What do fruit flies, day lilies and humans have in common?
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CIRCADIAN RHYTHM, to be exact. An internal clock that regulates their inner workings such as day lily petals opening every morning and closing again every night. It is believed that the origin of this phenomenon dates back to the beginning of life. As each species evolved, their circadian (from 'circa' meaning about and 'dia' meaning a day) rhythm also evolved to help them survive.
Man should rise at dawn and go to bed at dusk. This was the natural rhythm of our ancestors. They respected and even feared the dark. But modern man does the exact opposite. We artificially extend the day with electric lights; travel forward and backward across time zones; and work or play at night, then sleep in the day.
Key links developed between our circadian rhythm and our body functions. This was to ensure maximum performance with minimal energy expenditure. It has been determined that the following are known to follow a cycle driven by circadian rhythm:
CARDIOVASCULAR: blood pressure, heart rate, blood volume and flow, heart muscle function and responsiveness to hormones.
BRONCHIAL SMOOTH MUSCLE reactivity with increased asthma symptoms at night and early morning.
KIDNEY FORMATION and URINE FORMATION: urine volume, urine electrolytes.
IMMUNE SYSTEM and blood cell functions.
Fortunately these links still exist despite the widespread tendency to ignore the day-night cycle of our ancestors. On the daytime side of the cycle, memory, the ability to be logical, reaction time, manual dexterity and mood are also driven by circadian rhythm. The list below summarizes some other links:
10pmBody temperature starts to drop in anticipation of sleep. This allows for energy conservation through the slowing of other functions such as pulse, blood pressure & breathing.
11pm - 1am Peak for a growth hormone released from the endocrine system which enables the body to rebuild or restore the tissue, muscle and bone cells that were used up or damaged during the day.
6am - 9amSex hormones are at their highest levels contributing to the classic male early morning arousal.
9am - 11am or for the first two hours after waking, in people ages 45 to 85, blood pressure and the blood's clotting ability increase, causing a decrease in blood flow to the brain and heart. This circadian rhythm has been linked to morning being the most likely time for strokes and heart attacks.
9 am - noonAbility to perform analytical skills and to mentally be at our sharpest peaks.
Noon - 2 pmVerbal reasoning ability and ability to maintain mental alertness peaks.
3pm - 5pmEpisodes of drowsiness, daydreams and lapses in concentrationincrease. It had been thought that this was a post-meal phenomenon, but it has been discovered that the link is to another circadian dip in body temperature and the associated anticipation of sleep.
3pm - 7pm Long term memory peaks.
7pm - 9pm or at sometime in the evening, there is a second, shorter peak of blood pressure and blood clotting ability with another trend to increased incidence of strokes and heart attacks in people ages 45 to 85.
There are other rhythms besides Circadian, that play in our lives:
Seven-year rhythms tend to mark milestones in human development. For example, childhood, puberty, adulthood, middle age and retirement are all close to multiples of 7 years (7, 14, 21, 42, 70).
Circannual rhythms have an annual cycle. This may explain why birds fly south for the winter and bears hibernate and why some humans suffer seasonal mood swings. There is also a cirannual peak in March to cycle where blood pressure and blood clotting ability increase with a similar trend to increased incidence of strokes and heart attacks in people ages 45 to 85.
Infradian (Lunar) rhythms have a nearly month-long cycle and have also been associated with the rhythm of the moon. This cycle is illustrated by a woman's menstrual cycle.
So is there a best time to balance your checkbook?
Between 9 am and noon when your ability to
perform analytical skills is at its peak.
Circadian rhythm disorders can be short term, such as jet lag & shiftwork sleep disorders, or chronic such as Delayed Sleep Phase Syndrome. Read on for details.