Sleep: Dream on.
After approximately 30 to 40 minute of slow-wave sleep, your brain and body start to speed up again. You cycle back through stage II of non-REM sleep and then enter REM (rapid-eye-movement) sleep. REM sleep is a very active stage.Your breathing rate increases, and your heart beats irregularly. Blood flow increases to the genital area and may cause erections in males. However, your muscle tone significantly decrease, leaving the muscles extremely relaxed and essentially paralyzed. Figure 4.3shows that your REM brain-wave patterns are similar to your brain-wave patterns when you are wake. The brain slides labeled “awake” and “REM sleep” look almost exactly alike! You can see that portion labeled “non-REM sleep” look quite different.