Sleeping is how we regenerate and heal.  It also shuts off certain parts of our body for rest and allows them to take a break.  Your brain and body slow down and recovery begins to help you regain energy for the next day and promote long term health.  

There are 4 stages of sleep (in 2 categories) crucial to health:

1. REM (Rapid Eye Movement)
2. Non-REM

• The first 3 stages during sleep are in the second category (non-REM).  
  Stage 1 is basically dozing off or the beginning of sleep.
• Stage 2 is your body beginning to slow down and relax
  Note: It’s easiest to be awoken during these first two stages.
• Stage 3 is deep sleep where recovery really begins.  Brain activity slows down and the body stabilizes and regulates for its long night of sleep.  
• Stage 4 is REM sleep.  Brain activity shoots back up to the same levels we have when awake and this is when we begin to dream.  Our breathing and heart rate increase during this stage.  Most of our muscles are now paralyzed which prevents us from becoming an active participant in the dreams that are occurring.  

Each of these sleep cycles are about 70-120 minutes.  Most of the non-REM sleep is in the beginning of our sleep cycle and the REM sleep happens in the later portion of sleep.  

What happens to the Brain and Body during sleep?

• Breathing:
  Non-REM: slows down
  REM: speeds up
• Heart Rate:
  Non-REM: slows down
  REM: speeds up
• Muscles:
  Non-REM: relax and energy drops
  REM: Atonia (muscle paralysis).  Eye muscles do stay active and rapid eye movements can be seen under the eyelids.
• Brain:
  Stage 1: Very slow brain waves
  Stage 2&3: Quick bursts of brain activity
  REM: Brain activity enhances, this is why we dream in this stage.  
• Hormones:
  Our circadian rhythm is crucial for determining hormone activity.  If we are not consistent with sleep patterns our hormones will be affected.  The Pineal Gland regulates our circadian rhythm and analyzes dark and light environmental patterns.  Keeping lights off while sleeping is key for circadian rhythm.

  The most crucial hormones during sleep:
  
  

- Melatonin: which helps promote sleep. Released by the Pineal Gland.

- Growth Hormone: which supports bone and muscle development as well as metabolism. Released by the Pituitary Gland.

- Cortisol: which is part of the body’s stress response system. This should be de-activated during sleep.  

- Leptin and Ghrelin: which help control appetite. These should also be lowered when sleeping.  

Lack of sleep leads puts stress on our systems because they are working overtime.  Cognition, digestion, hormones, and systems all need time to recover and restore.  

What happens when we don't get enough sleep?

Our concentration, energy, moods and body basically "short circuit" and our body becomes stressed and confused.  We do not regain energy and run at lower frequencies leading to miscommunication and impairments.  

Not being able to sleep keeps your brain working harder and leads to irritability, anxiety, depression and make mental health issues escalate.  

Can you sleep too much?

There is a condition named Hypersomnia where someone sleeps too much.  This de-regulates your sleep patterns and has sufferers become tired during times when they need to be awake.  Such as at work, school or doing any other activity. If you are sleeping too much, it may mean your body is off or something is going on that needs healing, unless you have narcolepsy.  

Resources: 

https://www.therapedic.com/blog/what-is-your-spine-doing-while-you-sleep/