Study your flashcards anywhere!

Download the official Cram app for free >

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key


Play button


Play button




Click to flip

116 Cards in this Set

  • Front
  • Back
What is sound?
Longitudinal waves of air that consist of periodic pressure fluctuations.
How do soundwaves bouncing compare to a golfball bouncing on a table?
Sound waves are perfectly elastic; oscillate indefinetely
Golfballs are not perfectly elastic; they will come to rest when dropped on a table.
First part of hearing:
impingement of the wave's pressure and relaxation on the eardrum.
What is the Amplitude of a sound wave?
Its physical correlate of loudness
F/A - Newtons
Fxd - Joule
What does intensity take into account?
Force, time, and area
What are the characteristics of high intensity soundwaves?
-High force
-Short time
-Little area
What is the result of a high intensity sound wave?
Loud sounds
What is the unit of measurement for sound intensity?
The decibel
What is Reference intensity?
The softest sound that can be heard by normal adults; the threshold of hearing.
Why is sound measured in decibels?
Because as sounds get louder the perceieved loudness increases LOGARITHMICALLY.
Why do we care about measuring sound?
Because decibels is how we measure hearing loss.
What is the equation for measuring decibels?
dB = 10log(I/Io)

dB = 20log(P/Po)
how is intensity related to pressure?
I = P^2
How much louder are two stereos blaring at 1 dB each than 1 stereo blaring at 1 dB?
Doubling intensity raises loudness by 3 dB
what is the physical correlate of loudness?
What is the physical correlate of pitch?
What is the range of human sensation of frequency?
20-16000 Hertz
What is a Hertz?
What are the components of the outer ear?
1. Pinna
2. External auditory canal
Function of the pinna:
Shapes the frequency distribution to LOCALIZE SOUND - modifies it from different directions.
What is the function of the external auditory canal?
It is the resonant cavity - it amplifies sound at a given frequency.
How much is sound amplified by the external auditory canal at a frequency of 2.5 kHz?
by 15-20 dB
How much does sound intensity increase based on an increase in amplitude of 15-20 dB?
30-130 X the original intensity
What happens if the external auditory tube is SHORTER?
You can hear higher frequency sounds - dogs can hear dog whistles b/c they have short tubes.
What happens if the external auditory tube is LONGER?
You can hear lower frequency sounds.
What is the general function of the middle ear?
3 important components of the middle ear:
1. Tympanic membrane
2. Oval window
3. Apparatus for coupling sound energy from tympanic membrane to oval window.
What is the tympanic membrane?
The eardrum at the lateral boundary of the middle ear.
What is the oval window?
The medial boundary (innermost) of the middle ear.
What is the apparatus that couples sound energy from the tympanic membrane to the oval window?
The ossicle apparatus
What are the ossicles?
What is the function of the ossicles?
Coupling of sound waves impinging on the tympanic membrane to the cochlea for sound transduction.
Where does the stapes terminate?
On the oval window - the beginning of the cochlea
What else is in the middle ear other than bones?
-Tensor tympani
Which muscle is more important?
Why is the stapedius important?
Because when it contracts it reduces sound transmission by about 10 dB
Why does the middle ear attenuate sound energy?
To protect the ear from damage.
What is the mechanism of the stapedius and tensor tympani called?
The attenuation reflex
How does the attenuation reflex work?
When a person hears a loud sound the muscles tighten and keep the bones from moving - impedes energy transfer to cochlea.
What would it be like if you lacked the attenuation reflex?
Loud sounds would feel like someone jumping on your back
What is the attenuation reflex not good for?
Protecting against sudden loud sounds - because of its reflex time - takes .25 sec to occur.
What principle needs to be accounted for in transferring energy from the tympanic membrane to the cochlea?
Impedence - going from low impedence of air to higher impedence of cochlear fluids.
What is the acoustic impedance transformer principle akin to?
Belly flopping - easily move through air, then all of a sudden hit the water and whack you're impeded a lot more.
What eases the impedence transformation during a dive?
if you turn your body so that it has less surface area impacting the water surface.
What are the 3 principles used by the middle ear ossicle apparatus to couple sound energy from the tympanic membrane to oval window impedence transformer?
1. Hydraulic effect
2. Lever action
3. Buckling motion
What is the hydraulic effect?
going from larger area of tympanic membrane to lower area of oval window -> greatly increases the pressure exerted per unit force.
What is the lever effect?
-Decreased Distance/time for F mvmt
-E is constant
-Increased Force transferred.
What does the Buckling motion contribute to impedance transformation?
Buckling decreases the velocity and size of movements and hence amplifies Force at the oval window.
How much does the external acoustic canal increase force?
How much does the hydraulic effect increase force?
How much do the buckling and lever effects increase force?
So how much is the pressure of sound increased when it hits the oval window?
10000 times
What happens when the ossicles are broken and this sound amplification can't occur?
There is a 40 dB reduction in hearing at 2500 Hz.
How much more intense does sound have to be to be able to just hear it?
10000 times higher.
What does the inner ear consist of?
The cochlea
What is the cochlea?
A very tightly coiled, fluid-filled chamber that is embedded in bone.
Divisions of the cochlea:
Scala vestibuli
Scala media
Scala tympani
What is the scala vestibuli?
Where does it terminate?
