Science Questions

Why do I wake up before I need to?

Tue, 10th Nov 2015

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Renny McCullough asked:

I wake up most mornings around 6am, but don't have to get ready for work until 8am. During the two hours I lie in bed, trying to sleep, but it isn't until around 7.50am (or later) that I start to fall into a deep sleep.


Is there an actual biological reason?


SleepChris Smith held the answer to Renny's question...

Chris - The reason this happens is that weíre actually extremely good at keeping time. In common with pretty much every living process on Earth and I'm including in that bacteria even, we have body clocks. Bacteria have a body clock. They know what time of day it is chemically speaking. In us, the seat of that body clock is a small cluster of maybe something like 20,000 nerve cells which is in a part of the brain called the superchiasmatic nucleus. Itís in the bottom of the centre of your brain. These nerve cells are running a genetic programme where gene 1 turns on and that turns on gene 2 which in turn, turns on gene 3 and feeds back and switches off gene 1. And this genetic clock ticks around taking about 24.5 hours to complete its cycle. As it does so, it changes the activity of the nerve cells in the superchiasmatic nucleus and because they are connected to lots of other bodily systems, they can influence how different parts of your brain function and critically, they influence other parts of your so-called hypothalamus including the part of your hypothalamus that produces the hormone cortisol which comes out of your pituitary, goes around your bloodstream, and visits every cell in your body. And this is how your brainís body clock then sets slave clocks which are running in every single cell pretty much in your body. So, every cell in your body knows what time it is. When you get into a rhythm of always waking up at a certain time, your body has to anticipate that itís going to need a big surge of energy at a certain time of day because that means that when you leap out of bed in the morning, you're ready to go. Your metabolism is fired up, you have energy on tap, you're enthusiastic, rearing to go because you want to get to work because itís Monday morning. And the way it does that is by learning that process and cortisol setting all those clocks. Now, what that does mean is that when you change time zones, itís all off-whack and out of kilter because that learning needs to be relearned and readjusted. It also means that because your body clock hasnít catered for weekends, it still thinks itís going to be Monday to Friday. And so, your body clock gets you out of bed even on the weekend, and at least alerts you and wakes you up, and prepares you for the day ahead before you actually need to. It takes a little while to overcome that effect and try and drop off again, and by then of course, you should be rearing to go again. unfortunately, there's no simple answer apart from learning to get up later during the week which is not always possible.

Kat - I have seen some quite interesting stuff about schools and workplaces. It should be more catered towards people who have different sleep-wake cycles because I'm a real night owl. I struggle to fall asleep before about 1:00 oíclock in the morning. Luckily, I've got a bit of flexibility. I donít normally have to get to work until about 10:00. But I donít even wake up until at least lunch time in my brain.

Chris - The thing thatís really making a difference now though is screens. The change and the revolution in technology means that many, many people are sitting in front of computer screens, and flat screens which are LCD until well into the night. Social media have got very good data on whoís using it, what they're logged into andÖ

Kat - Itís basically all me I think.

Chris - The reason these screens are important is that they are using blue LEDs to produce the white light that you see from the screen. The blue is critical because it goes out of the screen, into your eye, and at the back of your eye is a population of retinal ganglion cells and they're called intrinsically photosensitive retinal ganglion cells. They're important because although you donít see with those cells, they contain a pigment thatís very sensitive to blue light and they're connected to your body clock, and they're used to reset your body clock and tell it when itís bright light coming in early in the morning, must be wake up time. So, by basting yourself in rays from your screens at night, you're actually sending a really strong wakeup signal to your brain which is what you shouldnít be doing last thing at night. As a result, you're actually waking yourself up and making it harder to fall asleep and people are robbing themselves of sleep chronically this way.



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Either you are being smitten by a wicked conscience every night or you are practicing inadequate sleep hygiene.

I betcha your GCSE scores leave you quite capable of looking up proper sleep hygiene to see what you are doing wrong.

Either that or you need to see the padre.

As an alternative, you could visit the web page of the Confraternity of Saint James and take the pilgrim road. It is halfway through the autumn season, so you should choose your underwear carefully, or wait until Spring. I guarantee that by the time you have crossed Asturias with 20-30 kilos on your back, you will be able to sleep soundly even in a co-ed alburgue dorm half full of Swedish, French, and German girls

Pleasant dreams. Thotmose the 3rd, Fri, 9th Oct 2015

Hi Renny

The average person requires about 7-8 hours of sleep per night. But when we actually "feel" tired and when we wake up is controlled by the body clock; this is a genetic domino effect operating in every cell in the body and governed by a master clock in the brain called the suprachiasmatic nucleus (SCN).

The SCN comprises a network containing about 20,000 nerve cells. These keep time by activating a cycle of genes that turn each other on and off in a sequence and at the same time alter the activity of the nerve cells. Signals from the clock are transmitted to other parts of the brain to influence behaviour. The clock also controls the release of wake-up signals like the blood hormone cortisol, which goes around the bloodstream setting the clocks of the cells in every tissue.

The SCN clock is itself set by signals coming from the eyes. This is how you adapt to changes in the day length or adjust to new time zones. However, this take a while to happen (about 1 day per time zone) because the clock signal is quite resilient (to stop it wandering by accident). And because it "learns" the rhythm of your life, and doesn't know about weekends, it still gets you up early every day, regardless of whether it's a Saturday or not!

Some people do wake early quite naturally; this is because the body produces a surge or cortisol in the early hours to stimulate metabolism and prepare for the day's activities. In some people, this can cause them to be an early riser. Another group of people who wake up early and struggle to fall asleep again are individuals with depression and anxiety. I hope that this doesn't apply to you. It's probably owing to a heightened cortisol release, which occurs in stressed individuals.

I hope that's helpful.

Chris chris, Mon, 12th Oct 2015

In this situation, I get up and start the day, it might mean I am tired later, but it usually means I sleep better the next night.
You don't say what your length of sleep is.
Are you exposing yourself to daylight equivalent (blue light eg computer screen) late eveining?
Do you get a good daylight 'fix' early morning?

I have read that we sleep in blocks or cycles of 90min, although some research suggests 90-120. This might suggest that Renny's early morning attempt to get back to sleep is putting him into the deep part of the cycle.
There are suggestions that we should set our alarms in multiples of 90 in order to avoid interupting a deep sleep period.
Do you have any views on this?
Colin2B, Mon, 12th Oct 2015

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