What Are Sleep Cycles?Once you fall asleep, there is still a lot of activity going on inside your brain as it enters different sleep stages or cycles. According to Psychology Today, ‚Äúone sleep cycle lasts about 90 minutes, and during that time we move through five stages of sleep.‚Äù The first four stages that occur in one complete cycle are NREM, otherwise known as the non-rapid eye movement stages. The fifth stage in one complete cycle is REM, otherwise known as the rapid eye movement stage. Each one of these sleep cycles is repeated four to six times per night.
What Goes On During One Sleep Cycle?Do you remember watching your favorite show on Netflix and then all of a sudden you weren‚Äôt? You swore you remembered what happened but you were also fast asleep. Digging deeper into each stage will help you understand things such as that weird falling sensation, why people can‚Äôt wake you no matter how hard they try, and when your dreams actually take place. The National Institute of Neurological Disorders and Stroke provides a little insight:
- Stage 1 (2% to 5% of total sleep time): In this first stage of NREM, you are greeted with a light sleep. You‚Äôre slowly tuning out your favorite show while your heartbeat and brain waves slow down. Your muscles relax with that occasional twitch you‚Äôre all too familiar with. Feel like you‚Äôre falling? Nope, you‚Äôre just in the throes of your first stage of sleep.
- Stage 2 (45% to 55% of total sleep time): Similar to the first stage, everything slows down even more. Your body temperature begins to drop, and your eye movement stops. Most of your repeated cycles are actually in stage two.
- Stages 3 and 4 (5% to 25% of total sleep time): These two stages are combined because they give you that rejuvenated ‚Äì‚ÄúI feel like I just slept for ages!‚Äù ‚Äì ¬†feeling. This occurs in longer periods during the first half of your sleep. In these stages, everything continues to decrease to its lowest level of frequency. Your heartbeat, brainwaves and body temperature all reach an optimum low. If someone were to try and wake you, good luck to them.
- Stage 5 (20% to 25% of total sleep time): This is where REM occurs, about 90 minutes after falling asleep. Your eyes move rapidly from side to side behind your closed eyelids, and your breathing becomes faster and irregular while your heart rate increases. This is where you dream. Your arm and leg muscles become temporarily paralyzed, preventing you from acting out your vivid dreams. In this stage, your brain is more active, but your body still knows that it‚Äôs time to rest. How cool is that?