考博英语阅读篇章复习材料精选 (29)

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考博英语阅读篇章复习材料精选 (29)　　　　　　　　　　　　

　　When the Head Rules the Heart

　　Some heart attacks may be all in your head. Scientists in Canada have found a region in the brain that may control the ac- tivity of the heart and blood vessels. They say that abnormalities in this region could account for the hundreds of thousands of otherwise unexplained cardiac arrests??? that occur every year.

　　Andrew King, David Cechetto and their colleagues at the University of Western Ontario in London reported at the meeting that they asked five subjects to carry out simple tasks that raise blood pressure. For instance, they were told to squeeze a cylinder as tightly as possible, or hold their breath for several seconds. As they did this, the researchers monitored the subjects' blood pressure and heart rate throughout.

　　The team then asked all the subjects to repeat the tasks while in a high-resolution functional magnetic resonance??? brain scanner, and watched which areas of the brain the tasks activated. It turned out that all the tasks activated a spot in the insular cortex, which is tucked inside a fold in the brain just above ear level.

　　The researchers suspect that the insular cortex controls the heart and blood vessels. This theory would fit in with a study Cechetto carded out several years ago, which showed that a region of cardiovascular control exists in rats' brains. By elec- trically stimulating that region, he could alter the heart rate, and even bring about lethal cardiac arrhythmia in the animals.

　　King and Cechetto believe that many unexplained heart at- tacks could be due not simply to the traditional factors like poor diet and clogged arteries, but to abnormalities in the brain's cardiovascular control center. “They may have a neural basis,” King told New Scientist. “There are people who run all the time, eat well, and yet they end up dying.”

　　The unexplained heart attacks include those that afflict about 6 per cent of all stroke patients, even though they have no history of heart problems. King speculates that the attacks arise because their strokes may have damaged the brain's cardiovascu- lar site.

　　This is the first time that a higher brain region that controls internal organs has been identified in humans. The researchers say they would like to know what their new results say about the link between stress and heart disease. It is well known that anger. and stress play a major role in sudden cardiac death, ether- sclerosis, heart attacks and strokes, but exactly why this happens is unclear.

　　The team says that their results might lead to ways of pre- venting many heart attacks. They hope to find out if people whose heart rates and blood pressure increase dramatically in response to stress also have more activation in these brain areas—and whether heart attacks apparently caused by stress and anger might be triggered in these regions. “There are definite clinical applications.” says King.

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