system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is happening in your brain when you undergo a panic attack?

What is the chemistry behind it? Why are some people prone to them?
gpt
Basically, at it's very core all animals have two sections of their brain. The Sympathetic nervous system and the Parasympathetic nervous system. These are what control our internals, stuff like homoeostasis and digestion. Basic functions of life that every animal has to do and not think about. Your parasympathetic nervous system handles stuff like digestion, arousal, bladder control stuff like that. Your sympathetic nervous system handles stuff like kick starting your heart so you can run away from that angry bear.

These two nervous systems work in opposition to each other. For example, you'd never lose bladder control randomly while watching TV (unless you were watching The Shining). For people with anxiety problems the sympathetic nervous system gets activated at anything the person finds scary/threatening. Our brains are dumb and really smart at the same time. For all our brain knows, we are scared of public speaking because we might die from it. So it'll tell the sympathetic nervous system to turn on until the threat is dealt with. That is what causes symptoms of fast heart rates, sweating and the feeling of wanting to get out of wherever you are. Your brain literally thinks what your doing is life threatening.

As for what causes it, we don't really know. The brain is very understudied/very new field of research so we're are finding about a lot of new things quickly. So as of now, there is no explanation for why the brain thinks meeting your new boss is the same level of danger as having a cage match with a wolf.