Auditory And Vestubukar System

Question 1

Difference between vestibular and auditory sensory systems

Answer 1

vestibular senses low frequency (=movement) and auditory senses high frequency (=sound)

• amplitude (volume → dB) & frequency (pitch → Hz)

Question 2

two relevant measurements for sound?

Answer 2

amplitude (volume → dB):sound,pressure,subjective attribute correlated with physical strength & frequency (pitch → Hz)cycles per second,perceived tone

Question 3

human range for hearing in each of these parameters?

Answer 3

20-20000 Hz, 0-120 dB

Question 4

outer ear functions?

Answer 4

capture sound

focus onto tympanic membrane

approx 10 dB amplification of upper range frequencies

protect from external threats

Question 5

middle ear function?

Answer 5

mechanical amplification (20-30 dB)

Question 6

inner ear function?

Answer 6

transduce vibration into nervous impulses
Cochlea
Captured rhe frequency and intensity of sound

Question 7

three compartments of the cochlea?

Answer 7

scala vestibuli → vestibular membrane → scala media → basilar membrane → scala tympani

Scala vestibuli and scala tympani are bone structures which contain peri lymph (high in sodium). Scala mediated is the membranous structure which contains endolymph (high in potassium). Here is where the hearing organ of corti is

Question 8

what are each filled with? key ingredient in these fillings?

Answer 8

scala vestibuli and tympani → perilymph (high in Na+)

scala media → endolymph (high in K+)

Question 9

what are each made of?

Answer 9

vestibuli and tympani → bony structures

media → membranous structure with hearing organ (organ of Corti)

Question 10

where is the organ of Corti and how is it organized

Answer 10

Basilar membrane
Like a xylophone (tonitopically)

narrow and tight base for high frequency, wide and loose apex for low frequency

hair cells pick up signals

Question 11

cell types within the organ of corti

Answer 11

Inner hair cells and outer hair cells

IHCs carry most auditory nerve afferent information → transduction of sound

OHCs carry most auditory nerve efferent information → modulation of response sensitivity

Question 12

how does cell depolarisation occur?

Answer 12

tectorial membrane above hair cells causes cell deflection

Question 13

hairs of the hair cells are called what?

Answer 13

Stereocillia

Question 14

What does the hair cells deflection do

Answer 14

deflection towards the longest cilium (kinocilium) opens K+ channels

Question 15

Effect of hair cells and outer deflection

Answer 15

cell depolarisation and subsequent vestibulocochlear nerve depolarisation

Question 16

what do higher amplitudes do?

Answer 16

cause greater deflection of the stereocilia → more K+ channels open → stronger signalling

Question 17

deflection in the other direction causes what?

Answer 17

closing K+ channels → hyperpolarisation

Question 18

vestibulocochlear nerve goes where after cochlea? And what happens next

Answer 18

ipsilateral cochlear nuclei in pons
Superior olive
Inferior colliculus
Medial geniculate body
Auditory cortex

Question 19

what happens at the level of the superior olive?

Answer 19

some auditory information crossing to the other side → bilateral from this point

Question 20

• types of hearing loss (anatomical distinction)? associated with issue where?
  -

Answer 20

• conductive hearing loss?outer or middle ear
• sensorineural hearing loss (most common)?cochlea or auditory nerve
• central hearing loss?rare, brain/brainstem issue

Question 21

types of hearing loss (onset distinction)?

Answer 21

sudden hearing loss (minutes to days)

progressive hearing loss (months to years)

Question 22

causes of conductive hearing loss in (open):

Answer 22

• outer earforeign body, earwax
• middle earotitis, otosclerosis

Question 23

causes of sensorineural hearing loss in (open):

Answer 23

• inner earnoisepresbycusis (old age degeneration)ototoxicity
• auditory nerveacoustic neuroma (vestibular schwannoma) → unilateral

Question 24

• tuning fork tests to assess gross hearing loss?

Answer 24

weber test (on skull) and rinne test (next to ear/on mastoid process)

Question 25

- audiometry signs of conductive/sensorineural hearing loss?

