The 2 mechanisms behind how awake or how sleepy we feel Video starts at 0:26 youtu.be/kzmAhaiD7m4?t=26 00:00:26,240 --> 00:00:29,760 there's one mechanism that's very clear, that's super important which is that 00:00:31,920 --> 00:00:33,760 the longer we are awake the more adenosine accumulates in our brain 00:00:37,040 --> 00:00:40,160 and adenosine binds to adenosine receptors no surprise there 00:00:43,200 --> 00:00:47,039 and it creates the feeling of sleepiness independent of time of day or night 00:00:50,399 --> 00:00:52,800 so there are two mechanisms 00:00:52,800 --> 00:00:55,440 one is we get sleepy as adenosine accumulates. 00:00:57,120 --> 00:00:58,719 the longer we've been awake the more adenosine is accumulated in our system 00:01:00,960 --> 00:01:04,640 but how sleepy we get for a given amount of adenosine depends on where we are in this so-called circadian cycle 00:01:09,280 --> 00:01:11,840 and the circadian cycle is just this very very well conserved oscillation 00:01:13,920 --> 00:01:16,000 it's a temperature oscillation where you go from a low point 00:01:17,520 --> 00:01:19,040 typically if you're awake during the day and you're asleep at night 00:01:20,560 --> 00:01:23,680 your lowest temperature point will be like 3 a.m 4 a.m and then your temperature will start to creep up as you wake up in the morning 00:01:28,880 and then it'll peak in the late afternoon and then it'll start to drop again toward the evening and then you get sleepy again 00:01:33,680 --> 00:01:35,920 that oscillation in temperature takes 24 hours 00:01:44 i do not think it's a coincidence that it's aligned to the 24-hour spin of the earth on its axis 00:01:52,000 --> 00:01:54,320 the fact that we tend to be bathed in sunlight for a portion of that spin and in darkness for the other portion of spin 00:01:58 so there are two mechanisms the adenosine accumulation and the circadian time point 00:02:04 and those converge to create a sense of sleepiness and wakefulness 00:02:08,080 --> 00:02:09,758 the simple way to reveal these two mechanisms, to uncouple them, is stay up for 24 hours 00:02:16 let's say you stay up midnight, 2 AM, 3 AM, provided you're on a regular schedule 00:02:26,080 --> 00:02:28,720 i will get very sleepy around 3 AM 4 a.m 00:02:29,920 --> 00:02:33,040 but then around 5 or 6 or 7 a.m which is my normal wake-up time i'll start to feel 00:02:35,680 --> 00:02:37,920 more alert even though adenosine has been accumulating further 00:02:40,000 --> 00:02:42,560 so adenosine is higher for me the longer i stay up and yet i feel more alert than i did a few hours ago 00:02:45 and that's because these are two interacting forces 00:02:47 SO ADENOSINE MAKES YOU SLEEPY 00:02:49 AND THEN JUST HOW SLEEPY OR HOW AWAKE YOU FEEL ALSO DEPENDS ON WHERE YOU ARE IN THIS TEMPERATURE OSCILLATION THAT TAKES 24 HOURS