Although on the exterior sleep may appear as one long drawn out affair, on the subconscious level many changes are occurring that facilitate restoration after a hard day’s work, and dreaming.
The discovery of the different stages of sleep is thanks to a device called an electroencephalograph, which allows researchers to see brain activity during sleep.
There are two noted types of sleep however, known as
- Non Rapid Eye Movement( NREM)
- Rapid Eye Movement( REM)
These two types of sleep are normally experienced over 5 phases of sleep, which we shall discuss now.
The initiation of sleep, it is considerably light and transient. It lasts only for a brief period, maybe 5-10 minutes, after which sleep proceeds to the next stage. During this first phase of sleep, a phenomenon referred to as a myoclonic jerk may be experienced. This is the motion of a sudden startling action randomly during sleep. It is very common, and most people at some point of their life will experience it. Persons are easily awoken during this phase of sleep and may report that they were never really asleep.
During this stage, deep sleep has still not been achieved; it is more of a continuation of the first phase, extending for about another 20 minutes. However, during this phase brain activity starts to increase, in short segments called sleep spindles. Your basal metabolic rate and body temperature also begin to drop, and heart rate decreases a bit.
This stage normally signals the beginning of deep sleep, although it has not necessarily been accomplished yet. It is considered the transitional phase that occurs from light sleep to deep restorative sleep.
Stage four sleep is a deep phase, commonly known as Delta Phase. Delta waves are slow restorative brain waves. This phase of sleep may last on average for about 30 minutes, following which sleep walking or bed wetting often occur.
This is the deepest phase of sleep, during which restoration of body processes occur. This phase is also called REM phase sleep, and is associated with dreaming. REM sleep is the most elusive phase of sleep, which may be either prolonged or shortened by use of certain drugs. It is for this reason that drugs which prolong this phase are reported to cause vivid dreams. It is also known as paradoxical sleep phase since the brain becomes hyper active but muscle tone is loss. This is a reflex that seeks to prevent persons from acting out their most lucid dreams.
The sleep cycle does not occur in stepwise fashion from 1-5; in fact it takes a detour. It progresses from stage 1-4 as normal, but then retraces through phase 3 and 2. After this backward trace, it then enters phase 5. After phase 5 is over, stage 2 is repeated, and the cycle goes on. An average person sleeping 8 hours per night will undergo about 5 complete cycles per night. REM phase sleep initially only lasts for a couple minutes, but can progress up to lengths of one hour as sleep continues.
Category: Sleep Disorders