Contrarian clock that defies sleep and logic
Everyone has it, an internal biological clock called circadian rhythm that regulates the body’s sleep-wake cycle, temperature and hormone function over a roughly 24-hour period. It’s ticking is determined by your genetic legacy and your exposure to sunlight.health and fitness Updated: Nov 12, 2011 22:50 IST
Everyone has it, an internal biological clock called circadian rhythm that regulates the body’s sleep-wake cycle, temperature and hormone function over a roughly 24-hour period. It’s ticking is determined by your genetic legacy and your exposure to sunlight. It helps all living things -- ferns (plants), rats (animals), yeast (fungi) and algae (cyanobacteria) included – function and do whatever they do best.
My body clock, unfortunately, is either ignorant, defunct or stubbornly contrarian. It scorns at the great circadian tradition of keeping order among the living and keeps me up at will – its will, not mine – at odd hours. And its contempt for regimentation is obvious in the fact that my sleep patterns are never the same on two consecutive nights: I’m an owl one night and a lark the next day at the whim of my defiant body clock.
My irrational timekeeper is a little part of my brain tissue called suprachiasmatic nucleus, which lies above the optic nerves. Its job is to set my body clock by the light that falls on the retina and relay the information to the rest of my body through nerve impulses and hormones. It clearly sleeps on the job, which keeps me up.
Of course, chronotypes can vary and everyone’s body functions optimally at different hours even when they largely follows the ‘sleep at night-wake at daybreak’ pattern. Since the sleep hormone melatonin secretion usually starts after 9 pm, normally you get your deepest sleep at 2 am, provided, of course, that you are in bed by 11 pm. Melatonin secretion stops at 7.30 am, after which you should be up and alert to face the day. But since chronotypes vary, there are always some owls and some larks who function out of sync.
Biological rhythms also vary at different stages of life of the same person. Most teenagers, for example, stay up late and get up even later because of natural delays in the secretion of the sleep hormone melatonin, which slows the body clock and makes it shift several hours backwards.
Circadian rhythm reset again for most people later in life, drifting forward in people over 60 years to make them ready for bed early in the evening and wake up at the crack of dawn. If they try to stay up later, they are likely to nod off or feel sleepy all through the day.
Apart from sleep, the body clock also regulates body temperature and hormone function to prepare us for tasks ahead. It controls digestion, immune function, cell division and body temperature, bringing down core temperature to its lowest at 4.30 when the body is at complete rest. Efficiency increases as body temperature and adrenalin levels peak in the afternoon, making your reaction time the fastest at 3.30 pm, and heart efficiency and muscle strength optimal at 5 pm.
Lack of sleep, on the other hand, causes the amygdala -- the region of the brain that alerts the body to protect itself in times of danger -- to go into an overdrive. This prevents the brain’s prefrontal cortex, which commands logical reasoning, from releasing chemicals needed to calm down the fight-or-flight reflex, keeping the sleepless restless and on edge through the day.
Scientists say circadian rhythms can be nudged forward by exposing the body to bright light in the morning. I’ve heard people boast how a walk in the sun resets their jet-lagged body clock to local time in a day.
Now that I understand the science behind it, all I need to do is figure out is how to convince my contrarian clock to fall in line.
First Published: Nov 12, 2011 22:48 IST