'Time is God's way of keeping everything from happening at once'
     ……….Anon

Rhythms from the endogenous 'biological clock' controls the physiological processes of all living beings.

How many of us are aware that inherent to each of our cells there is a remarkable clock that is incessantly ticking away? It has now been undoubtedly established that our body functions in accordance to a rhythm that traces its origin to this 'cellular timepiece'. Several basic functions like alertness, susceptibility to pain, the processing capacity of the liver and even the intensity of our hand shake is determined by these rhythms which are endogenous, and are orchestrated by external 'signals' like sunlight, darkness, weather or specific sounds. Sunlight is the most potent signal, around which the daily activities of all creatures revolve.

'Chronobiology' is a discipline of science that studies the phenomenon of biological rhythms and their cyclic pattern in living beings. The earliest rhythm was known to have originated in primordial cells when DNA replication was assigned to the dark, to protect the 'blue print of life' from UV assault.

Rhythms are of several kinds:

Infradian rhythms refer to long-term cycles, which include the migration of animals and birds.

Ultradian Rhythms are the short cycles, like the 90-minute REM cycle.

Tidal rhythm is a twelve hour cycle that influences marine life, and which fluctuates between the rising and the ebbing tide.

Circadian rhythm is a 24-hour light-dark cycle that controls the physiological processes of all living things. They determine the quantity, quality and timing of hormones that influence daily functions such as appetite, mood, libido, energy and sleep. Specific patterns of brain wave activity, hormone production, cell regeneration and other biological activities are associated with this cycle and the body makes significant changes, in response to it, through out the day. This sheerly- balanced, natural cycle is derived from our ancestors. Besides controlling our sleeping and feeding patterns, this daily rhythm controls migration, mating and reproduction in several forms of life.

The word 'Circadian' ('circa' means '24 hrs' and 'dian' means 'day') was coined by Franz Halberg. When the circadian rhythm is synchronized with nature our bodies respond to the glorious sunlight and secretes cortisol, serotonin, hormones and neurotransmitters that are required for normal functioning. Temperature and blood pressure are also elevated, as the body gears to face the challenges of a new day. At dusk, the body responds to the sinking sun, and the ensuing darkness helps to stimulate the production of melatonin. Temperature and pressure decreases, and the body prepares for rest and sleep.

The circadian rhythm is controlled by a group of cells, situated in the hypothalamus of the brain, called Supra Chiasmatic Nucleus (SCN), otherwise referred to as the 'Biological Clock'. Sunlight reaches the SCN through the photoreceptors in the retina of the eyes. The signal is transmitted to the pineal gland in the brain to stimulate melatonin production. The concentration of melatonin ebbs during the day and elevates by night.