国家地理:生存危机下的人体反应

In animals, this part of the brain evolved around the time of the dinosaurs before mammals existed. It's hardwired to beat starvation. For three days Jean-Luc has been trapped underground. He hasn't had a morsel to eat. He doesn't know it, but his brain is changing how his body functions and how he behaves.
There are a couple of different brain centers that graduate feeding behavior as well as hunger. They’re in different parts of the central part of the brain called the hypothalamus. And in that part of the brain you are really driven to seek out food to eat almost anything to try to stop yourself from starving to death.
To drive Jean-Luc’s search for food his brain first releases a hormone--orexin. Orexin comes in tiny doses, but it has a profound effect. This hormone makes us more alert, improves our muscle efficiency, making us better hunters. It even sharpens our problem-solving skills.
For days Jean-Luc scours the caves. He finds water but nothing to eat. He starts to fear the worst.
Even if when I had a little hope, I thought obsessively what would happen over the last few days or the last hours before dying. It was a big question: how I would die--was it going to be cold or hunger or… It was a question that I always had in my head.
Sure that he's doomed, he records a message. But as hope fades, Jean-Luc’s brain switches strategy to help him survive with no food. With his fuel stores depleted, his body becomes even more efficient. It makes him slow down. Now his muscles use less energy, so do all his internal organs. New cells grow more slowly. Nonessentials—fingernails, toenails, hair—hardly grow at all. Jean-Luc is entering a survival state that evolved to keep starving animals alive until they could get to food.
This enforced efficiency which kicks in when we're at our limit may have bigger implications. Some say, it could help us all live longer.
参考中文翻译：
对动物来说，大脑的这一部分在哺乳动物还不存在的恐龙时代就已经在进化了。它几乎无法打败饥饿的威胁。三天以来，Jean-Luc 都被困在地面一下 ，一口吃的都没有。他并不知道，他的大脑已经使它的身体机能和行为方式发生了改变。
在大脑中有两个不同的脑中心来产生进食行为和饥饿行为，他们位于大脑中不同的中心部位，叫做下丘脑。在大脑的这一部分，你被驱使着寻找任何可以吃的东西以免自己被饿死。
为了促使Jean-Luc寻找食物，他的大脑首先会分泌出一种荷尔蒙——食欲。所产生的食欲荷尔蒙量很微小，但是却有着深刻的影响。这种荷尔蒙让我们更加警惕，提高肌肉的效率，让我们变成更好的捕食者甚至会提高我们解决问题的技能。
几天来，Jean-Luc搜索了所有的洞穴，但是只是找到一点水，没有任何吃的东西。它开始感到前所未有的恐惧。
即使我还有一点希望，我也会沉迷地想象死前的最后几天或者最后几个小时会发生什么事。这是个大问题：我会怎么死——会被冻死还是被饿死呢?这是我头脑里一直闪现的一个问题。
当然这是他的命运，他记录了一个信息。但是当希望渐渐变得渺茫时，Jean-Luc的大脑开始改变策略，以使自己在没有食物的情况下也能生存下来。随着所储备的能量逐渐匮乏，他的身体变得更加高效。这使他的动作慢下来。现在他的肌肉利用更少的能量，内脏器官也是如此。新的细胞分裂速度减缓，那些不必要的——比如手指甲，脚趾甲，毛发几乎停止生长。Jean-Luc 进入了一种求生的状态，在找到食物之前，都会使饥饿的动物一直生存下来。
当我们达到身体的极限时，这种增强的效率作用更大，可以帮助我们生存更长时间。