The adrenal medulla produces adrenaline and noradrenaline in response to stimulation by the sympathetic nervous system.Adrenaline rapidly raises blood sugar levels by converting glycogen in the liver to glucose and increases the heart rate in order to increase blood flow to the brain and muscles.Noradrenaline is also a neurotransmitter. As a hormone its effects include increasing the heart rate, widening of pupils, widening of the air passages and the constricting of blood vessels to and around non-vital organs in order to raise blood pressure in response to stress.