By Levi Clancy for Student Reader on
The pineal gland secretes melatonin and is one of the brain's only unitary structures.
The pineal gland is located near the center of the human brain, and is stimulated by nerves from the eyes. In some other animals, the pineal gland is close to the surface of the skin and is directly stimulated by light. The pineal gland secretes melatonin at night (dark) and, as a result, secretes more melatonin in winter when the nights are longer.