Understanding Psychology (10th Ed)

 eardrum 
is aptly named because it operates as 
a miniature drum, vibrating when sound waves hit it. The more intense the sound, 
the more the eardrum vibrates. These vibrations are then transferred into the middle 
ear , a tiny chamber containing three bones (the hammer , the anvil , and the stirrup ) that 
transmit vibrations to the oval window, a thin membrane leading to the inner ear. 
Because the hammer, anvil, and stirrup act as a set of levers, they not only transmit 
vibrations but also increase their strength. Moreover, because the opening into the 
middle ear (the eardrum) is considerably larger than the opening out of it (the oval 
window ), the force of sound waves on the oval window becomes amplifi ed. The 
middle ear, then, acts as a tiny mechanical amplifi er.
The inner ear is the portion of the ear that changes the sound vibrations into a 
form in which they can be transmitted to the brain. (As you will see, it also contains 
the organs that allow us to locate our position and determine how we are moving 
through space.) When sound enters the inner ear through the oval window, it moves 
into the
 cochlea ,
a coiled tube that looks something like a snail and is fi lled with 
fl uid that vibrates in response to sound. Inside the cochlea is the
 basilar membrane ,
cochlea
(KOKE-lee-uh) A coiled tube 
in the ear fi lled with fl uid that vibrates 
in response to sound.
basilar membrane
A vibrating 
structure that runs through the center 
of the cochlea, dividing it into an upper 
chamber and a lower chamber and 
containing sense receptors for sound.
sound 
The movement of air molecules 
brought about by a source of vibration.
eardrum 
The part of the ear that 
vibrates when sound waves hit it.
Key Concepts
What role does the ear play in 
the senses of sound, motion, 
and balance? 
How do smell and taste 
function? 
What are the skin senses, and 
how do they relate to the 
experience of pain?