LEARN WORK AND EARN Inc 5

SENSE OF HEARING


EARS Source of distraction and delight

Sounds are vibration of sound waves in the air.
These are picked up by your outer visible ears, and conveyed through a canal to the ear drum
The middle ear lies beyond the ear drum.
Three bones (ossicles) carry the sound waves to the inner ear.
These three ossicles, vibrate on receiving the sound waves, and convey through their motions, the vibrations to the inner ear.

Inner Ear: Organ of Hearing

This inner ear, lies deep inside the skull slightly below, and behind the eye ball, one on each side.
The hair like receptor cells, for hearing are in the coiled cochlea.
This cochlea has a shape, almost like shell of the snail.

This shell like organ is filled with fluid and is coiled two and half times.
When the sound waves reach the inner ear through the oval window, which is filled with stirrup of the stapes bone, (the third ossicle) the vibration convey movements in the fluid in the inner ear, through the tiny window.

The hair like nerve endings, you have about 25,000 in each ear, are the receptors.
The receptor cells convert this movement into an electrical signals, and this is conducted by the acoustic nerve, to the hearing centre in the brain.

Inner Ear: Organ of Balance

Close to the cochlea there are three semi-circular canals.
One canal is parallel to the ground the other i.e the second is parallel to the side of your head, and the 3rd is parallel to your face, each is a hollow tube filled with fluid, the walls have hair cells responsive to movement of the fluid.

The movement in the fluid in these canals is created by the movement of your head.

You may have noticed that when you spin around fast, you feel dizzy for a few moments.
This is because the fluid in these canals, is set in motion, and continues to spin even when you stop, but soon the dizziness disappears when the fluid comes to a stand still.

This system conveys information on the position of the head. The receptor cells pass information to your cerebellum.


Ear
Symptom to remember
- constant hum in ears
- hearing loss
- loss of balance
- vertigo
vomiting
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