hearing part 2

Question 1

3 main parts of the ear

Answer 1

outer
middle
inner

Question 2

outer ear 3 main parts

Answer 2

pinna: focus sound towards ear canal and determine direction
auditory canal: protects eardrum and enhances frequency
eardrum/tympanic membrane: transmits sound as vibration to middle ear

Question 3

middle ear function and parts

Answer 3

eardrum causes ossicles to vibrate
1. malleus (hammer)
2. incus (anvil)
3. stapes (stirrup) - transmits vibrations to oval window
purpose is to amplify sounds by concentrating pressure from large surface to small
also uses mechanical leverage of stapes

Question 4

middle ear muscles

Answer 4

• tensor tympani
• stapedius
  control sound by contracting to dampen affect

Question 5

auditory reflex

Answer 5

stapedius contracts in response to high sound levels and own speech
reduces transmission of low frequency sound
protects inner ear and blocks out internal sounds

Question 6

inner ear

Answer 6

semicircular ducts- balance and equilibrium
part of vestibular system
cochlea- contains sensory receptors for sound

Question 7

cochlea 3 compartments

Answer 7

scala vestibuli - vestibular duct
scala tympani - tympanic duct
cochlear partition- cochlear duct

Question 8

purpose of cochlea

Answer 8

vibration of oval window from stapes sends pressure waves down and up scala vestibuli and tympani

Question 9

3 parts of cochlear partition

Answer 9

tectorial membrane
organ of corti- inner (1 row) and outer (3 rows) hair cells
basilar membrane

Question 10

how many inner and outer hair cells

Answer 10

3,500 inner hair cells and 12,000 outer hair cells

Question 11

how do the parts of the cochlea move in relation to pressure waves

Answer 11

basilar moves up and down
tectorial moves back and forth
cilia of hair cells bends

Question 12

hair cells

Answer 12

transudction: mechanical opening conducted to neural signal
- changes in membrane potential leads to release of NT
open and closing of K ion channels

Question 13

what is phase locking

Answer 13

action potentials in auditory nerves are synchronized with sound waves

• b/c movement of cilia follows the changes in presure
• at low frequencies firing can occur with each wave
• at high frequencies firing is intermittant because it cannot keep up

Question 14

what is Bekesys place theory of hearing

Answer 14

the base of basilar membrane is narrow and stiff
apex is wide and floppier
- position of sound depends on frequency
- location of maximum firing indicates its frequency
called frequency representation (low at apex, high at base)

Question 15

cochlear amplifier

Answer 15

shows that basilar membrane is not a passive object (he looked at dead animals)
outer hair cells can change shape to amplify and focus motion of basilar membrane

Question 16

tonotopic map

Answer 16

location of maximum response as a function of frequency

Question 17

frequency tuning curves

Answer 17

each auditory nerve cell responds to certain frequencies based on position along cochlea
- when outer hair cells are destroyed you lose certian frequencies because cochlear amplifier is important for frequency tuning

Question 18

ear summary

Answer 18

sound waves come in, focused by pinna down auditory canal, eardrum vibrates, pushes on oval window and sends vibrations down cochlea where hair cells convert to neurla signals which are received by auditory nerves and conducted out
transduces sound waves into a tonotopic neural signal