Sievert: Anatomy of the Ear Flashcards
1
Q
What makes up the external ear?
What is its limiting border?
A
auricle and external auditory meatus;
tympanic membrane
2
Q
What does the external ear do?
A
captures sound, funnels sound
3
Q
What’s this?
air-filled cavity behind the ear drum
A
middle ear
4
Q
What are the three middle ear ossicles? How do these bones develop? What do they do?
A
malleus, incus, stapes;
they develop as cartilagenous models;
transfer ear drum vibrations to oval window and fluid behind oval window
5
Q
What makes up the inner ear?
A
fluid filled cochlea and vestibular apparatus
6
Q
What does the inner ear do?
A
holds sensory hair cells for hearing and balance
7
Q
Where does the external auditory meatus come from developmentally?
A
branchial cleft 1
8
Q
Where does the middle ear/auditory tube come from developmentally?
A
branchial pouch 1
9
Q
Where do the malleus and incus come from developmentally?
A
1st branchial arch cartilage
10
Q
Where does the stapes come from developmentally?
A
2nd branchial arch cartilage
11
Q
What are two muscles that alter the movement of the middle ear ossicles? Which ossicle does each muscle attach to?
A
tensor tympani *attaches to malleus
stapedius *attaches to stapes
12
Q
The otic placode is a thickening of surface (blank). It invaginates to for the otic pit/vesicle. What does this form? (3 things)
A
ectoderm; membranous labyrinth, hair cells, ganglion cells
13
Q
What is interesting about the development of the inner ear?
A
- it develops slowly, so it is susceptible to environmental defects
- the otic placode is not neural ectoderm, but it does end up developing into a sensory neural structure (ganglion cells)
14
Q
The external ear is anti(blank) and anti(blank). Its walls are (blank) laterally and (blank) medially.
A
antibacterial; antibug; cartilagenous; bony
15
Q
The external ear contains these glands that produce antibacterial wax
A
ceruminous glands
16
Q
4 functions of the external ear
A
- collects sound
- ceruminous glands that produce antibacterial wax
- optimal for collecting sound in the speech range up to 100 fold
- helps localize sound in the vertical axis
17
Q
What’s an example of the external ear localizing sound on the vertical axis?
A
when you pin down the external ear, you can point to which side keys are jangling, but you cannot determine if they are high or low
18
Q
What nerves provide innervation to the external ear?
A
CN 5 *auriculotemporal nerve off of V3 cervical plexus (ventral rami of spinal nerves) *lesser occipital and greater auricular small auricular branch of the vagus to the external tympanic membrane
19
Q
What is notable about a child’s tympanic membrane?
A
Tympanic membrane and auditory canal changes slightly as you go from infant to adult (ex: can see infant’s eardrum better if you pull DOWN on the ear)
20
Q
What way is the tympanic membrane oriented?
A
Tympanic membrane points out laterally and inferiorly, so that the inferior anterior portion of the external auditory canal is longer than the superior portion.
21
Q
The middle ear is a (blank) filled compartment. Contains the middle ear ossicles. What do these do?
A
air; these bones transfer the vibration of the tympanic membrane to the inner ear
22
Q
How does the middle ear amlify the sound signal, and make up for the energy which is lost as sound moves from air into a liquid medium? *two things
A
- size difference between the tympanic membrane and the oval window
- mechanical advantage of the bony lever system
23
Q
Which two muscles of the inner ear help to reduce sound intensities by increasing the stiffness of the apparatus?
A
stapedius
tensor tympani
24
Q
What maintains air in the middle ear to effectively equalize pressure differences?
A
auditory tube
25
Where does the tensor tympani arise from? What nerve is it innervated by?
the lateral wall of the auditory tube; a branch of the undivided trunk of V3 (tensor tympani nerve)
26
What will happen to sound if you damage CN 7?
things will sound louder, and you will lose the ability to discern background noise from noise that you are trying to pick up (hyperacusis)
27
The middle is continuous with what two things? Why is this important?
mastoid air cells
nasopharynx via the auditory tube
*important, because infections of the mastoid sinus can move into the middle ear
28
What is the tympanic nerve a branch of? How does it enter the middle ear cavity? What does it carry sensory fibers to?
