SENSE of HEARING-Part 4

Like your other sense organs, your ears are extremely well designed.  In fact, they serve two very important purposes.  Do you know what they are?  You were probably able to figure out that your ears help you to hear sounds, but what you probably did not know is that your ears also help you to keep your balance.

How You Hear.  When an object makes a noise, it sends vibrations (better known as sound waves) speeding through the air. These vibrations are then funneled into your ear canal by your outer ear.  As the vibrations move into your middle ear, they hit your eardrum and cause it to vibrate as well. This sets off a chain reaction of vibrations.  Your eardrum, which is smaller and thinner than the nail on your pinky finger, vibrates the three smallest bones in your body: first, the hammer, then the anvil, and finally, the stirrup.  The stirrup passes the vibrations into a coiled tube in the inner ear called the cochlea.

The fluid-filled cochlea contains thousands of hair-like nerve endings called cilia.  When the stirrup causes the fluid in the cochlea to vibrate, the cilia move.  The cilia change the vibrations into messages that are sent to the brain via the auditory nerve.  The auditory nerve carries messages from 25,000 receptors in your ear to your brain.  Your brain then makes sense of the messages and tells you what sounds you are hearing.

How You Keep Your Balance. 
Near the top of the cochlea are three loops called the semi-circular canals.  The canals are full of liquid also.  When you move your head, the liquid moves.  It pushes against hair like nerve endings, which send messages to your brain.  From these messages, your brain can tell whether or how your body is moving.

If you have ever felt dizzy after having spun around on a carnival ride, it was probably because the liquid inside the semicircular canals swirled around inside your ears.  This makes the hairs of the sensory cells bend in all different directions, so the cells’ signals confuse your brain.

What Did You Say? 
 Did you know that some people have trouble hearing and others cannot hear at all?  Well it’s true.  When a person can’t hear well, a hearing aide can sometimes help them hear well.  However, people who are entirely deaf have to rely on all their other senses to help process all of the information from the world around them.  They are deaf because of an illness or they were born that way.  You can also lose your ability to hear at an early age by listening to things that are very loud.  Scientists measure loudness in decibels.  Below is a table of various noises and their decibel level.

FACT NOTES on HEARING:

 ð Babies can get earaches because of milk backing up in the Eustachian tube, which causes bacteria to grow and may cause hearing problems later in life.

       ð When you go up to high elevations, the change in pressure causes your ears to pop.

       ð Children have more sensitive ears than adults.  They can recognize a wider variety of noises.

       ð Too much fluid putting pressure on your eardrum causes an earache.  Earaches are often the result of an infection, allergies or a virus.

       ð Animals hear more sounds than humans.

       ð Dolphins have the best sense of hearing among animals.  They are able to hear 14 times