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Understanding Sleep & the Body Clock

Sleep is a crucial part of our daily routine – we spend about a third of our time doing it! Did you know that quality sleep and getting enough of it at the right times, is as essential to us as food and water? Without enough good quality sleep we are unable to carry out many bodily processes, especially processes in the brain involved with memory and concentration.

The human sleep cycle involves input from various structures within the brain and is regulated by our internal body clock which can be impacted quite easily by common factors most of us may not realise affect it. This blog will go through the stages of sleep, how our internal biological clock helps regulate our sleep and some common factors that can impact our natural sleep cycle.

The stages of sleep

Sleep isn’t just a matter of closing our eyes, resting and then re-opening our eyes when the alarm goes off – it consists of different stages known as REM sleep and non-REM sleep.

Non-REM (Rapid Eye Movement) Sleep

Non-REM Sleep consists of three stages. Stage one is the initial sleep stage that allows us to change over from being awake to falling asleep. It is a short stage lasting only minutes that slows down our heartbeat, breathing and eye movement, and allows our muscles to relax. During this stage, our brain waves begin to slow down from their stimulating daytime patterns.

Stage two is a period of light sleep before we enter deep sleep. This is actually the longest phase of sleep we enter. Here, our heartbeat and breathing rates slow down even further, our body temperature drops and so do our eye movements.

Stage three non-REM sleep is the period of deep sleep that helps us feel refreshed when we wake up. During stage three, our heartrate and breathing slow to their lowest levels and our muscles become very relaxed. Our brain waves are at their slowest during this stage, too.

Rapid Eye Movement (REM) Sleep

REM sleep occurs roughly 90 minutes after we fall asleep. As its name suggests, during REM sleep our eyes rapidly move from side to side behind our closed eyelids. Our brain wave activity becomes closer to what we see when we’re awake, our breathing become faster and irregular and our heartrate and blood pressure rise to almost waking levels. It is during REM sleep that we dream as our brain is quite active during this stage. Most adults spend around 20 to 25 percent of the night in this sleep stage, with each cycle lasting between 90 and 120 minutes. The rest of the night is spent in non-REM sleep.

How does our body get us to sleep?

Many different structures of the brain are involved with inducing sleep, such as the hypothalamus (a small structure that contains groups of nerve cells that act as a control centre for sleep and stimulation) and the pineal gland (responsible for the increase of melatonin, our sleep hormone).

We also have two internal biological mechanisms called the circadian rhythm and sleep-wake homeostasis. These two mechanisms work together to regulate when we are awake and of course, when we’re asleep. They form what is known as our ‘body clock.’

Many of us believe we have one circadian rhythm – well, we actually have many of them! They regulate a wide variety of functions like body temperature, metabolism and hormone release. In regards to sleep, they sync with environmental cues like light and temperature to help us stay awake when we need and get to sleep when it’s time to.

Sleep-wake homeostasis is responsible for keeping track of our need for sleep. It acts as a ‘reminder’ for our bodies to fall sleep after a certain time and also regulates how deep we sleep, too.

What factors can impact my biological clock?

There are multiple factors that can impact our body’s biological clock, so we’ve narrowed it down to three of the most common factors:

Irregular sleep routines

We all know the benefits of sticking to a routine, and achieving a better night’s sleep is one of them! We understand that weekday commitments are typically different to the things we do on the weekends, but getting to sleep and waking up around the same time each day helps our body’s biological clock and consequently, our quality of sleep.


Caffeine is a great energy booster but it’s not great at helping us get to sleep. Enjoy your coffee during the day and not too close to bed time so your body can wind down properly of an evening. If you love a warm mug of coffee after dinner, consider switching to a calming, herbal tea. Dandelion root tea is another option – it tastes very similar to coffee, without the caffeine content.

Excessive light exposure

Exposure to light is actually one of the biggest influencers of our body clock. When our eyes receive light, it stimulates the brain to stay awake. While this is great during the day, it’s not great when we’re watching TV or scrolling through our phones right before bed. Aim to switch off your devices around an hour before bed and dim the lights after dinner to help your eyes signal to your brain that it is almost time for sleep.

If you have long-standing sleep issues, please seek advice from your doctor or health care professional.


- Felson, S. 92018), Web MD, cited on 1/5/2020, What are REM and Non-REM Sleep?, accessed <>

- Sleep Foundation, 2020, cited on 4/5/2020 – How your baby’s sleep cycle differs from your own, available from