【英语时差8,16】手为什么会颤抖？（在线收听）

 Hold your hand out and try to keep it perfectly still. After a moment, it will probably begin to shake. Hold that same hand out just before you give a major presentation to your new boss, and you’ll notice that those normal small tremors increase substantially. Why? The answer has to do with how nervous feelings influence a response cycle between two parts of your brain. These parts are called the basal ganglia and the cortex. In order for your brain to control the steadiness of your hand, the cortex and the basal ganglia exchange signals with each other. First, the cortex sends a signal to the basal ganglia; the basal ganglia, in turn, responds returning a signal to the cortex. These signals are the basis of motor control. By exchanging signals, the cortex and the basal ganglia allow your hand muscles to hold their position. This cycle of signals repeats continuously the entire time your hand is extended.