CN 9; through the jugular foramen; carries sensory fibers to mucosal lining of the middle ear cavity
29
After supplying the middle ear cavity via the plexus on the promontory, CN 9 forms in to what nerve? Where does this nerve ultimately go?
lesser petrosal nerve- leaves the middle ear cavity back into the skull, travels anteriorly until it exits the foramen ovale, supplies reganglionic parasympathetics to the parotid gland after synapsing in the otic ganglion
30
CN 7 enters the middle ear cavity and is surrounded by what? It gives off a branch to the (blank), and just prior to leaving the stylomastoid foramen, it gives off a recurrent branch to the (blank) and leaves through the petrotympanic fissure. What does this recurrent branch carry?
thin lamina of bone; stapes; chorda tympani; this branch carries taste and parasympathetics to the submandibular and sublingual glands
31
What does the greater petrosal nerve supply?
preganglionic parasympathetics to the lacrimal gland
32
Cranial nerve 9 exits the skull through the (blank). It gives off the (blank) branch which reenters the skull and forms a plexus on the promontory
jugular foramen; tympanic
33
Which CN contributes a small sensory branch to the middle ear, too?
CN 7
34
What bone is attached to the medial side and is visible through an otoscope?
If there is infection in the middle ear, what happens to vibration of the membrane? What does the tympanic membrane look like as a result?
malleus; it is reduced; it appears red and fluid may be visible
35
Infection of the middle ear is very common. What is this called? What happens?
otitis media; middle ear fills with fluid, tympanic membrane appears red and inflamed
36
How do microoganisms enter the middle ear?
via the auditory tube
37
Otitis media is especially common in children. Why?
their auditory tube is angled slightly superiorly toward the nasal cavity
38
Movement of what bone against the oval window causes vibration of fluid in the inner ear?
stapes
39
Sensory cells in the (blank) respond to fluid vibrations in the inner ear to provide hearing
cochlea
40
Sensory cells in the (blank) respond to movements of the head to provide you with balance
vestibular apparatus
41
The scala vestibuli and scala tympani are filled with (blank) which is high in (blank). The scala media is filled with (blank), which is high in (blank).
perilymph; Na+; endolymph; K+
42
Apparatus of hearing
cochlea
43
Apparatus of balance
semicircular canals
utricle
saccule
44
This is where the pressure wave enters as the stapes pushes on the oval window
scala vestibuli
45
This is where the pressure wave exits out of the round window
scala tympani
46
This is where the pressure wave causes vibrations to set up a traveling wave
scala media
47
Movement of the stapes causes deflections of the (blank). When the stapes pushes in on the oval window, it creates a pressure that causes the (blank) to bulge out
oval window; round window
48
If you unroll the cochlea, you can see that the scala vestibuli is connected to the scala tympani at the (blank)
helicotrema
49
As pressure waves enter the ear, they cause a pressure wave to be generated along the (blank). The frequency of sound creating the pressure wave determines WHERE vibrations will occur along the scala media. In other words, the scala media will vibrate at different points for different (blank).
scala media; frequencies
50
All along the system of the inner ear, you preserve (blank) – a faithful representation of particular frequencies from the external world on a map of the brain.
tonotopy
51
What determines which frequencies the hair cells respond to?
their location on the basilar membrane
52
The basilar membrane is tuned to different frequencies. High frequency near the (blank) and low frequency near the (blank).
base; apex
53
What is located along the superior aspect of the scala media?
Reissner's membrane
54
This is a gelatinous membrane that sits down upon and touches the hair cells of the inner ear
tectorial membrane
55
The hair cells of the inner ear have a (blank) which stands up tall, and other cilia which do not stick up quite as high. These hair cells are in contact with the (blank)
kinocilia; tectorial membrane
56
What's the range of human hearing?
20 - 20,000 Hz
57
At the base of the cochlea, the basilar membrane is (blank), but at the apex the basilar membrane is (blank)
narrow; wide *counterintuitive
58
These cells change the tuning properties of the basilar membrane. They have efferent fibers going to them from CN 8, and so they contract and fine tune the basilar membrane
outer hair cells
59
CN 7 enters the (blank) and forms a T at the (blank)
internal acoustic meatus; geniculate ganglion
60
What nerve does CN 7 give off that passes anteromedially?
greater petrosal nerve
61
The main trunk of CN 7 passes posterolaterally into the (blank). As it descends toward the stylomastoid foramen, what two branches does it give off?
facial canal; chorda tympani and nerve to the stapedius
62
What does the chorda tympani pass through?
the petrotympanic fissure
63
What nerve does the chorda tympani jump on to provide taste to the anterior 2/3 of the tongue?
lingual nerve
64
What do parasympathetics that hop of the chorda tympani supply?
submandibular and sublingual glands
65
After passing through the sytlomastoid foramen, CN 7 is almost entirely (blank). It does give off a (blank) branch to the external ear, and branches to the stylohyoid and post belly of the digastric
motor to the muscles of facial expression
66
Parasympathetics on the greater petrosal take an interesting route to reach the lacrimal gland. Which two branches of CN 5 must they travel on at some point?
