When we stand to make our maiden speech before a large audience, our mouth dries up and heart rate increases and it is due to secretion of adrenaline hormone by adrenal glands. Adrenaline is the hormone which prepares the body to meet any emergency situation. Adrenaline makes the heart beat faster. At the same time, it stimulates the constriction of the arterioles of the digestive system reducing the blood supply of the digestive system which makes the mouth dry.