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Each person’s ears have a set of three hollow tubes filled with fluid that function like spirit-level, i.e. the fluid in the tubes maintains its level by flowing in the direction of the tilt to occupy the space created by the tilt. In order to understand the working of tubes take the example of a glass filled with water. So long the glass is standing upright on its base there is no problem but when it is tilted on one side the water is displaced towards that side to retain its horizontal level.
Similar action takes place in the semicircular tubes of the ear. As long as the head and torso are perpendicular the fluid in the semicircular tubes remains undisturbed. When the head tilts towards left, right, forward or backward, the liquid in the tubes is set in motion towards the direction of the tilt by the pressure. Very fine hair cells situated in the lower part of the tubes bend opposite to the flow. These hair cells function as sensors to gauge the flow of the fluid and by bending convey to the brain via the nerve cells that the body is not balanced. On receiving this information the brain immediately issues suitable commands to the legs, neck, arms, or the entire torso to carry out movements in a particular way so as not to fall down and to regain balance. The brain processes the data received from the ears and issues command signals to the limbs so quickly that the entire process of ‘watch out!’ appears normal. Even a powerful computer can not match this lightening speed.
The brain of the person who is pirouetting does not become dizzy. It is working as efficiently as before. The culprit is the fluid in the semicircular tubes which continue to shake for some time after the person has stopped pirouetting. Hair cells in the tube also take some time to come back in the original position but the brain acting on the misinformation commands the legs to plant themselves firmly. It is not the brain that trips but the legs that trip trying to position firmly on the ground.
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