To understand why our hair turns gray, you need to understand the processes that accompany growth and hair color.
Hair color of a person determined by the pigment melanin, which produce special cells melanocytes. Melanocytes are located in different parts of the body, namely the melanin can give the color of our skin, hair, and eyes.
Despite the fact that there are a huge number of shades of hair and skin, responsible for them two types of melanin – eumelanin gives a dark brown and black color, and pheomelanin gives a reddish/yellow. Mix the two types and determine the color of human hair.
After the mixture of melanin, its granules are in keratocan is a special type of cell that is found in hair follicles. Keratotomy produce keratin – a dead protein cells, which made our hair. When carattini die off, leaving the melanin, which gives color to hair.
Gray hair is caused by a low content of melanin in the keratin. The less melanin, the whiter the hair. Gray hair is absolutely not contain melanin.
During aging, the melanocytes become inactive, but are still present in our hair. The older we, the less remains of melanocytes. As a result, the body produces less and less melanin, until he disappears altogether. So we gradually turns gray, as long as our hair doesn't become completely white.
You can consider carefully why stress makes our hair gray. In 2011 and 2012 Nobel laureate in chemistry Robert Lefkowitz was the head of a research team that studied the mechanism of graying hair as a result of stress. Stress causes the release in the body a massive amount of neurotransmitters that are involved in the mechanism of our reaction of fight or flight. Under normal conditions these neurotransmitters are not stored for a long time and have incredibly useful for us effects – for example, accelerate the reaction and give strength to the muscles.