What is melatonin?
Melatonin is actually a natural hormone produced by the pineal gland located in top of the diencephalon. That’s why the side effects are minimal. The pineal gland controls the day-night rhythm of the brain and is highly affected by daylight. Actually it is more like affected by darkness. Since at night melatonin secretion is significantly increased from the pinealocytes.
The pineal gland is controlled by the suprachiasmatic nucleus located in the hypothalamus. Suprachiasmatic nucleus is the part of the brain which receives the signals from different receptors located in our bodies. These are mainly in our eyes, and controls the circadian rhythms.
The impulses coming from the retina make the suprachiasmatic nucleus stimulate the pineal gland and so the pinealocytes produce melatonin. So, what this means is that the more the light we have coming in our eyes, the less melatonin håndkøb is produced. This is one of the reasons why people living in the parts of the world where there is more daylight are perkier during the days. Their eyes get more light and their pinealocytes produce more melatonin.
Although as a down side they might have trouble getting sleep during the night if it is light in the late hours. This is usually not a problem because night falls very dark in the southern hemisphere and usually quite early. The day-night rhythm is much more distinct, and our bodies can react to it much easier.