Physiology of Hearing

Question 1

What is the function of the external ear?

Answer 1

receives sound

channels sound to tympanic membrane

Question 2

What is the structure of the middle ear?

Answer 2

air filled cavity in temporal bone

Question 3

What is the function of the middle ear?

Answer 3

amplifies sound waves and transmits them to fluid filled inner ear

Question 4

Where are the ossicles located?

Answer 4

middle ear

Question 5

What is the function of the ossicles?

Answer 5

conduct sound vibrations from tympanic membrane to oval window

Question 6

What is impedance?

Answer 6

a mediums resistance to movement

pressure waves when in relation to sound

Question 7

What is impedance matching?

Answer 7

amplification of pressure so that there is sufficient energy to move through fluid

Question 8

When does impedance matching occur?

Answer 8

transfer of incoming vibration from the comparatively large, low impedance tympanic membrane to the much smaller high impedance oval window

Question 9

What is the importance of impedance matching?

Answer 9

prevents sound loss

Question 10

What are the oval and round windows?

Answer 10

two openings of the cochlea to the middle ear

Question 11

What is the function of the oval and round windows?

Answer 11

permit transmission of pressure wave in enclosed canal and vibration of the basilar membrane

Question 12

What is the cochlea?

Answer 12

part of the auditory system of the inner ear

shell shaped part of the bony labyrinth

Question 13

What is the scala media?

Answer 13

endolymph filled cavity inside the cochlea between the tympanic duct and the vestibular duct

Question 14

What is the ionic composition of endolymph?

Answer 14

high potassium concentration
low sodium concentration
negligible calcium

Question 15

Where is perilymph located?

Answer 15

fills the scala vestibuli and tympani

Question 16

What is the ionic composition of perilymph?

Answer 16

high sodium concentration

low potassium and calcium concentration

Question 17

Where does scala vestibuli begin?

Answer 17

oval window

Question 18

Where does scala tympani end?

Answer 18

round windows

Question 19

What is the advantage of endolymph having a high potassium concentration and perilymph having a low potassium concentration?

Answer 19

only apical end of hair cells in endolymph
passive potassium influx at apical end
passive potassium efflux at other end
saves ATP

Question 20

What is the organ of Corti?

Answer 20

sensorineural organ of the cochlea

Question 21

What is the organ of Corti composed of?

Answer 21

supporting cells
basilar membrane
cochlear hair cells

Question 22

What is transduction?

Answer 22

conversion of sound vibrations (mechanical energy) to electrical energy

Question 23

How does transduction occur in the organ of corti?

Answer 23

sound waves delivered to the oval window are transmitted to the perilymph and vibrate the basilar membrane
cilia of the cochlear cells are bent by the vibration of the basilar membrane

Question 24

Where are the cell bodies of the afferent fibres from the organ of Corti?

Answer 24

spiral ganglion of the cochlear nerve

Question 25

What is the auditory pathway?

Answer 25

vestibulocochlear nerve (CN VIII) - cochlear nuclei - superior olivary cortex - lateral lemniscus - inferior colliculus - thalamus - primary auditory cortex

Question 26

What is the pneumonic to remember the auditory pathway?

Answer 26

``` ECOLI E - Eighth CN C - Cochlear nuclei O - superior Olivary complex L - Lateral Lemniscus I - Inferior colliculus ```

Question 27

Where is the auditory cortex located?

Answer 27

superior temporal gyrus

Question 28

What connects the middle ear to the nasopharynx?

Answer 28

eustachian tube

Question 29

What is the role of the eustachian tube?

Answer 29

opens briefly during swallowing and yawning to allow equalisation of pressure either side of the tympanic membrane

Question 30

What muscles open the eustachian tube?

Answer 30

tensor veli palatini | levator palatine