The ear has two main functions. It receives sound and converts it into signals that the brain can understand. It also helps us to balance. The two functions are closely connected.
The hearing system
The ear is the first part of the hearing system. The pinna catches sound waves and directs them down the ear canal. The waves then cause the eardrum to vibrate. These vibrations are passed across the middle ear by three tiny bones. These are known as the malleus, incus and stapes. They are sometimes called the hammer, anvil and stirrup. The bones increase the strength of the vibrations before they pass through into the cochlea via the oval window.
The cochlea looks like a snail’s shell. It is filled with fluid and contains many thousands of tiny sound-sensitive cells. These cells are known as ‘hair cells’. As the vibrations from the bones in the middle ear enter the cochlea they cause movement in the fluid. This causes the hair cells to bend. The movement of the hair cells is like the movement of seaweed on the sea floor when waves pass over it. As the hair cells move they create a small electrical charge. These move along the auditory nerve to the brain where they are converted into signals that can be understood as sound.
For an ear to function fully and give us access to sound, all of these elements must work well. Deafness happens when at least one part of this system is not working effectively.
Balance is controlled by the semicircular canals. These are three tubes that are filled with liquid. As we move the fluid in our semicircular canals moves. This creates a signal that is sent to the brain. This information, along with information from other senses, allows us to be aware of our position and helps us to keep our balance.
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