The natural state of rest
in which eyes are closed, body is inactive, and mind does not think- Sleep.
We all need it right....! But why?
Circadian system, colloquially known
as our internal clock is the body’s response (physical, mental and behavioural)
to change in the environment around especially the light. This rhythm dips and
rises throughout the day, which is responsible for us feeling wakeful and
sleepy at different times.
Melatonin (released from the pineal gland
at the base of the brain) is the main hormone (chemical regulator) of this
system that is responsible for our sleep/wake cycle. Light especially blue, inhibits the hormone and hence disturbs
the sleep; whereas, if the person maintains dark surrounding around before
slipping into slumber, sleep quality gets enhanced. The quality of sleep also
depends upon noise level and the temperature of the surrounding.
Stages
of the sleep cycle are 5 that typically last for 90-120 minutes as a whole. In
which stage the person is at the given moment can be confirmed by EEG
(Electroencephalogram).
In the first stage (1-7 minutes), person is half-awake
and half-asleep, when the eyelids are heavy and head starts to drop. In second (10-25 minutes),
eyes stop moving, but the person can still be woken easily. Third Stage (20-40 minutes) is characterized
by start of the delta wave of the brain signifying that its activity has slowed
down; so it becomes difficult to wake the person up. Fourth stage (20-40
minutes) shows only delta waves and the person becomes extremely hard to wake up.
This will also relax the muscles and breathing becomes slow and
rhythmic, which can lead to snoring. Last stage (10-60 minutes)
shows that the brain activity start to pick up the normal electrical activity. Muscles are temporarily paralysed, and
eyes dart back and forth, giving this stage its name, rapid eye movement (REM)
sleep.