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The anatomy of the hearing system can be divided into four components.
These divisions are the:
- Outer Ear
- Middle Ear
- Inner Ear
- Central Auditory Pathways
- The Outer Ear
-is made up
of the pinna or auricle and the external auditory canal. The pinna
collects and funnels sound down the ear canal. The ear canal is curved,
“S” shaped, and about 1 inch long in adults.
It has hairs and glands
that produce wax called cerumen. Cerumen helps to lubricate the skin,
keeping it moist.
-(tympanic membrane) is a membrane
at the inner end of the ear canal. On that inner side of the tympanic
membrane is an air filled space called the middle ear cavity. The
vibrations of the tympanic membrane are transmitted through the
malleus (hammer), incus (anvil) and stapes (stirrup), also called
the ossicles. The stapes footplate transmits the vibrations into
the inner ear.
-The inner ear has two divisions: one for hearing, the
other for balance.
The hearing division consists of the cochlea
and the nerve of hearing. The cochlea is snail-shaped, bony structure
that contains the sensory organ for hearing called the organ of
Corti. The organ of Corti releases chemical messengers when the
vibrations from the stapes activate its tiny hair cells. These
then excite the nerves of hearing which carry sound to the brain.
-The
central auditory system is a complex network of neural pathways in
the brain that is responsible for sound localization, speech understanding
in noisy listening situations and other complex sounds, including
music perception.
Sound is transformed into mechanical
energy by the tympanic membrane. It is then transmitted
through the ossicles to the inner ear where it is changed
again into hydraulic energy for transmission through the
fluid filled cochlea. The cochlea’s hair cells are stimulated
by the fluid waves and a neurochemical event takes place
that excites the nerves of hearing. The physical characteristics
of the original sound are preserved at every energy change
along the way until this code becomes one the brain can
recognize and process. Hearing loss misleads our brain
with a loss of audibility and introduces distortion into
the message that reaches the brain. Changes in the effectiveness
of the brain to process stimuli, from head trauma, disease,
or from aging, can result in symptoms that mimic hearing
loss. The ears and the brain combine in a remarkable way
to process neural events into the sense of hearing. Perhaps
it’s fair to say that we “hear” with our brains, not with
our ears!
The signs of hearing loss can be subtle and emerge slowly, or they
can be significant and come on suddenly. Either way, there are common
indications. You should suspect hearing loss if you experience any
of the signs below. You might have hearing loss if you...
- Require frequent repetition.
- Have difficulty following conversations involving
more than 2 people.
- Think that other people sound muffled or like
they’re mumbling.
- Have difficulty hearing in noisy situations,
like conferences, restaurants, malls, or crowded
meeting rooms.
- Have trouble hearing children and women.
- Have your TV or radio turned up to a high volume.
- Answer or respond inappropriately in conversations.
- Have ringing in your ears.
- Read lips or more intently watch people’s faces
when they speak to you.
- Feel stressed out from straining to hear what
others are saying.
- Feel annoyed at other people because you can’t
hear or understand them.
- Feel embarrassed to meet new people or from
misunderstanding what others are saying.
- Feel nervous about trying to hear and understand.
- Withdraw from social situations that you once
enjoyed because of difficulty hearing.
- Have a family history of hearing loss.
- Take medications that can harm the hearing system
(ototoxic drugs).
- Have diabetes, heart, circulation or thyroid
problems.
- Have been exposed to very loud sounds over a
long period of time or single exposure to explosive noise.
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