Dr. Matt Walker

So the way we think about it in sleep science, and there is some argument that it's maybe even more complex than this, but for the most part, there are two main forces, two main processes that will determine when you want to be awake and when you want to be asleep.

The first of those we've spoken about, which is your circadian rhythm.

And that circadian rhythm

is you have a clock inside of your brain.

You have a central 24-hour clock, and it's a master clock.

And that clock, as you've spoken about many times, is called the suprachiasmatic nucleus.

We don't have to get hung up on the statement.

Just think about it as your master 24-hour clock.

And it beats out this rhythmic sort of message of activity for us because we're diurnal during the day and then inactivity at night, activity during the day.

And it just goes up and down, up and down every single day.

That's your circadian rhythm, and that's the suprachiasmatic.

The reason I say it's the master clock, we've now learned that there are these circadian rhythm clocks in almost all cells of the body.

You've got clocks all over your body in these tiny little clocks, but a little bit like Lord of the Rings, just like there's one ring to rule them all, well, there's one clock to rule them all, and that is the central brain clock, the suprachiasmatic nucleus.

Now you can dissociate those different clocks and you can get them kind of doing some funky things, but for the most part, it's the central time giver.

So you would think that, well, that's all you need to tell your brain and your body it's time to sleep or it's time to be awake.

It's not.

There is a second force in place here and it is called, we sometimes call it as process S or sleep pressure.

So you've got your circadian rhythm on the one hand going up and down every 24 hours, but then you've got this funny thing called sleep pressure.

Sleep pressure comes down to a chemical

that is called adenosine.