Midterm 2: Equilibrium and Audition Flashcards
What does the inner ear consist of?
structures dedicated to equilibrium and audition – ie. cochlea
What is the pinna?
visible part of outer ear
What are the two structures that detect changes in motion (acceleration/deceleration) and head position (head tilt) slightly differently?
- otolith organs: sacculus and utricle
- ampullae: at base of semicircular canals
What are the two types of hair cell projections?
- kinocilium
- stereocilia (more of this type)
What does sound consist of?
sinusoidal waves of air pressure changes
ie. tuning fork produces rippling changes in air pressure
What is pitch?
frequency of wave – how many cycles per second
What is volume?
intensity of sound – amplitude of wave
What is membrane potential defined by?
inside relative to outside
What are the two things that affect the flow of ions across membranes?
- concentration gradient
- membrane potential
What is the stapes?
(on oval window) last of 3 bones that vibrate against cochlea, near its base
What is the cochlear base?
thinner, less flexible part of basilar membrane tuned for high frequencies
What is the apex?
thicker, floppier part of basilar membrane tuned for low frequencies
Why doesn’t the loss of high frequency detection in older adults affect their day-to-day much?
communication and much what we use auditory system for is only a very small part of the range we can actually hear
Why do we need to take advantage of temporal information in encoding?
below 3000 Hz is where we spend most of our time listening to sounds ∴ there are also temporal aspects of the activity of these neurons that could give us more information
tonotopy is great along cochlea, but to be as precise as possible to what the pitch of the sound is, need to also take advantage of temporal information
How is auditory information relayed?
relayed through superior olive, inferior colliculus, and MGN of thalamus before reaching cortex
Is there tonotopy in auditory cortex?
yes – via labelled line
- coding of pitch is a continuous parameter (like touch on body)
- particular regions that respond to particular pitches
Why are bat calls so high pitched (high frequency) and loud (high intensity)?
because high pitch sounds are more rigid (bounce off things with more structure), and intensity allows detection of echoes from larger distances
How do classes of echolocating bats differ?
use different cell structures
How are classes of echolocating bats similar?
- use information from echoes
- make FM calls in harmonics
What is harmonics?
integer multiples of a particular frequency
ie. if first one is at 30, second one is at 60, third one is at 90, etc.
What is delay time?
how long it takes echo to come back
measure of distance – b/c sound always travels at a constant speed
What is the inferior colliculus?
intermediate in pathway from cochlea to cortex
How do moths jam bat sonar?
as bat gets closer to moth, call frequency gets higher
- when far away from moth, bat just need to know the general direction of where the moth is
- when closer to the moth, bat needs to know exactly where it is, and therefore increases call frequency to get more and updated information
clicking sounds from moth interfere with bat call frequencies (echolocation)
- bat call frequencies no longer increase reliably (speed varying) because the bat is confused and unsure of where the target is
How is escape behaviour in moths evoked?
moths can often hear the loud ultrasound pulses before bats can hear the returning echoes
