Hi there, it's Matt here and welcome back to the podcast. Now, in our last episode. We spoke about sleep pressure and adenosine how it makes you tired in the evening. And then after sleep has cleared that adenosine away why you will feel in livened and awake the following day, but sleep pressure is only one half of the sleep-wake story.
There is a second Force at play in the sleep-wake negotiation, as it were, it's called your circadian rhythm or in plain speak your 24-hour body clock. Well, it's actually the wrong word for. It's not a body clock as will discover. It's a brain clock. As it turns out. Now, your 24-hour clock, will drum out a daily and a nightly Rhythm, and The Tick Tock rhythm of your clock will make.
Feel sleepy at night, and then makes you feel alert during the day. Now, although you have cicada in clocks, in almost every cell of your body. As I mentioned. There is a master clock that sits deep at the center of your brain. You can think of it almost like, Lord of the Rings, one ring to rule them all. Well, here there is one clock to rule them all, and that Central brain clock, regulates all of
The other body clocks. Now, if you were to give your circadian rhythm a personality trait, it would be labeled as a creature of habit. It never stops ticking out. It's rising and falling Rhythm day after day night. After night, for diurnal species, that are active. During the day, like us human beings. The Circadian rhythm will start drumming out. It's loud activating beat.
Full, you wake up in the morning and that drumbeat just gets louder and stronger into the mid morning hours and into the early afternoon. And this is when you will hit your Peak alertness, your Peak Performance on several different measures that we can assess in the laboratory will come back to what happens in the middle of the afternoon in just a second. But by the end of the evening, the Circadian Tick-Tock beat begins to
slow down. And is it tips into? It's awesome downswing. So to will drop your alertness and other words, you're going to start feeling sleepy and the drumbeat of your circadian rhythm keeps slowing down throughout your night of sleep, and it will hit its lowest point in the middle of your sleep phase. And once it hits that low Point, what we call the nadir, it will stay low for a few hours and then
The beat picks back up and it starts to rise just before you naturally wish to wake up. Should you allow yourself to wake up without an alarm clock? And then it starts all over again rising in. Its loud, beat to create the breadth of daytime wakefulness and dropping to create the calm, exhale of sleep at night. So a rising and dropping the waking. Inhale, the
Sleeping, exhale, inhale and exhale. And if you were to sort of draw out this circadian rhythm, it would look like a sinusoidal wave like a rising mountain peak of wakefulness and then a descending restful Valley of sleep, your circadian rhythm. By the way, knows nothing about your levels of adenosine sleep pressure and your levels of sleep pressure, know nothing about your circadian rhythm. They are.
Entirely independent. However, when you're keeping a standard sleep schedule, these two independent factors will beautifully coincide with a synchronicity that any to dance. Partners would be proud of sort of Fred and ginger as it were or probably Beavis. And Butt-head is closer to my style. But anyway, I'm getting off track. The take-home message. Is this as the
The weight of adenosine sleep pressure hits, its peak in the evening. It should arrive on the wings of the Slowdown turn, exhale of your circadian rhythm. And if those two things aligned in Perfect Harmony, you will be beautifully. Pulled down into sleep. That arrives with wonderful alacrity. Then with the full clearance of adenosine, the next morning and the removal of all of that sleep pressure. It will
So arrived as the drumbeat of your circadian rhythm starts to ramp back up again and combined. These two things will naturally eject you from sleep and they will Rouse you into full natural wakefulness. And so it's a beautiful story of sort of star-crossed lovers as it were. Maybe that's taking it a bit too far, but you get the sort of non Romeo and Juliet picture here of the dance between.
Tween your circadian rhythm and your sleep pressure, but wait, there's more. What about the
afternoons?
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episode.
A funny thing happens to your circadian rhythm beat after the peak late morning and into the early afternoon, your circadian rhythm. Oddly slows down for a few hours and I'm sure you've experienced this. It's sort of people around the meeting Table after lunch at work. And all of a sudden, you start to see those really ugly head drops. They're sort of the jaw goes into the chest and all of a sudden the head snaps back up again. I mean, it's a dead giveaway of
What's happening here? It's not that these people with their head. Bob's are listening to good music. Rather. They are falling prey to what we've discovered is a pre-programmed hardwired drop in your alertness in the afternoon. And for most of us. It happened somewhere between the one to four pm Mark as I mentioned. It happens after lunch, but counter to popular myth, it has nothing to do with you eating lunch. I can have you skip your lunch and it will
I'll still happen. And indeed, if I were to place electrodes on your head, I could show you this reliable drop in your brains. Physiological alertness that happens each and every afternoon. And what this means is that as humans may not have been designed to sleep in a single bout at night, which is what we call Mono phasic sleep, rather. We may have been designed to sleep in two bouts. In other words, one longer bout at night.
And then a siesta like nap in the afternoon. Now, don't worry naps will be treated in an entirely separate episode and we'll double-click and dive deep into naps. But for now just know that this fading of your alertness in the afternoon is nothing to necessarily be worried about. You're not to blame. It's natural. It's all part of your circadian rhythm. So that is your circadian rhythm briefly. Explain.
And which combined with sleep, pressure will accurately explain when you want to be awake and when you wish to be asleep, so why then are we all a little different in our timing? Why is it that some people will cash it out in the evening, you know, very early on and they'll be embed your by 8 or 9, p.m. In the evening. And why is it that other people don't wish to get into bed and fall asleep through until the wee hours.
Of the morning. This is what we call your chronotype and that will be the topic of the next several episodes in this podcast series instead. I will simply now sign off. I will say good night and thank you so much again for listening to the podcast. As I mentioned before in the previous episode. If there's any advice that you have for how I can be doing this better, please just say hello. And drop me a message on Instagram.
I am there as the handle. Dr. Matt, Walker dr. With a Dr. And I just want to make clear that I'm not a medical doctor and none of the content in this podcast should be considered as medical advice in any way shape or form and no prescriptive in. Anyway, thanks very much, and I'll see you in the next
episode.
