system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does anger and frustration make you feel very hot?

Often I find myself having to take off my coat during particularly difficult tests, or feel myself boiling in lab when something refuses to work for any explainable reason. I wasn't feeling hot at all before becoming frustrated.

Does it have to do with dilated vessels? If so, why does that happen when angered/frustrated?
gpt
It's part of your "fight or flight" instinct. Getting angry is the natural response to a potential physical threat on your person (getting attacked), so the body does some really interesting things to itself to get you pumped up for the fight.

One of the things it does is dilate your blood vessels to allow more oxygen to flow through your body. It will flood your brain with pain-killing chemicals, too. It raises your temperature as well, likely as a byproduct of burning more calories.  There are lots of other interesting effects. 

You just have to remember that human evolution has primarily taken place during periods before all this technology and safety made these responses difficult to deal with. We never used to get "angry" or "frustrated" because of silly stuff like driving or taking hard tests.  Anxiety and anger are really great evolutionary responses in the wilderness. Not so great in the workplace.