The Ear

Question 1

what does the helicotrema connect?

Answer 1

the scala vestibuli to the scala tympani

Question 2

what is the ductus reuniens?

Answer 2

small duct connecting the saccule to the cochlear duct

Question 3

what is the vestibular membrane (reissner’s membrane)

Answer 3

roof of the cochlear duct that is composed of two simple squamous epithelial sheets separated by a basal lamina

Question 3

What is the organ of corti responsible for?

Answer 3

hearing

Question 3

do the bases of the hair cells in the organ of corti rest on the basilar membrane?

Answer 3

NO

Question 4

what membrane are the stereocilia embedded in in the sensory maculae?

Answer 4

otolithic membrane

Question 5

where does blood supply to the inner ear arise from?

Answer 5

the labyrinthine artery

Question 6

what is the cupula? how does it function in sensation?

Answer 6

it is a gelatinous membrane that encapsulates the stereocilia and kinocilia. Acts like a sail: if the head rotates, the endolymph moves within the semicircular duct to push against and deviate the cupula resulting in deflection of the stereoclila; direction of deviation determines the polarity of the receptor potential

Question 6

what does the tectorial membrane of the organ of corti contain?

Answer 6

keratin like protein

Question 6

can hypothyroidism lead to hearing loss?

Answer 6

yes

Question 8

what is the spiral ligament

Answer 8

outside wall of the cochlea that is made of dense CT

Question 9

How does the kinocilium location determine functional polarity?

Answer 9

if the stereocilia are tilted TOWARD the kinocilium = depolarization; if the stereocilia are tilted AWAY from the kinocilium = hyperpolarization

Question 9

what is the function of the otoliths?

Answer 9

increase the mass of the membrane surface to augment the effect of accelerating forces on the membrane and thus on the stereocilia

Question 10

what compartments are part of the osseous labyrinth? what compartments of the cochlear are part of the membranous labyrinth?

Answer 10

scala vestibuli + scala tympani = osseous scala media = membranous

Question 11

what causes K+ channels in the stereocilia to open?

Answer 11

mechanoreception via connection of stereocilia to the adjacent stereocilia

Question 11

what supports the hair cells bases in the organ of corti?

Answer 11

phalangeal cell and a process of the phalangeal cell surrounding the apex of the hair cell

Question 12

what inserts on the oval window of the vestibule?

Answer 12

stappes

Question 13

what is located on one end of each semicircular canal?

Answer 13

the ampulla (swelling)

Question 14

what is the boney central axis of the cochlea?

Answer 14

modiolus (towards modiolus = inner, away from modiolus = outer)

Question 15

what is the stria vascularis?

Answer 15

pseudostratified, vascularized, epithelium that secretes endolymp

Question 15

what is the structure of kinocilum

Answer 15

9 doublet microtubules; immotile; longest stereocilia is adjacent to the kinocilium

Question 16

pendred syndome

Answer 16

genetic disorder causing hearing loss in children (SLC26A4 = carrier gene

Question 17

what is the osseous spiral lamina?

Answer 17

spiraling shelf off of the modiolus that indents the inner edge of the cochlea

Question 17

what are the sensory areas of the inner ear?

Answer 17

1. crista ampullaris (of semicircular ducts) 2. sensory maculae (of utricle and saccule) 3. organ of corti (of cochlear duct)

Question 17

what are the two types of hearing loss? what are the main differences?

Answer 17

1. conductive losses = disruption in the conductive pathway of soundwaves traveling (ie: disruption of tympanic membrane) 2. sensorineural loss = loss of hair cells of VIII nerve fibers

Question 18

what is motion sickness caused by?

Answer 18

over stimulation of the utricle/saccule

Question 19

what forms the floor the cochlear duct?

Answer 19

the basilar membrane; the organ of corti is located on it

Question 20

How does the organ of corti transmit sound?

Answer 20

the cohclear duct hair cells transduce mechanical energy into sound frequency, and the frequency response is represented as a continuous gradient along the organ of corti.

