Flashcards in Section 3 Auditory System Deck (108):
Sound can be categorized according to:
freq and amp
Vibration, per second, freq determines:
Typical speech is __ Hz:
Amplitude is measured in:
Loudness is measured in:
vibrations per second
How many decibels is normal conversation, whisper, and lawnmower?
60dB, 15dB, and 90dB
0 dB is:
Where is the auditory system most sensitive?
Above what dB do you no longer hear tone, but it turns to pain or noise?
What is the perception limit of humans?
about 4 kHz (this is at about 100dB)
The far L side of the Freq vs dB graphs starts at how many dB?
90. This is the dB level around which the lowest frequencies can be heard
How many decibels are we at when the perception limit has been reached?
about 100 dB
T or F? The eardrum is located in the middle ear.
F. outer ear.
Parts of the outer ear:
pinna, external auditory meatus/canal, and ear drum
ear drum is aka:
What structure is physically connected to the eardrum?
Parts of the middle ear:
malleus, incus, stapes (hammer, anvil, stirrup)
How many tiems do the ossicles amplify the amplitude of sound?
25 times the amplitude
T or F? The moves of the tympanum are very large.
Human ear can detect sounds that involve air moves of less than:
Most efficient frequency range:
Interruption or calcification of the ossicle chain can result in a hearing loss of:
What muscles protect the cochlea from damage due to very loud noise?
Stapedius and tensor tympani
When does the stapediius contract?
Just before we speak or chew, in response to loud external sound
Damage to what can cause an intolerance to noise and difficulty hearing in noisy surroundings?
The tensor tympani m. acts:
reflexively with stapedius
To what is the tensor tympani attached?
malleus and tympanic membrane (pulls inward to make more tense)
What takes place in the cochlea?
Sound energy is transduced into neural signals
How is the cochlea divided?
Into 3 sub-tubes separated by 2 membranes
The basilar membrane separates:
endolymph from perilymph
What does the basilar membrane contain?
The cochlear hair cells
Hair cells project into:
Info is transferred from the cochlea to the brain via this ganglion:
All neural action takes place here:
Hair cell bundles are always associated with:
What causes vibration of the basilar membrane?
Movements of cochealr fluids in response to head moves
Most medial portion of the inner ear:
What region of the basilar membrane vibrates the most in response to high frequencies?
What region of the basilar membrane vibrate the most in response to low frequencies?
The basilar membrane gets narrower and stiffer going toward this end:
What allows for the different parts of the basilar membrane to respond differentially to different parts of sound?
variability in width and stiffness
Are higher or lower Hz frequencies hear in the center of the coiled cochlea?
Parts of the organ of corti:
tectorial membrane and hair cells
2 kinds of hair cells:
inner hair cells and outer hair cells: (outside of spiral) about 12,000/ cochlea, to discrimination bw sounds, tune up the fxn of the basilar membrane (lengthen and contract in response to sound coming in)
Vestibular system and this system:
air cells are associated with a flexible membrane
inner hair cells:
middle of spiral, X section through the cochlear will only reveal 1 in each section, 3,500/ cochlea, send info about sound to CNS
outer hair cells:
outside of spiral, about 12,000/ cochlea, to help to discriminate bw sounds, tune up the fxn of the basilar membrane (lengthen and contract in response to sound coming in)
How do the outer hair cells help to discriminate bw sounds?
lengthen or contract in response to sound or msg brought to the cochlea form the brain via efferent axons which selectively controls the motion of the basilar and tectorial membranes
What helps to reduce the cochlea's response to constant background noise, allowing a greater response to transient and selectively-attended sounds?
Outer hair cells
When can a cochlear implant be placed to directly activate the correct nerve endings?
When damage or a genetic anolmaly has destroyed hair cells but not 8th nerve fibers
How does a cochlear implant work?
Decode freq, tells the processing system what range of freq are coming in, transmit to a receiver that has been transplanted, send info to cochlear implant
Implant electrodes are activated according to what?
frequencies needed at a given time
Causes of hair cell loss:
drugs (streptomycin), diuretics (furosemide), anticancer chemotherapeutics (cisplatin)
How does loud noise lead to hearing loss?
Cell death induced by ROS
What break easily with eposure to noise?
T or F? Tip links can regenerate.
T. within hours
What causes temporary hearing loss after a loud blast of sound?
