Throughout the ages humans have been intrigued by the effect of the sun, moon, and stars on their daily lives. Additionally, the day to night cycle and seasonal changes have been at the forefront of religious beliefs and scientific inquiry. Biological rhythms (or biorhythms, for short) genuinely regulate human existence.
We know that the pineal gland, in addition to being an independent timekeeper, is a photosensitive organ, interpreting sensory messages from the retina. This gland, for example, is responsible for the production of melatonin, which is regulated in a circadian rhythm. Melatonin is an important derivative of the amino acid tryptophan, which also has other functions in the central nervous system.
The production of melatonin by the pineal gland is stimulated by darkness and inhibited by light. The gland therefore translates environmental messages of the light-dark cycle of day and night and seasonal changes into hormonal messages sent throughout the body. This results in an internal daily biorhythm called the circadian rhythm.
The length of time it takes to complete a single cycle of the circadian rhythm is referred to as the period of the rhythm and is usually a full day. Secretion of melatonin by the pineal reaches a peak during the night. This is one way that the pineal communicates with other organs and acts as the body's daily timekeeper.
If for some reason this communication is disturbed, we can experience depression, lethargy, and changes in sleeping and eating patterns. A familiar example of out-of-synch biorhythms is jet lag after a long flight. Jet lag appears to be more noticeable if you arrive in a gloomy, wintery environment rather than a bright, sunny one which suggests that the brightness of light is one factor involved in setting circadian biorhythms.
Seasonal and circadian (daily) rhythms are conspicuous features in most biological systems. ‘Clock’ mechanisms regulate many aspects of physiology, metabolism, and behavior. Our own circadian clocks have an intrinsic period of 23 to 25 hours, and have to be reset frequently by environmental cues such as daylight and darkness.
We are now learning that circadian biorhythms include your intuitive or psychic cycle. This 38 day rhythm cycle coincides with Plato's "four aspects" and with Carl Jung’s "four functions". Jung, the world famous psychologist and teacher, described the four functions as sensation, thinking, feeling and intuition. These four functions directly relate to your regular four biorhythm cycles of physical, intellectual, emotional and intuitional and they all work together to regulate your physical and mental abilities and well being.