Adrenal medulla releases two hormones adrenaline and noradrenaline. In the stress conditions, these hormones increase alertness, pupillary dilution, piloerection (raising of hairs), sweating etc. Both of these hormones increase the heart beat. Catecholamines (adrenaline and noradrenaline) also stimulate the breakdown of glycogen resulting in an increased concentration of glucose in blood. In addition they also stimulate the breakdown of lipids and proteins