THE EAR AND HEARING Flashcards

1
Q

what is humans frequency range for sound?

A

20-20,000 Hz

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2
Q

what is the part of the ear we can see called?

A

the pinna aka auricle

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3
Q

what is the name of the ear canal?

A

external auditory meatus

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4
Q

whats the name of the ear drum?

A

the tympanum

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5
Q

whats the function of the pinna?

A

to funnel sound into thr external auditory meatus and filters sounds

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6
Q

in other mammals what other roles does the pinna have?

A

signalling mood and assisting with thermoregulation

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7
Q

outline the structure of the external auditory meatus?

A

a sigmoid shaped tube that extends from the deep part of the concha to the tympanic membrane. The walls of the external 1/3 are formed by cartilage, whereas the inner 2/3 are formed by the temporal bone.

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8
Q

the tympanic membrane is a concave structure, what do we call the most depressed region?

A

the umbo - also where the handle of the malleus attached

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9
Q

whats the function of the tympanum?

A

vibrate in response to sound pressure waves and thus transmit sound energy into the middle ear

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10
Q

whats the blood supply of the external ear?

A

posterior auricular branch of the external carotid artery.

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11
Q

what nerves innervate the skin of the auricle?

A

greater auricular nerve
lesser occipital nerve
auriculotemporal nerve

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12
Q

what innervates the external auditory meatus?

A

auriculotemporal nerve and branches of facial and vagus nerves

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13
Q

what inervates the deeper aspect of the auricle?

A

branches of facial and vagus nerves

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14
Q

why do some individuals complain of an involuntary cough when cleaning their ears?

A

due to stimulation of the auricular branch of the vagus nerve which is also responsible for the cough reflex

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15
Q

what is within the middle ear?

A

ossicles and eustachian tube

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16
Q

whats the function of the ossicles?

A

transmit sound and amplify it

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17
Q

what are the 3 ossicles?

A

malleus (hammer)
incus (anvil)
stapes (stirrup)

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18
Q

why are mammals much better at hearing than birds?

A

as mammals have 3 ossicles and birds have 1

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19
Q

whats the function of the Eustachian tube?

A

to allow pressure equilisation between middle ear and outside world - important to prevent damage to tympanic membrane

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20
Q

how can you open the Eustachian tube?

A

lower and protrude the jaw

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21
Q

what are the 2 middle ear muscles and where do they attach?

A

tensor tympani attaches to malleus

strapedius atached to the stapes

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22
Q

whats the function of tensor tympani and stapedius muscles?

A

pulls the eardrum inward and decreases the area over which sound energy may be collected. = acoustic reflex

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23
Q

what is the acoustic reflex?

A

the contraction of the stapedius muscle elicited by the presentation of an acoustically loud sound

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24
Q

what is tensor tympani innervated by?

A

branch of mandibular nere

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25
Q

what is the stapedius muscle innervated by?

A

facial nerve

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26
Q

whats the 2 main functions of the inner ear?

A

converting mechanical signals from the middle ear into electrical signals
to maintain balance by detecting position and motion

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27
Q

where is the inner ear located?

A

in the petrous part of the temporal bone

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28
Q

what are the 2 main components of the inner ear?

A

bony labyrinth and membranous labyrinth

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29
Q

what is within the bony labyrinth?

A

cochlea, vestibule and 3 semicircular canals

30
Q

what is within the membranous labyrinth?

A

cochlear duct, semi-circular ducts, utricle and saccule

31
Q

whats the fluid in the bony labyrinth?

A

perilymph

32
Q

whats the fluid in the membranous labyrinth?

A

endolymph

33
Q

what are the 2 openings in the inner ear that connect to the middle ear?

A

oval window - separates middle ear and vestibule

round window - separates middle ear from scala tympani

34
Q

what is the vestibule?

A

the central part of the bony labyrinth in the inner ear that is separated from the middle ear bu the oval window
contains the saccule and utricle

35
Q

what is the cochlea?

A

a bony structure that twists around the modulus and contains the cochlea duct of the membranous labyrinth. Its presence creates the scala vestibuli and scala tympani which are 2 perilymph filled chambers

36
Q

where is the scaal vestibule?

A

superior to the cochlear duct

37
Q

where is the scala tympani?

A

inferor to cochlear duct - terminates at the roudn window

38
Q

what are the 3 semicircular canals and what do they contain and what is their function?

A

anterior lateral and posterior
contain the semi-circular ducts
responsible for balance along with utricle and saccule

39
Q

whats hold the cochlear duct in place?

A

the spiral lamina

40
Q

what is the organ of Corti?

A

the basilar membrane with contains epithelial cells of hearing
it produces nerve impulses in response to sound vibrations.

41
Q

whats the difference in electrokyte balance within endolymph and perilymph?

A

endolymph is rich in K+ and perilymph is rich in Na+

42
Q

what liquid can be found in the scala media, scala vestibuli and scala tympani?

