The adrenal medulla secretes two hormones called adrenaline or epinephrine and noradrenaline or norepinephrine  (also known as, catecholamines). They are rapidly secreted in response to stress of any kind and during emergency situations, hence called emergency hormones or hormones of Fight or Flight. These hormones increase alertness, pupillary dilation, piloerection (raising of hairs), sweating etc. Both the hormones increase the heartbeat, the strength of heart contraction and the rate of respiration. Catecholamines also stimulate the breakdown of glycogen resulting in an increased concentration of glucose in the blood. In addition, they also stimulate the breakdown of lipids and proteins.