Auditory system

Question 1

How is the ear divided?

Answer 1

Outer - pinna, external auditory canal
Middle - tympanic cavity, 3 bones; malleus, incus, stapes
Inner - cochlea, semicircular canals

Question 2

3 function of outer ear

Answer 2

capture sound
amplify frequencies
protect ear from external threats

Question 3

how does the outer ear amplify sounds?

Answer 3

by resonance

Question 4

Function of middle ear?

Answer 4

Amplification

Question 5

how is amplification of the middle ear achieved?

Answer 5

focusing vibrations from the tympanic membrane - LARGE SA
to the oval window

uses the ossciles
tympanic membrane projects onto malleus which projects onto incus which projects onto stapes ( which rests on the oval window)
use of incus -stapes joint increases the force on the oval window

Question 6

simple answer of how amplification occurs in middle ear?

Answer 6

focusing of vibration from large SA to small SA - increases amplificationas pressure is increased

Question 7

function of inner ear?

Answer 7

hearing via Cochlea
transduces vibration into nervous impulses
- frequency/ pitch and intensity analysis of sound occurs here

Question 8

scala vestibuli contain?

Answer 8

perilymph- high in Na+

Question 9

scala tympani contain?

Answer 9

perilymph- high in Na+

Question 10

scala media contains?

Answer 10

Endolymph- high in K+

Question 11

structures which contain perilymph in the inner ear are __ structures?This is high in sodium

Answer 11

bony structures

vestibuli, tympani

Question 12

membranous structures like the _____ contain ______ high in K+

Answer 12

membranous structures like the SCALA MEDIA contain ENDOLYMPH- high in K+

Question 13

basilar membrane arrangement

Answer 13

same principle as xylophone

narrow at base and wide and loose at apex

Question 14

high frequency is sensitive at which part of basilar membrane?

Answer 14

BASE - narrow andtight

Question 15

low frequency is detected at what part of basilar membrane?

Answer 15

apex

loose and wide

Question 16

where is the tectorial membrane ?

Answer 16

Inner ear
Organ of Corti
above the hair cells
only outer hair cells are in contact with tectorial membrane

Question 17

___ carry 95% of afferent information of the auditory nerve.

Answer 17

inner hair cells carry 95% of afferent information of the auditory nerve.

Question 18

efferent information of auditory nerve is via __

Answer 18

efferent information of auditory nerve is via OUTER HAIR CELL

Question 19

hearing acuity test

Answer 19

pure tone audiometry

PTA

Question 20

TYMPANOMETRY

Answer 20

Examination used to test the condition of the middle ear and mobility of the eardrum (tympanic membrane) and the conduction bones by creating variations of air pressure in the ear canal.

Question 21

common result of tympanometry

B

Answer 21

Middle ear effusion
Perforation of tympanic membrane
Eustachian (pharyngotympanic) tube dysfunction
Occluded ear canal

Question 22

newborn hearing screening test

Answer 22

otoacoustic emissions
normal cochlea produces these sounds
low intensity sound
outer hair cells as they expand and contract

Question 23

Conductive hearing loss

Answer 23

Problem is located in outer or middle ear.

Question 24

Sensorineural hearing loss

Answer 24

Problem is located in the inner ear or the auditory nerve.

Question 25

Mixed hearing loss

Answer 25

Conduction and transduction of sound are affected. Problem affects more than one part of the ear.

Question 26

transduction

Answer 26

Organ of corti sits in basilar membrane
when that vibrates organ of corti vibrates
hair cells move and deflect the tectorial membrane
hair cells depolarise and potassium moves from outside to inside the cells
this then causes action potential to travel
calcium gated channels open on basal end
glutamate release is evoked
electrical impulse sent

Question 27

movement of hair cells in transduction

Answer 27

stereocilia move towards longest cilium
deflection causes opening of potassium channels
depolarisation of cells occur
glutamate release
higher amplitude causes greater deflection so more potassium channel release

Question 28

auditory pathway

Answer 28

spiral ganglion - from each cochlea
auditory vestibular nerve
ipsilateral cochlear nuclei

crossing over happens at superior olive level (midbrain)

Question 29

Ageing and hearing

Answer 29

hearing acuity decreases with age - high frequency loss first