Auditory Flashcards
(66 cards)
1
Q
What is sound?
A
- a compression wave generate by vibrating air molecules
2
Q
What can complex sounds be represented as?
A
- the sum of multiple simple sine waves
3
Q
What does the amplitude of the sound correspond to?
A
- intensity
4
Q
What does the speed of the sound depend on?
A
- the conduction medium
5
Q
We and other animals are ____ to some frequencies than others.
A
more sensitive
6
Q
What are the lower and upper limits of frequency sensitivity called?
A
- lower limit: threshold
- upper limit: perception limit
7
Q
We can hear sounds within the range of frequencies of what?
A
- 20 - 20K Hz
8
Q
Small mammals are sensitive to ____ frequencies.
A
higher
9
Q
What do animal auditory systems emphasize detection of?
A
- frequencies that are in their vocalizations
10
Q
What kind of frequencies do echolocating animals rely on?
A
- very high frequency vocalizations to resolve spatial features of target
11
Q
What specifications in frequency range do animals that have to avoid predators have?
A
- often emphasize the low frequencies that conduct through the ground from movements of approaching predators
12
Q
What are the different parts of the middle ear?
A
- malleus
- incus
- stapes
- tympanic membrane
- oval window
13
Q
What do the external and middle parts of the ear do?
A
- collect sound waves and amplify their pressure to transfer that energy to the fluid filled cochlea of the inner ear
14
Q
What are the parts of the external ear?
A
- pinna (upper lobe)
- concha (cartilage rings)
- auditory meatus (tunnel)
15
Q
How does the external ear amplify and focus energy?
A
- does so selectively for frequencies around 3 kHz by passive resonance effects
16
Q
What is the other function of the outer ear?
A
- contributes to localization of sound in space
- specifically elevation of sound source
17
Q
Why is it a problem that the sensory “detectors” are immersed in fluid?
A
- the sound signal is due to moving air
- fluid is much heavier than air
18
Q
What is the tympanic membrane?
A
- “ear drum”
- large relative to the base of the stapes where contact is made (concentrating large area)
19
Q
What are the ossicles?
A
- inner ear bones
- malleus, incus, stapes
20
Q
What function does the lever action of the ossicles provide?
A
- provides mechanical advantage to increase pressure on stapes
21
Q
What are the muscles called that regulate efficiency of transmission of sound to the inner ear and how do they function?
A
- tensor tympani and stapedius
- control the tension on the bone joints by a reflex response to loud sounds
22
Q
Why do crickets have central circuits that gate out input from their singing?
A
- because they don’t have a peripheral system to attentuate loud sounds and they do not block their own song
23
Q
Which sounds is a 60 yr old particularly insensitive to?
A
- average loss of 35 dB from 500 Hz to 4 kHz
- birds chirping, whspering, alarm clock, leaves rustling, tap dripping
24
Q
What is presbycusis or presbyascusis?
A
- high frequency hearing loss with age
25
Where are the auditory sensory cells located? What nerves are also located here?
- in the inner ear
| - vestibular nerve and auditory nerve
26
What are some important parts of the cochlea?
- basilar membrane
- inner hair cells
- outer hair cells
27
What are the ear chambers called?
- scala vestibuli
- scala media
- scala tympani
28
What is the general function of the inner hair cells?
- convey sound information to the CNS
29
What are the mechanical "tuning" properties of the basilar membrane?
- the base is tuned for high frequencies
| - apex is tuned for low frequencies
30
What is tonotopy?
- topographical mapping of frequency
| - set up in cochlea and retained by projections to brainstem, thalamus and cortex
31
What does the tonotopy result primarily from?
- the physical resonant properties of the basilar membrane
32
What do the deflections in frequency that occur across a large section of the basilar membrane indicate?
- tuning is not very "sharp"
33
Sensorineural hearing loss can be "treated" with what?
- a cochlear implant
- it has an external microphone and implantable cochlear stimulator
- better to have earlier so brain can learn ear shape
34
The topography of the primary auditory cortex corresponds to?
the topography of the cochlea
35
What does deflecting a hair bundle cause?
