two+different+types+of+sleeping+!

** 1390/2/26 **   ** Two different types of sleep ** In studying the phenomenon usually referred to as sleep, we are actually dealing with more than one phenomenon. In fact, we spend the night alternating between two different types of sleep, each with different brain mechanisms and different purposes. As people fall asleep, their brain waves develop a slower and less regular pattern than in a waking state. This is called //orthodox sleep.// In this state, the brain is apparently resting. Its blood supply is reduced, and its temperature falls slightly. Breathing and heart rate are regular. The muscles remain slightly tensed. After about an hour in this state, however, the brain waves brain to show a more active pattern again, even though people are apparently asleep very deeply. This is called //paradoxical sleep,// because it has much in common with being awake. Paradoxical (active) sleep is marked by irregular breathing and heart rate, increased blood supply to the brain, and increased brain temperature. Most of the muscles are relaxed. There are various jerky movements of body and face, including short bursts of rapid eye movement, which indicate that we are dreaming. Thus, we spend the night alternating between these two vital restoration jobs: working on the brain (paradoxical sleep) and working on the body (orthodox sleep).
 * Nadia Azizi **