Sensation and Perception

5. It is a very light sleep similar to stage one in which there are vivid dreams and nightmares.
7. Difficulty to fall asleep and stay asleep. It is the most common sleep disorder.
8. It is happening when you are aware of that fact that you are dreaming.
9. Sleep disorder in which a person falls immediately into REM sleep during the day without warning.
11. Evolutionary theory based on the fact that many predatory animals hunt at night.
14. The caffeine blocks the receptor sites of that hormone.
15. What you see in a dream.
16. Hormone inducing sleep.
17. There are five of them.
18. Sleep disorder, common in children because of the development of their nervous system.
19. Hidden meaning in dreams.
20. Our awareness of ourselves and of our environment.

1. Theory that the we sleep at night because the body heals itself at night.
2. Natural loss of consciousness.
3. Scientific theory that explains the dreams as being the brain's attempt to make sense of random neural activity.
4. Disorder in which the person stops breathing for nearly half a minute or more during sleep.
6. Biological clock regulating body function on a 24 hours cycle.
10. People who consistently need less sleep than the average.
12. It registers UV light and increases the level of melatonin.
13. Sequences of images, feelings, ideas that occur in the REM sleep.