W04_03 Hearing

Question 1

what range of frequencies do we hear?

Answer 1

20Hz - 20 kHz

Question 2

speed of sound in air?

Answer 2

343 m/s

Question 3

what kind of joints are at the auditory ossicles?

Answer 3

synovial joints;

these can fuse in later years - less flexibility results in hard of hearing.

Question 4

tensor tympani innervated by which CN?

Answer 4

V3 (T rigeminal)

Question 5

stapedius innervated by which CN?

Answer 5

VII (S even)

Question 6

what do you call the perception of loud sound due to lesion of V3 or VII?

Answer 6

hyperacousis

Question 7

middle ear connects to which cavity via eustacian tube?

Answer 7

nasopharynx.

Question 8

fact: tympanic cavity connected to mastoid air cells.

Answer 8

good.

Question 9

the cochlea spirals around this bony core:

Answer 9

modiolus

Question 10

what are the three spaces in the cochlear cross section?

Answer 10

scala vestibuli;
scala media;
scala tympani

Question 11

in the scala vestibuli/tympani is this fluid:

Answer 11

perilymph (~CSF)

Question 12

in the scala media is this fluid:

Answer 12

endolymph (high [K+])

Question 13

endolymph is secreted by which structure?

Answer 13

stria vascularis (along lateral wall of scala media)

Question 14

this bony protrusion extends from the modiolus into the cochlear space:

Answer 14

spiral lamina

Question 15

this opening connects the scala tympani and scala vestibuli:

Answer 15

helicotrema

Question 16

the organ of corti is covered by and intimately connected to this:

Answer 16

tectorial membrane

Question 17

what’s another name for the organ of corti?

Answer 17

spiral organ

Question 18

what type of neurons transmit sound sense from the cochlea?

Answer 18

bipolar

Question 19

fact: outer hair cells are connected to the tectorial membrane, while inner hair cells are not.

Answer 19

good.

Question 20

when the basilar membrane moves up, the stereocilia move this way:

Answer 20

outward

Question 21

this structure isolates endolymph from perilymph; is connected to hair cells

Answer 21

reticular lamina

Question 22

how does the transduction of sound energy convert to electrical energy via hair cells?

Answer 22

bending stereocilia opens K+ channels;
depolarization opens v-gated Ca2+ channels;
depolarization increase neurotransmitter release to axon.

Question 23

even though outer hair cells outnumber inner hair cells 3:1, 95% of spiral ganglion neurons get inputs from IHCs. what do outer hair cells do?

Answer 23

amplify movement of basilar membrane, especially in low volume sound.

Question 24

name the auditory pathway

Answer 24

cochlea;
ipsilateral cochlear nucleus;
bilateral inferior colliculus;
MGN of thalamus;
1º auditory cortex