Lecture 15 Flashcards
(52 cards)
hearing and balance depends on _____ of stereocilla?
mechanical bending
what are the properties of sound?
- sound and 2.pitch
- Sound
- pressure disturbances produced by a vibrating object (altering areas of high and low pressure)
- consists of many waves that pass a given point in a given time
What is the property of pitch?
- perception of different frequencies
normal range 20 - 20,000 hertz (hz, cycles per second)
- higher frequency = higher pitch
how does sound get to the inner ear?
- sound enters external ear
- sound transmission to middle ear
- stapes transmits sound through the oval window
- sound passes through cochlear duct (to move stereocilia)
where are sound waves transmitted?
into the cochlear duct causing the bending of Stereocilia
The stereocilia are protrude into _____ and the longest are connected to the gel like ______?
into the endolymph, into the tectorial membrane
how does the bending toward the tallest stereocila?
- opens mechanically gated ion channels
- activates K+ and Ca+ current causing depolarization
(graded potential and release of glutamate)
How does bending away from the tallest stereocilia?
- closes mechanically gated ion channels
- hyperpolarization inhibits release of glutamate
cochlear nerve fibers transmit impulses where?
The brain
fibers near the oval window produce what sound?
(short and stiff)
- resonate with high frequency
fibers near apex (or away) from the oval window produce what sound?
(longer more floppy)
- resonate with lower frequency waves
The pitch of the sound is determined by where the stereocilia are on what?
based on the positions along the basilar membrane
How can loudness be detected?
by an increased number (frequency) of action potentials in the activated position
- (louder noise means greater amplitude and stereocilia remain in the activated position for a longer period of time)
What is sensorineural deafness?
damage to neural structures at any point from
- cochlear hair cells to auditory cortex
typically from gradual hair cell loss (loud noises, music)
what is tinnitus?
ringing in ears, in some cases damaged hair cells keep sending signals to the brain
- still hearing b/c of hair cells are still dropping neurotransmitters
what is conduction deafness?
blocked sound conduction to fluids of inner ear
causes:
- impacted ear wax
- perforated eardrum
- otosclerosis of the ossicles (hardening of the ossicles) elderly
- otitis media (middle ear infection)
What is otits media? causes and treatement?
middle ear infection
- cause of hearing loss in children
- shorter, more horizontal Eustachian tubes
Treatment?
- with antibiotics
- tubes are inserted through tympanic membrane
What does hearing aids do compared to cochlear implant?
hearing aids = amplifies sound
cochlear:
- bone conduction = passes through bone to tell inner ear
- cochlear implant = passes through all to tell cochlear with electrode on it to hear
What helps us with equilibrium and balance?
Saccule and utricle (macula)
Central cavity of the bony labyrinth contains what 2 membrane sacs?
Saccule - continuous with the cochlear duct
utricle - continuous with semicircular canals
Saccule and Utricle house what?
linear equilibrium receptor region (macula)
- respond to gravity and changes in position in head
What do the Semicircular Canals do in response to movement?
- rotational movement
- lie in 3 planes of space
- membranous semicircular ducts line each canal
Ampulla of each canal houses rotational equilibrium receptor region called?
Crista ampullaris
what is kinocilium and stereocilia?
Both are the longest stereocilium and are embedded in the otolith membrane
- studded with otoliths (tiny CaCO3 stones)