Breaking of tip links and their regeneration
T or F? Hair cells regenerate.
How many genes have been connected to deafness?
Are the genetic causes of hearing loss dominant or recessive?
Genetic mutatins can cause deafness due to:
no hair cells, incorrect orientation of hair cells, disorganized hair cell bundles, etc.
What frequencies are lost faster with age?
Higher thershold =
greater hearing loss
Are men or women more vulnerable to hearing loss?
loss of inner hair cells w age, fewer cells to signal different sound frequencies AND a loss of outer hair cells - fewer to tune up the freq selectivity of the basilar membrane
Tips are associated with:
the tectorial membrane.
Explain sound induced membrane moves:
Sound enters the cochlear and causes basilar and tectorial mems to move/flex, they pivot around 2 separate points, the relative movement and shear of the fluid bw them will cause the hair bundles to move
Amount of moves depends on:
Louder sounds cause:
bigger amp vibrations, more NT release from hair cells, higher firing rate
How is intensity coded?
In populations of 8th nerve fibers with different thresholds
T or F? A single fiber can respond over the full listening range of 120 dB.
The auditory n. is associated with what ganglion?
T or F? Most of the neurons form the spiral ganglion innervation the outer hair cells.
F. relatively few
There are ___ times as many spiral ganglion cells as outer hair cells
About __ % of the spiral ganglion innervate only one inner hair cell.
What do the spiral ganglion neurons transmit?
inner hair cell activity to the brain
Each inner hair cell is innervated by __-__ auditory fibers.
Why is each inner hair cell innervated by so many auditory fibers?
A single fiber can not respond over the full range of sound. Full intensity range is over a billion to one.
Why have so many 8th n. cells contact each hair cell?
to encode diff sound intensities
What happens when a fiber maxes out at high vibrations?
another fiber takes over for the higher intensity (loudness) range. Divided up to tell you about different parts of the loudness
How is loudness coded?
in populations of 8th n. fibers w different thresholds
Efferent innervation to the cochlear comes from:
neurons in the superior olivary complex of the brainstem terminate in the cochlea, control the outer hair cells (shape and stiffness)
What controls the outer hair cells shape and stiffness?
Efferent innervation from neurons in the sup olivary complex
sounds produced by ears in response to healthy stimulations.
Otoacoustic emissions are used to clinically test:
whether newborn babies have a functional auditory system
How does the otoacoustic emissions test work?
A reflection of the vibrations entering the ear, from hair cells into the brain, and back out through the efferents
Otoacoustic emissions are a byproduct of:
the activity of the outer hair cells in the cochlea
What's the name of the frequency coding map for hearing?
What are there tonotopic map for?
both the hair cells and the nerve cells
At what freq is our hearing most sensitive? What is the lowest B we can hear at that point?
4 kHz, 2?
What happens as we make the sounds louder (higher dB) than the most sensitive frequency?
we can respond to a wider range of freq
T or F? Each hair cell and each auditory nerve axon has a particular characteristic frequency.
What is the freq threshold?
the quietest sound that elicits a response at a particular freq
T or F? Hair cells and axons can respond to nearby frequencies if they are loud enough.
What does the 8th n. activity encode?
freq and loudness of sound
Which axons are firing faster determines:
freq of sound
How many axons are firing, and how fast they are firing determines:
T or F? Cells in the cochlear nuclei can respond like 8th fibers.
T Respond to one freq, and can respond to nearby freq as the sound bc louder
Do the cells in the cochlear nuclei respond to a narrow or wide range of frequencies?
depends on the cell type
What are cells in the cochlear nuclei inhibited by?
higher and lower frequencies
T or F? Some cells in the cochlear nuclei only respond to sound when there is a change in loudness.
How do cells at higher levels respond differently than those in the cochlear nuclei?
many are more selective for a particular frequency than the cells in the cochlear nuclei
What complex property do some cells at higher levels possess?
selectivity for freq modulation, these only respond to changes in freq
T or F? Some cells at higher levels are intensity-tunes; they respond best at a particular loudness.
2 kinds of binaural cues that help in localizing sound sources:
Timing and intensity
Fxns of pinna:
help in localizing where sound is coming from, directional amplifier of sound
How does the pinna act as a directional amplifier of sound?
the frequency of a particular sound will be altered depending upon where it comes from