The Ear Is Involved in Hearing and Equilibrium
structures of the ear, including those of
the outer ear, middle ear, and inner ear.
how the ear converts sound waves into
nerve impulses and the path those impulses
take to the brain.
the structures of the ear involved in
static and dynamic equilibrium.
the neural pathways involved in equilib-
onsider a ballet dancer. She must hear the mu-
sic so that she knows her cues as well as the
proper timing and rhythm for the execution of
her steps. Her body must be aware at all times
of the positions of her limbs with respect to gravity and
make minute changes in muscles so she can stay balanced
T he e a r consists o f th re e p arts: th e o u te r ear,
th e m iddle ear, and th e inner e a r • Figure 8.11
on her toes. The receptors for both the sense of hearing and
the sense of balance, or equilibrium, are located in the ears.
Let’s take a closer look at the structures of the ear.
The Ear Is Composed of
Three Distinct Regions
The ear consists of three parts: the outer ear, middle
ear, and inner ear (
). The outer ear mainly
receives and directs sound waves into the ear canal. The
middle ear conveys sound vibrations to the inner ear,
which houses the receptors for hearing and balance. The
middle ear and inner ear are located within the temporal
bone of the skull. The spaces of the outer ear and middle
ear are filled with air, which allows
vibrate rapidly and freely.
Small bones of the
protects ear from
Auricle collects sound
waves and directs
them to external
directs sound waves to
Auditory ossicles transmit vibrations
to oval window of inner ear
(Malleus, incus, stapes).
membrane) vibrates with
incoming sound waves.
(] Middle ear
that have been
Semicircular canals are
also involved in balance.
Vestibule contains two
sacs involved in balance
nerve transmits nerve
impulses to brain:
• Vestibular branch
• Cochlear branch
fluid pressure waves
into action potentials.
Auditory (eustachian) tube
connects middle ear with
nasopharynx and equalizes
air pressure behind eardrum.
The Ear is involved in Hearing and Equilibrium 241