V2 and V1
67
CN 7 gives off the (blank), which travels right alongside the lesser petrosal along the floor of the middle cranial fossa. These two nerves diverge. The lesser leaves out of (blank). The greater enters the (blank) and travels to the pterygopalatine fossa.
greater petrosal nerve; foramen ovale; pterygoid canal
68
CN 8 has two different ganglion cells. What are they?
spiral ganglion
| vestibular ganglion
69
The motor branch of CN 7 arches up and over the top of what nucleus?
CN 6
70
Where is the only place in the brainstem where tase and general visceral afferents can go?
nucleus solitarius
71
CN 8 enters the (blank)
Branches to the (blank) and (blank) branches
Special somatosensory cell bodies are in the (blank) and (blank) ganglia
internal acoustic meatus; vestibular; cochlear; vestibular; spiral (cochlear)
72
The vestibular and spiral ganglion (SSA) for CN 8 are around what notable structure?
the middle cerebellar peduncle
73
What are the two components of CN 9 that are associated with the middle ear?
GSA for the mucosal linings
| GVE for the parotid gland
74
Two components of IX associated with the middle ear are GSA (ends in sp. V) for the (blank) and GVE (from inf. Salivatory nuc.) for the innervation of the (blank) via the lesser petrosal and the auriculotemporal.
muscosal linings; parotid gland
75
For human hearing, sound is expressed in terms of wavelength and amplitude. Along the sound wave, there are areas of (blank) and (blank)
condensation
| rarefaction
76
This is a gelatinous mass that sits on the cilia of hair cells. Outer hair cells project into it and can change the amount of tension that it has relative to the basilar membrane
tectorial membrane
77
(blank) receive efferents and modulate the stiffness of the tectorial membrane by some contractile property, while (blank) are for frequency recognition
outer hair cells; inner hair cells
78
Kinocilia and stereocilia of hair cells are connected to each other and these hair cells are under the influence of the (blank)
tectorial membrane
79
What does movement of the stereocilia toward the kinocilium cause? What does movement away from the tallest cause?
depolarization; hyperpolarization
80
Hair cells have mechanically-gated K+ channels. Some of these K+ channels are always open to allow for some K+ flux. What is unique about this system?
This is a mechanical system, so it is much faster than our chemically-gated channels. This allows us to hyperpolarize and depolarize these cells 1000x a second. These channels can respond very fast, and they respond to minimal displacements.
81
What maintains the compartmental ionic potential differences that prevent fatiguq during prolonged stimulation?
stria vascularis
82
What will rupture of Reissners membrane do to endocochlear potential across the compartments?
it will eliminate it
83
What affect do ototoxic drugs like gentamycin have on hair cells and the K+ pump of the stria vascularis?
they permanently damage hair cells and other antibiotics can damage the K+ pump
*when you lose hair cells at the basilar membrane, you lose the ability to hear high frequency and these cells can not regenerate :(
84
The scala media is an area of high (blank), while the scala vestibuli and scala tympani are high in (blank). The upper hair cells are bathed in the (blank) and the lower hair cells are bathed in (blank). This creates a (blank) of about 125mV across the cells.
K+; Na+; endolymph; perilymph; potential difference
85
What exaggerates the amount of displacement of the stereocilia as the basilar membrane is displaced?
staggered pivot points between the basilar membrane and the tectorial membrane
86
The basilar membrane does not vibrate as one unit, but rather in segments. So, basilar hair cells are only stimulated in a specific area. What causes this?
hair cells respond to different frequencies based on their place on the basilar membrane
87
What's this?
Inner hair cells respond to different frequencies depending on their
location on the basilar membrane
place principle
88
What's this?
| The basilar membrane is tuned to different frequencies
stiffness phenomenon
89
Basilar membrane is tuned and when a traveling wave moves along the membrane it causes maximal displacement at different points depending on the (blank).
frequency
| *which hair cells fire is dependent on the frequency
90
Tonotopic organization along the basilar membrane because it is tuned to vibrate maximally for different frequencies along its length.
(blank) frequency at the base where it is narrow
(blank) frequency at apex where it is wide
high; low
91
The basilar membrane is (blank) at the base, and (blank) at the apex
narrow; wide
92
A single auditory nerve fiber responds to a specific frequency.
This is because of the (blank) which states that the position of a hair cell along the basilar membrane determines its response property
place principle
93
Auditory fibers are also governed by the (blank) which says that auditory nerve fibers lock in to a specific point along the sine wave.
time principle
94
What's this?
