Exam 2: Lecture 19 Hearing and balance

Question 1

where is the labyrinth embedded within the skull?

Answer 1

along the Petrous ridges of the temporal bone

Question 2

labyrinth

Answer 2

(inner ear) the structure comprised of the cochlea, vestibule (utricle and saccule) and semicircular canals

Question 3

cochlea

Answer 3

(hearing) spiral tube shaped like a snail shell as the organ that transduces sound into nerve impulses ⇒ part of the labyrinth

Question 4

semicircular canals: what they do and where they connect

Answer 4

(balance) organs that transduce angular acceleration (rotation) into nerve impulses
- connecting at the vestibule

Question 5

vestibule components

Answer 5

• utricle and saccule)
• (balance) organs that sense linear acceleration, including gravity

Question 6

external ear components (2)

Answer 6

• Air filled; open chamber
• Pressure from sound moves the ear drum

Question 7

middle ear

Answer 7

ossicles

Question 8

ossicles

Answer 8

transmit pressure exerted by sound to the cochlea
- maleus, incus, stapes

Question 9

inner ear

Answer 9

cochlea
- Sound vibrations are transmitted to liquid filled, closed chamber
- Basilar membrane: floor of chamber vibrates in response to sound
- On the anterior medial side of the labyrinth

Question 10

oval window

Answer 10

how the sound gets transmitted to the cochlea
- Footplate of the stapes ⇒ movements can move fluid
- Fluid flows through the tube to the apex and then out at the round window

Question 11

spiral ganglion

Answer 11

auditory primary afferents for hearing that contains the cell bodies responding to sound by hair cell vibration
- includes the cochlear nerve

Question 12

basilar membrane

Answer 12

hair cells sit on here and are innervated by the spiral ganglion

Question 13

hair cells

Answer 13

separate cell that communicates with the spiral ganglion neurons
- Acting as receptor cells (innervate) to sense vibrations and transmit that to the spiral ganglion

Question 14

what effect does sound have?

Answer 14

when sound hits the eardrum there is compression of the tympanic membrane which compresses the fluid in the cochlea
- Displaces the basilar membrane

Question 15

compression

Answer 15

downward movement of the basilar membrane

Question 16

rarefaction

Answer 16

upward movement of the basilar membrane

Question 17

how are the base and apex of the basilar membrane different?

Answer 17

Base: narrow, thick, tense ⇒ cross section is small
- Responds to high frequency sounds
Apex: wide, thin, flaccid ⇒ cross section is wider
- Responds to low frequency sounds

Question 18

what resonant frequency does the round window have?

Answer 18

high frequency

Question 19

low frequency would be Xhz and high frequency would by Yhz

Answer 19

low = 100; high = 10,000

Question 20

what kind of mathematical property does the basilar membrane have?

Answer 20

logarithmic organization

Question 21

how do hair cells work?

Answer 21

• cell has a nucleus and from one end of the cell there are fibrous hairs at different length
• the longest hair bending causes depolarization which excites the cell to release a neurotransmitter onto the spiral ganglion neuron = on
• vice versa

Question 22

regions involved in processing sounds (5)

Answer 22

• cochlear nuclei
• superior olivary nuclei
• inferior colliculus
• medial geniculate nucleus
• auditory cortex

Question 23

cochlear nuclei

Answer 23

sound localization and identification (medulla)

Question 24

superior olivary nuclei

Answer 24

more involved in sound localization and volume control (pons)

Question 25

inferior colliculus

Answer 25

identification of and reflexive responses to sounds (midbrain)

Question 26

medial geniculate nucleus

Answer 26

thalamic relay nucleus (relays audition to our primary auditory cortex right on top of the temporal lobe)

Question 27

auditory cortex

Answer 27

tonotopic organization and sound identification

Question 28

tonotopic organization

Answer 28

different areas of the top of the temporal lobe respond to different frequencies of sound

Question 29

pitch

Answer 29

a single frequency

Question 30

conducting deafness

Answer 30

ear wax or issues with ossicles (bone growths; arthritis) - Easiest to treat - Arthritis prevents the bones form moving

Question 31

sensorineural

Answer 31

result from exposure to loud noises or age related loss of high frequency hearing ⇒ treated with hearing aids - Most common form of deafness

Question 32

tinnitus

Answer 32

ringing in ears - Common and associated with hearing loss

Question 33

endolymph

Answer 33

the name of the fluid inside the ear ⇒ exerts a force at the cupula base of the semicircular canal

Question 34

cupula

Answer 34

has hair cells embedded in it and depending on the motion of the fluid the cells are hyperpolarized or depolarized - at the base of the semicircular canals

Question 35

excitation

Answer 35

includes depolarization of the hair cell and increased impulse frequency

Question 36

inhibition

Answer 36

includes hyperpolarization of the hair cells and decreased impulse frequency

Question 36

what do the semicircular canals vs the vestibule sense?

Answer 36

rotation vs linear acceleration

Question 37

utricle

Answer 37

hair cells in the horizontal sheet (side ways too) - Detects acceleration front-back; left-right

Question 38

saccule

Answer 38

hair cells in the vertical sheet - Mid Sagittal vertical plane detecting acceleration front-back; up-down

Question 39

flocculondular lobe

Answer 39

part of the cerebellum involved in balance

Question 40

where do the central vestibular apparatus project axons to?

Answer 40

the vestibular nuclei in caudal pons and flocculonodular lobe

Question 41

where do the vestibular nuclei project axons to? (3)

Answer 41

1. Spinal cord (for when we sense balance is changing) 2. Cerebellum 3. Cranial nerve nuclei controlling eye movements ⇒ oculomotor (3), trochlear (4), abducens (6)

Question 42

functions of the vestibular nuclei (3)

Answer 42

1. projections to spinal cord 2. cerebellum 3. projections to nuclei innervating extra ocular muscle

Question 43

what do projections to the spinal cord and cerebellum do?

Answer 43

- Coordinate eye movements with head and neck movements - Coordinate vestibular input with anti-gravity muscles such as reflex

Question 44

what do projections to nuclei innervating the extra ocular muscle do

Answer 44

Track object while turning your head

Question 45

what are the 3 input systems to tell us how our body is oriented?

Answer 45

1. vestibular => balance 2. proprioception => feet and floor 3. vision

Question 46

vertigo

Answer 46

sensation of turning in the absence of motion

Question 47

Menderes disease

Answer 47

disorder of entire inner ear ⇒ hearing + balance (type of vertigo)

Question 48

nystagmus

Answer 48

repetitive tracking eye movements in the absence of movement

Question 49

motion sickness

Answer 49

vestibular input to reticular formation => autonomic centers