Answer 25

conductive: air conduction hearing much worse than bone conduction sensorineural: air and bone same, hearing inconsistent between frequencies (some are weaker than others) a normal threshold is between 0-20dB

Question 26

what are OAEs?

Answer 26

otoacoustic emissions → normal sounds produced by cochlea used in newborn hearing screening

Question 27

treatments for hearing loss?

Answer 27

address underlying cause, use hearing aids, cochlear implants and brainstem implants

Question 28

vestibular system input and output?

Answer 28

input: movement and gravity output: postural control and ocular reflex

Question 29

what is the vestibule made up of?

Answer 29

utricle and saccule These are otolith organs

Question 30

what else makes up the vestibular system?

Answer 30

three semicircular canals: anterior, posterior, lateral - utricle Comnected to ampulla where hair cells sit

Question 31

- what do the maculae in the utricle and saccule contain?

Answer 31

hair cells, gelatinous matrix, otoliths (carbonate crystals)

Question 32

what is the orientation in each organ?

Answer 32

horizontally placed in utricle thus detects horizontal movement, vertically placed in saccule thus detects vertical movement

Question 33

what do the semicircular canals contain?

Answer 33

ampulla contains crista and hair cells, surrounded by cupula to help with movement rest of canal has endolymph → high in K+

Question 34

- hair cell resting activity in terms of neural signalling?

Answer 34

they have a basal discharge rate to the nerve increased by movement of stereocilia toward kinocilium → depolarisation decreased by movement of stereocilia away from kinocilium → hyperpolarisation

Question 35

vestibular nerve primary afferents synapse where?

Answer 35

vestibular nuclei in brainstem (pons)

Question 36

what are the two main vestibular reflexes?

Answer 36

vestibulo-ocular reflex and vestibulospinal reflex

Question 37

what does VOR do?

Answer 37

Keeps images fixed in retina

Question 38

by what mechanism does vor workers

Answer 38

vestibular nuclei connected to oculomotor nuclei eye movement in opposite direction to head movement but same velocity and amplitude

Question 39

different types of vestibular disorder → how to categorise?

Answer 39

timing (acute/slow onset) and laterality

Question 40

characteristics of each disorder

Answer 40

acute unilateral main complaints are dizziness, vertigo, nausea, imbalance slow onset unilateral / any bilateral → main complaints are imbalance and nausea with no vertigo

Question 41

can also be characterised by location into what? (VD)

Answer 41

peripheral (vestibular organ or vestibulocochlear nerve) central (brainstem/cerebellum) Eg peripheral: vestibular neuritis, benign paroxysmal positional vertigo (BPPV), meniere’s disease central: stroke, multiple sclerosis, tumours

Question 42

core examination areas for vestibular disease?

Answer 42

Ear eyes legs

Question 43

red flag symptoms? For vd

Answer 43

headache, gait problems, hyper-acute onset, hearing loss, prolonged symptoms (>4 days)

Question 44

Exam for acute and intermittent

Answer 44

- acute → vestibular neuritis, stroke HINTS exam - what is this? head impulse test (horizontal rotational VOR → abnormal usually indicates peripheral issue) nystagmus (repetitive uncontrolled eye movements) test of skew deviation (vertical ocular misalignment → usually absent for peripheral diseases, done by alternate cover test) - intermittent → BPPV Dix-Hallpike test

Question 45

BPPV pathology?

Answer 45

vertigo on certain maneuvers caused by displaced otolith crystals. Fixed by epley maneuver Dix hallpike manouver can help identify

Question 46

Semi circular canal planes

Answer 46

Anterior and posterior canals form a 90 degree angle Lateral canals are horizontal to other canals so work in pairs

Question 47

Vestibular neuritis

Answer 47

Nause and vomiting Severe vertigo Nystagmus Usually due to heroes,epstein barr and influenza virus Occurs as attacks

Question 48

Ménière’s disease

Answer 48

Fullness and pressure in ear Hearing loss Vertigo May be due to genetic migraines etc

Question 49

Nystagmus

Answer 49

Slow phase is where eyes start drifting of away from focus of object Fast phase is where eyes correct themselves back to original position Nystagmus named after direction of fast phase