Lecture 42 4/25/24

Question 1

What is hearing?

Answer 1

the collection, neural processing, and analysis of vibrations generated by an object some distance away

Question 2

What is sound?

Answer 2

the vibrations of air molecules

Question 3

What are the characteristics of sound frequency?

Answer 3

-measured in Hertz/cycles per second
-tone of sound
-higher hertz means higher pitch

Question 4

What are the characteristics of sound amplitude?

Answer 4

-measured in decibels
-loudness of sound
-higher decibels means louder sound

Question 5

What are the characteristics of the pinnae?

Answer 5

-cartilage core with typical skin
-inner surface has less hair and more glands

Question 6

What are the characteristics of the external acoustic meatus?

Answer 6

-vertical and horizontal portions
-cartilage lined by sparsely-haired skin
-sebaceous and ceruminous glands present

Question 7

What are the characteristics of ear wax?

Answer 7

-composed of sebum and cerumen
-keeps tympanic membrane moist and flexible
-protects the ear canal
–antimicrobial
–water repellent
-removes debris

Question 8

What is the function of the external ear?

Answer 8

collect and direct sound waves to the tympanic membrane

Question 9

How does otitis externa differ from pinnal dermatitis?

Answer 9

-otitis externa is inflammation of external ear canal
-pinnal dermatitis is inflammation of the skin on the pinna

Question 10

What are the characteristics of otitis externa in dogs?

Answer 10

-common, especially in long-eared breeds
-can be bacterial, fungal, or parasitic in origin
-can decrease ability to hear
-predisposes dogs to neoplasia

Question 11

What is the main cause of otitis externa in cats?

Answer 11

ear mites

Question 12

What is conduction deafness?

Answer 12

when the brain aspect of hearing works, but sound cannot be conducted

Question 13

How can conduction deafness occur at the level of the external ear canal?

Answer 13

-ear wax that occludes external canal
-swelling and debris that occludes external canal
-tumor that occludes external canal

Question 14

What are the characteristics of the tympanic membrane?

Answer 14

-separates external ear and middle ear
-in contact with bones of the middle ear

Question 15

What are the bones of the middle ear?

Answer 15

-malleus
-incus
-stapes

Question 16

What are the three layers of the tympanic membrane?

Answer 16

-outer cuticular layer (epithelial)
-middle fibrous connective tissue layer
-inner mucus layer (epithelial)

Question 17

How does the tympanic membrane function in hearing?

Answer 17

transforms the energy of sound pressure wave into physical vibration of the auditory ossicles

Question 18

How can conduction deafness occur at the level of the tympanic membrane?

Answer 18

failure of the tympanic membrane, due to inflammation, fibrosis, rupture, etc.

Question 19

What is the middle ear?

Answer 19

air-filled space surrounded by bone and the tympanic membrane

Question 20

Which structure partially divides the middle ear?

Answer 20

septum bulla

Question 21

Which animals have a honeycomb-like structure in their tympanic bullae?

Answer 21

-cow
-goat
-pig
-camelid
-horse

Question 22

What does the stapes bone connect to?

Answer 22

the oval window/entrance to the inner ear

Question 23

Which middle ear bone contacts the tympanic bulla?

Answer 23

malleus

Question 24

Which types of epithelium line the middle ear?

Answer 24

-simple squamous
-simple cuboidal
-pseudostratified ciliated columnar

Question 25

What are the characteristics of the Eustachian/auditory tube?

Answer 25

-continuous with nasopharynx -lined by pseudostratified ciliated columnar epithelium with goblet cells

Question 26

Why is it important that sound waves are reflected when moving from the air-filled middle ear to the fluid-filled inner ear?

Answer 26

the sound must be amplified to account for any waves lost to reflection

Question 27

What is impedance matching?

Answer 27

mechanism that compensates for differences in resistance between air in the external ear and fluid in the inner ear

Question 28

How does impedance matching work?

Answer 28

-vibration of the middle ear bones magnifies the vibration of the tympanic membrane; creates fluid waves in inner ear -sound pressure is transferred from large area of the tympanic membrane to the small area of the oval window; concentrates sound

Question 29

How does the middle ear protect the inner ear from excessive noise?

Answer 29

contraction of the small muscles associated with the middle ear bones can dampen noises

Question 30

What are the characteristics of otitis media?

Answer 30

-inflammation of the middle ear -typically bacterial in origin

Question 31

How can conduction deafness occur at the level of the middle ear?

Answer 31

-inflammation -bone fractures -muscle/nerve issues -fibrosis -masses

Question 32

What is the petrous temporal bone?

Answer 32

bone that encases the inner ear

Question 33

What are the two portions of the inner ear?

Answer 33

-bony labyrinth -membranous labyrinth

Question 34

Where is the perilymph located?

Answer 34

within the bony labyrinth, around the membranous labyrinth

Question 35

Where is the endolymph located?

Answer 35

within the membranous labyrinth

Question 36

What are the three parts of the inner ear?

Answer 36

-vestibule -semicircular canals -cochlea

Question 37

What are the characteristics of the vestibule?

Answer 37

-anteroom to the bony labyrinth -entrance is the oval window -exit is the round window -filled with perilymph

Question 38

Which structures are found within the vestibule?

Answer 38

-utricle -saccule

Question 39

What are the characteristics of the utricle and saccule?

Answer 39

-filled with endolymph -contain maculae

Question 40

What are maculae?

Answer 40

patches of special hair cells in gel covered with otoliths

Question 41

What are the characteristics of the semicircular canals?

Answer 41

-filled with endolymph -one end of each is dilated/has an ampulla -contain cristae; similar to maculae but without otoliths

Question 42

What are the components of the vestibular system?

Answer 42

-vestibule -semicircular canals -associated nerves, ganglia, and nuclei

Question 43

What are the functions of the vestibular system?

Answer 43

-signal up to the cerebrum for awareness and processing -signal down the spinal cord to control/correct/adjust body position