Biologist here:\n\nAdrenaline re-prioritizes blood flow. One of the big ones is *away* from the stomach. If you have stuff in your stomach when you get a big ol' blast of adrenaline there's a good chance you'll throw up. The gore and fear aspect really amplify the level of stress hormones and the response you'll have to adrenaline. The term "shit your pants" also stems from the bodily adrenaline response related to reducing blood flow to non-vital (relative to the moment) functions. 