- a change in membrane potential
36
What is the threshold for detecting a deflection as a change in voltage above noise?
about 100 nm
37
What do cochlear movements cause?
changes of voltage in hair cells
38
When the hair cells are "stretched" what happens?
- tip links pull the k channels open and K+ influxes
| - depolarization
39
How is an inward current of K+ possible?
- because external K+ concentration is high
40
What are voltages measured relative to?
- perilymph due to low K+ here
41
Why is inward K+ current generated in the distal part of each cilium?
- due to a positive EK in the cilium because cilia are floating in high K+ endolymph (in scala media)
42
What is needed to maintain the high K concentration?
- stria vascularis
43
_____ modulation is presynaptic to the _____ terminal.
- efferent
| - afferent
44
What transmits APs to CNS from hair cell excitation?
- secondary sensory cells
45
What is the "best" frequency?
- frequency where quietest sound will produce a measurable change in firing rate
46
What do type I spiral ganglion neurons connect to?
- single ending radially connected to inner hair cells
| - each inner hair cell is connected to multiple type I afferents
47
What do type II spiral ganglion neurons connect to?
- these are small, unmyelinated neurons
- branch to connect to about ten outer hair cells in the same row
- one type II afferents per outer hair cell
48
What do outer hair cells do in response to sound?
- they contract
49
How do the outer hair cells contract?
- a deflection of the hair bundle opens mechanotransduction channel that depolarizes the cell
50
What is prestin and what is it's function?
- a transmembrane motor protein
| - depolarization causes up to 3nm of shortening of prestin
51
Where is the outer hair cell tip embedded?
- in the base of tympanum which adds to the sound driven wave of motion of the tympanum (acoustical amplifier)
52
What does the loss of outer hair cells result in?
- 100 fold loss of sensitivity to sound
53
Where does the outer hair cell afferents innervate?
- cochlear nuclei
- lateral superior olive
- medial superior olive
- floor of 4th ventricle
54
What do some fibres of the medial superior olive do for outer hair cells?
- regulates sensitivity of outer hair cell
| - control gain of outer hair amplifier
55
Where is the first place that auditory information interacts with the motor system?
- inferior colliculus
56
How is the auditory space map formed in the inferior colliculus?
- synthesized from brainstem inputs
57
What kinds of sounds does the inferior colliculus process?
- complex temporal patterns
- ex. frequency modulated sounds or sounds of specific duration
- sounds specific to predators or intraspecific communication
58
What sound is processed in the superior olivary complex?
- first place where information from both ears interacts
- initial site where spatial locations of sounds is processed
- largely mediated by external ears
59
How do we process sound localization?
- based on relative intensity (solid objects (head) shadow shorter wavelengths)
- synaptic potentials from left and right ears summate to bring MSO cells to threshold
60
What could be used to increase MSO cells sensitivity to time differences?
- local lateral inhibition
61
How is relative intensity resulting from head shadowing encoded?
1. stronger stimulus (from left or right) excites lateral superior olive
2. this stimulus inhibits the other side of lateral superior olive via medial nucleus of the trapezoid body
3. net excitation on one side, net inhibition on the other which travels to higher centers
62
What is crossed inhibition?
- same principle as relative intensity
- side activated first blocks activation of other side
- important note: electrical synapse, fast?
63
What are the key features of vestibular hair cells?
- low frequency sensitive
- increased calcium causes slippage of the myosin on the actin filament
- decreased calcium allows tension to be restored to spring
64
What is the purpose of vestibular hair cells?
- to reset the tension in the tip link
- allows the hair cell to adapt to sustained activation and remain responsive to changes in position or intensity
- redefines dynamic range
65
Do mammals have vesitbular hair cells?
- no
| - mammalian hair cells are sensitive to voltage and extracellular calcium but not intracellular calcium
66
What do low frequency vestibular hair cells have that mammalian auditory hair cells do not?
- calcium channels at the tension release mechanism
| - mammalian have no calcium channels here
