Hearing is the sense by which sound isunderstood.
Like a wave in the ocean, a sound wave isa repeating disturbance or movementthat transfers energy through matter orspace.
Just as the crest of a water wave is followed
by a trough, the compression part of asound wave is followed by an area where theparticles are far apart.
Sound waves can travel through solids,liquids, and gases.
When the waves enter your ear, theystimulate nerve cells deep within your ear.
Messages are sent to your brain.
When the sound reaches the hearingarea of the cortex, it responds and youhear a sound.
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Your outer ear takes the sound wavesand sends them down the ear canal tothe middle ear.
The sound waves cause the eardrum tovibrate like the skin of a musical drum whenyou tap it.
These vibrations then move through threetiny bones called the hammer, anvil, andstirrup.
The cochlea (KOH klee uh) is a fluid-filledstructure shaped like a snail’s shell.
When the stirrup vibrates, fluid in thecochlea begins to vibrate.
These vibrations bend haircells in the brain by anerve.
Depending on how thenerve endings arestimulated, you hear adifferent type of sound.
Structures in your inner ear also control yourbody´s balance.
Structures called cristae ampullaris (KRIHStee. Am pyew LEER ihs), and the maculae(MA kyah, lee), sense different types of bodymovement.
Both structures contain tiny hair cells.
As your body moves, gel-like fluidsurrounding the hair cells moves andstimulates the nerve cells at the base of thehair cells.
This produces nerve signals that are sent tothe brain, which reads body movements.
Then, the brain sends signals to skeletalmuscles, resulting in body movements thatmaintain balance.
