The Sleep Cycle
Just as basic as food and vital to both emotional and physical well being, sufficient sleep is a basic human need. And it has been found that sleep comes in cycles, on a daily rhythm. You have heard this referred to as the biologic clock. It’s the daily cycle of life, which includes sleeping and waking.
The sleep-wake cycles in humans, per scientific study, are shown to be sparked by light signals coming through the eyes. The response to these light signals in the brain is an important factor in sleep and also in keeping the normal rhythm.
The approach of dusk each day prompts the pineal gland in the body to produce the hormone called melatonin. Experts believe that this hormone is critical for the body's time sense. Levels of melatonin increase in darkness and the levels drop after staying in bright light. In proof of these researches, it has been found that people who are totally blind often have trouble sleeping and have other body rhythm problems.
Daily rhythms can get interference or be changed by individual patterns. The monthly menstrual cycle can shift the pattern of sleeping and waking in women. Changes in season can unsettle the sleeping pattern.
Sleep consists of two separate stages, and understanding these is all part of understanding the sleep cycle. A person progresses through each of these stages about five or six times each night.
The first is called Non-Rapid Eye Movement Sleep (Non-REM). Also called quiet sleep, it is further subdivided into three stages:
- Stage 1 (light sleep).
- Stage 2 (so-called true sleep).
- Stage 3 to 4 (deep "slow-wave" or delta sleep).
Rapid Eye-Movement Sleep (REM) sleep is called active sleep. This is where most vivid dreams occur. REM-sleep brain activity during REM-sleep is comparable to brain activity in awake time, but the muscles are as if paralyzed. These phenomena could possibly be a protective mechanism of the body that prevents people from acting out their dreams.
All this appears to be pretty simple and easy to understand, but why do some people have problems with these cycles?
Continue reading through the following article to find out:
