Lecture 12-Hearing

Question 1

What are sound waves:

Answer 1

-When an object vibrates, its movement causes the molecules of air surrounding it to alternately condense and rarely pull apart.
-These fluctuations in air pressure travel away from the source as a sound wave at approximately 700 miles per hour.

Question 2

Explain audition (hearing)

Answer 2

-the human ear can transude fluctuations in air pressure if the length of the soundwave is between 1.7 centimeters and 17 meters.
-corresponds to sound waves that oscillate at frequencies between 20 and 20,000 times per second

Question 3

What are the 3 dimensions of sound?

Answer 3

Loudness: amplitude or intensity of the molecular vibrations

Pitch: frequency of molecular vibration, measured in Hertz (Hz)

Timbre: complexity of the sounds. To help identify the sources of the soundwave.

Question 4

3 anatomical components of the ear:

Answer 4

1. Pinna: where sound is funneled through
2. Tympanic membrane: vibrates when sounds come through the ear canal, transferred to the middle ear.
3. Middle ear; 3 ossicles (small bones): malleus, incus, stapes,

Question 5

Cochlea is divided into 3:

Answer 5

scala vestibuli,
scala media,
scala tympani

Question 6

Organ of Corti, receptive organ contains:

-Basilar membrane:
-Tectorial membrane:
-Hair cells:

Answer 6

-Basilar membrane: bottom
-Tectorial membrane: top
-Hair cells: in the middle

Question 7

Cilia:

Answer 7

hair-like extensions that transduce sound
-cilia of hair cells are connected by tip links; elastic filaments
-The point of attachment of tip link to cilium is called insertional plaque; single ion channel.

Question 8

Inner vs outer hair cells:

Answer 8

-3 times more outer hair cells than inner hair cells (only inner transmit auditory info)

-Outer hair cells contract like muscles to adjust the sensitivity of the tectorial membrane to vibrations

-People who do not have working inner hair cells are deaf
-People that do not have functioning outer hair cells can hear but not well.

Question 9

The effects of loud noise:

Answer 9

-Can easily break the tip links that interconnect cilia, making the hair cells not transmit auditory info
(Tip links can grow back within a few hours, temporary hearing loss)

-This is a protective measure because too much glutamate release into the cochlear nerve causes permanent cell death.
-20% of 20 yr olds have noise induced hearing loss

Question 10

Place coding vs rate coding (2 perceptions of pitch)

Answer 10

Place: approach encoding sensory info, positions of active hair cells in cochlea indicated frequency of the sound wave

Rate: encoded by very low frequencies

Question 11

Loudness, Timber and Overtone:

Answer 11

Loudness: corresponds to the total number of hair cells that are active and their overall activity levels.

Timber: is perceived by assessing the precise mixture of hair cells that are active throughout the entire cochlea.

Overtone: sound wave frequency that occurs at integer multiples of the fundamental frequency

Question 12

Fundamental frequency:

Answer 12

the lowest and most intense frequency of a complex sound. Is what is most often perceived as basic pitch

Question 13

cochlear implant:

Answer 13

-20-24 electrodes positions along length of cochlea. Speech best when frequency position is 250-6500 Hz are stimulated-

Question 14

Phase differences and low frequency sounds:

Answer 14

-we detect the source of continuous low pitch sounds by means of phase differences

-Are the ears detecting compressed air at the same time? If so the source must be equidistant from two ears

Question 15

Loudness and high frequency sounds:

Answer 15

-we detect the source of high pitched sounds by analyzing differences in loudness between the ears.

Question 15

Different parts of the auditory cortex responds best to different frequencies,
Tonotopic representation:

Answer 15

Organization where different frequencies of sounds are analyzed in different places of the auditory cortex, known as tonotopic representation.

Question 16

Primary auditory cortex,
Auditory associated cortex,
Posterior auditory pathway:

Answer 16

Primary auditory cortex: is in the upper section of the temporal lobe, mostly hidden in lateral fissure.

Auditory association cortex: belt and parabelt regions

Posterior auditory pathway: involved in sound localization. This pathway meets up with the vision pathway.

Question 17

Auditory agnosia vs Amusia

Answer 17

Auditory agnosia: brain damage can result in auditory association cortex can cause very specific types of auditory agnosia

Amusia: inability to perceive or produce melodic music, unable to sing or recognize happy birthday songs, they can converse to understand speech and recognize environmental sounds.
Unable to tell consonant and dissonant music (pleasant or unstable)

Question 18

Vestibular system:

Answer 18

detects gravity and angular acceleration of the head; not necessarily definable conscious sensations, it helps with balance, position, and corrects eye movement.
Cochlea: detects sound

Question 19

Semicircular canals,
Cupula,
Vestibular sacs:

Answer 19

Semicircular canals: three ring like fluid filled structures that detect changes in head rotation

Cupula: gelatinous mass found in the ampulla of the semicircular canals, moves in response to the flow of fluid in canals.

Vestibular sacs: a set of two receptor organs in each inner ear that detects changes in the tilt of head.
=responds to force of gravity and inform the brain about the heads orientation