HEENT

Question 1

what are the two structures in the vestibule that contain endolymph

Answer 1

utricle and saccule

Question 2

what layers of the cochlea are perilymph vs endolymph?

Answer 2

upper: scala vestibuli (oval window) Perilymph

Middle: scala media (cochlear duct) endolymph

lower: scala tympani (round window) perilymph

Question 3

what do perilymph and endolymph contain?

Answer 3

endolymph: K+

perilymph: similar to CSF, low protein, mostly sodium chloride solution

Question 4

where is the tympanic cavity found

Answer 4

within the petrous part of the temporal bone

Question 5

function of the tensor tympani and its innveration?

Answer 5

CN V: trigeminal

it pulls malleus away from TM, dampens sound waves to stop excessive decompression

Question 6

function of stapedius and innervation?

Answer 6

CN 7 (VII): Facial
to dampen the vibrations transmitted from stapes to oval window
*can be damaged in bells palsy

Question 7

what is the acoustic impedance mismatch?

Answer 7

difference in resistance to sound wave transmission between two media. Sound waves travel differently through air (low impedance) and denser materials like bone or fluid (higher impedance).

Question 8

Static equilibrium vs dynamic?

Answer 8

Static: detects position of head when body is not moving (vertical/linear ex/ elevator)

dynamic: detects angular movements of head (horizontal)

Question 9

what do the semicircular canals sense? vs the utricle and saccule?

Answer 9

SC: rotary acceleration and motion

U and S: linear acceleration and static position (think maculae is here also static)

Question 10

what is the function of each semicircular canal?

Answer 10

anterior: detects side tilts

posterior: Yes nod

lateral: No nod

Question 11

what does the maculae detect? vs the crista ampullaris

Answer 11

Macule: linear accerleration or deceleration and STATIC head position

crista ampullaris: Dynamic

Question 12

rotation of the head in a particular direction causes the movement of endolymph fluid in canals to go in what direction?

Answer 12

opposite direction

Question 13

that does salt sensitivity involve in taste perception?

Answer 13

activation of epithelial sodium channels

Question 14

what does sour taste result from?

Answer 14

proton (H+) stimulation

Question 15

how is sweet taste perceived?

Answer 15

G protein coupled receptors, T1R2 and T1R3

Question 16

how is umami taste perceived?

Answer 16

glutamate receptor, mGluR4

Question 17

what is otosclerosis

Answer 17

abnormal bone deposition in the middle ear. progressive hearing loss that affects both ears due to immobilization of the oval window.

minimal degrees of derangement is common (10%)

Question 18

where do inner hair cells project?

Answer 18

freely into the endolymph

Question 19

where do outer hair cells project?

Answer 19

into the gelatinous tectorial membrane

Question 20

where are high frequency sounds detected on the BM? Low frequency?

Answer 20

high: closer to oval window

low: closer to helicotrema

Question 21

what is pitch based on?

Answer 21

what part of the organ of corti detects the sound

Question 22

how is loudness distinguished?

Answer 22

how much the BM vibrates, move movement caused more release of glutamate

= higher frequency of APs

Question 23

what causes transduction channels to open in the OUTER hair cells?

Answer 23

when hair bundles tilt toward the longer stereovilli, this allows K+ to flood in, depolarizing the outer hair cells

Question 24

what does this depolarization of the hair cell and influx of K+ cause?

Answer 24

contraction of prestin -> contraction of outer hair cell (very fast)

Question 25

after the depolarization of the outer hair cells, what causes transduction of the INNER hair cells?

Answer 25

basilar membrane moves upwards even more due to contraction of outer hair cells, endolymph moves under the tectorial membrane.

inner hair cells bend towards longer stereovilli

Question 26

what happens after depolarization of the INNER hair cells?

Answer 26

Voltage gated calcium challens open to release glutamate

Question 27

how long does an acute attack of transient rotatory vertigo lasat in benign paroxysmal postitional vertigo?

Answer 27

seconds to minutes

accompanied by rotatory nystagmus

Question 28

how long does Meniere’s disease last? (tinnitus, hearing loss, vertigo)

Answer 28

minute to hours

inadeqaute absorption of endolymh

Question 29

what is the diagnositic criteria for Menieres disease (must have all 3)

Answer 29

2 spontanous episodes of
- rotational vertigo
- sensorineural hearing loss
- tinnitus and or aural fullness

Question 30

how long does vestibular neuronitis last? (nausea, vomiting, imbalance without hearing loss)

Answer 30

days to weeks

Question 31

what are the clinical features of cholesteatomas

Answer 31

painless otorrhea (hallmark)
conductive hearing loss

Question 32

briefly describe the pathogenesis of cholesteatomas

Answer 32

the inner surface of the TM migrates (postero-superior) in response to chronic inflammation, it becomes stuck to the incus, mucous accumulates in the pouch, conversion of cells in the cyst to keratinized epithelial -> growth and activation of osteoclasts in temporal bone

Question 33

90% of otitis externa is ____?

Answer 33

bacterial

staphylococcal, psuedomaonas aeruginosa, or E. coli

Question 34

what is otomycosis?

Answer 34

fungal infection of the external auditory canal, up to 10% of otitis externa, usually aspergillus (80%)

Question 35

describe the general pathogenesis of AOM?

Answer 35

obstruction of auditory tube

air absorbed in middle ear

negative pressure

edemea of muscosa with exudate and fluid

infection from nasopharyngeal secretions

Question 36

what is the principle function of the eustachian tube?

Answer 36

to aerate the middle ear cavity, thereby sustaining pressure equailibrium commensurate with atomspheric pressure

Question 37

what is suspected about the pathophysiology of benign paroxysmal positional vertigo?

Answer 37

Otoconia (otoliths) have detached from the otolith membrane resulting in abnormal sensory perception.