L8: Auditory Senses

Question 1

conduction pathway sequence of the ear

Answer 1

tympanic membrane
ossicles
oval window

Question 2

auditory ossicles

Answer 2

malleus
incus
stapes

Question 3

malleus

Answer 3

attaches tympanic memb to incus

Question 4

incus

Answer 4

intermediate bone between malleus and stapes

Question 5

stapes

Answer 5

stirrup shape for stapedial artery to pass

connects incus to oval window

Question 6

openings of the middle ear

Answer 6

oval window

round window

Question 7

oval window

Answer 7

opens into the scala vestibuli

Question 8

round window

Answer 8

a membrane covered window at the end of the scala tympani

Question 9

muscles of the middle ear

Answer 9

tensor tympani

stapedius

Question 10

tensor tympani

Answer 10

inserts on the malleus

pulls handle of malleus inward

Question 11

stapedius

Answer 11

inserts on the stapes and pulls it outward

Question 12

function of middle ear muscles

Answer 12

contract reflexively in response to loud sounds

in order to dampen the vibrations

Question 13

impedance matching

Answer 13

tympanic memb is 17x smaller than stapes surface area

this increases the force from ossicular lever system to cochlear by 22x

Question 14

importance of impedance

Answer 14

fluid has greater inertia than air and thus requires this increase in force in order to create vibration in fluid

Question 15

who provides impedance

Answer 15

tympanic memb and ossicles

Question 16

cochlea components

Answer 16

3 side by side coiled tubes

scala vestibuli, media, tympani

and reissner’s memb also called vestibular memb

Question 17

what does reissner’s membrane separate?

Answer 17

scala media from scala vestibuli

Question 18

explain width of reissner’s membrane

Answer 18

is so thin that the scala media and vestibuli are considered a single chamber when discussing sound

Question 19

purpose of reissner’s membrane

Answer 19

keeps special fluid w/in scala media

Question 20

what does the basilar membrane separate

Answer 20

scala media from scala tympani

Question 21

trace basilar membrane fibers

Answer 21

project from modiolus of cochlea outer wall
to
basilar membrane

but the distal fiber ends are not fixed

these fibers can vibrate

Question 22

function of basilar fibers

Answer 22

transfer vibrations

stiff short fibers near oval window = higher frequency

long limber fibers near apex of cochlea = low frequency of vibration

Question 23

function of organ of corti

Answer 23

generates nerve impulses in response to vibration of basilar membrane

Question 24

sensory receptors of organ of corti

Answer 24

hair cells
single row of internal cells
3-4 rows of external cells

Question 25

contents of scala media and tympani

Answer 25

endolymph

perilymph

Question 26

hair cell stimulation

Answer 26

stim nerve fibers that lead to the spiral ganglion of corti

Question 27

how do hair cells transmit signals

Answer 27

stereocilia of hair cells touch or embed in tectorial memb

bending of the hair cells = depolarization

bending in opposite direction = hyperpolarization

Question 28

outer ends of hair cells are tightly attached to ?

Answer 28

reticular lamina
supported by rods of corti
which are attached to basilar fibers

thus creating a rigid unit

Question 29

axons of neurons in the ganglion

Answer 29

axons are sent to upper medulla via cochlear nerve

CN VIII

Question 30

basilar fibers length increases from ?

Answer 30

oval window to apex of cochlea

Question 31

diameter of basilar fibers decrease from ?

Answer 31

oval window to apex of cochlea

Question 32

mvt of basilar fibers causes mvt of _________ , which causes shearing forces on _______ against the _______________. thus whenever basilar membrane moves ?

Answer 32

reticular lamina
hair cells
tectorial memb

hair cells become excited

Question 33

hair cell stereocilia

Answer 33

about 100 on their apical border

are longer on side farther from modiolus

Question 34

depolarization of hair cells

Answer 34

occurs when cilia are bent towards longer ones

a tensile force is created on shorter ones

creates mechanical transduction that opens K channels

Question 35

endolymph

Answer 35

high K conc
low Na conc

+ charge = endocochlear potential

Question 36

voltage potential of endo/peri-lymph

Answer 36

+80 difference between them

scala media is + = endocochlear potential

Question 37

tops of hair cells project thru ?

Answer 37

the reticular lamina

thus bathed in endolymph

Question 38

lower bodies of hair cells

Answer 38

surrounded by perilymph

Question 39

intracellular potential of hair cells

Answer 39

• 150 apical ends in endolymph

- 70 lower bodies in perilymph

Question 40

place principle

Answer 40

nervous system detects sound frequencies by determining positions along the basilar memb that are most stimulated

Question 41

6 components of the nervous system pathway for sound

Answer 41

1. spiral organ of corti
2. dorsal n ventral cochlear nuclei
3. superior olivary nucleus
4. lat lemniscus nucleus
5. med geniculate nucleus (in the thalamus)
6. auditory cortex

Question 42

auditory cortex

Answer 42

located in temporal lobe

dif areas associated w/ high vs low sound frequencies