Question 22

what is the function of the organ of corti:

Answer 22

to transduce auditory signals

Question 24

what type of cells are found in the spiral ganglion?

Answer 24

bipolar

Question 26

what is perilymph high in? low in? vs endolymph

Answer 26

peri = high in Na low in K+ endo = high in K+ low in Na

Question 27

what are the two types of cells on the crita ampularis?

Answer 27

both columnar epithelium: 1. supporting cells = have secretory granules; tall columnar 2. sensory hair cells = stereocilia and kinocilia are embedded in gelatinous membrane (cupula) which acts like a sail

Question 28

what happens if sensory cell of the ear is depolarized

Answer 28

it will release more neurotransmitter on VIII afferent processes and cause an increase in signal to the vestibular or auditory centers of the brain

Question 29

where are neurotransmitters released from in the inner tunnel (of organ of corti)

Answer 29

spiral ganglion cells

Question 31

what is the function of the utricle and saccule?

Answer 31

detection of linear acceleration (tripping over something)

Question 33

what is the vestibular aqueduct

Answer 33

small boney channel that connects to the vestibule

Question 33

what keeps the endolymph and perilymph from mixing?

Answer 33

the occluding zonules of the cells lining the membranous labyrinth

Question 34

what is the crista ampullaris? where is it found?

Answer 34

a sensory structure in the ampulla (swelling at end of semicircular canal); detects rotational movements of the head

Question 34

what is vertigo? what is it caused by

Answer 34

dizziness; caused by disturbances of vestibular function such as infection of the vestibule or lesions of the central or peripheral nervous system

Question 35

the modiolus contains fibers for what nerves?

Answer 35

VIII + peripheral ganglion (spiral ganglion) for auditory system

Question 36

what is menieres disease?

Answer 36

swelling of the membranous labyrinth leading to dizziness (vertigo) tinitus (ringing of ears) and low frequency hearing loss

Question 38

what is the membranous labyrinth? what is it derived from?

Answer 38

it is a continuous series of epithelially lined membrane channels derived from the otocyst containing endolymph

Question 39

presbyacusis

Answer 39

poor high frequency perception due to age related loss of hair cells at the basal turn of the cochlea

Question 40

what is the membranous labyrinth composed of?

Answer 40

1.semicircular ducts 2. utricle 3. saccule 4. endolymphatic duct and sac 5. cochlear duct

Question 42

what does the otolithic membrane contain?

Answer 42

crystalline includes (otoliths) in its surface

Question 43

what cells line the inner tunnel of the organ of corti?

Answer 43

pillar cells

Question 44

where is perilymph secreted from?

Answer 44

the blood vessels in the CT of the ossesous labyrinth

Question 45

what does the vestibule connect anteriorly? posteriorly?

Answer 45

anteriorly: cochlea posteriorly: semicircular canals

Question 47

where is the sensory maculae located?

Answer 47

in the utricle and saccule

Question 48

how do the hair cells at the base of the organ of corti transduce sound vs those at the apex of the cochlea?

Answer 48

base = transduce highest frequencies apex = transduce lowest frequencies

Question 50

what does the scala vestibuli connect with?

Answer 50

oval window ( to cochlea)

Question 52

what does the scala tympani connect with?

Answer 52

round window ( to cochlea)

Question 53

what is prominent in the pillar cells and the phalangeal cells? what is the significance of their structure?

Answer 53

microtubules and intermediate filaments; This allows for the pillar and phalangeal cells to form a rigid RETICULAR LAMINA in which the apical portions of the hair cells are locked via zonular adherens and zonula occludens junctions

Question 54

why is it important that the basilar membrane upon which the organ of corti rests is collagenous and not rigid?

Answer 54

because sound causes compression of waves in the perilymph which shifts the two rigid plates to the deviate the stereocilia and produce receptor potntials in the sensory cells

Question 55

what is unique to the hair cells of the organ or corti

Answer 55

don't have a kinocilium, have a basal body instead

Question 56

What do all of the sensory areas of the inner ear contain?

Answer 56

1. sensory hair cells with sterocilia an single kinocilum (or basal body in the auditory cells)