Overview
Your heart pumps your blood around your body, all hours, every day of the week, to keep you alive. Your heart is about the size of your fist, and it’s made of special muscle called “cardiac” (KAR-dee-ak) muscle. Cardiac muscle lets your heart keep the beat, it can also speed up or slow down, depending on what your body needs. Your heart works like an automatic pump – it squeezes, or contracts, and un-squeezes, or relaxes, to push blood through the four different sections of your heart. Valves, special one-way openings, are like little doors between the sections – making sure your blood moves in only one direction through your heart, to your lungs, back to your heart, and then around your body again.
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4 - 1Rivers & Streams November 03, 1995 -
4 - 2Nutrition November 10, 1995 -
4 - 3Marine Mammals November 17, 1995 -
4 - 4Earthquakes November 24, 1995 -
4 - 5NTV Top 11 Video Countdown December 01, 1995 -
4 - 6Spiders January 05, 1996 -
4 - 7Pollution Solutions January 12, 1996 -
4 - 8Probability January 19, 1996 -
4 - 9Pseudoscience January 26, 1996 -
4 - 10Flowers January 27, 1996 -
4 - 11Archaeology January 28, 1996 -
4 - 12Deserts January 29, 1996 -
4 - 13Amphibians January 30, 1996 -
4 - 14Volcanoes January 31, 1996 -
4 - 15Invertebrates February 07, 1996 -
4 - 16Heart February 14, 1996 -
4 - 17Inventions February 21, 1996 -
4 - 18Computers April 25, 1996 -
4 - 19Fossils September 05, 1997 -
4 - 20Time September 12, 1997