If you stand to make your maiden speech before a large audience, your mouth dries up and heart rate increases. What brings about these changes?

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.

During stress situation, a large amount of adrenaline is secreted which increases our heart beat. It constricts the arterioles of the digestive system as a result less blood is supplied to the digestive system and one of its effects is dry mouth.