The kind of adrenaline rush that results from being woke from a deep sleep or a loud unexpected noise reflect our body's fight-or-flight mechanism (something practically all creatures have for survival). Interesting in its own right, but even more interesting in FM patients (and ME/CFS patients, too?).
My FM was diagnosed long before my ME/CFS, and one thing I learned was just how many FM patients had histories of big scary events happening to them (one or more). Examples of this include: car accidents, sexual abuse, muggings and (in my case) a horseback riding accident in which my horse rolled over my head, leaving me crumbled in the dust (my fault, not his!). In all of these cases, our bodies go into a fight-or-flight, heart-pumping freak-out that seems to use up almost all available adrenaline. This adrenaline depletion is why, before I was diagnosed with FM, Addisons Disease had to be ruled out.
In other ways, it's a lot like PTSD, which I swear I got from having a beeper (OK, now I age myself) when I was a newly graduated intern on call every other day. For two whole years after I turned that damn beeper in after transferring to another position, if someone else's beeper went off across the room, my heart would race, my face would pale and I would crumble to the ground, not fainting, just unable to move.
All a good topic for another thread, so as not to go too far off topic here. I appreciate you mentioning it, tho!!
Lynne