Your Third Eye, Melatonin and Sleep

This is part of our ongoing The Best Kept Secrets to Healthy Aging spotlight. Each day, we will be posting some of the great information that’s packed into our book, The Best Kept Secrets to Healthy Aging.

Today’s topic:
Your Third Eye, Melatonin and Sleep

The pineal gland (the historical “third eye”), once thought to possess magical, supernatural or psychic powers, is now known to control daily body rhythms (“chronobiology”) in conjunction with light/dark information supplied by the eyes. The major output of the pineal gland is melatonin, a compound made from L-tryptophan and named for its ability to “trick” skin melanocytes (the cells that normally darken upon exposure to sunlight) into lightening their color as if they had never been exposed to light.

Although melatonin has critical functions in the regulation of many circadian (day/night) and seasonal cycles in human physiology and neurobiology, it is best known (and most studied) for its roles in the control of the sleep/wake cycle.

Pineal secretion of melatonin is linked to the absence of daylight – bright light triggers the transmission of electrical signals from the retina along a special nerve to the brain’s central circadian pacemaker area in the hypothalamus. Because these signals suppress brain secretion of the hormone (norepinephrine) that activates melatonin secretion, lack of bright light (dim light or darkness) allows norepinephrine release by the hypothalamus; in turn, melatonin secretion is activated (in response to lack of light).

In most people, melatonin secretion begins about 2 to 4 hours after sunset and ends about 1 to 3 hours after dawn. The amount of melatonin secreted overnight depends on the length of time the retina remains unstimulated by light.

Next Best Kept Secrets to Healthy Aging topic:
Melatonin Secretion with Age


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