ABSTRACT
Rhythms of living things are called bodily rhythms or biorhythms. These are patterns of physiological or psychological processes which are repeated over periods of time. Michel Siffre was studied for seven months in 1972 when he volunteered to live underground in caves out of any contact with daylight and without any other clues about what time of day it was, that is no watch or clocks or TV. Human menstruation is the best-researched infradian rhythm. This cycle is innate In females of reproductive age, regardless of culture. It is an example of a bio rhythm which is controlled by hormones biochemical messengers which are synthesised by glands of the endocrine system. Some brain neurotransmitters have seasonal variations which may be circannual. Our nervous system has a large number of different neurotransmitters, some within the brain and some in the nerves.
