Lecture Notes: Vertebrate Ear

Question 1

external structure

Answer 1

pinna- reception

auditory canal- transmission

Question 2

middle ear structure

Answer 2

a. tympanic membrane, vibrates, amplification
b. ear bone: malleus, incus, stapes amplification and transmission
c. eustachian tube

Question 3

eustachian tube

Answer 3

connects the middle ear to throat for pressure equilibrium

Question 4

inner ear

Answer 4

oval window vibrates

cochlea:
divided into 3 canals by basilar and reissner’s membrane
organ of court with hair cells (stereo cilia in contact with tectorial membrane)

Question 5

ossicles

Answer 5

malleus, incus, stapes

Question 6

steps to hearing

Answer 6

1. auditory canal
2. tympanic membrane
3. ossicles
4. oval window
5. pressure waves through cochlear canals
6. waves flex basilar membrane
7. bends stereo cilia in tectorial membrane (organ of court)
8. movements traduced as AP’s in cochlear nerve

different sets of hairs activated at different sites

Question 7

Proximal end vs distal end of basilar membrane

Answer 7

proximal side is thin and stiff, suited for picking up high frequency
distal side is thick and flexible,suited for picking up low frequency

Question 8

Balance and equilibrium

Answer 8

semilunar canals (at right angles with each other) are filled with endolymph
as endolymph moves it displaces a chapel sitting on of stereo cilia of hair cells of ampullae

vestibule with two chambers: saccule and utricle
stereo cilia of hair cells covered by a layer of gelatin with otoliths of calcium carbonate, and as head moves, the otoliths move and bend the stereocilia