Sound and neural transduction of sound

Question 1

What causes sound?

Answer 1

Things that vibrate

Question 2

What does a Fourier analysis do?

Answer 2

Breaks up a complex waveform into its constituent frequencies and amplitudes

Question 3

What does a Spectrogram represent?

Answer 3

A sandwich of rotated Fourier analyses over time (amplitude is represented by the Z axis of color)

Question 4

True/False? Your cochlea is essentially a Fourier analyzer

Answer 4

True/False? Your cochlea is essentially a Fourier analyzer

Question 5

The base of the cochlea is (more/less) narrow than its apex

Answer 5

More narrow (despite like all the literature?)

Question 6

(low/high) frequencies of sound are transduced in the (apex/base), whereas (high/low) frequencies are transduced in the (base/apex)

Answer 6

High frequencies - Apex

Low frequencies - Base

Question 7

What is the order of the ossicles from Tympanic membrane to oval window?

Answer 7

Malleus, Incus, Stapes

Hammer, Anvil, Stirrup

Question 8

Sound from the oval window travels through the Scala _____ to the apex, then back through the Scala _____ until the round window

The Scala _______ is largely unperturbed

Answer 8

Scala Vestibuli

Scala Tympani

Scala Media

Question 9

Between the tympanic membrane and the oval window, which is stiffer?

Answer 9

Oval window (shirt fluttering vs poking a finger)

Question 10

True/False? Air pressure in the middle ear could dampen sound outside the cochlea

Answer 10

True

Question 11

True/False? A person needs to be alive and have their nerves intact to measure the mechanical frequency selectivity of their cochlea

Answer 11

False (cadavers are often used since they don’t mind having their skulls sawed open)

Question 12

Describe the structure of the organ of Corti

Answer 12

Basilar membrane (sits between scalas tympani and media)

made p of outer and inner hair cells, nerve fibres and the archc of Corti

Tectorial membrane sits on top, connected by the hair cells

Question 13

Influx of what ion causes depolarization in hair cells?

Answer 13

Potassium

Question 14

What are 2 differences between inner and outer hair cells?

Answer 14

Inner hair cells are afferent (transmit sound to the brain)

Outer hair cells are mostly efferent (some afferent, but mostly serve to reduce movement of basilar membrane)

IHCs are much fewer in number than OHCs

Question 15

What happens when outer hair cells shrink?

Answer 15

Shrinking enhances shearing forces to boost sensitivity

Happens at a very small location along the membrane, allowing for frequency selectivity