Do you know what’s going on with your body and brain when you’re catching zzz’s every night? It’s quite fascinating. Each night you go through 5 sleep stages and you cycle through each of these approximately 4-6 times per night. Scientists and researchers are continuously learning more and more about the mechanics and effects of sleep. From brain activity, twitches, and heart rate changes, each stage has a completely different purpose than the next.
Let’s look closer at just what happens every time your head hits your pillow.
Stage 1: The Lightest Sleep
This is the lightest stage of sleep. During this phase, you’re still hearing noises and have a sense of awareness. You feel yourself drifting off and it typically only lasts about 5-10 minutes. Sometimes people refer to this stage as taking a “cat nap”. It’s a choppy, unrestful type of sleep. You also experience stage 1 minutes just before waking up. Stage 1 only takes up about 4-5% of our sleep each night.
- Eye movements slow down
- Muscle activity decreases
- Muscle twitches occur
- Breathing slows, heart rate becomes regular
- “Hypnic jerks” happen (feeling of falling)
- Brain produces alpha and theta waves which help relax the body
Stage 2: Light Sleep
The second stage is still considered light sleep. Your brain activity, heart rate and breathing all slow down even more so than in stage 1. The brain increases wave frequencies produces “spindles” which slows brain waves down. People that take “power naps” want to wake up right after this stage to feel more rested and not groggy. We spend the most amount of time sleeping in stage 2 sleep, about 45%.
- Slowed heart rate
- Decrease in body temperature
- Brain emits larger waves
- Metabolic functions slow down
- Blood pressure decreases further
- Becomes harder to wake you up
- Body & brain prepare for deeper sleep to come
Stage 3: Slow Wave Sleep
Deep sleep in stage 3 starts setting in after about 35-40 minutes of falling asleep. It’s also known as the “slow wave” sleep cycle. Your brain waves start producing very slow delta waves for restorative sleep, but at the same time may produce beta waves which create short bursts of fast brain activity. If you are suddenly awakened during this stage you will wake up groggy, annoyed, and disoriented. We only spend 4-6% of our total sleep in stage 3 per night.
- No eye movement
- No muscle activity
- Less responsive to outside stimuli (sleep through loud noises without reactions)
Stage 4: Deep Sleep
This stage is very similar to stage 3 but is an even deeper type of sleep. It’s the deepest you’ll experience all night. Your brain is only producing slow delta waves, and it’s extremely difficult to wake someone up in stage 4. It’s also the stage when your body does a lot of its repairs. We spend 12-15% of our sleep in stage 4 every night.
- Repairs muscles & tissues
- Stimulates growth development
- Boosts immune functions
- Builds up energy for the next day
- People more likely to bed wet or suffer from night terrors
Stage 5: REM Sleep
REM sleep stands for rapid eye movement sleep or “active sleep”. Your brain is very active and your body is not. It’s the period of sleep when you dream and is responsible for memory and emotion regulation. If you were to take an EEG, your brain activity would look the same as if you were awake. The first cycle of REM sleep happens about 90 minutes after you fall asleep, and lasts for 10 minutes. Each period of REM sleep gets longer, with the final cycle lasting about an hour. We spend 20-25% each night sleeping in stage 5.
Another interesting aspect of stage 5 is that since our body is so inactive, our arms and legs go through periods of paralysis. Scientists think this may be our body’s way of protecting us from actually acting out our dreams in the real world while we’re sleeping.
- Blood flow increases
- Brainwaves speed up (creating dreams)
- Muscles relax
- Heart rate increases
- Breathing is rapid and shallow
- Clears the brain of information not needed, stores long-term memories
- Peak of protein synthesis at the cellular level (keeps body working properly)
Sleep is Critical
Your body is an amazing machine. While everyone may not spend the same amount in each sleep stage, your body will figure out its own rhythm on its own. Most adults should be getting between 7-9 hours of sleep per night to avoid any sleep disorders.
Sleep deprivation is very serious and can cause negative effects such as weight gain, high blood pressure, mood changes, diabetes, heart disease, and memory issues just to name a few. Sleep is critical to maintaining a healthy life, so make sure you’re getting those quality zzz’s in every night. You’ll wake up refreshed, focused, and ready to take on the world. If you’re feeling tired and groggy after a night of sleep, there could be an underlying cause. Visit Sleep Science Clinics today to learn about potential sleep disorders and how you can get better quality sleep.