Hearing

Question 1

sound waves

Answer 1

1) traveling vibrations of air
- regions of high pressure (compression of air molecules) alternate with regions of low pressure (rarefaction of air molecules)
2) sound energy gradually dissipates farther from the original sound source
- the waves do bend

Question 2

anatomy of the ear

Answer 2

1) external middle and inner ear
- external and middle ears trnasmit sound waves (air) to the inner ear
2) the inner ear
- cochlea: sound waves into nerve impulses => hearing
- vestibular apparatus => equilibrium / balance

Question 3

pinna and ear drum

Answer 3

1) ear, skin covered cartilage)
- collects count waves and channels into the external auditory meatus (Ear canal)
2) ear canal tunnels into tympanic membrane (ear drum)

Question 4

vibration

Answer 4

1) sound waves cause ear drums to vibrate
- alternating higher and lower pressure regions of a sound wave cause the eardrum to bow inward and outward in unison with the wave’s frequency
2) resting air pressure on both sides of the tympanic membrane must be equal for the membrane to move freely

Question 5

eustachian tube

Answer 5

1) balances pressure on both sides of eardrum due to rapid changes in altitude
2) infections originating in the throat can spread via the tube to the middle ear
- fluid accumulation is painful and inhibits sound conduction

Question 6

the middle ear

Answer 6

1) middle ear transfers vibrating movements of the tympanic membrane to the fluid of the inner ear
2) facilitated by three small bones
- malleus, incus, and stapes
3) oval window = the entrance to the fluid filled cochlea

Question 7

cochlea

Answer 7

1) hearing portion of the inner ear
- pea size, snail shape
- coiled tubular system
2) three fluid filled compartments
- cochlear duct
- scala vestibuli
- scala tympani
3) perilymph
- fluid in scala tympani
4) endolymph
- fluid in cochlear duct

Question 8

helicotrema

Answer 8

1) region beyond the tip of the cochlear duct
- perilymph in the scala vestibule and scala tympani is continuous

Question 9

small openings separate the cochlea and middle ear

Answer 9

1) oval window
- separates the scala vestibuli from the middle ear
2) round window
- separates the scala tympani from the middle ear

Question 10

vestibular membrane

Answer 10

forms the ceiling of the cochlear duct separates it from scala vestibuli

Question 11

basilar membrane

Answer 11

forms the floor of the cochlear duct and separated it from the scala tympani

Question 12

organ of corti

Answer 12

on the basilar membrane, houses the sense organ for hearing

Question 13

auditory hair cells

Answer 13

1) mechanoreceptors in the organ of corti
- endolymph movement => deformation of surface hairs => neutral signals
- four parallel rows along basilar membrane
- one row of inner hair cells and three rows of outer hair cells

Question 14

stereocilia

Answer 14

1) 100 hairs
2) protrude from the surface of each hair cells
2) contact the tectorial membrane

Question 15

pressure waves => round window

Answer 15

1) pressure on the membrane of the oval window generate pressure waves in the scala vestibuli
2) perilymph is incompressible
- displacement of the round window
- deflection of the basilar membrane
3) perilymph movement
- scala vestibule => around the helicotrema => into scala tympani => round window
4) membrane of the round window bulge outward into the middle ear
5) pressure waves in the scala vestibuli => vestibular membrane => cochlear duct => basilar membrane
6) the basilar membrane vibrates in synchrony with the pressure wave => the organ of corti vibrates => the hair cells move

Question 16

electromotility

Answer 16

1) rapidly adjusting the length of the hair on outer hair cells in response to changes in membrane potential
- depolarization => shorten
- hyperpolarization => lengthen
- changes in length amplify or accentuate the motion of the basilar membrane
2) outer hair cells enhance the response of the inner hair cells
- make inner hair cells sensitive to sound intensity and increase discrimination between various pitches of sound

Question 17

tip links

Answer 17

1) stereocilia of each hair cells are organized into rows of graded heights ranging from short to tall
2) tip links (cell adhesion molecules) link adjacent rows)
- attached to mechanically-gated

Question 18

pitch ( tone)

Answer 18

1) determined by frequency of vibrations
2) greater frequency means higher pitch
3) we are sensitive to 20-20,000 Hz but highest sensitivity to 1000-4000

Question 19

pitch discrimination

Answer 19

1) depends on the shape and properties of the basilar membrane
- narrow and stiff near oval window
- wide and flexible near the helicotroma
2) different regions of the basilar membrane vibrate maximally at different frequencies
- nearest the oval window (narrow) vibrates best with high-frequency pitches

Question 20

timbre

Answer 20

1) quality depends on overtones
- additional frequencies that are superimposed on the fundamental pitch or tone
2) allows the source of sound waves to be distinguished
3) basilar membrane is fine tuned
4) overtones can cause many points on the basilar membrane to vibrate simultaneously but less intenselyintensity than the fundamental tone

Question 21

intensity

Answer 21

1) loudness is dependent on amplitude of sound waves
2) loudness is measured in decibels (dB)
3) causes greater hair bending

Question 22

deafness

Answer 22

1) temporary or permanent
2) partial or complete

Question 23

neural presbycusis

Answer 23

1) damage to hair cells over time
2) most common cause of partial hearing loss
3) common everyday sounds even at moderate levels
4) age related
5) 65 years old = 40% of cochlear hair loss

Question 24

conductive deafness

Answer 24

1) sound waves are not adequately conducted through the external and middle portions of the ear
2) perilymph and endolymph do not vibrate
3)causes
- blockage of ear canal
- rupture of ear drum
- middle ear infection with fluid
- bone adhesion
- osteoporosis of ossicles

Question 25

sensorineural deafness

Answer 25

1) sound waves are transmitted to the inner ear but they are not translated to nerve signals
2) causes
- defect with organ of corti
- defect with auditory nerves
- defect with ascending auditory pathways or auditory cortex