • Cochlea (cochlear ossificans)
  • Cochlear nerve
  • Cortical connections
  • Brain stem
76
Q

What are the 3 semicircular canals

A

Anterior, posterior and lateral

77
Q

Semicircular canals

A
  • actually deserve 2/3 of a Circle
    -at right angles to each other therefore one in each plane so are important for balance
    -semi circular ducts inside each canal
78
Q

What are semi circular ducts

A

Communicate with the utricle
Each have ampulla at one end

79
Q

Semi circular ducts ampullae

A
  • Ampullae contain a sensory area, the ampullary crest
  • Crests contain hair cells
  • Sense movement of endolymph cause by movements of the head in that plane
80
Q

Anterior duct

A

Anterior detects rotational movement inn the sagittal plane

81
Q

Posterior duct

A

Posterior detects rotational movement in the coronal plane

82
Q

Lateral duct

A

Lateral detects rotational movement in the transverse plane

83
Q

What does the inertia of the endolymph do

A

Cause hairs in cupola to bend

84
Q

Vestibule of the bony labyrinth

A
  • An oval chamber about 5mm long
  • Contains utricle and saccule of membranous labyrinth.
  • Lateral wall has an oval window
  • Baseplate of the stapes sits in the oval window
  • Communicates with: the cochlear anteriorly, the semi circular canals posteriorly and the posterior cranial fossa via the aqueduct of the vestibule.
85
Q

Vestibular labyrinth

A
  • Comprised of two sacs, the utricle and saccule
  • Joined by utriosaccular duct.
  • Utricle is continuous with the semicircular ducts
  • Saccule is continuous with the cochlear duct via the ducts reuniens
  • Both utricle and contain sensory epithelium- maculae
86
Q

Hair cells

A

Hair cells
- Hair cells of maculae involved in equilibrium
- Hair cells of macule are Innervated by vestibular division of the vestibulocochlear nerve (CN VIII)

87
Q

Maculae

A
  • Macula of the utricle is in its floor, parallel with the cranial base.
  • Macula of the saccule is place vertically against its medial wall.
  • Saccule: detects vertical linear motion and tilting of the head out of the horizontal (transverse) plane
  • Utricle: detects horizontal linear motion (in the transverse plane) and tilting of the head out of the verticle plane