If your brain chemistry was changing in that same way,

假如你大脑的化学物质也这么变化
then you'd be slipping in and out of consciousness

那么你的意识将在清明与模糊之间徘徊
and you notice that you do a little bit right after lunch.

你会注意到午餐后你会有这种感觉
It's a little bit harder to pay attention than before lunch

午餐后想要集中注意力的话会比较难
because the chemistry is changing,

因为体内的化学物质发生变化
but that change in chemistry is muted by the blood brain barrier

但血脑屏障对这些化学变化进行缓冲
or the fact that molecules can't get very easily into the brain.

事实上这些分子不太容易进入大脑
Why else might drugs be administered in different ways?

还有什么其他原因导致给药方式的不同
Think about insulin, what do you know about insulin

想想胰岛素你们对它有什么认识
as a drug?

作为药物
Speed of action is an important thing

起效速度是重要的一点
and we're going to talk in a few minutes about some drugs

我们将花几分钟讨论的一些药物