Types of Sleep

1. Non-REM Sleep

Stage 1: Light sleep; easily awakened; muscle activity; eye movements slow down.

Stage 2: Eye movements stop; slower brain waves, with occasional bursts of rapid brain waves.

Stage 3: Considered deep sleep; difficult to awaken; brain waves slow down more, but still have occasional rapid waves.

Stage 4: Considered deep sleep; difficult to awaken; extremely slow brain waves.

2. REM Sleep

Usually first occurs about 90 minutes after you fall asleep; cycles along with the non-REM stages throughout the night. Eyes move rapidly, with eyelids closed. Breathing is more rapid, irregular, and shallow. Heart rate and blood pressure increase. Dreaming occurs. Arm and leg muscles are temporarily paralyzed.