A

scala media - endolymph

scala vestibuli and scala tympani - perilymph

43
Q

what separates the scala vestibuli and media?

A

reissners membrane

44
Q

what separates the scala media and scala tympani?

A

Baslar membrane

45
Q

how does the ear detect movements in 3D space?

A

as the 3 semicircular canals are positioned at right angles to one another

46
Q

what in the ear detects angular acceleration?

A

semicircular canals

47
Q

outline how the semicircular canals detect angular acceleration?

A

when the head rotates, the inertia of the endolymph causes it to lag, exerting a pressure that deflects the capula in the opposite direction. This deflections stimulates hair cells by bending their stereocilia in the opposite direction. Bending the stereocilia towards kinocilium depolarizes the hair cell and bending away causes hyperpolarization and decreases firing
This causes the hair cell neurones to fire and send the information down the vestibular branch of the vestibular cochlea nerve (CN 8)

48
Q

how do we detect linear acceleration?

A

The otolith organs have hair cells embedded in a matrix with is weighed down by calcium carbonate crystals. this allows them to detect linear acceleration in the horizontal (utricle) and vertical plane (saccule) Again if the stereocili move towards kinocilium then we get depolarization and if hair cells are bent away you get hyperpolarizarion

49
Q

outline how we hear

A

sound waves travel through air, and into ear where they set up vibrations in tympani and this causes ossilations in the ossicles. this moves the stapes in and out causing a wave in the perilymph which moves down the cochlear and, depending on frequency, at some point crosses sets up vibratons in the basilar membrane which results in sound waves in the scala tympani. These waves then travel in the reverse direction until it reaches the round window which absorbs the sound waves. Crossing the basilar membrane also causes vbration of organ or corti which leads to displacement of hair cells

50
Q

which areas in the brain are for hearing?

A

brodmann areas 41 and 42 in the temporal lobe

51
Q

which nerve transmits sound from the inner ear to the brain?

A

The vestibulocochlear nerve

52
Q

outline how frequency alters where the sound waves start displacing the basilar membrane?

A

close to the base of the cochlear the basilar membrane is very stiff but at the helicotrema its way more flexible so the point at which the sound waves cross depends on frewuency and having enough energy to displace this membrane

53
Q

what can detect the time lag between acoustical signals entering the two ears?

A

medial superior olivary nucleus

54
Q

what detects which direction sound is coming from?

A

lateral superior olivary nucleus

55
Q

why on recording do people tend to not like the sound of their voice?

A

as recordings only pick up air conducted sound so you cannot hear the bone conducted sound you get when you are speaking

56
Q

why does your voice sounds lower than people perceive it to be?

A

as bones conduct lower frequencies better than higher ones and other people only hear the air conducted sound whilst you hear air conducted and bone conducted

57
Q

what are the 2 types of hearing loss?

A

conductive - problems conducting sound waves through ear

sensorineural - problems in cochlea, vestibulocochlear nerve or auditory cortex of brain

58
Q

what are common causes of conductive hearing loss?

A

ear wax
otitis externa or media
perforated ear drum
membrane tenson

59
Q

what are some causes of sensorineural hearing loss?

A
congenital
presbycusis - age related
inflammatory disease
menieres disease
ototoxic drugs
physical trauma
noise induced
60
Q

what are the 2 main hearing tests?

A

rinne test

weber test

61
Q

how does rinne test work?

A

Place the base of a struck tuning fork on the mastoid bone behind the ear. Have the patient indicate when sound is no longer heard. Move fork (held at base) beside ear and ask if now audible. In a normal test, AC > BC; patient can hear fork at ear.

62
Q

what does it mean if patient in rinne test cannot hear tuning fork at ear?

A

bone conduction > air conduction = conductive hearing loss

63
Q

what does it mean if patient in rinne test can hear tuning fork at ear?

A

air conduction > bone conduction

normal hearing or sensorineural hearing

64
Q

how do you carry out the weber test?

A

Tap the tuning fork strongly on your palm and then press the butt of the instrument on the top of the patient’s head in the midline and ask the patient where they hear the sound. Normally, the sound is heard in the center of the head or equally in both ears.

65
Q

what does it mean if, during the weber test, sound is hear louder in affected ear?

A

conductive hearing loss

66
Q

what does it mean if, during the weber test, sound is heard loudest in unaffected ear?

A

hearing loss in sensorineural

67
Q

whats the problem with the weber test?

A

you need to know which ear is affected to be able to carry out this test

68
Q

whats the purpose of the weber test?

A

to distinguish between conductive and sensorineural unilateral hearing loss

69
Q

what innervates the meatus side of the tympanum?

A

auriculotemporal nerve

70
Q

what innervates the lateral aspect of the external ear?

A

greater auricular nerve

71
Q

what innervates the concha of the external ear?

A

auricular branch of vagus nerve

72
Q

what innervates the most medial half of the external ear?

A

auriculotemporal