Physiology of Hearing and Balance Flashcards
(44 cards)
what dictates the pitch and intensity of sound?
frequency of wave = pitch
amplitude of wave = intensity
what frequency of sound can human perceive?
20Hz - 20,000Hz
what is the normal reference for normal hearing?
should be below 20 (0 is the healthy hearing ability of a 20 y/o male for reference)
20-40 = mild hearing loss
40-60 = moderate etc
what is impedence matching?
the transfer of vibration/waves from air to liquid
occurs at the oval window where vibration of the stapes causes pressure waves in the endolymph in the cochlear duct
what does the ossicular chain do?
acts as a piston or lever arm with varying efficiency depending on frequency of sound transmitted
what is the ratio of malleus handle to incus long process and what is the significance of this?
1.3:1
mechanical gain of decibels
what is the eustachian tube?
ventilation pathway for middle ear mucosa
joins middle ear to nasopharynx
what does the eustachian tube do?
equalises pressure in the middle ear to the outside pressure
closed at rest
opened by tensor veli palatine and levator palatine muscles in order to change pressure
what are the 2 openings in the cochlea and what are their functions?
oval and round windows
allow transmission of pressure wave in enclosed canal and vibration of the basilar membrane
hair cells in the cochlea are of varying length, what is the implication of this?
particular wavelength/frequency of sound hits a particular area/length of hair cells in cochlea
signals from this area travel to the brain and the brain can therefore determine pitch of sound
if this part damaged - cant hear that pitch
where are short/long hair cells found in the cochlea and what frequency of sound stimulates each?
short hair cells at base of cochlea = stimulated by high frequency sound
long hair cells at tip of cochlea spiral = stimulated by low frequency sound
how are hair cells used in universal neonatal screening?
outer hair cells
produce otoacoustic emission (OAE - basically a little sound) which can be identified in a normal cochlea in response to sound
can suggest a problem if absent
used for screening
normal speech ability at 3 months?
cooing
recognizes mother’s voice
normal speech development at 6 months?
babbling
turns to sound or eyes towards sound
normal speech and hearing development at 12 months?
may make simple noises
mama/dada
follows intructions
turns to sound
normal speech difficulties at 12-24 months?
syllable deletion (retain stressed syllable e.g not say the “ba” in “banana”)
syllable simplification (leave out the S in stop)
substitutions (replace R with L or W)
may use single words to describe a situation
speech at 18 months?
may say a few words
recognise body parts, animals, simple commands
speech at 24 months?
2 word phrases
50+ words
understands questions and follows commands
speech at 24-36 months?
3 word sentences aware of rhyme start with adjectives understand order positioning
how many turns in cochlea?
2.5
describe the structure of the cochlear canal
tube divided into parts upper portion = scala vestibuli (perilymph) bottom portion = scala tympani scala media (cochlear duct) sits between the layers - suspended by spiral ligament
what is contained within the cochlear duct?
basillar membrane
organ of corti
endolymph
what drives the production of current in the cochlea?
difference in ion concentrations between scala media (endolymph) and scala vestibuli (perilymph)
stimulation opens channels for the movement of potassium
what is the function of inner vs outer hair cells in the cochlea?
inner = sound perception outer = sound amplification (have motor ability so beat to increase vibration of basilar membrane)
