Auditory/Vestibular Physio

Question 1

Endolymph characteristics

Answer 1

K+ rich/Na+ poor (like ICF)

• Fills cochlear duct and membranous labyrinth
• Bathes apical end of hair cells

Question 2

Where is endolymph found?

Answer 2

Scala media (fills cochlear duct and membranous labyrinth)

Question 3

Perilymph characteristics

Answer 3

K+ poor/Na+ rich (like ECF)

- Bathes basal end of cochlear hair cells

Question 4

Where is perilymph found?

Answer 4

• Scala vestibuli and scala tympani

Question 5

Where is the motion in the basilar membrane the highest?

Answer 5

@ the base (for high frequencies)

basilar membrane is narrower here

Question 6

Where is the motion in the basilar membrane the lowest?

Answer 6

@ the apical regions (for lower frequencies)

basilar membrane is wider here

Question 7

What type of cells are hair cells?

Answer 7

Mechanoreceptors (they convert mechanical signals to electrical signals)
- Also polarized epithelial cells

Question 8

Where are the neural synapses on hair cells?

Answer 8

Basal side

Question 9

Where are the stereocilia on hair cells?

Answer 9

Apical side

Question 10

Process of stereocilia moving?

Answer 10

1. Hair cells deflected
2. K+ ions enter and depolarize cell
3. Ca2+ enters via voltage-gated channels
4. Glu released
5. Post-syn neurons stimulated

Question 11

How does depolarization occur?

Answer 11

Deflection toward tall stereocilia

excitation

Question 12

How does hyperpolarization occur?

Answer 12

Deflection away from tall stereocilia

inhibition

Question 13

What channel is responsible for letting K+ into hair cells?

Answer 13

TRPA1 (ion channel)

Question 14

How is TRPA1 stimulated?

Answer 14

As stereocilia is stretched, the tips are opened

Question 15

Purpose of stria vascularis?

Answer 15

Maintains electrochemical properties of the endolymph by pumping K+ into endolymph

Question 16

Role of inner hair cells?

Answer 16

• Only one row

- Primary source of auditory info

Question 17

Role of outer hair cells?

Answer 17

• 3 rows
• Amplifier for the inner hair cells by boosting mechanical vibrations of basilar membrane
• Sensitivity and tuning of responses susceptible to injury of outer hair cells
• Otoacoustic emissions

Question 18

Where do hair cells receive afferent innervation from?

Answer 18

Spiral ganglia

Question 19

Where do hair cells receive efferent innervation from?

Answer 19

Superior olivary complex

Question 20

Are inner hair cells afferent or efferent?

Answer 20

ONLY afferent (Type I)

Question 21

Are outer hair cells afferent or efferent?

Answer 21

Both afferent (Type II) and efferent

Question 22

Where are low pitch sounds sent?

Answer 22

Apical region

Question 23

Where are high pitch sounds sent?

Answer 23

Basal region

Question 24

Function of dorsal cochlear nuclei?

Answer 24

Integrates acoustic info with somatosensory info for localization of sound

Question 25

Function of ventral cochlear nuclei?

Answer 25

Begins processing the temporal and spectral features of sound

Question 26

What makes up the cochlear nuclear complex?

Answer 26

Ventral and dorsal cochlear nuclei

Question 27

Where does info from both ears first converge?

Answer 27

Superior Olivary Complex

Question 28

What is the primary nucleus of the superior olivary complex?

Answer 28

Medial superior nucleus and lateral superior nucleus

Question 29

Function of medial superior nucleus?

Answer 29

- Receives EAA projections | - Generates map of interaural time differences (helping to localize sound)

Question 30

Function of lateral superior nucleus?

Answer 30

- Generates map of interaural intensity differences (helping to localize the source of sound)

Question 31

Role of superior colliculus?

Answer 31

Takes location data from the IC and adds final dimension (vertical height) to create spatial map of sound's location

Question 32

Role of inferior colliculus?

