maybe you're a world traveler and you think nothing across in a half a dozen time zones in a couple hours or maybe you work at night and it's finals week and sleep is less important than passing calculus or maybe you just co-hosted a 48 hour live stream with your brother hey it's your choice but if take it to the extreme living the night life can mess you up leaving you exhausted and confused and probably sick that's because you like most other inhabitants of the Earth have a special biological system that keeps your body in sync with the cycles of day and night it's your circadian rhythm and unlike your alarm clock it doesn't have a snooze [Music] button our internal timekeeping device is logically enough synchronized to the rising and setting of the sun many of your body's systems are calibrated to the appearance and disappearance of natural light and when we mess with that things can get out of whack in a hurry circadian comes from the Latin circadium or approximately a day and pretty much all living organisms down to algae and bacteria have their own circadian rhythms whether you're an insect or aamal those rhythms affect the three big Necessities eating sleeping and mating everything from testosterone secretion to bowel movement suppression is controlled by this daily cycle in humans scientists are slowly beginning to understand how these natural oscillations take place every day what we're pretty sure about is that the main regulator of circadian rhythm can be found in the hypothalamus a small area at the base of your brain that's responsible for connecting the nervous system to your endocrine system our biological clock is dictated by a group of nerve cells within the hypothalamus called the supermatic nucleus or scn this is connected to our optic nerves allowing the scn cells to respond to light and dark so in the morning when our optic nerve sense light the scn sends signals to raise our temperature heart rate blood pressure and delay the release of hormones like melatonin that helps us with the sleeping researchers have found that as our body temperatures rise throughout the morning our memory alertness and concentration also sharpen so we tend to be at our cognitive best in the late morning and that is generally followed by an afternoon lull in fact while our desire to sleep is strongest from 2:00 a.m. to 4:00 a.m. a close second is between 2:00 p.m. and 300 p.m. that may sound counterintuitive unless you have ever had a class at 2: p.m. in a nice warm room and suddenly that wooden desk starts to feel a lot like a featherbed this suggests that napping is an important and natural part of our daily rhythms so don't feel bad about it no other species exhibits the same once a day sleep pattern that most humans have become accustomed to and there's grow evidence that mid-afternoon napping might be in all of our best interests that afternoon lull is followed by another period of alertness but in the evening as the sun disappears The scn again picks up those signals of changing light from our eyes organs shift into low gear our body's temperature cools and sleep induced hormones are activated problem is that our daily schedules do not correlate with sunrise and sunset anymore but with working and studying and late night riting we're constantly fighting that Master Clock that's been trying to keep us in sync since we were babies scientists have linked disruptions to our natural rhythms to health issues ranging from diabetes and obesity to depression and dementia it's believed that up to 15% of our genes may be regulated by circadian rhythms so when you get off that next transatlantic flight or finish pulling that all night or do yourself a favor listen to your body and take some more naps I'm going to go down for one right now cuz if we're approaching the 2 p.m. thing so I'm not sure how this is going to look with the great screen you guys but but I don't care I'm sleepy thank you for watching this SI show do and an extra special reverent thank you to president of space kurgazat you could check out his YouTube channel to find out how you can be decreed president of space by me and a whole slew of other ways you can help keep us going here at sow you can go to subbable.com if you have any questions or comments or ideas for us we're on Facebook and Twitter and of course down in the comments below and if you want to keep getting smarter with us you can go to youtube.com/ show And subscribe [Music]