until it gets a negative signal to turn off.

它就会一直开着
When does that negative signal happen?

什么时候会产生关闭信号呢
When the temperature gets above the level you want it to be.

就在当温度超过你想要的温度时
So that's a negative feedback control system.

这就是负反馈控制系统得名的原因
The heater is on,

加热器会开着
it's producing heat until a negative signal is registered,

一直产生热量直到它得到一个关闭的信号
'oh we've gone too high', and then it turns off.

噢我们弄得太热了然后就关闭了
Our bodies have mechanisms like that,

我们的身体有着与之类似的机制
that mainly use the principle of negative feedback

主要依靠负反馈原理来
in order to control the parameters that are important for life within a certain range.

将与生命息息相关的指标控制在一定范围
So why is temperature, for example, such an important thing to control?

那为什么体温是如此重要的调控指标呢
Why are all of us in this room

为什么这间教室里所有的人