The Auditory System Flashcards
What is a sound wave
Vibrations of air that alternate between regions of compression and non compression (rarefaction)
Sound waves are distinguished by their ?
Amplitude and frequency
What is amplitude
The height of the waves
Determines intensity (loudness)
Measured in decibels
Frequency
Number of waves per second
Measured in hertz
Determines pitch
External ear
Receives and transmits sound pressure waves to the middle ear
Middle ear
Transfers sound energy from air to the liquid inner ear (turns sound energy to fluid waves)
Inner ear
Tranduces signal to a change in membrane potential (converts fluid to a change in membrane potential)
The oval and round window seperate…
Seperate air filled middle ear from fluid filled inner ear
Malleus, Incus & Stapes pass on vibrations to the inner ear at the …
Same frequency
Eustachian Tube
Release a build up of pressure; for ex: in a plane @ high altitudes, you tru to yawn to open that tube to releive pressure
External ear consists of: (2)
the outer ear (pinna) and the ear canal
What does the penna do
Direct sound waves into the ear
That your canal is sealed and it’s internal and by a thin membranous called
Tympanic membrane
Sound waves that vibrate the Tympanic membrane move the three middle ear bones at
The same frequency
What is the malleus/the hammer connected to?
Tympanic membrane
T or F: the incus (anvil) is in the middle
True
Stapes (stirrup) is connected to??
The oval window
The pressure of the sound waves is _____ by the middle war
Amplified
Movement of the bones trigger movement of fluid in the cochlea at
The same frequency
The Inner ear consist of two major sensory structures:
The vestibular apparatus and the cochlea
Step one of Sound transaction
Soundwaves strike the Tympanic membrane and become vibrations
Step two of sound transduction
The sound wave energy is transferred to the three bones of the middle ear which vibrate
Step three of sound transaction
The stapes is attached to the membrane of the oval window. Vibrations of the oval window create fluid waves with in the cochlea
Step four of sound transduction
The fluid waves push on the flexible membranes of the cochlear duct. Hair cells bend and ion channels open, creating an electrical signal that alters neurotransmitter released
Step five of sound transduction
Neurotransmitter release onto sensory neurons creates action potential that travel through the cochlear nerve to the brain
Step six of sound transduction
Energy from the waves transfers across the cochlear duct into the Tympanic duct and is dissipated back into the middle ear at the round window
Where does sound transaction occur
In the cochlea
What are the three fluid filled channels in the cochlea
Top: vestibular duct - consists of perilymph (plasma/CSF)
Middle: cochlear duct - consists of endolymph (extracellular fluid very high in K+)
Bottom: Tympanic duct - consists of perilymph (plasma/CSF)
What happens if fluid waves can’t dissipate back into the middle ear at the round window
The waves will stay in the cochlea
Where are high frequency sounds on the basilar membrane
At the stuff end of the basilar membrane near the oval window
Where do low-frequency sounds deflect on the basilar membrane
At the apical end close to the end of the basilar membrane
Specific populations of hair cells respond to…
Specific sound frequencies
Hi and low frequency sounds are specially mapped onto the…
Basilar membrane
Spacial coating is preserved in the
Auditory cortex
What is included in the organ of Corti (4)
The basilar membrane, tectorial membrane, hair cells, afferent and efferent axons
What happens when the basilar membrane is displaced
It moves hair cells which pushed against the tectorial membrane and generate action potential’s in the hair cells out through the axons
What is the role of the inner hair sell
To relay information to the brain
What is the role of the outer hair cells
To amplify the signal and excite cells more
The direction of displacement determines whether hair cells are…
Depolarized or hyperpolarized
True or false? Hair cells don’t have axons and don’t generate action potential’s, but they can release neurotransmitters
True
What makes up a hair bundle
Stereocilia
Why are there sensory and inhibitory synapses onto the hair cells?
Usually to inhibit, allows for by directional flow, so you can get a cleaner sound and drown out others
Displacement towards the tallest stereocilia causes?
A depolarization
Displacement towards the shortest stereocilia causes what?
Hyperpolarization
Where does the ion exchange takes place in the hair cell
Between stereocilium in the tip link
What is going on in the tip links at rest
Some channels are open at rest so a little bit of neurotransmitters can be released but there is no obvious noise, just background noise
What happens in the hair cells during excitation
More channels open
Caption entry depolarizes
AP generated
What happens to the hair cell during inhibition
The channels clothes. Less cat ion and entry hyperpolarizes the cell. No neurotransmitters are released
True or false? Excitation produces more action potential’s then at rest
True
What does cranial nerve eight contain
The vestibule or nerve for balance and the cochlear nerve for hearing
What is conductive hearing loss
Sound waves are not adequately conducted to the External and middle portions of the ear
Sensorineural hearing loss
Sound waves are not translated into nerve signals that are interpreted by the brain as sound sensations
Central Hearing Loss
Damage to the nerve pathways between the ear and the auditory cortex or to the cortex itself
