system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is that electrical shock feeling throughout your body when you get suddenly scared (like missing a step on the stairs)?
gpt
Stimulation of the sympathetic nervous system, inhibition of the vagus nerve and, soon after that, adrenaline.

The initial spike is entirely nervous, being dominated by rapid firing of the fastest signals your body sends - adrenaline takes a few seconds before it surges.