Dr Sutapa Mukherjee

There's actually a characteristic pattern that happens.

So you've got to be in stage one sleep for a while and a while might be different depending on your age and also how tired you are.

But maybe, let's say, you know, after around 45 minutes, you might start going into stage two, stage one or two, depending on what your bedroom's like.

And then you stay in stage two sleep for a while.

And then you start to go into slow wave sleep, which is even different again.

The characteristic waves are different.

And slow wave sleep is really a time when...

the waves are even slower than stage one or two with characteristic pattern.

And then you get your first lot of REM sleep, which usually has taken about 90 minutes of this cycle before you can go into your first lot of rapid eye movement sleep or REM sleep.

And this is where your muscles are very relaxed.

Your

eye movements will be very quick.

And so that's why when we monitor sleep, we look carefully at whether the eye movements are there or not.

And that tells us when you're in REM sleep.

We don't know why it happens, but it definitely occurs and it doesn't happen in non-REM sleep.

So your eyes are not moving, but you've got these very quick eye movements.

Your breathing actually becomes very irregular too in REM sleep.

So physiologically, it's very, very different.

to the other stages of non-REM sleep where breathing is quite regular.

And even in slow wave sleep, our blood pressure drops.