(8.1) Auditory Systems

Question 1

Sound waves have a…

Answer 1

frequency and amplitude

Question 2

What is Frequency (=pitch)?

Answer 2

refers to the speed of vibrations (number of vibrations per second - Hertz, Hz)

Question 3

What are Rapid vibrations?

Answer 3

high frequency = high pitch sound

Question 4

What are Slow vibrations?

Answer 4

low frequency = low pitch sound

Question 5

What is Amplitude?

Answer 5

(=loudness) refers to the size of the vibrations

Question 6

What are Large vibrations?

Answer 6

high amplitude = loud sound

Question 7

What are Small vibrations?

Answer 7

low amplitude = quiet sound

Question 8

What is Medium?

Answer 8

substance that surrounds objects

Question 9

What is sound?

Answer 9

Sound is vibrations of medium (like air or water)

Question 10

A sound at a single frequency is a…

Answer 10

pure tone

Question 11

A pure tone looks like a…

Answer 11

sine wave

Question 12

Any sound can be created by…

Answer 12

summing many pure tones (sine waves) at different frequencies and different amplitudes

Question 13

any sound can be ‘decomposed’ (taken apart) into…

Answer 13

its pure tone components (component frequencies)

Question 14

The auditory system works by…

Answer 14

taking apart sounds into their component frequencies and ‘measuring’ the amplitude of each component

Question 15

What can the ear be divided into?

Answer 15

Divided into outer, middle, and inner

Question 16

Auditory sensory neurons are located in the…

Answer 16

inner ear

Question 17

What function does the ear have?

Answer 17

to amplify sound

Question 18

The middle ear amplifies sounds so…

Answer 18

they can pass from air to water (inside the inner ear)

Question 19

The eardrum (tympanic membrane) is much larger than…

Answer 19

the oval window, giving a proportional amplification

Question 20

The ear bones (ossicles) act as levers…

Answer 20

by magnifying the force of vibrations

Question 21

Sound makes ear drum…

Answer 21

vibrate

Question 22

The inner ear consists of the …

Answer 22

cochlea (‘snail’) and the semicircular canals

Question 23

What is the Semicircular canals?

Answer 23

part of the vestibular system

Question 24

What is the cochlea?

Answer 24

The cochlea is a hollow spiral tube (like a snail)

Question 25

The cochlea contains the...

Answer 25

organ of Corti - the sensory organ of hearing

Question 26

The organ of Corti runs along the...

Answer 26

length of the cochlea

Question 27

The organ of corti sit between...

Answer 27

It sits between the two liquid-filled tubes (scala vestibuli and scala tympani) of the cochle

Question 28

What are hair cells?

Answer 28

Hair cells are the sensory neurons of hearing - the neurons that respond to sound vibrations

Question 29

What are the two types of hair cells?

Answer 29

There are two types of hair cells, outer hair cells (OHCs) and inner hair cells (IHCs)

Question 30

What do outer and inner haircells form?

Answer 30

form two sets of rows along the length of the cochle

Question 31

Bending of the 'hairs' (stereocilia) of hair cells pulls...

Answer 31

filaments (strings) connecting stereocilia - These filaments (tip links) are believed to connect mechanically to ion channels in the hair cells, opening them (like lifting a lid by a string) - This causes the hair cells to depolarize and fire action potentials

Question 32

Do hair cells respond fast?

Answer 32

Hair cells respond very fast - less than 10 us

Question 33

Fast responding hair cells allow...

Answer 33

Allows hair cells to fire in synchrony with sound vibrations but only up to about 3 kHz

Question 34

Different frequencies are instead coded by hair cells preferring different frequencies at...

Answer 34

different locations in the cochlea

Question 35

What is tonotopy?

Answer 35

Each location along the basilar membrane is most sensitive to one sound frequency -high frequencies near base, low frequencies near tip (apex)

Question 36

Different sounds cause different patterns of activity along...

Answer 36

the membrane

Question 37

Only the inner hair cells send out...

Answer 37

axons, these are the neurons that respond to sound

Question 38

The outer hair cells (3x as many!) instead receive...

Answer 38

neural input from the auditory nerve

Question 39

in response to stimulation, outer hair cells can...

Answer 39

contract and modify stiffness of basilar membrane - allowing fine tuning of sound sensitivity (can cause tinnitus)

Question 40

Hair cells are easily damaged by...

Answer 40

strong sounds, one cause of deafness

Question 41

Cochlear implants are...

Answer 41

electrodes placed inside cochlea that directly stimulate auditory nerve, mimicking function of hair cells

Question 42

Information travels along axons from the inner hair cells...

Answer 42

to join to form the auditory nerve

Question 43

When information joins the auditory nerve it....

Answer 43

This connects the cochlea with the olive (olivary nucleus) in the brainstem

Question 44

The olive is involved in...

Answer 44

Olive is involved in sound localisation

Question 45

What passes through the MGN?

Answer 45

Auditory information then passes through the MGN in the thalamus to the auditory cortex

Question 46

Sounds are localised by two mechanisms...

Answer 46

Time differences between the ears (<3 kHz) and Intensity differences between the ears (>3 kHz)

Question 47

Time differences between the ears (<3 kHz) are process in...

Answer 47

Processed in the medial superior olive (MSO)

Question 48

Intensity differences between the ears (>3 kHz) are processed in...

Answer 48

Processed in the lateral superior olive (LSO)

Question 49

Sound information is processed in the...

Answer 49

primary auditory cortex, located in the superior temporal lobe

Question 50

Sound localisation utilises...

Answer 50

Utilise differences in sound arrival

Question 51

Sound information is processed in the...

Answer 51

primary auditory cortex, located in the superior temporal lobe

Question 52

Each sound frequency is represented where?

Answer 52

Like in the cochlea, each sound frequency is represented in a different location - tonotopy