Auditory and Vestibular Systems I&II

Question 1

what is amplitude (loudness) measured in?

Answer 1

decibels (dB)

-sensitivity is inconsistent

Question 2

what is wavelength (frequency) measured in?

Answer 2

hertz (Hz)

• normal range 20-20000 Hz
• sensitive to 1000-3000 Hz to detect human voices

Question 3

outer ear

Answer 3

pinna (funnel) and auditory tube (canal)

• where foreign bodies are located
• contain air

Question 4

middle ear

Answer 4

amplifies sound; deep surface of tympanic membrane

• malleus, incus, stapes
• contain air
• tensor tympani attaches to malleus - innervated by trigeminal (mandibular branch)
• stapedius - facial nerve
• limit vibratory capacity by contracting tensor tympani and stapedius

Question 5

inner ear

Answer 5

contains cochlea - converts sound from air into liquid and contains afferent fibers

• cells convert waves in liquid into electrical signals
• higher frequencies –> narrow region near base
• lower frequencies –> wider region near apex

Question 6

organ of corti

Answer 6

contains inner and outer hair cells

-also supporting cells

Question 7

role of kinocilium and stereocilia

Answer 7

project into endolymph turning wave signals into electrical signals

Question 8

endolymphatic hydrops

Answer 8

too much perilymph

associated with Meniere’s disease

Question 9

inner vs. outer hair cells

Answer 9

inner - perceive sound, high sensitivity

outer - amplify sound wave propagation, can be killed by prolonged ototoxic drugs/antibiotics –> hearing loss

Question 10

otoacoustic emissions

Answer 10

sound travels from cochlea to auditory canal (reverse)

-tests auditory ability

Question 11

ascending hearing pathway

Answer 11

• inner hair cells –> spiral ganglion by CNVIII –> cochlear nuclei (1st synapse) –> superior olivary nucleus –> inferior colliculus (2nd synapse) –> auditory cortex
• left and right auditory cortices ALWAYS receive input from BOTH ears
• contralateral or ipsilateral fibers

Question 12

auditory cortex frequencies

Answer 12

• high frequency sounds - processed more medially, deeply

- low frequency sounds - processed more laterally, superficially

Question 13

brodmanns areas

Answer 13

• 41,42 = basic properties, detect thunder from gun shot

- 22 = pitch, intensity, emotion - pick up tone, sarcasm

Question 14

descending hearing pathways

Answer 14

• lateral olivocochlear efferents –> inner hair cells (go through spiral ganglion)
• medial olivocochlear efferents –> outer hair cells (bypass spiral ganglion)

Question 15

hearing reflex - ways to decrease volume

Answer 15

• contract stapedius or tensor tympani –> dampen sustained loud noises
• can also dampen with outer hair cells

Question 16

hearing disorders

Answer 16

1. hypoacusis = decreased hearing
2. hyperacusis = increased hearing
3. deafness = loss of hearing
4. hallucinations
5. neuroma
6. tinnitus = hear sound with no sound present

Question 17

acoustic neuroma aka vestibular schwannoma

Answer 17

benign tumor on cranial nerve VIII

-tinnitus, loss of hearing, dizzy

Question 18

conductive hearing loss

Answer 18

• outer ear - foreign body

- middle ear - dysfunction of auditory ossicles, fluid accumulation –> upper respiratory tract inflammation

Question 19

sensorineural hearing loss

Answer 19

dysfunction of hair cells

• CNVIII works fine
• treat with cochlear implants

Question 20

presbycusis

Answer 20

hearing loss due to aging

Question 21

where does sound/hearing occur?

Answer 21

cochlea

Question 22

where does balance occur?

Answer 22

saccule, utricle, cristae of semicircular ducts

Question 23

vestibule system

Answer 23

• contains otolith organs - utricle and saccule
• contain semicircular canal
• suspended in perilymph - bony labyrinth

Question 24

what is affected by stapes induced pressure changes?

Answer 24

the cochlea, not the vestibular apparatus

Question 25

role of the cupulla w/I the ampulla

Answer 25

contains receptor and supporting cells | -rotation --> endolymph stagnant and displace semicircular canals --> deflect cupula and detracted by receptor cells

Question 26

semicircular duct

Answer 26

detect angular or rotational movement

Question 27

utricle

Answer 27

detect linear movement (side to side) - macula inferiorly - stereocilia superiorly

Question 28

saccule

Answer 28

detect linear movement (vertical) - macula medially - stereocilia laterally

Question 29

otoconia

Answer 29

in saccule and utricle - switch positions with linear movement - continued stimulation of hair cells in absence of semicircular duct (acceleration)

Question 30

ascending vestibular pathway

Answer 30

vestibular nuclei - input from accessory optic nuclei --> no change in gate if damaged

Question 31

descending vestibular pathway

Answer 31

vestibular nuclei transmit info to: - cranial nerves 3,4,6 --> extra ocular muscles - MVST --> CN11 --> head and upper body - LVST --> lower limbs - MLF --> connection b/w extra ocular muscles and MVST

Question 32

3 types of info. go to vestibular system

Answer 32

- eyes, inner ears, proprioception - loss of 2 --> lose balance, dizzy, vertigo - overseen by cerebellum

Question 33

vestibulo-ocular reflex

Answer 33

turn head to left and eyes pull back toward right - ex. excitation increases contraction of right lateral rectus and left medial rectus - more affective than visual tracking

Question 34

damage to medial leminscal pathway vs. cerebellar damage

Answer 34

Romberg test - DML --> lose balance when closing eyes, loss of proprioception - cerebellar --> lose balance with eyes open

Question 35

nystagmus

Answer 35

normal - visual tracking | abnormal - vestibular dysfunction (CN8) --> dysfunctional tracking

Question 36

vertigo

Answer 36

positional hallucinations - loss of balance | -can be caused by acrophobia and can cause vestibular dysfunction

Question 37

benign paroxysmal positional vertigo

Answer 37

forceful head movement dislodges otoconia --> vertigo when head is in a certain position

Question 38

alcohol effects on vestibulocochlear system

Answer 38

infiltrates cupulae faster dropping density --> hair cells move quicker - spinning room (overly sensitive to movement) - rebound effect - alcohol leaves cupulae raising density and decreasing hair cell movement --> exaggerate movement - gate compromised

Question 39

alcohol effect on stapedius and tensor tympani muscles

Answer 39

reduces contraction of muscle increasing the sensitivity to sound (muscle tone relaxant)