We are always reminded that having poor sleeping habits is bad for our health and well-being, but it is also important to know the right time of the day when we should sleep. The study of the body's circadian rhythm suggests that the daily schedule of doing things plays an important role in maintaining good body functions.
What is Circadian Rhythm?
Circadian rhythm refers to the natural, physical, mental, and behavioral changes that happen in the body of an organism during a 24-hour cycle. It is part of the body's internal clock and runs in the background to carry out essential bodily functions and processes. Most plants and animals have a circadian rhythm, and in humans, it affects the way people sleep, wake up and eat.
Various systems of the body follow circadian rhythms which are synchronized with a biological clock in the brain. This internal clock is directly affected by environmental cues like light, which is why circadian rhythms are also related to the cycle of day and night.
According to the National Institutes of Health, the body's master clock is controlled by the suprachiasmatic nucleus (SCN) which is located inside the brain's control center called the hypothalamus. The SCN receives various signals from the body which it responds to for body clock setting.
One of the important ways the SCN sets the body clock is by instructing the body to release hormones such as melatonin and cortisol. Melatonin, the "master regulator" of the circadian clock, is released in dark or dim-light conditions about two to three hours before sleep. Meanwhile, cortisol is present in the highest levels in the morning just before waking up, preparing the metabolism for the day.
There are several factors that can affect the circadian rhythm of a person. When a person passes through time zones, they can adjust their watch, but not their body clocks. It will try to function on the time it is at home, which is why a person may experience jet lag during long travels. The body clock will reset to the time they are in, but it can take a few days.
Screen time can also affect the body's circadian rhythm. Any amount of light signals the brain that it is time to be up and alert. Even the blue light from the tablet, smartphone or television. It is highly suggested to unplug from all screens 2 to 3 hours before going to sleep. Meanwhile, night shift work can also disrupt the internal body clock. A person working at night will need to sleep during the day. This can be a struggle since the body is programmed to be awake when there is light outside.
Circadian Rhythm and Sleep Pattern
Some examples of circadian rhythm in humans are hormonal activity, body temperature, digestion, and immune function. Among these, the most important and well-known is the sleep-wake cycle.
During the day, exposure to light causes the internal body clock to send signals which generate alertness and help keep a person awake and active. As night falls, the internal clock initiates the production of melatonin to prompt sleep. It keeps transmitting these signals to help a person stay asleep through the night. This way, circadian rhythms align sleep and wakefulness with day and night to create a stable cycle of restorative rest which enables increased daytime activity.
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