Hearing and Vestibular Sense 2.3

Question 1

Vestibular Sense

Answer 1

ability to both detect rotational
and linear acceleration and to use this information to inform our sense of balance and spatial orientation.

Question 2

Pinna (auricle)

Answer 2

• Cartilage outside ear
• Channels sound waves

Question 3

External auditory canal

Answer 3

• directs the sound waves to the tympanic membrane (eardrum)

Question 4

What determines rate which the tympanic membrane vibrates?

Answer 4

Frequency

Question 5

Relationship between intensity and sound?

Answer 5

• Directly proportional
• Increased amplitude of vibration

Question 6

Pathway for how sound travels

Answer 6

Outer ear: [ Pinna (auricle) -> External Auditory Canal -> Tympatic Membrane (eardrum) ]

Middle ear: connected to eustachian tube [ Ossicles (malleus hammer) -> Incus (Anvil) -> Stapes (Stirrup) ]

Inner Ear: [ Bony Labyrinth temporal bone (cochlea, vestibule, semicircular canal) ]

Inside Bony Labyrinth [ Membranous Labyrinth (surrounded by perilymph & filled with endolymph) ]

Question 7

Cochlea

Answer 7

• spiral-shaped
• contains the receptors for hearing
• divided into three parts called scalae

Question 8

Organ of Corti

Answer 8

• In middle scala
• In cochlea
• actual hearing apparatus
• On basilar membrane
• composed of thousands of hair cells
• bathed in endolymph
• Tectorial membrane is on top
• Surrounded by two scalae

Question 9

Round Window

Answer 9

a membrane-covered hole in the cochlea, permits the perilymph to actually move within the cochlea

Question 10

How do hair cells process sound?

Answer 10

hair cells transduce the physical stimulus into an electrical signal, which is carried to the CNS by the auditory (vestibulocochlear) nerve.

Physical stimulus -> Hair cells -> Auditory (vestibulocochlear) nerve

Question 11

Vestibule

Answer 11

• the portion of the bony labyrinth that contains the
  utricle and saccule
• sensitive to linear acceleration, so used for balance and proprioception
• Contain otoliths (special hair cells) As the body accelerates, otoliths will resist that motion

Question 12

Semicircular canals

Answer 12

• sensitive to rotational acceleration
• arranged perpendicularly to each other, and each ends in a
  swelling called an ampulla, where hair cells are located
• When the head rotates, endolymph in the semicircular canal resists this motion, bending the underlying hair cells, which send a signal to the brain.

Question 13

What is the 1st step in sound processing in brain?

Answer 13

medial geniculate nucleus
(MGN) of the thalamus via vestibulocochlear nerve

Question 14

Superior Olive

Answer 14

localizes sound location

Question 15

Inferior Colliculus

Answer 15

involved in the startle reflex and vestibulo–ocular reflex

Question 16

Sound Pathway

Answer 16

Sound -> vestibulocochlear nerve -> MGN -> auditory cortex

Question 17

How hair cells work

Answer 17

Vibration to basilar membrane -> hair sway -> opens channels -> receptor potential

Question 18

How do hair cells amplify sounds?

Answer 18

• Via hair cells connected to the immobile tectorial membrane

Question 19

Frequency and basilar membrane

Answer 19

• highest-frequency pitches cause vibrations of the basilar membrane very close to the oval window, whereas low-frequency pitches cause vibrations at the apex, away
  from the oval window
• basilar membrane changes thickness depending on its location in the cochlea