新托福阅读模拟试题
文章作者 100test 发表时间 2008:07:25 12:08:52
来源 100Test.Com百考试题网
Hormones in the Body
Up to the beginning of the twentieth century, the nervous system was thought to control all communication within the body and the resulting integration of behavior. Scientists had determined that nerves ran, essentially, on electrical impulses. These impulses were thought to be the engine for thought, emotion, movement, and internal processes such as digestion. However, experiments by William Bayliss and Ernest Starling on the chemical secretin, which is produced in the small intestine when food enters the stomach, eventually challenged that view. From the small intestine, secretin travels through the bloodstream to the pancreas. There, it stimulates the release of digestive chemicals. In this fashion, the intestinal cells that produce secretin ultimately regulate the production of different chemicals in a different organ, the pancreas.
Such a coordination of processes had been thought to require control by the nervous system. Bayliss and St
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