Answer 32

Suppresses info related to echoes, which would interfere with localization and arrives at a final estimation of localization of sound

Question 33

Role of medial geniculate nucleus?

Answer 33

Convergence from distinct spectral and temporal pathways, allowing for processing features of speech inflections

Question 34

Role of primary auditory cortex?

Answer 34

- Essential in conscious perception of sound | - Higher order processing of sound (loudness, modulations in volume)

Question 35

Role of primary auditory cortex?

Answer 35

- Essential in conscious perception of sound | - Higher order processing of sound (loudness, modulations in volume)

Question 36

Which area is more activated by low frequency sounds?

Answer 36

Rostral areas

Question 37

Which area is more activated by high frequencies?

Answer 37

Caudal areas

Question 38

What is the auditory association complex?

Answer 38

Composed of multiple areas (Broca's, Wernicke's, etc.)

Question 39

What is the role of the auditory association complex?

Answer 39

- Less specificially organized tonotopically than primary auditory cortex - Responds to more complex sounds (like music or naming sounds/songs)

Question 40

What are the efferent inputs to the auditory system?

Answer 40

- Olivocochlear efferents - Middle ear muscle motoneurons - Autonomic innervation of inner ear

Question 41

What are olivocochlear efferents?

Answer 41

- Originate in superior olivary complex - Medial OC neurons IN outer hair cells - Lateral OC neurons IN inner hair cells

Question 42

Role of olivocochlear efferents?

Answer 42

- Shifts responses to higher sound levels - Decreases adaptation - Reduces response to noise (protecting hair cells)

Question 43

What are middle ear efferents?

Answer 43

- Tensor tympani to malleus (CN V) | - Stapedius to the stapes (CN VII)

Question 44

Role of middle ear efferents?

Answer 44

- Bilateral response to loud sounds | - Act at low frequencies to decrease transmission of sound, thus preventing damages

Question 45

What are otoacoustic emissions?

Answer 45

- Low intensity/inaudible sounds emitted from ear | - Can be spontaneous or evoked (for testing)

Question 46

What end of cochlea is more susceptible to damage?

Answer 46

BASE (high frequencies)

Question 47

What is angular acceleration?

Answer 47

Motion involving rotation around one/more planes

Question 48

What is linear acceleration?

Answer 48

Motion in the horizontal or vertical plane

Question 49

What type of acceleration do semicircular canals detect?

Answer 49

Rotational acceleration

Question 50

What type of acceleration does the utricle detect?

Answer 50

Linear acceleration (forward/backward)

Question 51

What type of acceleration does the saccule detect?

Answer 51

Linear acceleration (up/down)

Question 52

Where is rotation in the horizontal plane best detected?

Answer 52

Horizontal SC canal

Question 53

Where is rotation in the vertical plane backwards best detected?

Answer 53

Posterior SC canal

Question 54

Where is rotation in the vertical plane forwards best detected?

Answer 54

Anterior SC canal

Question 55

Which way do eyes move when falling forward?

Answer 55

UP

Question 56

Which way do eyes move when falling backward?

Answer 56

DOWN

Question 57

Which muscles activated with rotational acceleration in the IL eye?

Answer 57

- Medial rectus activated - Lateral rectus inhibited *CL eye does opposite

Question 58

Which muscles activated with falling backwards?

Answer 58

- Superior oblique activated | - Inferior oblique inhibited

Question 59

Which muscles activated with falling forwards?

Answer 59

- Superior rectus activated | - Inferior rectus inhibited

Question 60

Which liquid resides in the vestibular apparatus?

Answer 60

Endolymph

Question 61

Which liquid surrounds the vestibular apparatus?

Answer 61

Perilymph

Question 62

Main theme of cortical and cerebellar involvement in the vestibulooptic reflexes?

Answer 62

Suppress the reflex to allow for voluntary motion