system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do hormone responses occur so rapidly? When people are frightened/surprised, they can almost immediately feel a rush of adrenaline and heart rates rise, faces flush, etc. How do hormones reach appropriate organs so quickly? Why isn’t there more of a delay for the hormones to travel?
gpt
So there are already a ton of responses in this thread which explain it better than i can, i just want to add a reason why your heart can change its tune so quickly. You have a node in your heart which is called the sinus node. It has a "natural" tact of approximately 120 Beats per minute. As you know your resting heartrate is quite a bit lower  (around 60-80). This is because your sinus node gets constantly throttled by your parasympathetic nervous system. Imagine someone who is pushing against a door -your sinus node- and someone holding against it from the other side -your nervous system-. If you experience a stimulus which needs a higher heartrate your parasympathetic system just stops blocking  the door. Your sinus node suddenly has no resistance and burst through the door with full speed. This change can occur between two heartbeats so that this is the fastest way for your body to raise its heartrate.