What makes you want to sleep? What makes you sleep well?
Sleep, much like a finely-tuned symphony orchestra, is an intricate and harmonious process. The balance is essential for our well-being. We need our hormones to play their part at the right time to get refreshing slumber.
I’ll quickly explain the main hormones involved with sleep regulation then come back full circle to the orchestra metaphor. These hormones are not the complete picture of what regulates sleep but these hormones are the ones which are most affected by our daily behaviours. I have chosen to focus on them.
- Adenosine
- A chemical in the brain which is formed as the by-product of metabolism (when your cells use energy)
- This chemical builds up in your brain the more you think. The more you think, the more energy you use in your brain, the more adenosine is created as a result of this.
- Adenosine makes you ‘sleepy’ and is your main driver to sleep (gives you the urge to get some shut eye)
- Melatonin
- This is the hormone released under the control of the the Suprachiasmatic Nucleus (the SCN – the conductor who keeps you to time).
- This hormone tells you when to sleep and to tell your body’s systems when they can rest and repair.
- It is released from the pineal (’pea-sized’) gland right in the control centre of the brain.
- Cortisol
- A “stress” hormone that helps you wake up in the morning.
- Good in small doses and vital to get you ‘up and at them’.
- We want cortisol at some stages throughout the day – but prolonged cortisol (long term stress) is really not good for us for many reasons – but especially because it affects the quality of our sleep.
The sleep orchestra
Our sleep regulation is very complex and not fully understood but I have created our sleep orchestra to focus on the parts which we have some control over with our lifestyle choices – i.e. our behaviour.
Main components of the sleep orchestra include:
- The Conductor (suprachiasmatic nucleus) – the part of the brain which helps keeps the beat to allow us to stick to schedule.
- The Strings (adenosine) – a neuromodulator that slowly builds up throughout the day with a crescendo in the evening to drive us to sleep
- The Woodwinds (melatonin) – relaxing soft airy tones from the flute, clarinet and oboe which come on at night to assist the strings to get us to sleep and keep us asleep
- The Brass (cortisol) – the big bold brass section peaks in the morning to wake us up and prepare us for the day
The conductor – Suprachiasmatic Nucleus
In order for our orchestra to keep to time we need a conductor – the Suprachiasmatic Nucleus (SCN). This guy lives in the big hormonal control centre of the brain called the hypothalamus.
The conductor gets input from multiple sources in the brain but its main input to help regulate sleep is light. It also listens to other things like hormones and body temperature to get a real sense of what time of day – acting as the ‘body clock’ keeping track of where you are in your 24 hour sleep-wake cycle (your ‘circadian rhythm’).
The conductor, in my imagination, is like a person who thrives in darkness, almost like a vampire. He is extremely sensitive to light and is unable to perform his best when there is light present. This is primarily because the conductor receives direct input from specialized cells in the eye – even individuals without vision have a conductor who is responsive to light! That’s right, light can affect the sleep of people who are blind – that’s how sensitive this guy is to light.
So if we want the conductor to function optimally, we must minimize the amount of light he is exposed to – discussed in next section but best done by mimicking the sunset at home (turning off overhead lights and screens – or at a minimum dimming lights and using night mode on phones)
The conductor knows when it is time for bed as it approaches your regular bed time, and when our eyes are exposed to less light – i.e. the sun sets. When this happens the conductor gets the body ready for sleep. They do this by signalling parts of the brain and body via directly but mainly through the release of release of melatonin (the woodwinds) which create a calming environment where everything slows down ready for sleep.
The Strings – Adenosine
Adenosine is a critical neuromodulator in the brain and it acts as your main sleep driver – your urge to sleep. It does this by activating special adenosine receptors all over the parts of the brain that cause you to stay awake – and slows these parts of the brain down making those parts of the brain and yourself less excitable. It makes the neurons and yourself slow and sluggish making you want to fall asleep – much like the beautiful strings of the orchestra.
It is formed by the breakdown of the body’s main source of energy adenosine triphosphate (ATP). Thinking takes up a lot of energy (25% of the body’s glucose consumption) so throughout the day, adenosine gradually accumulates in the brain as a natural consequence. During wakefulness (thinking all day), the brain struggles to clear adenosine at the same rate it’s produced, leading to an increase in adenosine levels the longer you stay awake. This leads to a crescendo of sleepiness at the end of the day – the strings section gradually building a serene night-time melody urging you to sleep. Whilst this seems great in order to get us to sleep we don’t really want this urge to sleep to be there when the alarm goes off in the morning. Basically we want the strings to get us to sleep but stop playing once we have had enough sleep.
To get rid of this sleep drive (urge to sleep) you need sufficient sufficient time in the work-shop – deep sleep. In the work-shop a lot happens as we know but for adenosine the long synchronised brain waves are vital. These ocean like big waves flow throughout the brain and washes the adenosine away from our brain – which therein turns down the string section lulling us to sleep.
Without this clearance you may wake up with a lingering sense of drowsiness, disrupting the harmony of the brain’s orchestra. We need those long slow, ocean like, waves in our Deep sleep (the workshop) to clear the adenosine, get the strings to stop playing, and allow us to wake up feeling refreshed.
