SBI4U - Our Ears: Organs of Hearing and Balance

Our Ears:

Organs of Hearing and Balance (Mackwiz.K)

The Ear

-The organ of hearing and balance in humans and other vertebrates. The ear is responsible for collecting sounds, processing the sounds and sending sound signals to the brain. Not only does the ear deal with sound but also helps you balance!

Sections

-The ear is made up of three parts and each part has a different role. There's the outer ear that catch the wave, the middle ear which deals with vibrations, and the inner ear where the nerve signals start.

http://kidshealth.org/en/kids/ears.html#

http://www.hear-it.org/

The outer ear

Pinna;

the external part of the ear (visible part of the ear that we can see)
collects sound waves and directs them into the ear acting like a funnel; without this part the sound would take a different route making it hard to hear
helps control the difference in pressure inside and outside the ear (resistance must not be too high for the best sound)

The Ear Canal;

it's 3 cm
transports sound from the Pinna to the eardrum
it's the area where wax is produced; wax protects the canal, contains chemicals to fight off infections, and collects dirt (so it's gross but helpful)

The Eardrum;

a membrane that separates the outer ear and the middle ear
8-10 mm in diameter
thin piece of skin stretched tight like a drum by small muscles
very sensitive; pressure sound waves make it vibrate;
protected by the canal and earwax

The middle ear

When sound waves enter the middle ear, its main job is to turn the sound waves into vibrations that get delivered to the inner ear (middle ear works as an acoustic).

The ossicles

These are the 3 smallest bones in the body;

malleus (the hammer; attached to the eardrum)
incus (the anvil; attached to the malleus)
stapes (the stirrup; attached to incus)

The oval window

a membrane covering the entrance to the cochlea
when the vibration hits the sound waves go through the malleus, then the incus, then the stapes, and then to the oval winwo
smaller surface (increased pressure)

The round window

vibrates in opposite phase to vibrations
allows fluid in the cochlea to move

The Eustachian tube

connects the ear to the palate
equalizes air pressure on both sides making sure pressure doesn't increase (does this when we swallow)

the inner ear

This is the part of the ear where the nerve signals start. It is full of tubes and passages (the labyrinth)

The Cochlea

shape of a snail shell (curled tube)
filled with liquid that get into action when the ossicles vibrate
it has tiny cells covered in tiny hairs. When the sound goes to the cochlea, the vibrations make the hairs move which creates nerve signals to the brain so the brain understands it as sound (through the auditory nerve)
Cochlea has a hole (the helicotrema) which ensures that the vibrations from the oral window gets transmitted to all the fluid in the cochlea

The auditory nerve

a bundle of nerve fibres
carries info between the cochlea and the brain
it transfers signals from the inner ear to the brain
the tiny hairs of the cochlea are connected to the auditory nerve
when the hairs move they send electrical signals to the auditory nerve that is connected to the centre of the brain

Now it has been said that the ear is the organ that helps the human body with balancing. How so? the vestibular is the reason why.

The Vestibular (organ of equilibrium)

the balance mechanism that's part of the inner ear
it functions to register the body's movements
consists of 3 ring shaped passages (semicircular canals) filled with fluid that moves by the body's movements
the passages have hair fibres that react to movement that send impulses to the brain to help with our balance
Why do you get dizzy? When you spin and then stop, the passages (semicircular canals) are still moving hence why you feel dizzy. Your brain is getting 2 different messages and is confused

Bibliography

http://kidshealth.org/en/kids/ears.html#

http://www.hear-it.org/

Our Ears : Balance

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