Hearing Flashcards
Audiology
The study, assessment, management and rehabilitation of adults and children with hearing, auditory and balance disorders.
Loss of signal
Reduced audibility, usually higher frequencies
Loss of clarity
Difficulty picking out sounds from noise
Loss of amplitude sensitivity
Harder to hear quieter sounds
If you loose frequency range what is the kind of sounds most likely to go
Higher frequency sounds
Eg fricative sounds
What does spectral detail mean
Inability to differentiate different frequencies of sound
What is frequency measured in
Hertz
How do you calculate Hz
1 / period (in seconds)
What is the function of the central auditory system
-function is to transform the neural code from the periphery into meaningful precepts of the world
-there are a series of auditory areas (primary, secondary) responsible for sound processing
-these regions project to different sensory and cognitive systems
2 Ear canal functions
-channel sound into the tympanic membrane
-protect the tympanic membrane
How does the ear canal protect the tympanic membrane
-wax and hair traps dirt and foreign objects
-epithelial skin cells migrate slowly outwards, carrying wax and debris out of the ear canal
2 middle ear functions
Impedance matching
Acoustic reflex
What does impedance matching mean
There is a mismatch in mediums. Energy comes in as pressure changes and ends up being fluid vibrations in the cochlea
What does acoustic reflex mean
Middle ear muscles contract in response to loud sounds. Reducing energy transferred
Thought to protect cochlea from damage
Inner ear function
Oval window - interface between middle ear and cochlea
Stapes is fused to the oval window
Movement of stapes causes vibration of the cochlea fluids
What does the tectorial membrane in the cochlear do
Extends above organ of corti
Made from gelatinous material
Reissners membrane in cochlear
Separates fluid in scala media from that in scala vestibulaire
Very thin
Helicotrema of cochlea
Hole that connects scala vestibulu and scala tympani
Basilar membrane
One membrane forming the cochlear partition
Movement of cochlear fluid causes basilar membrane to move to
How many rows of outer hair cells do you have
Three rows
What do the outer hair cells act as
Cochlear amplifier
How do the outer hair cells act as a amplifier
-steroilia movement causes +ve ions (potassium primarily) to enter cell from scala media
-this causes depolarisation of the cell
-which causes the cell body to change shape (length) in a process called electromotility
Amplification
-largest stereocilia of the outer hair cell is embedded In the tectorial membrane. When the hair cell shortens (due to polarisation) they pull the tectorial membrane down toward the basilar membrane
-this amplifies the motion of the basilar membrane
Inner hair cells
-around 3500 in the cochlea
-converts movement of the tectorial membrane into action potentials
-movement of the stereocilia causes the same depolarisation as for the outer hair cells
-this triggers a release of neurotransmitter at the base of the cell
Hair cell loss
-outer hair cells are susceptible to damage (drugs/noise)
-leads to a loss of amplification so we loose sensitivity to sounds ie hearing loss
-electromotility decreases with age (Presbycusis)
Cochlear implants
-as a treatment for profound deafness, an array of electrodes on a wire can be inserted which will send electrical signals to the auditory nerve
-bypasses the outer ear, middle ear and the cochlear hair cells.
