Your brain has a clump of nerve cells known as the suprachiasmatic nuclei (SCN), which acts as your "body clock", as it prepares your body to either wake up or go to sleep.
A human body undergoes a series of events that occur once every twenty four hours. This rhythm is known as the "circadian rhythm". Going to sleep and waking up are some of the several circadian rhythms that your body goes through everyday.
The SCN resets itself everyday, which is somewhat similar to the resetting of an alarm clock. The way it resets itself depends on the regular appearance of sunlight and the darkness that follows, without which, the SCN will not be able to regulate the body's natural sleep-wake cycle properly.
When light falls on your eye, a special chemical in the eye is released. This chemical signals the SCN, which in turn informs the nearby pineal gland to produce a sleep chemical called "melatonin". The pineal gland controls the production of melatonin, based on the signals it receives from the SCN.
Melatonin functions as a "messenger of sleep" as it has a mild sleep-inducing effect.
Melatonin also regulates your body temperature, to help you to sleep and wake up. Therefore, throughout the day the body temperature changes, from high to low, with a variation as high as one degree, between both. Melatonin will cause a rise in your body temperature when it is time to wake up and be active, and a fall in temperature when it is time to sleep.
Melatonin travels through your body, telling your cells to slow down their activities. During the day, the pineal gland releases hardly any melatonin. Therefore, at that time, the body cells run in full force.
Towards the later part of the day that is at sunset, the pineal gland starts pouring out the melatonin into the body, which slows down the activity of the cells while the body gradually prepares for sleep. The flow of melatonin in your body reaches it peak at around midnight.
Exposure to light late in the evening can reduce the level of melatonin in your body to daytime levels, thereby effecting your body's natural sleep-wake cycle.
The variations in melatonin levels affect teenagers the most. Therefore, during the early to mid-teen years, the pineal glands start releasing melatonin later than usual. Because of this, teenagers and young adults can stay up later at night, without feeling drowsy or tired.
Submitted by M T on March 9, 2010 at 12:36