Yesterday I mentioned importance of sleep and today I would like to talk a little more about brain 'self-cleaning' miracle.
The brain produces about 2 cups of cerebrospinal fluid (CBF) per day and that fluid is constantly reabsorbed during the day leaving about quarter of a cup at any one time. It acts like a cushion for our brain during the day and at night the miracle happens... In the deep-sleep mode the brain turns on the cleaning cycle, much like a dishwasher.
When awake, neurons fire constantly to keep the brain alert, causing the brain cells to expand to about 86% of the volume of the brain. During deep sleep brain's cells shrink, leaving more space for the brain and spinal cord's fluid to move and pickup toxic waste. A sleep-deprived brain has reduced efficiency in garbage removal. And as we get older we sleep more lightly, getting less of deep sleep and as a result we are having more often those 'senior's moments' (that's my own very personal opinion).
Now, just in a few words about our sleep stages:
Stage 1 (5-10% of total sleep in adults) - Your eyes are closed, but it's easy to wake you up.
Stage 2 (45-55% of total sleep in adults) - You are in light sleep. Your heart rate slows down and your body temperature drops. The body is getting ready for deep sleep.
Stage 3 (15-25% of total sleep in adults) - This is the deep sleep stage. It's harder to rouse you during this stage, and if someone woke you up, you would feel disoriented for a few minutes. During the deep stages of sleep, the body repairs and regrows tissues, builds bone and muscle, and strengthens the immune system. (The brain shrinks and turns the cleaning cycle).
Human sleep occurs in periods of 90 minutes on average and usually we have four or five cycles per night. There is a stage after deep sleep when we are returning to stage 1. It's called REM (rapid eye movement) and takes 20-25% of total sleep in adults. During this stage most muscles are paralyzed, and heart rate, breathing and body
temperature become unregulated, the sleeper may experience vivid dreams. The function of REM sleep is uncertain but a lack of it impairs the
ability to learn complex tasks. Functional paralysis from muscular weakness
in REM may be necessary to protect organisms from self-damage through
physically acting out scenes from the often-vivid dreams that occur
during this stage.
Stay tuned, tomorrow I will talk about brain food.