Hearing is the ability to sense sound. Sound travels through the air in waves, much
like the waves you see in the water pictured below.
Sound waves in air cause vibrations inside the ears. The ears sense the vibrations.
Sound waves travel through the air in all directions away from a sound, like
waves traveling through water away from where a pebble was dropped.
Imagine the sound of a honking horn or any loud noise.
What is the path of sound through the ear? Put the steps in order (classroom)
check your answers
1.The sound waves travel to the ear canal (external auditory canal in the figure). This is a
tube-shaped opening in the ear.
2.At the end of the ear canal, the sound waves hit the eardrum (tympanic membrane).
This is a thin membrane that vibrates like the head of a drum when sound waves hit it.
3.The vibrations pass from the eardrum to the hammer (malleus). This is the first of three
tiny bones that pass vibrations through the ear.
4.The hammer passes the vibrations to the anvil (incus), the second tiny bone that passes
vibrations through the ear.
5.The anvil passes the vibrations to the stirrup (stapes), the third tiny bone that passes
vibrations through the ear.
6.From the stirrup, the vibrations pass to the oval window. This is another membrane like
the eardrum.
7.The oval window passes the vibrations to the cochlea. The cochlea is filled with liquid
that moves when the vibrations pass through, like the waves in water when you drop a
pebble into a pond. Tiny hair cells line the cochlea and bend when the liquid moves.
When the hair cells bend, they release neurotransmitters.
8.The neurotransmitters trigger nerve impulses that travel to the brain through the
auditory nerve (cochlear nerve). The brain reads the sound and “tells” you what you are
hearing.
Anatomy of an ear
There are three main parts of the ear: the outer, middle, and inner ear.
outer ear
the pinna, ear canal and ear drum
transmits sound, prevents entry of foreign bodies
middle ear
3 small bones: hammer, anvil, stirrup
These small bones act as sound transitters.
They amplify the sound waves.
inner ear – labyrinth
vestibule, semicircular canal, cochlea
In the inner ear, the vibrations are changed to electrical signals by hair cells lining the cochlea.
The electrical signals then travel to the brain.
The semicircular canals are involved in balance.
watch the animation and answer the
questions.
http://www.bbc.co.uk/science/humanbody/body/factfiles/hearing/hearing_animation.shtml
1.The outer ear canal ends at the __________.
2.The __________ is the cavity between the eardrum and inner ear.
3.The snail-like __________ is filled with fluid.
4.The spiral organ of __________ consists of hair cells.
5.Nerve impulses travel along the cochlear nerve to the __________.
6.Because we have two ears, we are able to locate the __________ of
sounds.
What do these 2 activities have in common?
Ears do more than just listen.
They also sense the position of the body and help maintain balance.
Have you ever tried to stand on one foot with
your eyes closed? Try it and see what happens,
This gymnast is using the semicircular canals in
her ears, along with the cerebellum in her
brain, to help keep her balance on the balance
beam.
The parts of the ears involved in balance are the semicircular canals.
The canals contain liquid and are like the bottle of water pictured below.
When the bottle tips, the water surface moves up and down the sides of the
bottle. When the body tips, the liquid in the semicircular canals moves up and
down the sides of the canals.
Tiny hair cells lining the canals sense the
movement of liquid and send messages to the
brain.