The Sleep Cycle

While we sleep, our bodies go through a pattern known as the sleep cycle. The

sleep cycle consists of five stages. It can take around 90 minutes to 110 minutes to complete. This cycle repeats itself many times throughout the night.

The first stage is quite a light or drowsy sleep. During this time, our eyes and

muscles are still active but much slower than when we are awake. Our heart rate and breathing also slow down. We can be aware of the noises around us. We are easily woken from this stage. Dreaming is very rare during this stage. Sometimes our muscles will contract, and we get the feeling of falling!

During stage two, our bodies prepare themselves for deep sleep. Our eyes stop moving, and our body temperature gets lower. Our brain waves and heart rate slow down further. We completely relax! We become unaware of the sounds around us. Our brains start to process information we have gathered throughout the day. This tends to be the longest part of our cycle. It makes up over 45% of our total sleep time.

In the third stage of our sleep patterns, our brain activity changes yet again. Our slow brain waves (which are called delta waves) are interrupted by little bursts of faster waves. However, this is also the stage when some people can talk in their sleep or even sleepwalk! This is rare but usually happens when our cycle moves from non-REM to REM sleep.

The fourth stage is the final non-REM stage of our cycle. We are now in a deep sleep with our brain waves mostly staying slow (remember, they are called delta waves). At this point, our heart rate and body temperature are at their lowest points. If you wake up during this stage, you can feel confused for a couple of minutes.

Finally, we enter REM (rapid eye movement) sleep. Our brain waves change yet

again! During REM sleep, our brain waves look the same as when we are awake. Our temperature, heart rate, and breathing rate all rise during REM. Our eyes move very quickly from side to side but stay closed. This is when we have most of our dreams. As we get older, we spend less time in this stage. For example, babies may spend 80% of their total sleep in REM, whereas an adult spends around 25%.