Ear Physiology

Question 1

Proprioception

Answer 1

knowing where the body is

• not part of the vestibular system
• systemic

Question 2

What are the two main portions of the vestibular system

Answer 2

1. Semicircular canals

2. Otolith system

Question 3

What do the semicircular canals detect?

Answer 3

rotational movement

Question 4

what does the otolith system detect?

Answer 4

• linear acceleration

- gravity

Question 5

What are the three anatomical parts of the semicircular canals

Answer 5

1. canals
2. ampulla
3. Crista ampularis

Question 6

What are the three semicircular canals

Answer 6

Anterior semicircular canal
Posterior
Lateral

Question 7

What is the ampulla of the semicircular canals?

Answer 7

• swollen end

- contains the crust ampularis

Question 8

What is the crista ampularis?

where located?

Answer 8

• the sensory organ of the semicircular canals

- located in the ampulla

Question 9

What nerve innervates the semicircular canals

Answer 9

Vestibular portion of the vestibulocochlear nerve

Question 10

Crista ampullaris

• cell type (description)
• what CN does it synapse on?

Answer 10

• hair cells

- synapse on vestibular fibers of CNVIII

Question 11

what is the structure that sits above the hair cells of the crista ampullaris?

Answer 11

cupola

Question 12

Describe cupola

Answer 12

• gelatinous
• moves with the fluid in the semicircular canal
• stereo cilia of hair cells is embedded in it

Question 13

Semicircular canal hair cell excitation

- what is sensed

Answer 13

• rotational movement moves the fluid which rocks the cupola

- the rocking cupola moves the stereocilia hairs

Question 14

What four structures are involved in the otolith system

Answer 14

• Utricle
• Saccule
• Otolith membrane
• otolith

Question 15

How are the macula arranged in the Utricle

Answer 15

horizontal - senses movement in the horizontal plane

Question 16

How are the macula arranged in the saccule

Answer 16

vertical - senses movement in the vertical plane

Question 17

What are the macula composed of?

Answer 17

• hair cells

- sustenacular cells

Question 18

What two types of hair cells are in the macula

Answer 18

• stereocilia

- kinocilium (type of stereocilia)

Question 19

Otolith membrane

• composition
• what is embedded in it?
• what sits on it?

Answer 19

• gelatinous
• stereocilia embedded in
• otolith rest on top

Question 20

What are the otolith made of?

Answer 20

CaCO3

Question 21

What do the otolith do?

Answer 21

• provide weight and inertia

- negative inhibition by dampening the gelatinous otolith membrane: takes more movement to affect the hair

Question 22

Where do the axons first travel out of the vestibular system?

Answer 22

into the vestibular nuclei

located low in the brainstem

Question 23

What 5 areas does the vestibular pathway radiate to from the vestibular nuclei?

Answer 23

1. Cerebellum
2. CN III, CN IV, CN VI nuclei for vestibular-oclear reflex
3. reticular formation
4. Spinal cord
5. thalamus -> cortex

Question 24

Two main vestibular related diseases

Answer 24

1. nystagmus

2. vertigo

Question 25

4 main causes of vertigo

Answer 25

1. Labyrinthitis 2. Meniere's Disease 3. CN VIII pathology (acoustic neuroma, etc.) 4. systemic illness

Question 26

What are the parts of the outer ear?

Answer 26

auricle - helix, antihelix, lobule, tragus, antitragus | External auditory canal

Question 27

General list of structures within the middle ear

Answer 27

- tympanic membrane - auditory canal - ossicles: malleus, incus, stapes - auditory muscles: tensor tympani, stapedius

Question 28

tensor tympani

Answer 28

attached to manubrium of malleus; contraction pulls malleus from TM

Question 29

stapedius

Answer 29

attached to stapes; contraction pulls stapes away from oval window; mediated by tympanic reflex - response to loud sounds

Question 30

Structures of the inner ear

Answer 30

- bony labyrinth | - membranous labyrinth: cochlea (organ of corti), vestibule, semicircular canals

Question 31

Perilymph

Answer 31

contained within the bony labyrinth, surrounding the membranous labyrinth

Question 32

What fluid fills the membranous labyrinth?

Answer 32

endolymph

Question 33

chambers of the cochlea

Answer 33

- scala vestibuli - scala media: cochlear duct; endolymph - scala tympani

Question 34

reissner membrane

Answer 34

separates the cochlear duct from the vestibular canal (roof of cochlear duct)

Question 35

basliar membrane

Answer 35

separates the cochlear duct from the tympanic canal (floor of cochlear duct)

Question 36

What structure of the ear generates the impulse for hearing?

Answer 36

Organ of Corti

Question 37

Describe the sound waves at the oval window

Answer 37

high frequency

Question 38

Describe the sound waves at the apex of the cochlea

Answer 38

low frequency - slower wave length

Question 39

The organ of Corti generates what?

Answer 39

nerve impulses in response to basilar membrane movement

Question 40

hair cells

Answer 40

mechanoreceptors that synapse w/ cochlear nerve endings through stereocilia touching the tectorial membrane

Question 41

hair cells are equivalent to what cells in the eye?

Answer 41

photoreceptors

Question 42

What excites the hair cells?

Answer 42

movement of the basilar membrane. it rocks and excites hair cells.

Question 43

General makeup of the stereocilia on the hair cells

Answer 43

mechanically sensitive cation channels. When they depolarize and release a neurotransmitter they synapse at the spiral ganglion on cochlear nerve endings. When repolarized a resting potential is established.

Question 44

How is ionic potential of the hair cell maintained?

Answer 44

endolymph: high K+ and low Na+ perilymph: low K+ and high Na+

Question 45

Auditory pathway

Answer 45

the impulse leaves the ear through the spiral ganglion and terminate in the dorsal/ventral chochlear nuclei. From there the axons project to the inferior colliculus, then to the MEDIAL geniculate nucleus and into the auditory cortex to be interpreted.

Question 46

amplitude

Answer 46

intensity of sound wave

Question 47

frequency

Answer 47

pitch and tone of sound wave

Question 48

short wavelength

Answer 48

more waves, high frequency, high sound

Question 49

long wavelength

Answer 49

less waves, low frequency, low sound

Question 50

conductive hearing loss

Answer 50

ear canal or middle ear; obstruction

Question 51

sensorineural hearing loss

Answer 51

most common; occurs in nerves and is permaneny

Question 52

mixed hearing loss

Answer 52

combo of conductive and sensorineural