The upper chamber; terminates at the oval window where the footplate of the stapes is.
What is within the scala vestibuli and what is it like?
Perilymph - similar to ECF in composition.
What does the scala vestibuli communicate with and how?
With the scala tympani at the helicotrema - at the extreme end of the cochlea.
What is the scala media also called?
Cochlear duct
What does the scala media contain?
the transducer and endolymph
Endolymph is like what:
intracellular fluid - high in K and low in Na.
Where does the scala tympani terminate? What is its function there?
At the round window; functions to alleviate the pressure that occurs when the oval window is pushed in by the stapes.
What is contained in the scala tympani?
Perilymph - again similar to ECF in its composition.
What separates the Scala Vestibuli from the Scala media?
Reissner's membrane
What separates the Scala media from the Scala tympani?
Basilar membrane
What sits on top of the basilar membrane?
The organ of Corti - which contains the receptors for hearing.
Function of reticular lamina
forms a true chemical division between the ions in the endolymph of scala media and perilymph of scala tympani.
What membrane covers the organ of Corti? What is its structure like?
The tectorial membrane - a gelatinous and fibrous flap.
2 cell types that make up the organ of Corti:
1. Hair cells
2. Supporting cells
What are the support cells for the organ of corti?
Glial cells
2 types of hair cells:
(what percentage is each?)
Inner hair cells - 20%
Outer hair cells - 80%
How many hair cells are there on average in man?
What types of innervation is there to hair cells?
Afferents and Efferents (efferents not well understood)
Where are the cell bodies located for
Afferents - spiral ganglion
Efferents - superior olivary nucleus in brain stem
What type of hair cells have more afferents?
Inner - even though they're lower in number, 95% of afferents contact them.
How many contacts with axon afferents does each inner hair cell have?
How many contacts with axon afferents does each outer hair cell have?
1; actually each axon branches to itself contact about 10 outer hair cells.
What type of axons contact inner hair cells?
Myelinated axons of bipolar cells
What type of axons contact outer hair cells?
Unmyelinated axons of unipolar cells.
How does the basilar membrane structure change going from the base to apex of the cochlear duct?
Base: narrow/rigid
Apex: wide/floppy
What is the functional significance of the change in basilar membrane structure?
Base: more sensitive to high frequency sounds
Apex: more sensitive to low frequency sounds.
How do we know that the basilar membrane responds differently to different sound frequencies at different areas on it?
Via Von Bekesy's experiments with cadaver cochleae.
What were Von Bekesy's observations?
1. High frequency tones produce waves that peak in displacement near the BASE
2. Low frequency tones produce waves that peak in displacement near the apex.
What do we call the differential sensitivity to frequencies of the basilar membrane?
Frequency selectivity
What is the frequency selectivity of the basilar membrane like at SINGLE POINTS along it in a cadaver?
How do low frequencies move along the basilar membrane in a cadaver?
They travel all along the entire length of the membrane.
How do high frequencies move along the basilar membrane in a cadaver?
They move only near the base.
What is the frequency selectivity of the basilar membrane like at SINGLE POINTS along it in a live cat?
Quite selective - narrowly tuned
What does not cause the narrow tuning of a living cochlear neuron?
Lateral inhibition does not cause fine tuning!
What is responsible for the fine tuning of the basilar membrane in living cochleae?
Probably outer hair cells
Why do we think the OHC might be responsible for the basilar membrane's fine tuning?
Because when poisoned with kanamycin or furosemide the tuning curve is broadened.
What is a cochlear emission?
An echo generated by the ear in response to a sound
What is absence of cochlear emission caused by?
Sensorineural deafness
What is prolonged cochlear emission associated with?
Tinnitus (ringing in the ears)
What generates the echo that is Cochlear emission?
Outer hair cells, acting like little moters.
What do we call these outer hair cells?
the Cochlear Amplifier
How is it that OHC's can generate the cochlear echo?
They have motor proteins in their membranes.
What activates the motor proteins in OHCs? What is their response?
Potassium influx into the cells; activates them to lengthen.
How do outer hair cells cause echoing?
-Activation is caused by sound pushing on the basilar membrane; In turn the OHCs vibrate the membrane back and forth.
What allows outer hair cells to vibrate the basilar membrane?
Motor proteins activated by K influx into the cells.
How do OHC vibratory movements affect the basilar membrane?
Increase its bending and amplify the effect of mechanical vibration originally caused by the sound.
Where on the soundwave does the OHC motor activity magnify it?
At the POINT of maximal deflection - result is that frequency is MUCH more sharply tuned than if no OHCs.
How exactly do hair cells cause sound transduction into electrical signals?
Vibration of the basilar membrane and organ of Corti result in hair cell stereocilia bending.
What happens when stereocilia bend?
Depends on the direction of bending; one way results in depolarization; the other way results in hyperpolarization.
What happens when hair cells hyperpolarize or depolarize?
It changes the amt of NT released by the cells.
What does NT release from stereocilia do?
Activates the auditory nerve fibers.
Where exactly are the stereocilia located (between)?
Between the basilar membrane and tectorial membrane.
What happens when stereocilia bend at 90' right angles?
How do stereocilia work together?
They are linked into TRANSDUCTION LINKS
When are stereocilia transduction links active?
When stretched