Mrs. Deal's Science Class



Bears Have Healthy Hearts—But Why? ArticlePAGE 10104775000Photo credit: AP PhotoResearchers are studying hibernating grizzly bears to learn why the animals have such healthy hearts.PULLMAN, Washington (Achieve3000, August 13, 2010). Grizzly bears will eat just about anything. They can have 50 percent body fat. The bears weigh over 800 pounds (363 kilograms). They will spend nearly half the year sleeping. If people lived like that, they would quickly develop health problems that would likely lead to heart attacks. Yet these furry mammals rarely have heart illnesses. In fact, their hearts are very healthy. Scientists want to know why some seemingly unhealthy habits don't affect grizzlies. They hope the answers they find will help humans avoid heart disease. This is the leading cause of death in the U.S.Lynne Nelson is an animal cardiologist. She has spent seven years studying grizzlies. Nelson works at the Bear Center at Washington State University (WSU). In her studies, Nelson takes blood samples from bears. She also measures their blood pressure. Some of the bears, Nelson said, are well trained. These animals are used to the tests. In fact, they will willingly stick a limb out of the cage to be tested—even as they hibernate.The information Nelson and her coworkers have gathered has sparked their interest. For example, the team has learned that a bear's heart changes during hibernation. Two of the heart's four chambers shut down. The chambers shut down without causing any damage. A grizzly's heartbeat also plunges. A bear's heart beats at more than 80 beats per minute when it is awake. When it is hibernating, the heartbeat drops to less than 20 beats. Tests also show that blood begins to pool in the bear's heart. However, the bears do not experience blocked blood flow. Blocked blood flow is dangerous because it can cause heart attacks."The changes in the heart that [happen] in hibernation are things you and I couldn't [live through]," said Nelson. "Yet bear hearts are very healthy."Thus far, Nelson and other scientists can't explain exactly how bears' hearts stay strong. The scientists do know that bears' hearts become stiffer during hibernation. This allows the heart to keep its shape. It allows blood to continue flowing unblocked. The team thinks this might help a grizzly to avoid heart problems.Nelson's research could also prove lifesaving for humans. Researchers hope to learn how bears deal with being asleep for so long. What they find could have meaning for astronauts during long space flights. The findings could also prove useful for humans who are bedridden.Harry Reynolds has also researched bears. According to Reynolds, bears make excellent stand-ins for people in health research. This is because bears and humans share many biological similarities."If there is any model species for human medicine and health studies, it's got to be bears," said Reynolds.Nelson's research is important because of what it means for humans. But it could also mean lifesaving information for the bears. Grizzlies are currently listed as a threatened species. The center's mission is to better understand the animals. By doing so, the grizzlies and other bear species can be conserved.Scientists outside of the Bear Center are also studying bear hibernation. They hope their discoveries will lead to improved health in humans. Seth Donahue is a researcher at Michigan Tech. Donahue researches black bears. He has found that the bears' bones stay strong during hibernation. A bear's cells, he found, continue to create new bone-making material as the animal sleeps.Scientists have also learned that bears keep muscle strength and mass during hibernation. Scientists learned that bears appear to exercise several times a day as they sleep. During hibernation, bears move from head to toe. They start at the neck and move downward. This explains why bears can move with ease shortly after hibernation."There are many, many interesting questions with hibernation and bears," said Reynolds.Associated Press contributed to this story.PAGE 2Dig DeeperLike you, grizzly bears are mammals. All mammals have a four-chambered heart which is the main organ of the circulatory system. This is a pretty important body system. Why? The circulatory system moves blood around a mammal's body. This blood carries life-supporting oxygen to all the cells of its body while also removing carbon dioxide waste.?Mammals have other important organ systems, too. For example, the respiratory system allows mammals to breathe and the skeletal system allows them to move. These systems aren't exactly the same in different animals. But they do serve similar purposes in keeping the animal alive.Dictionarybedridden (adjective) ? ?having to stay in bed for a long time due to illnessbiological (adjective) ? ?having to do with living thingscardiologist (noun) ? ?a doctor who specializes in the treatment of the heartcirculatory system (noun) ? ?a system inside a person or animal's body that includes blood, blood vessels, and the heart; this system moves blood through the bodyhibernate (verb) ? ?to spend the winter months in a state of deep sleepresearch (noun) ? ?a study or experiment done to better understand somethingrespiratory system (noun) ? ?parts of the body that help a person or animal to breathe; the lungs are part of the respiratory systemskeletal system (noun) ? ?the bones and tissues in the body that hold people and many animals upBears Have Healthy Hearts—But Why?ActivityPAGE 11. Which best replaces the question mark in the box above?? The bear's heartbeat drops during hibernation.? The bear's heart can keep its shape.? The bear can keep muscle mass during hibernation.? The bear has 50 percent body fat.2. The news article says all of the following except __________.? A researcher found that a bear's bones stay strong during hibernation.? A bear's heart beats at more than 80 beats a minute during hibernation.? Bears move from head to toe during hibernation.? Bears and humans share many biological similarities.3. Which of these is a fact?? Lynne Nelson cares too much about helping bears and fish.? Lynne Nelson deserves an award for training grizzly bears so well.? Lynne Nelson works at the Bear Center at Washington State University.? Lynne Nelson has the most knowledge in the field of animal research.4. The article states:The center's mission is to better understand the animals.Which is the closest synonym for the word mission?? Future? Demand? Claim? Goal5. This article mainly talks about __________.? The exercises that bears appear to do during hibernation? The methods that researchers use to train grizzly bears at WSU? The ways that researchers are trying to protect grizzly bears? The research on bears that may help prevent heart disease in humans6. Suppose you were writing a summary of this article. Which of these is most important to include in a summary?? Grizzly bears can have as much as 50 percent body fat.? Grizzly bears can weigh as much as 800 pounds.? Scientists are studying bears to help humans avoid heart disease.? Scientists learned that bears exercise several times a day.7. The article states:The center's mission is to better understand the animals. By doing so, the grizzlies and other bear species can be conserved.Which would be the closest synonym for the word conserved?? Adapted? Solved? Saved? Adopted8. Mary wants to learn more about grizzly bears. She can find most of her information __________.? On a Web site about how scientists perform research? On a Web site about Washington State University? In a book about threatened species living in the U.S.? In a book about the likely causes of heart disease ................
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