Light and Circadian Rhythms : natural partners in sleep
I have always found that Circadian Rhythms sounds either like a great name for band or something to with insects… I was wrong on both counts. Infact Circadian Rythms (meaning “about a day”) is commonly referred to as the biologic closk and is the daily cycle of life, including sleeping and waking.
Hundreds of bodily functions follow biologic clocks, but sleeping and waking are the most prominent circadian rhythms.
Light is the critical signal for the reset the circadian cycles each day. The response to light signals in the brain is an important key factor in sleep and in maintaining a normal circadian rhythm.
Light signals travel to a tiny cluster of nerves in the hypothalamus in the center of the brain, the body’s master clock, which is called the supra chiasmatic nucleus or SCN. This nerve cluster takes its name from its location, which is just above (supra) the optic chiasm. The optic chiasm is a major junction for nerves transmitting information about light from the eyes.
The approach of dusk each day prompts the SCN to signal the nearby pineal gland (named so because it resembles a pine-cone) to produce the hormone melatonin.
Melatonin is an important hormone released in the brain that some experts believe is critical for the body’s time-setting. The longer a person is in darkness the longer melatonin is secreted. Levels drop after staying in bright light. Research is ongoing to determine if high levels of melatonin cause sleep regardless of whether it is dark.
The sleep-wake cycles in humans are designed to produce activity during the day and sleep at night. There is also is a natural peak in sleepiness at mid-day, the traditional siesta time. The sleeping and waking cycle is approximately 24 hours. If confined to windowless apartments, with no clocks or other time cues, sleeping and waking as their bodies dictate, humans typically live on slightly longer than 24-hour cycles.
Daily rhythms intermesh with a number of biologic and physical factors that may interfere or change individual patterns. For example, the firing of nerve cells in the brain may be faster or slower in different individuals. Such differences are fractions of a second but they can cause variations in the type, timing, and duration of a person’s sleep.
In women, their monthly menstrual cycle can shift the sleep/wake pattern. Changes in season or various exposures to light and dark often unsettle the sleeping pattern.
The importance of sunlight as a cue for circadian rhythms is dramatized by the problems experienced by people who are totally blind: they commonly suffer trouble sleeping and other rhythm disruptions.
So, what can we do with this insight into light and circadian rythms?
1. Ensure that you sleep in a dark (cool) room. The darkness is a signal to your body that it is actually time to sleep (that includes not having the TV on or falling asleep with reading lights etc on).
2. Investigate whether a melatonin based (synthesised) supplement can assist you and your body to get back into a ‘sleep groove’. Here is one that has a free trial : Melatonin supplement.
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