國家地理:生存危機下的人體反應

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.
參考中文翻譯：
對動物來說，大腦的這一部分在哺乳動物還不存在的恐龍時代就已經(jīng)在進化了。它幾乎無法打敗饑餓的威脅。三天以來，Jean-Luc 都被困在地面一下 ，一口吃的都沒有。他并不知道，他的大腦已經(jīng)使它的身體機能和行為方式發(fā)生了改變。
在大腦中有兩個不同的腦中心來產(chǎn)生進食行為和饑餓行為，他們位于大腦中不同的中心部位，叫做下丘腦。在大腦的這一部分，你被驅(qū)使著尋找任何可以吃的東西以免自己被餓死。
為了促使Jean-Luc尋找食物，他的大腦首先會分泌出一種荷爾蒙——食欲。所產(chǎn)生的食欲荷爾蒙量很微小，但是卻有著深刻的影響。這種荷爾蒙讓我們更加警惕，提高肌肉的效率，讓我們變成更好的捕食者甚至會提高我們解決問題的技能。
幾天來，Jean-Luc搜索了所有的洞穴，但是只是找到一點水，沒有任何吃的東西。它開始感到前所未有的恐懼。
即使我還有一點希望，我也會沉迷地想象死前的最后幾天或者最后幾個小時會發(fā)生什么事。這是個大問題：我會怎么死——會被凍死還是被餓死呢?這是我頭腦里一直閃現(xiàn)的一個問題。
當然這是他的命運，他記錄了一個信息。但是當希望漸漸變得渺茫時，Jean-Luc的大腦開始改變策略，以使自己在沒有食物的情況下也能生存下來。隨著所儲備的能量逐漸匱乏，他的身體變得更加高效。這使他的動作慢下來。現(xiàn)在他的肌肉利用更少的能量，內(nèi)臟器官也是如此。新的細胞分裂速度減緩，那些不必要的——比如手指甲，腳趾甲，毛發(fā)幾乎停止生長。Jean-Luc 進入了一種求生的狀態(tài)，在找到食物之前，都會使饑餓的動物一直生存下來。
當我們達到身體的極限時，這種增強的效率作用更大，可以幫助我們生存更長時間。