Sleep

SLEEP

Sleep like many other mystries in human behaviour, is the least understood phenominon. We really don't know why we need to sleep. Nevertheless, we are certain about one thing that we all need to sleep. Human's physical, mental & spiritual health depends of certain hours of sleep daily. It is also necessary for survival. Without sleep individual will not last long.

Sleep is the state of natural rest in humans & many animals. It is characterized by
a reduction in voluntary body movements, decreased reaction to external stimuli, an increased rate of anabolism ( synthesis of body tissue ) & a decrased rate of catabolism ( break down of body tissue ). Even though sleep is a form of unconsiousness, technically it is much different from it.

Optimal sleep amounts to 8 hours in 24 hours. However, a life span study of sleep amount shows that those who sleep 4 - 7 hours live the longest, with those sleeping less than 4 or more than 9 hours living shorter lives. Incidently it only applies to adult. Children need much longer sleep depending on their age.

A good night sleep does wonders. It :-

i, Improves performance in test
ii, Reduces risk of accidents
iii, Increases immune system
iv, Sharpens memory
vi, Reduces irritibility, anger & many negative emotions
v, Creates a general sense of well being


Stages of sleep :-

There are 4 stages of sleep.

First stage is characterized by disappearance of alpha waves seen in awake state & appearance of heta waves on EEG. This stage is sometimes refered to as somnolence or drowsy sleep. During this stage the subject loses some muscle tone & consious awareness of surrounding, develops some muscle twitches & occasionally hynogogic hallicination. This stage is gateway between wake & sleep. This stage lasts for few minutes. Subjec can be awakened very easily during this stage

Second Stage results in complete disappearance of conscious awareness. This occupies 45-55% of sleep. One can be awakened easily at this stage also.

Third stage is also known as REM (rapid eye movements) sleep. During his stage dreaming takes place. This occupies about 10% of total sleep. Dreaming is extremely essential for psychological well being. Deprivation of this stage results in icreased irritibility,anger & all kind negative emotions. Continued loss of dreaming (REM deprivation) for 4-5 days cause hallucinations & psychosis. Sleeping pills & alcohol diminish this stage.

Fourth stage is the stage of deep sleep. Also known as NREM (Non rapid eye movements) stage. During this stage subject is very difficult to be awakened. Night terrors ( bad & fightening dreams ), bed wetting & sleep walking take place during this stage. It occupies 10-15% of total sleep. This stage can be labelled as the restorative stage of physical fatigue. Anabolic activity ( i.e. physiological process of growh & rejuvination of organism's immune, nervous & musculoskeletal system ) is marked in this stage.