Why Do We Sleep?
Sleep is a complex process made up of different stages that keep both our bodies and brains in top shape.
Two main types of sleep:
NREM Sleep (75–80% of sleep):
- Has 3 stages, from light sleep to deep sleep (slow-wave).
- Important for body repair, muscle growth, and boosting the immune system.
- The brain’s glymphatic system flushes out waste proteins that could build up and harm brain cells.
REM Sleep:
- When most dreaming happens.
- The brain is very active, but the body is still.
- Helps with memory, learning, and sorting emotions.
Effects of Lack of Sleep
Skipping sleep disrupts the two critical stages and can mess with your body and mind.
- Interrupted NREM sleep: Less time to repair tissues and build muscle, and a weaker immune system.
- Missing REM sleep: Trouble with concentration, creativity, and emotional balance.
- Catching up: Get more REM and deep sleep by sleeping longer after a late night, but scientists say you can’t fully pay back a “sleep debt.” Lost sleep still leaves effects on memory and mood.
- Mood and thinking: Without balanced NREM and REM, people are more forgetful, easily stressed, and less able to solve problems.
Fun Facts
Here are some interesting facts about sleep:
- Humans spend about one-third of their lives sleeping — roughly 25 years asleep if you live to 75!
- Teenagers need 8–10 hours of sleep each night.
- Dolphins sleep with half their brain awake to still swim and breathe.
- On the International Space Station, astronauts have special sleep pods that are dark, quiet, and cozy to help them sleep well in zero gravity.
Review
Let’s quickly recap what we learned about the science of sleep:
- What type of sleep helps clean waste from the brain? NREM
- During which kind of sleep do most dreams happen? REM
- Which body system gets weaker without enough sleep? Immune System
- If you miss REM sleep, what gets harder to control? Emotions and Mood
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