The adrenal glands or suprarenals are located anatomically right on top of the kidneys. The glands have an inner portion, the medulla, and an outer portion, the cortex. The adrenal medulla secretes hormones directly into the bloodstream or general circulation. Epinephrine or adrenaline is one of those hormones. Epinephrine is called a stress hormone because your body secretes it under conditions of stress, (physical or emotional).
The hormones secreted by the medulla and the autonomic nervous system are very closely related and have similar physiological actions. Hormone secretion is an endocrine function, the endocrine and nervous systems act to control the organism and act to facilitate communication between the various parts of the organism.