7. The inner ear (lecture)

Question 1

what does the inner ear consist of?

Answer 1

vestibular apparatus and cochlea

Question 2

what is the function of the cochlea?

Answer 2

converts sound vibration into an electrical signal (AP) - which is perceived as sound

Question 3

what does the vestibular apparatus consist of?

Answer 3

vestibule (utricle + saccule)

3 semi-circular canals (comes off utricle)

Question 4

what is vestibular apparatus involved in?

Answer 4

maintaining our sense of Position and Balance

Question 5

what is the cochlea?

Answer 5

organ of hearing

fluid filled tube

Question 6

what sets up movements of the fluid in the cochlea?

Answer 6

movements at the oval window from sound wave (vibrating the tympanic membrane –> ossicles –> stapes vibrate up to 20x, vibrating oval window –> cochlea)

Question 7

what do the waves of fluid within the cochlea cause?

Answer 7

movement of special sensory cells within the cochlear duct - which fire AP

Question 8

what happens if the waves of fluid within the cochlea doesn’t cause movement of special sensory cells within cochlear duct to fire AP?

Answer 8

sensorineural hearing loss

(bone conduction better than air) - Weber, louder in bone conduction than air

Question 9

what are the ampullae within the inner ear?

Answer 9

swelling at the end of semi-circular canals which attach to the utricle of vestibule

Question 10

what does the cochlear consist of?

Answer 10

bony labyrinth (cochlea) 
and 
membranous labyrinth (cochlear duct)

Question 11

what are the openings in the inner ear?

Answer 11

round window and oval window

Question 12

what is the round window?

Answer 12

a membrane-covered opening between the middle ear and the cochlea

Question 13

function of round window?

Answer 13

allow for pressure changes between the middle ear and the cochlea

Question 14

what is the membrane covering the round window called?

Answer 14

secondary tympanic membrane

Question 15

what is another term for round window?

Answer 15

fenestra of cochlea

Question 16

what do vibrations of the ossicles set up?

Answer 16

vibrations / movement in cochlear fluid

Question 17

what are vibrations / movement in cochlear fluid sensed by?

Answer 17

sensed by nerve cells (called spiral organ of Corti) in the cochlear duct

Question 18

what do movement of receptions in spiral organ of Corti (nerve cells in cochlear duct) trigger?

Answer 18

action potentials in CN VIII, transmitted to the brain (conceived as sound)

Question 19

how do we hear?

Answer 19

Vibrations of the ossicles (stapes at the oval window) from EAM –> TM
Sets up vibrations / movements in cochlear fluid
Sensed by nerve cells in the cochlear duct (spiral organ of Corti)
Movements in receptors in organ of Corti trigger AN in CN VIII
Sent to brain, perceived as sound

Question 20

what is the vestibular apparatus?

Answer 20

fluid-filled series of channels and sacs

Question 21

what does the vestibular apparatus respond to?

Answer 21

position and rotation

maintain our balance

Question 22

what are the semicircular canals of the vestibular apparatus?

Answer 22

bony labyrinth

Question 23

what is the membranous labyrinth of vestibular apparatus?

Answer 23

the membranous labyrinth - surrounding the bony labyrinth (semicircular canals)

Question 24

how can the vestibular apparatus be affected?

Answer 24

by:
1. Meniere’s disease
2. Benign Paroxysmal Positional Vertigo (BPPV)

Question 25

what do Meniere’s and BPPV cause?

Answer 25

Vertigo

Question 26

what is vertigo?

Answer 26

a person feels as if they or the objects around them are moving when they are not (room spinning)

Question 27

what can vertigo caused by labyrinthitis be accompanied by?

Answer 27

nausea, vomiting, hearing loss, tinnitus (ringing in ear)

sometimes high temperature

Question 28

what is Meniere’s disease?

Answer 28

disorder of the inner ear that causes episodes of vertigo, fluctuating hearing loss with a progressive, ultimately permanent loss of hearing, tinnitus, and sometimes a feeling of pressure in your ear

Question 29

symptoms of (BPPV) benign paroxysmal positional vertigo

Answer 29

brief periods of vertigo with movement (of head)