The video below gives a basic overview of what happens in your body when you experience nerves/ anxiety.
What is Anxiety?
Anxiety involves triggering of the primal fight/ flight/ freeze parts of our brain. Fortunately, the actual life threatening experiences which once threatened us as species for which our brains evolved to protect us, have been replaced by every day anxiety provoking experiences like job interviews, public speaking etc. However the brain still perceives these events in the same life threatening way.
Understanding your physiological responses and triggers helps to deal with it. Also utilising a mindfulness approach helps to decrease the response.
Credit to Asap Science.