equilibrium and hearing (theory)

Question 1

what are the two functions of the structures of the ear?

Answer 1

1. hearing
2. balance

Question 2

what are the 3 subdivisions of the ear?

Answer 2

1. external ear
2. middle ear
3. inner ear

Question 3

components of the external ear

Answer 3

1. auricle
2. external acoustic meatus
3. elastic cartilage

Question 4

components of the middle ear

Answer 4

1. tympanic membrane
2. auditory ossicles (MIS)
3. tympanic cavity
4. stapedius
5. tensor tympani

Question 5

components of the inner ear

Answer 5

1. cochlea
2. round window
3. oval window
4. vestibule
5. semicircular canals (vestibular region)
6. cochlea branch (CN VIII)
7. vestibular branch (CN VIII)
8. facial nerve (CN VII)
9. auditory tube (eustachian)
10. bony labyrinth
11. utricle
12. saccule

Question 6

external acoustic meatus function

Answer 6

1. air conduction of the sound waves
2. cone shape lends itself to sound wave collection

Question 7

tympanic membrane function

Answer 7

AKA the ear drum

to vibrate when struck by incoming sound waves

this moves the malleus ossicle which moves the stapes

Question 8

malleus function

Answer 8

the malleus facilitates air to bone conduction

this is the transition of sound waves of the air to bone movement which can be transferred into an impulse by hair receptors

Question 9

stapes function

Answer 9

the foot of the stapes is imprinted onto the oval window which transfers the bone vibrations to the cochlea

Question 10

cochlea function

Answer 10

to receive transmitted sound waves

the smaller diameter receives low pitch sound

the larger diameter receives high pitch sound

Question 11

auditory tube function

Answer 11

AKA eustachian tubes

these minimize the air pressure of the middle ear

you can open your auditory tubes by swallowing

Question 12

stapedius function

Answer 12

it is attached to the round window and contracts with high sound intensity protect the cochlea

Question 13

which is better air or bone conduction of sound?

Answer 13

air

Question 14

ceruminous gland function

Answer 14

a modified apocrine gland

this secretes earwax which moistens the external ear canal

if there was no moisture, the canal would crack which would be VERY painful

Question 15

3 auditory ossicles (MIS)

Answer 15

1. malleus
2. incus
3. stapes

Question 16

tensor tympani function

Answer 16

protects the tympanic membrane from high intensity sound

it contracts and stops the tympanic membrane from moving

it is attached to the malleus bone

Question 17

semicircular canal function

Answer 17

to establish orientation and provide balance, it is part of the vestibular complex

Question 18

what does the vestibular complex detect?

Answer 18

1. rotation
2. gravity
3. acceleration and deceleration

Question 19

what does the vestibular complex consist of?

Answer 19

1. semicircular canals
2. utricle
3. saccule

Question 20

semicircular canal duct contents

Answer 20

contains…

1. endolympth (fluid)
2. cupula (gel)
3. ampulla
4. crista (within the ampulla)
5. kinocilium
6. stereocilia

Question 21

head movement and endolympth

Answer 21

due to physics the endolymph fluid inside the ducts of the semicircular canals, the fluid moves with the rotation of the head (opposite) and bends the stereocilia and kinocilium which fires an AP

Question 22

endolymph and dizziness

Answer 22

moving ones head in a circle and stopping abruptly results in dizziness because the hair cells bend back and forth causing confused signaling

Question 23

utricle and saccule

Answer 23

they are connected to each other and to the ampulla

Question 24

macullae

Answer 24

clustered hair cells of the utricle and saccule

Question 25

cupula

Answer 25

a gel like material that encases the hair cells and has a crystal layer of calcium carbonate on top of it (statoconia) the capula moves according to gravity

Question 26

otolith

Answer 26

the cupula and the statoconia

Question 27

anterior semicircular duct

Answer 27

for forward head movement (nodding yes)

Question 28

lateral semicircular duct

Answer 28

for lateral head movement (shaking no)

Question 29

posterior semicircular duct

Answer 29

for tilting the head up

Question 30

vestibular branch sensory relay

Answer 30

the vestibular branch of the vestibulocochlear nerve synapses onto the vestibular nuclei between the pons and the medulla

Question 31

where does the vestibular nuclei signal to?

Answer 31

1. to the cerebellum 2. to the accessory nerve 3. to the abducens nerve 4. to the trochlear nerve 5. to the oculomotor nerve 6. to the red nucleus 7. to the superior colliculus 8. vestibulospinal tract 9. cerebral cortex

Question 32

why does the vestibular nuclei signal to nerves of eye?

Answer 32

because the eye is also involved in orientation of balance and position

Question 33

what is the main structure involved in hearing

Answer 33

the cochlea

Question 34

the center of the cochlea

Answer 34

called the modiolus which contains sensory neurons

Question 35

what cranial nerve innervates the cochlea?

Answer 35

the cochlear branch of the vestibulocochlear nerve (CN VIII)

Question 36

spiral organ of the cochlea

Answer 36

organ of corti

Question 37

3 layers of the cochlear spiral

Answer 37

1. scala vestibuli 2. scala tympani 3. scala media

Question 38

scala vestibuli

Answer 38

the vestibular duct it contains perilymph and the vestibular membrane

Question 39

scala tympani

Answer 39

the tympanic duct contains perilymph also

Question 40

scala media

Answer 40

the cochlear duct contains endolymph, this layer is between the vestibuli and the tympani

Question 41

basilar membrane of the cochlea

Answer 41

there is a basilar membrane between each of the 3 layers the scala vestibuli and tympani are attached apically to the cochlea sense organs rest on the basilar membrane in the scala media

Question 42

the organ of corti function

Answer 42

AKA the spiral organ this rests on the basilar membrane between the scala media and tympani it contains hair cells which are contact with tectorial membrane of the scala media

Question 43

tectorial membrane movement and hair cell firing

Answer 43

sound waves cause the tectorial membrane to move which causes hair cells to bend and fire APs down the cochlear branch of CN VIII

Question 44

hair cell damage (hearing)

Answer 44

1. loud work environments 2. loud music this is not felt immediately but later in life

Question 45

perilymph function

Answer 45

it is present in the scala tympani and vestibuli as the stapes pushes against the oval window causing the scal tympani to move, so does the perilymph which causes the scala media to move

Question 46

where does auditory info end up?

Answer 46

in the inferior colliculus of the midbrain (corpus quadrigemina)

Question 47

if sound is loud enough

Answer 47

if sound is loud enough to reach the inferior colliculi, it will rotate the head in the direction of the sound

Question 48

what is the nucleus that auditory info goes to? (MGN)

Answer 48

medial geniculate nucleus

Question 49

where does the auditory info ultimately end up?

Answer 49

in the auditory cortex of the temporal lobe

Question 50

auditory pathway

Answer 50

1. specific section of the cochlea is stimulated 2. fire AP down cochlea branch 3. reach the cochlear nucleus 4. reach the inferior colliculus of the midbrain 5. send to the medial geniculate nucleus 6. send to the auditory cortex of the temporal lobe

Question 51

distribution of high, middle and low frequency sounds in the auditory cortex

Answer 51

1. high --> innermost 2. middle --> middle of the cortex 3. low --> periphery of the cortex

Question 52

inferior colliculi signalling to the ipsilateral side

Answer 52

normally, most auditory information crosses over at the cochlear nucleus onto the contralateral side but the inferior colliculi does receive some auditory information and sends it to the auditory cortex on the same side of the body