Anatomy & Physiology

Question 1

The ear as a transducer

Answer 1

The cochlea transforms sound energy that enters the ear into electro-chemical energy that the brain can understand and respond to.

Question 2

The ear as an amplifier

Answer 2

Sound hitting the eardrum presses in and causes it to travel on the ossicles and amplify at the stapes.

Question 3

Name the 5 portions of the ear

Answer 3

1) Outer or external ear
2) middle ear
3) Inner ear
4) auditory (8th) nerve
5) Central auditory system

Question 4

How many peripheral and central auditory mechanisms do we have?

Answer 4

Two peripheral systems, one on each side. Only one central auditory system; this is the place where information from the two systems join and form an integrated body.

Question 5

Where is the auditory mechanism located in the skull?

Answer 5

Within the temporal bones lie the mechanisms for hearing and equilibrium

Question 6

What is the main function of the external ear?

Answer 6

1) Pinna or auricle: gathers sound; small amount of sound amplification
- Pinna is a flap that hangs at the sides of our skulls; it has several furrows and crevices and is of little importance as far as our hearings concerned
- In animals it collects sound waves and aids in localization, and keeps foreign objects from the ear
- The pinna does provide for a small increase in hearing sensitivity in man (resonant characteristics).
2) External auditory canal (meatus): function is to propagate the entering sound to the eardrum and to discourage insects from entering the ear (because of hair and cerumen). Cerumen also keeps the canal from drying out.

Question 7

What are the main portions of the outer ear?

Answer 7

1) Pinna

2) External auditory canal

Question 8

Name the structures that encompass the middle ear

Answer 8

1) Tympanic membrane
2) Malleus
3) Incus
4) Stapes
5) Oval window
6) Round window
7) Two muscles: tensor tympani and stapedious muscle
8) Eustachian tube

Question 9

Name the ossicles

Answer 9

Malleus, Incus, and Stapes

Question 10

What is the function of the ossicles?

Answer 10

amplification of acoustic stimuli. Takes area difference between tympanic membrane and oval window; amplifies large sound onto small sound area.

Question 11

How is proper air pressure maintained in the middle ear?

Answer 11

The Eustachian tube equalizes the air pressure in the middle ear cavity with that of the outside.

Question 12

A great deal of sound energy is lost when going from the air medium of the middle ear to the fluid medium of the inner ear. How does the ear compensate for this?

Answer 12

It compensates in two way: lever action of the ossicles (less important), and more importantly by the area difference between the oval window and the tympanic membrane

Question 13

The inner ear is comprised of two labyrinths. Name them.

Answer 13

1) The osseous or bony labyrinth

2) The membraneous labyrinth (within bony labyrinth)

Question 14

Name the fluid found in each labyrinth.

Answer 14

The osseous labyrinth: perilymph fluid

The membranous labyrinth: endolymph fluid

Question 15

The inner ear has two major functions. Name them.

Answer 15

Hearing and balance; hearing transducer, sound energy converted from waves to electrical energy

Question 16

Sound enters the inner ear as a fluid wave. What form of energy exists when the sound waves exits the inner ear?

Answer 16

Electrochemical energy

Question 17

What parts of the inner ear are responsible for balance?

Answer 17

The semicircular canals: contribute to angular acceleration (going in a circle) and head turning.
The Utricle and Saccule: responsive to the forward and sideways movements of the head - linear acceleration (elevator or car).

Question 18

What part of the inner ear is responsible for the transformation of sound from waves to electrochemical energy?

Answer 18

The organ of Corti within the cochlea.

Question 19

Sound can reach the inner ear by two mechanisms. Name them.

Answer 19

Air conduction

Bone conduction

Question 20

There are two branches of the auditory or 8th nerve. Name them.

Answer 20

Vestibular division: come from sensory cells of the semicircular canals and the utricle and saccule and terminate at the pons and medulla.
Cochlear division: receives messages from the hair cells in the organ of Corti after stimulation and terminates in the medulla

Question 21

Messages from the sense organ to the brain are referred to as what?

Answer 21

Ascending fibers (afferent)

Question 22

Messages from the brain to the sense organ are referred to as what?

Answer 22

Descending fibers (efferent)

Question 23

Name three functions from the auditory portion of the brain.

Answer 23

auditory memory, mediating acoustic reflex, frequency characteristics of sound, temporal aspects of sound, and localization.