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Ever notice your body seems to do certain things around the same time each day?
有没有注意到你的身体似乎每天都会在同样的时间做同样的事情？
You wake up around the same time, feel peckish around the same time, and are tired and ready for sleep around the same time.
同一时间醒来，在同一时间感到肚子饿，在同一时间感到困倦，也在同一时间准备睡觉。
You might think it's habit, but it's actually thanks to biological processes that keep your body in lock step as the day progresses.
你可能会觉得这都是习惯，然而，实际上，这要归功于让你的身体随着时间的推移保持同步状态的生物学过程。
That daily clock is called a circadian rhythm, and most living organisms have one, from fruit flies to daffodils to microscopic organisms.
这一日常时钟即“昼夜节律”，大多数生物体，从果蝇到水仙花到微生物，都有昼夜节律。
If it lives under the sun chances are there's something that keeps it in tune with the sun's 24-hour pattern.
凡是生活在太阳底下的生物，其体内就很有可能有保持与太阳的24小时升落模式一致的东西。
In humans, there are proteins in nearly every tissue and organ that help maintain proper timing.
就拿人类来说，人体几乎每个组织和器官中都有能够帮助维持合理的时间表的蛋白质。
But they don't function independently.
但这些蛋白质并不是独立发挥作用。
Inside your brain is something like a master clock that all other biological clocks sync up to.
我们的大脑里有一个类似于控制其他所有生物钟同步的主时钟。
This master clock is called the suprachiasmatic nucleus,
这个主时钟也就是“视交叉上核”，
and it's made up of around just 20,000 neurons arranged in two tiny wing-like structures nestled inside your hypothalamus.
由大约2万个位于下丘脑内两个小翼状结构中的神经元组成。
The hypothalamus plays a big role in releasing hormones and controlling appetite, among other things,
下丘脑在释放荷尔蒙和控制食欲等方面起着重要的作用，
so the suprachiasmatic nucleus' place here makes sense if it's going to be in charge of keeping your body clock synchronized.
因此，要负责保持大家的生物钟同步的视交叉上核位于下丘脑这个部位也就说得通了。
But it's not run by gears or bits in a computer, it's run by biological processes.
然而，视交叉神经核不是由齿轮，也不是由计算机的单元驱动的，而是由生物过程驱动的。
In the suprachiasmatic nucleus, there are proteins produced on a negative feedback loop.
视交叉上核中有负反馈环蛋白质。
The proteins (called PERIOD and cryptochrome) switch off their own production when they build up,
这些蛋白质（即“PERIOD”和“隐花色素”）堆积后就会切断细胞继续生产同类蛋白，
and cells resume production once the proteins degrade.
而他们降解，细胞就会恢复生产。
These protein cycles peak about every 24 hours, though it's not exact.
这些蛋白质的含量大约每隔24小时达到一次巅峰，但这一时间并不完全准确。
A 1974 study left 15 people without clocks or daylight for up to 13 days.
1974年的一项研究让15名受试者在没有时钟也没有日光的环境下生活了长达13天。
The researchers found the humans tended to live on a day of between 25 and 27 hours.
研究人员发现，人类一天的作息时间通常在25至27个小时之间。
Since these proteins are so important to staying in sync,
由于这些蛋白质对于保持日常作息同步异常重要，
genetic mutations that change their structure can throw a person's internal clock out of whack.
发生改变这些蛋白质结构的基因突变就会造成生物钟紊乱。
People with say familial advanced sleep phase syndrome produce an unstable PERIOD 2 protein, which speeds up their circadian rhythm.
家族性睡眠状态提前综合征患者体内会产生不稳定的PERIOD 2蛋白，从而加速其昼夜节律。
As a result they're up at 3am and they are in bed by 7pm, so no partying for them I guess.
这样一来，你就会发现他们可能早上3点就起床，晚上7点就睡觉了，派对他们是参加不了的了。
You may have noticed though that when you travel or set your clock forward for daylight savings, your body eventually adjusts.
你可能已经注意到了，当您旅行或将时钟设置为夏令时时，你的身体最终也会适应过来。
That's because light has a big influence on your suprachiasmatic nucleus too.
那是因为光对你的视交叉上核也有很大的影响。
The light your eyes take in turns certain genes in the cells on or off, coding the proteins that keep time.
进入眼睛的光会激活或关闭细胞中的某些基因，从而对记录时间的蛋白质进行编码。
This is why light is the biggest external factor in keeping a steady rhythm,
这就是为什么光是保持稳定的作息节奏的最大外在因素的原因，
and why you don't seem to get tired when you stay up late looking at a phone screen.
也是为什么熬夜玩儿手机时你似乎并不觉得累的原因。
But light isn't the ONLY factor, your body clock is influenced by things like eating cues and social cues as well.
但光并不是影响作息的唯一因素，你的生物钟还会受到饮食信号和社交信号等因素的影响。
An unstable or abused circadian rhythm can have medical implications.
不稳定或放纵的昼夜节律还可能引起疾病。
Lack of sleep and disrupted circadian rhythms have been linked to obesity, depression, and other chronic illnesses.
例如，睡眠不足，昼夜节律中断与肥胖、抑郁等慢性疾病也有关。
So if it's late at night and you're watching this, do yourself a favor, put the phone down and get some rest.
所以，如果你看这个视频的时候已经是深夜了，那就请你心疼心疼自己，放下手机，好好休息。
Or turn on night mode and watch just one more episode.
或者你也可以打开夜间模式，再看一集。
Like staying up all night watching science videos?
喜欢熬夜看科幻视频？
Cuz you should definitely subscribe and check out my video on how blue light from this very screen is messing with your body clock RIGHT NOW.
你绝对需要订阅我们的栏目，去看我那期关于手机屏幕的蓝光是如何扰乱你的生物钟的视频。
Also Fun fact: The term circadian comes from the latin words circa, meaning around, and diem, meaning day.
老规矩，又到了我们的“趣味事实”环节：“昼夜节律”这一术语来自拉丁语，“circa”的意思是“大约”，“diem”的意思是“天”。
It's your rhythm around the day.
合起来就是一天的节奏。
Neat right? Thanks for watching.
是不是很清楚明白？感谢大家的观看。
