Hearing LO2, LO3

Question 1

Three major areas of the ear

Answer 1

1. External (outer) ear – hearing only
2. Middle ear (tympanic cavity) – hearing only
3. Internal (inner) ear – hearing and balance

Question 2

auricle (pinna) (external ear)

Answer 2

– funnels sound waves into the external acoustic meatus

Question 3

external acoustic meatus (external ear)

Answer 3

• sound waves entering external acoustic meatus travel to and vibrate tympanic membrane
• earwax secreting glands to traps foreign particles

Question 4

tympanic membrane (external ear)

Answer 4

thin translucent membrane
- vibrates in response to sound waves which then transfers sound
energy to bones of middle ear

Question 5

Tympanic cavity (middle ear)

Answer 5

• air-filled cavity in the temporal bone
• located between the tympanic membrane laterally
  and medially by bony wall containing: oval window and round window
• contains auditory ossicles: malleus, incus and stapes
• contains pharyngotympanic tube

Question 6

auditory ossicles (middle ear)

Answer 6

malleus, incus and stapes transmit and amplify the vibratory motion of the tympanic membrane to the oval window

Question 7

Pharyngotympanic Tube (middle ear)

Answer 7

• connects middle ear to
  nasopharynx
• equalises air pressure in the middle
  ear cavity with external air pressure

Question 8

Bony labyrinth (inner ear)

Answer 8

tunnels subdivided into
‒ vestibule
‒ semicircular canals
‒ cochlea filled with perilymph

Question 9

membranous labyrinth (inner ear)

Answer 9

series of interconnecting sacs and ducts within
the bony labyrinth
- filled with endolymph

Question 10

Cochlea (inner ear)

Answer 10

spiral, bony chamber that extends from the vestibule
* contains cochlear duct that
houses spiral organ (of Corti)

Question 11

Spiral Organ (of Corti) (inner ear)

Answer 11

• organ for hearing
• sits within cochlear duct on top of basilar membrane
• composed of cochlear hair cells – sandwiched between basilar membrane
  and tectorial membrane
• pressure waves travel through the perilymph of the cochlea creating
  movement of the basilar membrane. This movement causes the hair cells
  to move or bend against the tectorial membrane, initiating depolarisation
• action potentials generated in hair cells - vestibulocochlear nerve (CN VIII)

Question 12

Cochlea and stapes (inner ear)

Answer 12

• stapes embedded within the oval window
• oval window is on the wall of the bony labyrinth at the entrance
  of cochlea
• cochlea filled with perilymph
• movement of stapes back and forth creates movement
  (pressure waves) in perilymph

Question 13

Pathway of sound waves

Answer 13

• Pinna
• External acoustic meatus
• Tympanic membrane
• Auditory Ossicles
• Oval window
• Cochlea
• pressure waves in perilymph
• movement of basiliar membrane within spiral organ
• Vestibulocochlear nerve

Question 14

Oval window

Answer 14

opening in the
bone that partitions middle ear to the start of the cochlea.
Movement causes pressure
waves within the perilymph.

Question 15

round window

Answer 15

Thin membrane
that separates the end of the
cochlea from middle ear.
Absorbs pressure waves

Question 16

Auditory Pathway to the Brain

Answer 16

bending the hair cells in spiral organ generates action potentials in sensory (auditory) neurons.
* the axons of the auditory neurons form the cochlear branch of the vestibulocochlear nerve (CN VIII).
* action potentials travel to the medulla oblongata then the auditory reflex center of the midbrain then to auditory cortex in the temporal lobe to where the stimulus is interpreted
as sound