Midterm 2: Equilibrium and Audition

Question 1

What does the inner ear consist of?

Answer 1

structures dedicated to equilibrium and audition – ie. cochlea

Question 2

What is the pinna?

Answer 2

visible part of outer ear

Question 3

What are the two structures that detect changes in motion (acceleration/deceleration) and head position (head tilt) slightly differently?

Answer 3

• otolith organs: sacculus and utricle
• ampullae: at base of semicircular canals

Question 4

What are the two types of hair cell projections?

Answer 4

• kinocilium
• stereocilia (more of this type)

Question 5

What does sound consist of?

Answer 5

sinusoidal waves of air pressure changes

ie. tuning fork produces rippling changes in air pressure

Question 6

What is pitch?

Answer 6

frequency of wave – how many cycles per second

Question 7

What is volume?

Answer 7

intensity of sound – amplitude of wave

Question 8

What is membrane potential defined by?

Answer 8

inside relative to outside

Question 9

What are the two things that affect the flow of ions across membranes?

Answer 9

• concentration gradient
• membrane potential

Question 10

What is the stapes?

Answer 10

(on oval window) last of 3 bones that vibrate against cochlea, near its base

Question 11

What is the cochlear base?

Answer 11

thinner, less flexible part of basilar membrane tuned for high frequencies

Question 12

What is the apex?

Answer 12

thicker, floppier part of basilar membrane tuned for low frequencies

Question 13

Why doesn’t the loss of high frequency detection in older adults affect their day-to-day much?

Answer 13

communication and much what we use auditory system for is only a very small part of the range we can actually hear

Question 14

Why do we need to take advantage of temporal information in encoding?

Answer 14

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

Question 15

How is auditory information relayed?

Answer 15

relayed through superior olive, inferior colliculus, and MGN of thalamus before reaching cortex

Question 16

Is there tonotopy in auditory cortex?

Answer 16

yes – via labelled line

• coding of pitch is a continuous parameter (like touch on body)
• particular regions that respond to particular pitches

Question 17

Why are bat calls so high pitched (high frequency) and loud (high intensity)?

Answer 17

because high pitch sounds are more rigid (bounce off things with more structure), and intensity allows detection of echoes from larger distances

Question 18

How do classes of echolocating bats differ?

Answer 18

use different cell structures

Question 19

How are classes of echolocating bats similar?

Answer 19

• use information from echoes
• make FM calls in harmonics

Question 20

What is harmonics?

Answer 20

integer multiples of a particular frequency

ie. if first one is at 30, second one is at 60, third one is at 90, etc.

Question 21

What is delay time?

Answer 21

how long it takes echo to come back

measure of distance – b/c sound always travels at a constant speed

Question 22

What is the inferior colliculus?

Answer 22

intermediate in pathway from cochlea to cortex

Question 23

How do moths jam bat sonar?

Answer 23

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

Question 24

How is escape behaviour in moths evoked?

Answer 24

moths can often hear the loud ultrasound pulses before bats can hear the returning echoes