Why do we close our eyes when we are attempting to get to sleep or while we are sleeping?

Question: Why do we close our eyes when we are attempting to get to sleep or while we are sleeping?

Asked by christiancox to Fiona, Jane, Joanna, Michelle, William on 18 Jun 2010 in Categories: General.
- Michelle Murphy answered on 16 Jun 2010:
  
  I think it is mainly because it helps us to relax
- Joanna Brooks answered on 16 Jun 2010:
  
  Well, one reason for this could be because we need to shut out all other stimuli (everything around us in our environment) in order for our brain to get some rest. If our eyes are open the brain will continue to process information.
- Fiona Randall answered on 18 Jun 2010:
  
  When we are sleeping the eyes close to keep them moist, that is why we blink all the time when we are awake. I actually have a friend who’s eyes stay open when he sleeps… scary!!
- William Davies answered on 18 Jun 2010:
  
  Not sure of the actual physiological reasons, but I imagine it’s to block out light, and to prevent our eyes drying out/getting things in them whilst our body shuts down. Don’t dolphins sleep with one side of their brain at a time? Presumably they just shut one eye too?
- Jane Henry answered on 18 Jun 2010:
  
  Blocks out some sensory information making it easier for those parts of the brain that turn off when we are asleep to turn down.

Question: Why do we close our eyes when we are attempting to get to sleep or while we are sleeping?