Sleep is a dynamic process with a complex ‘architecture’ all its own.
Sleep is being divided in to 2 stages:
| 1. |
Non-REM sleep |
| 2. |
REM-sleep Non-REM sleep (sometimes called ‘delta’ or slow-wave sleep): |
This period is divided up in 4 stages:
| 1. |
light sleep |
| 2. |
fall asleep |
| 3. |
sleep |
| 4. |
deep sleep |
Stages 3 and 4 of the non-REM sleep are most important for the body. For the biological recovery and especially for the brain itself.
REM-Sleep:
Since in this phase of the sleep, there are rapid bursts of eye movements, we call this stage of the sleep, R(apid) E(ye) M(ovement) sleep. It’s a complex activity, fundamentally different from waking, but just as active. So your brain waves are almost the same as if you were awake. The muscles become ‘paralyzed’, the heartbeat and breathing becomes faster and fairly irregular. This stage is when most dreaming occurs.
Scientists found that brain activity during REM sleep begins in the pons (a structure in the brainstem and neighboring midbrain regions.) The pons sends signals to the thalamus and to the cerebral cortex (which are responsible for most thought processes.) It also sends signals to turn off motor neurons in the spinal cord, causing a temporary paralysis that prevents movements.
Normally somebody falls asleep within 10 to 15 minutes after going to bed. You begin your nightly journey by descending into stage 1, a light sleep. Your muscles relax, your brain waves are irregular and rapid. In stage 2, brain waves become larger, with bursts of electrical activity. Then you move into deep sleep (stages 3 and 4 of the non-REM sleep), in which the brain produces large, slow waves.
After an hour or so, you shift into a highly active stage and the first REM-sleep occurs. Suddenly your brain waves are almost the same as if you were awake. You’re in the dreaming stage. Dreams vary in length according to the length of REM-sleep. After the REM-sleep the deep sleep (stages 3 and 4 of the Non-REM sleep) starts again. The different sleep stages follow each other, in a certain variety, with a certain regularity during a full night sleep. One non-REM sleep and one REM-sleep is called a cycle. During the night several cycles occur, about once every 90 minutes in humans.
About 75% of your night is spent in non-REM sleep and about 25% in REM-sleep. REM periods tend to become longer and more plentiful as the night wears on. |
