system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do our hands begin to shake in panic situations ?
gpt
Your brain senses a stressor (note this may be a real stressor or an imagined one), and activates the sympathetic nervous system.  This prepares you for "fight or flight" response, juicing you up with adrenaline, widening your musculoskeletal blood vessels, and opening your pupils to let more light in.

All of that puts you on edge and may make your hands tremble.