Sleep is an incredibly important part of our natural biological processes.  It involves important chemicals known as neurotransmitters, those being serotonin, norepinephrine, acetylcholine, and dopamine.  It also involves a hormone called melatonin.  

The parts of the brain that are particularly involved in sleep include:

  • the brainstem – which helps regulate wakefulness
  • the pineal gland – which regulates melatonin production
  • the suprachiasmatic nucleus – which helps regulate our circadian rhythms

What is sleep exactly?

There are  2 main types of sleep – REM sleep and non-REM sleep. REM stands for rapid eye movement or dreaming sleep, and is important for memory consolidation. Stage 1, Stage 2, and Stage 3 (also known as deep sleep) are collectively known as non-REM sleep.  Deep sleep is very important for growth and development in children because growth hormone is released during this time.  Most healthy adults will have 4 to 5 “episodes” of REM sleep throughout the night.  Stages 1 to 3 occur throughout our sleep cycles, with stage 3 occurring mostly in the first half of the night.

What are the different stages of sleep and what do they mean?

  • Stage 1 of sleep is similar to those experiences you have nodding off in a super boring lecture.
  • Stage 2 of sleep is the majority of our sleep (around 50%). This is your lightest stage of sleep.
  • Stage 3 of sleep is our “restful” or deep stage of sleep.  In normal healthy adults, this starts 30 to 40 minutes after we begin sleeping.  Most of our restful sleep occurs in the first 3 to 4 hours after we begin sleeping.
  • REM sleep starts about 90 minutes after sleep onset and continues episodically throughout the night.  During this stage our heart rates, blood pressure, and breathing rates change.  Our brains are quite active during this phase, and this is where dreaming occurs.  Most of our REM sleep happens in the last 3 or so hours of sleep.

The patterns of our sleep change over the lifetime, depending on our age, our health, and any medical illnesses or medications we take.