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BACK ISSUES | NOVEMBER 2009 | CURRENT ISSUE
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NOVEMBER 2009
Sharp eyes
Your eyes are probably the most sensitive optical instruments ever invented, by man or by nature. In good light, your eyes can tell the difference between some 10 million colors! Some people with very good vision can recognize faces from more than a mile away!
In a spin!
The organs that control your sense of balance are actually inside your ears. Three arched tubes, called semicircular canals, inside each ear, are filled with liquid called lymph. Each tube helps to control your sense of balance in one dimension: width, height, and depth. Inside these canals are stiff hairs attached to nerve cells. When you move, the lymph inside the canals moves too and the movement of the liquid is felt by the hairs. The way these hairs move tells your brain what it needs to know to keep you balanced. If you spin around very quickly and then stop suddenly, the lymph in your semicircular canals keeps moving for a time. This tells your brain that you’re moving, but the rest of your senses tell it that you’re not. The result is the sensation we call dizziness!
What makes your body tired?
When you move the muscles in your body, they produce a substance called sarcolactic acid, also called the ‘acid of fatigue’. When too much of this acid forms around a muscle, the muscle becomes ‘tired’. The same acid is found in your blood too, as it travels to all parts of your body. So your entire body becomes tired after a period of time. When you sleep or rest, however, your body clears away these acids from around the muscles and from your blood, giving your body a chance to repair or replace cells.
