The adrenal glands are a pair of large hormone producing glands that are located immediately above each kidney. They are responsible for the production and release of most of the hormones that relate to the human response to stress. These include:
- cortisol - Cortisol increases blood pressure, allows the increase of blood sugar levels, and suppresses the immune system. A deficit of this hormone results in Addison's disease. Overproduction of the hormone results in Cushing's syndrome.
- adrenaline or epinephrine - Adrenaline is released when the body is under severe stress and has a number of immediate effects. It boosts the uptake of oxygen and glucose to the brain and muscles, and suppresses almost all other bodily processes, particularly the digestion of food. As a result, the heart rate rises, the volume of blood in each heart beat similarly rises, the pupils dilate, and arterial capillaries in the digestive tract and skin constrict, while they grow larger in skeletal muscles. It also increases the liver's rate of converting glycogen to glucose in the liver, and encourages the breakdown of fat. On top of all this, it also suppresses the immune system, typically the histamine response that is typical of anaphylactic shock.