However, the red-yellow pheomelanin is believed to cause the warm, golden, or auburn tones found in some types of brown hair. The range of colors produced by melanins is limited to shades of yellow, brown, red, and black. Grey hairs contain only a few melanin granules, spread out through the hair.
Hormones are your body's chemical messengers. They travel in your bloodstream to tissues or organs. Endocrine glands, which are special groups of cells, make hormones. The major endocrine glands are the pituitary, pineal, thymus, thyroid, adrenal glands, and pancreas. In addition, men produce hormones in their testes and women produce them in their ovaries.
How stress affects brain performance. Stress hormones affect our memory and cognition. When we get upset, our cortisol levels elevate in the blood, and the part of our brain in which learning and memory resides -- the hippocampus -- starts dumping neurons as a reaction to stress. By getting smaller, our hippocampus negatively impacts our memory and learning capacity.