6-Audition

Question 1

Which key structure contains hearing receptors?

name

Answer 1

basilar membrane

Question 2

Which aspect of the basilar membrane varies across species?
Which aspect of hearing does this affect and how?

Answer 2

Length

Longer basilar membrane = wider range of frequencies can be percieved

Question 3

Which category of species typically can process the widest range of frequencies?

eg: reptiles, birds, fish…

Answer 3

mammals

Question 3

What does the eardrum move in response to and how?

Answer 3

density of air (pressure) moves the eardrum

more dense air –> ED moves inwards
less dense air –> ED moves outwards

Question 4

What are the 3 quantitative qualities of a sound wave?
How do we process these qualities?

Answer 4

wavelength or frequency: pitch
amplitude: loudness
purity: timbre (complexity of sound)

Question 5

How do we measure loudness?

quality + unit + example value

Answer 5

Amplitude: dB - decibels (logarithmic scale)

eg: conversation is roughly 60dB

Question 6

How do we measure pitch?

quality + unit + example value

Answer 6

wavelength or frequency: Hz - Hertz

eg: humans can hear between roughly 100 - 10 000 Hz

Question 7

How do we measure timbre (complexity of sound)?

quality + example explanation

Answer 7

purity: overlaying sound waves

eg: we can hear the difference between a guitar and a violin, even if they play the same note, because they have different timbre

Question 8

Ear anatomy 3 basic segments

name + purpose

Answer 8

External: detect pressure changes
Middle: amplification of sounds
Inner: changes in fluid pressure

see diagram in notes

Question 9

External ear anatomy

labels + purpose (see diagram in notes)

Answer 9

• pinna: directs sound waves to ear canal
• auditory canal: amplify sound waves
• !ear drum: vibrates with sound waves

!also called tympanic membrane

Question 10

Middle ear anatomy

labels + purpose (see diagram in notes)

Answer 10

• ossicles: further amplify sound waves
  
  • stirrup (or stapes)
  • anvil
  • hammer
• oval window: vibrates with sound

Question 11

Inner ear anatomy

labels + purpose (see diagram in notes)

Answer 11

• cochlea: transfer fluid motion to neural impulses
  
  • round window: accommodates fluid movement
  • basilar membrane: moves up and down with

Question 12

How does the basilar membrane move in response to the oval window?

Answer 12

if oval window pushes fluid in, basilar membrane moves down

fluid out, membrane up

Question 13

Which portions of the basilar membrane vibrate for different frequency sounds?

Answer 13

high frequency: base - thinner portion, closer to oval window

low frequency: apex - wider portion, further from oval window

see diagram for visual explanation

Question 14

Auditory neural pathway (from hair to cortex)

structures + order (see diagram in notes)

Answer 14

• hair cell
• bipolar cell
• cochlear nerve
• medulla: cochlear nucleus (dorsal and ventral streams)
• pons: superior olivary nucleus
• midbrain: inferior colliculus
• temporal lobe: primary auditory cortex (A1)

Question 15

What are the differences between inner and outer hair cells?

Answer 15

Inner:
- less numerous
- more connections to brain
- send pitch information
- axons to these are thick and myelinated

Outer:
- more numerous (4x more)
- fewer connections to brain
- amplify sound stimulus
- axons to these are thin and unmyelinated

Question 16

How is the auditory system organized in the brain?

Answer 16

tonotopic organization: organized by frequency in primary auditory cortex

Question 17

How do humans localize sounds?

anatomy responsible (if applicable) + metric + meaning

Answer 17

Superior olivary complex:
- Medial superior olive: time it takes for sound to reach each ear –>direction of sound source
- Lateral superior olive: intensity of high Hz sounds between ears –> direction

Pinna cues: changes sound with angle of entry –> direction, elevation

Question 18

What happens if we alter the pinna shape of an individual?

Answer 18

Their localization ability is greatly hindered until they adapt to the new pinna cues caused by the change in shape

They will need to readapt once the changes in shape are removed

Question 19

Echolocation

definition + characteristics they perceive

Answer 19

Process by which a reciever emits sound pulses and analyzes the returning echo to perceive and map objects in the environment

Echoes will vary with an objects:
- proximity
- motion (still vs moving)
- texture

Question 20

Co-evolution

definition

Answer 20

When one species evolves traits which then influence the evolution of traits in another species

eg: the parasite birds evolving similar inner beak markings