Quick note on caffeine the adenosine receptor blocker:
Imagine caffeine as the mischievous fiddler in the orchestra, disrupting the strings’ serene melody orchestrated by adenosine. Caffeine, akin to a lively fiddler in the orchestra, doesn’t actually clear away the adenosine build-up but rather takes centre stage with its lively solo, temporarily masking adenosine’s gentle serenade. This masking effect makes you feel alert and awake, as if the strings section (adenosine) had to take a backseat. However, overindulging in caffeine can lead to adenosine still quietly accumulating in the background, waiting for its turn to play its soothing tune. In essence, while caffeine can provide a short-lived burst of energy, it’s essential not to let the fiddler steal the show for too long, as it might disrupt the delicate harmony of the strings and leave you feeling out of sync with your natural sleep-wake rhythm.
The Woodwinds – Melatonin
Melatonin, the sleep hormone from the tiny pea-sized pineal gland has many roles. Many of these roles we are still learning about but it’s main role is to let the body know when it is bedtime and time for sleep. By doing this it helps us keep our sleep-wake cycle as the levels in our body have a 24 hour pattern.
To keep this 24 routine it’s release is under the control of the conductor (suprachiasmatic nucleus). The conductor loves routine and keeping things to time – and he or she does not like light.
Melatonin’s role in the orchestra is like the soft, airy tones of the flute, clarinet, and oboe. It steps onto the stage at night, working in harmony with the Strings to guide us into the realm of slumber and to keep us asleep, creating a tranquil and restful atmosphere.
Just as the woodwinds softly serenade in the orchestra, Melatonin plays a crucial role by signalling to the wakefulness-promoting parts of our brain to relax and quiet down, ensuring a smooth transition from wakefulness to deep sleep.
However, Melatonin’s performance is intricately linked to the lighting conditions – as it is controlled directly by the conductor who really doesn’t like light (the vampire conductor). The pineal gland in the brain releases melatonin when it gets the signal from the conductor that it is time for sleep. So when there is light hitting your eyes – the conductor thinks it is day time, and doesn’t tell the woodwinds to play.
Basically more light at night = less melatonin = less quality sleep.
The bold brass – Cortisol
a.k.a the ‘stress hormone’ but for sleep purposes – the “wake up hormone”
Cortisol, the bold brass section, heralds the morning with its energising fanfare, signalling a new day. We have a natural peak of cortisol in the morning as it rises to help get us up and going from hopefully a restful nights sleep.
Called the stress hormone as it plays a vital role in our response to stress – however it is also vital for life so it’s not the bad guy it is sometimes made out to be. There are serious disorders associated with not producing cortisol and these are life threatening. We need it.
It gets a bad wrap when we are exposed to sustained stress (prolonged high levels of cortisol) as it can lead to detrimental health effects – including issues with sleep. As humans we are meant to have bursts of stress and this is good for us. However this is to be placed in amongst times of rest. We are not made to be on edge 24 hours a day – just like the brass section is great to get us up and moving but we don’t want it to be playing all day. Cortisol should follow a fairly typical typical 24 hour pattern. It has a time and a place – and that is better in the morning and not before bed as cortisol works against the slowing hormones of adenosine and melatonin as it creates ‘wakefulness’ in the brain. Much like the bold brass section of a band doesn’t always work that well when trying to compete with the calming strings and woodwinds.
Chronic stress / burnout / chronic fatigue syndrome – have thought to be partly a issue with cortisol release and rhythm of that release. Disorders and generally being stressed can lead to that “tired but wired” feeling when trying to sleep at night. This Tired but Wired feeling is like the brass section trying to play their big ‘up and about’ number when your strings and woodwinds are trying to lull you to sleep.
In Summary – the complex Symphony of slumber
With this slightly stretched metaphor of the sleep orchestra I have tried to take the complex world of sleep hormones and make them palatable – like a simple beatles pop tune.
First, we meet the diligent strings section: Adenosine. Picture these guys as the steady, hard-working cellists, building up sleepiness throughout the day. The more you think, the more they play, crescendoing into a blissful urge to hit the hay.
Then, there’s Melatonin, our smooth woodwinds. These cool cats come out at night, under the command of our nocturnal maestro, the Suprachiasmatic Nucleus (SCN). They’re the ones who tell your body, “Hey, it’s time to chill,” helping you transition into dreamland.
And who could forget the bold brass section? That’s Cortisol, the “wake-up hormone.” They’re like the trumpets blaring at sunrise, essential for kick-starting the day but not so great if they’re still tooting their horns at bedtime.
Our SCN conductor, sensitive to light and master of timing, ensures this hormonal orchestra keeps to the rhythm of your circadian beat. Dimming lights at night helps this vampire-like conductor do his job, paving the way for Melatonin’s smooth tunes.
But, life’s not always a smooth concert. Enter Caffeine, the mischievous fiddler, sneakily disrupting Adenosine’s mellow strings with a burst of energy. And if Cortisol gets too loud (hello, stress!), it’s like a brass band crashing a lullaby, leaving you “tired but wired.”
This post is a backstage pass to the sleep orchestra, showing how our daily actions influence the harmony of these hormonal musicians. So, embrace your inner conductor, make wise lifestyle choices, and let your body’s symphony lull you into the sweetest slumber.
