problem 6 - the ear

Question 1

parts of the outer ear

Answer 1

• the pinnae
• auditory canal
• tympanic membrane (ear drum)

Question 2

parts of the middle ear

Answer 2

the ossicles:
* malleus/hammer
* incus/anvil
* stapes

• oval window

Question 3

parts of the inner ear

Answer 3

• cochlea
• vestibular canal
• middle canal
• tympanic canal
• auditory nerve
• eustachian tube
• organ of corti
• basilar membrane
• reissner’s membrane
• tectorial membrane

Question 4

the pinnae

Answer 4

the structures that stick out from the sides of the head

Question 5

auditory canal

Answer 5

a tubelike structure about 3 cm long - protects the delicate structures of the middle ear
* has ear wax for protection

Question 6

tympanic membrane (ear drum)

Answer 6

vibrates in response to sound, boundary between outer and middle ear

Question 7

the ossicles

Answer 7

1. The malleus (aka the hammer): is set into vibration by the tympanic membrane & transmits its vibrations to the incus
2. The incus (aka the anvil): transmits its vibration to the stapes
3. The stapes (aka stirrup): transmits its vibrations to the inner ear by pushing on the membrane covering the oval window

all 3 amplify the sound

Question 8

the cochlea

Answer 8

• a snail-like structure
• liquid inside the cochlea is set into vibration by the movement of the stapes against the oval window

has 3 chambers:
1. vestibular canal - Reissner’s membrane (between vestibular and middle canal)
2. middle canal - basilar membrane (between middle and tympanic canal, forms the base of the Cochlear partition)
3. tympanic canal

Question 9

organ of corti

Answer 9

A structure on the basilar membrane of the cochlea composed of hair cells and dendrites of auditory nerve fibers

Question 10

hair cells

Answer 10

are the receptors for hearing
* the cilia (which protrude from the tops of the cells): are where the sound acts to produce electrical signals

two types of hair cells:
1. Inner: responsible for transduction
2. Outer: responsible for increasing vibration of the BM

Question 11

bekesy’s place theory of hearing

Answer 11

States that the frequency of a sound is indicated by the place along the cochlea at which nerve firing is highest
* low frequencies cause max activity at the apex of the BM
* high frequencies cause max activity at the base (by the stapes) of the BM

Question 12

auditory masking

Answer 12

ability to hear 1 sound is decreased by the presence of other tones

Question 13

auditory masking experiment: egan & hake

Answer 13

• Threshold is highest around the masking tone→intensity (dB) has to be much higher for the frequency to be detected in presence of the masking tone
• Masking stimulus is asymmetrical→higher frequencies are affected more than lower frequencies

Question 14

phase locking

Answer 14

Firing of a single neuron at one distinct point in the cycle of a sound wave at a given frequency
* The neuron need not fire on every cycle, but each firing will occur at the same point in the cycle

Question 15

temporal coding

Answer 15

the connection between the frequency of a sound stimulus and the timing of the auditory nerve fiber firing

Question 16

conductive hearing loss

Answer 16

Blockage of sound from reaching the receptors

Question 17

sensorineural hearing loss

Answer 17

damage to the hair cells or to the auditory nerve

Presbycusis: loss of sensitivity that is greatest at higher frequencies - accompanies aging & affects males more severely

Noise-induced hearing loss: occurs when loud noises cause degeneration of the hair cells

Question 18

what & where streams for hearing

Answer 18

Ventral (what) stream: starts in the anterior part of the core & belt - identifies sounds

Dorsal (where) stream: starts in the posterior part of the core & belt & extends to the parietal cortex & the prefrontal cortex - locates sounds