Question

why does our mouth dries up and heart beat increases during a maiden speech

Answer 1

This is because you are nervous. Once you are able to overcome your anxiety you will not face this problem. :)

Answer 2

Generally,it happens that during our maiden speech we get tensed and feared.So to neutralize the stress the hypothalamus sends a signal to the adrenal glands which secrete adrenaline which makes our breathing faster and dries out our mouth by stopping the production of saliva.