Lecture 4 - Ears

Question 1

What does the external ear consist of?

Answer 1

auricle (pinna)
the external acoustic meatus (auditory canal).

Question 2

What is the ear drum ( tympanic membrane)?

Answer 2

thin connective tissue membrane that transfers sound energy to the auditory ossicles.

Separates outer and middle ear

Question 3

Middle ear (tympanic cavity)

Answer 3

small, air- filled, mucosa-lined cavity in the temporal bone

Question 4

What allows pressure to be equalized between middle and external ear?

Answer 4

When the pharyngotympanic (auditory) tube (also called the eustachian tube) links the middle ear with the nasopharynx

Question 5

Bony labyrinth; what does it include?

Answer 5

series of channels carved into the temporal bone

the scala vestibuli
scala tympani of the cochlea.

filled with a fluid called perilymph, similar to cerebrospinal fluid.

Question 6

Membranous labyrinth; what does it include?

Answer 6

made of membranous ducts within the bony labyrinth

the scala media or cochlear duct).

filled with endolymph (contains more K+
than perilymph)
The ion difference between these fluids is important for receptor cell depolarization.

Question 7

Cochlea

Answer 7

Spiral shaped

extends from the anterior part of the vestibule and contains the cochlear duct, which houses the spiral organ (organ of Corti)

the receptor organ for hearing

Question 8

Three divisions of cochlea cavity

Answer 8

scala vestibuli (next to the oval window)

the scala media (cochlear duct)

scala tympani (terminates at the round window).

Question 9

Basilar membrane

Answer 9

Floor of cochlear duct

Important for sound reception

Question 10

Hair cells

Answer 10

detect vibrations between the basilar membrane and the tectorial membrane.

Question 11

How is sound produced?

Answer 11

by a vibrating object and propagated by the molecules of the medium.

Question 12

What do short and stiff fibres near oval window respond to?

Answer 12

High frequency sound waves

Question 13

What do long fibres near apex respond to?

Answer 13

Low frequency sound waves

Question 14

What are vibrations transmitted along?

Answer 14

Auditory ossicles to oval window

Producing pressure wave within perilymph

Question 15

How is sound transmitted to inner ear?

Answer 15

Sound enters external acoustic meatus causing tympanic membrane to vibrate

Vibrations transmitted along auditory ossicles to oval window

Sounds with high frequencies create pressure waves that vibrate basilar membrane