Each cell firing goes to a specific area of cortex, which recognizes that frequency. Our cortex is tonotopically arranged. These fibers are predestined to convey a specific frequency.
labeled line mechanism
95
What's this?
Use electrode in cochlear duct to try to reproduce the ability of hair cells to fire for specific frequencies. Can’t completely replicate the range that these fibers would convey, but attempt to at least gather the range of speech
cochlear implant
96
What is the ascending pathway in the auditory pathway?
lateral lemniscus
97
Where do you get bilateral representation in the auditory pathway? Where does crossing occur?
after the cochlear nuclei;
| crossing occurs at the trapezoid body and after the inferior colliculus
98
Where are the "must stop" nuclei in the auditory pathway?
1. cochlear
2. inferior colliculus *for position of sound
3. thalamus (medial geniculate nucleus)
99
In the auditory pathway, there are several places where information processing can take place. Name a few.
superior olivary complex
medial nucleus of the trapezoid body
nucleus of lateral lemniscus
inferior colliculus
100
The whole auditory system is designed to preserve tonotopy. However, it is not designed to preserve this representation in space. How is this done?
via the inferior colliculus
| *this is where we get a special map of the position of sound before it relays on to the medial geniculate nucleus
101
There are multiple crossing sites along the auditory pathway AFTER the dorsal and ventral cochlear nuclei that yield bilateral representation. Why is this important?
To have one sided deafness, there must be a lesion to the cochlear nuclei or anything peripheral to them. Damage to other nuclei tracts will cause more subtle deficits like poor sound localization
102
This is the gateway to the cortex. Everything passes through here, with one exception.
thalamus *exception: olfactory
103
The auditory paths preserve (blank) along the way, that they stop at many stations through the brainstem, and various forms of (blank) occur at all the nuclei.
tonotopy; processing
104
What are the two nuclei involved in localizing sound on the horizontal axis?
medial superior olive
| lateral superior olive
105
Is space mapped on the auditory receptors? What do we need to tell us information about sound in space?
no; MSO and LSO
106
What is used to detect low frequency sounds (below 3000Hz)? What nucleus codes for this information?
difference in time that the sound is heard from one ear to the next *interaural time difference;
medial superior olive (MSO)
107
What is used to detect high frequency sounds (above 3000 Hz)? What nucleus codes for this information?
difference in intensity of sound from one ear to the next *interaural intensity difference;
lateral superior olive (LSO)
108
Time differences are coded by the (blank) for frequencies below 3000Hz, while intensity differences are coded by the (blank) for frequencies above 3000Hz
MSO; LSO
109
relays information to the primary auditory cortex via the sublenticular part of the internal capsule
medial geniculate nucleus of the thalamus
110
Would a lesion in the cortex cause one sided deafness?
No! There is lots of crossing over after the cochlear nuclei *bilateral representation
111
What's this?
| damage to the cochlea, eighth nerve or the auditory pathway
nerve deafness
112
What's this?
| damage to the components of the outer or middle ear
conduction deafness
113
List some examples of nerve deafness
presbycusis
acoustic neuroma
ototoxicity
114
List some examples of conduction deafness
plugged external auditory canal
tympanic membrane rupture
otitis media
otosclerosis *malleus, incus, stapes lose their synovial cavity
115
What's this?
distinguishes nerve from conduction deafness
Place tuning fork on forehead; where should sound be heard the loudest
Weber test
116
In the Weber test, if someone has "nerve deafness," where will sound localize when you place the tuning fork on their head? If someone has "conduction deafness," where will it localize?
to the good ear!
if it localizes to the "bad ear" then they have a conduction deafness, because something in the external auditory canal is blocking extraneous sounds (background noise) from the conduction system causing the sound to be heard better
117
What's this?
compares air conduction to bone conduction
Tuning fork on mastoid process, after it can no longer be heard, place it next to ear and they should hear it again because air conduction is better than bone conduction.
Rinne test
118
In the Rinne test, if a patient cannot hear sound when the tuning fork is in the air, what kind of deafness do they have?
conduction deafness
119
Hearing test graphs
• If air is worse than bone, then it’s a (blank) deficit.
• If bone and air are getting worse with higher frequency, but bone and air are similar, this is (blank) deficit.
• If there is a drop off in bone conduction, and a drop off in air conduction, it is a (blank) deficit
conduction;
nerve;
combined conduction and nerve
120
What nerves can an acoustic neuroma affect?
CN 5, 6, 7, 8, 9. 10
