Hearing

Question 1

Physical properties of sound

Answer 1

• Amplitude (dB)
• Frequency (Hz): waves per second
• Purity

Question 2

Explain the pathway of sound

Answer 2

the outer ear, auditory canal, vibrate eardrum, sets bones of the middle ear in motion (this amplifies waves 20x), waves vibrate oval window, vibrations cause fluid in the cochlea to bend the hair cells, the stimulation of the hair cells transduces sound vibrations to electrical impulses, electrical impulses can generate action potentials in the auditory nerve which are sent to the thalamus then the auditory cortex for processing and interpreting

Question 3

Part of the inner ear

Answer 3

• semicircular canals

- cochlea

Question 4

What are the functions of the semicircular canals?

Answer 4

These have a key role in maintaining balance

Question 5

What is the cochlea?

Answer 5

• The site of transduction
• The basilar membrane running through the cochlea contains hair cells which are sound sensory receptors
• Vibrations on the oval window send movement through the cochleas fluid-filled cavity which can bend these hair cells

Question 6

Explain hair cells

Answer 6

• Sound sensory receptors
• named hair cells because the cilia that extend from the top of the cell into the cochlea fluid look like small hairs
• Vibrations of the oval window can cause these to bend
• The bending opens ion channels in the membrane of the cell which alters electrical properties causing a transmitter release which results with synapse of cochlear nerve cells

Question 7

What is the auditory nerve made up of?

Answer 7

• Axons of the cochlear nerve cells

Question 8

What are the two methods the cochlea uses to code for the frequency of sounds?

Answer 8

• Phase locking

- Phase coding

Question 9

Explain phase locking

Answer 9

• When cilia bend at the same frequency of the sound wave

- happens below 3000 Hz

Question 10

Explain phase coding

Answer 10

• When certain frequencies activate cells in particular locations
• smaller cells are stimulated to higher frequencies
• larger cells are stimulated to lower frequencies

Question 11

How are we able to interpret that some sounds are loud?

Answer 11

bigger vibrations -> hair cells greatly stimulated -> very fast action potential rate -> loud sound recieved

Question 12

What is the auditory pathway?

Answer 12

Cochlea -> inferior colliculus (located in brain stem) -> medial geniculate nucleus (MGN) of the thalamus -> auditory nerve in the temporal lobe

Question 13

How does hearing loss occur?

Answer 13

-Hair cells in the cochlea are damaged or have died
can be: age-related
noise exposure

Question 14

What is the link between noise exposure related hearing loss and iPods?

Answer 14

iPods volume can go up to 115-120 dB
This is about the same loudness/ volume of a rock concert

NOTE*** 10 dB increase is a 10x intensity which is twice perceived loudness

Question 15

What is the basilar membrane?

Answer 15

The membrane in the cochlea that contains the auditory sensory receptor hair cells