Thanks for your question. Not everyone has the same physiological experience during a panic attack. Different people experience different symptoms. So, in case you think you are having a panic attack, you may want to consult a licensed professional in your area.
Take care and be safe.
Dr. Lata Sonpal
So, those of us who get reminded by panic attacks are reminded in situations we call "triggers". That is, you have a trigger that somehow is reminiscent of what happened just before or during or just after your injury, most likely, just before. So, if I were in your situation, I'd keep a pillow in my car or in a briefcase, and when I have my next panic attack, I'd go out to my car or into a private space and scream bloody murder fear screams into my pillow. I'd cry. I'd shake. I'd sit there and allow myself to feel every feeling and hear every thought. After exhaustion, I'd think about why this event won't happen again and how it's over. I'd feel the relief. I would reassure myself that I am truly safe now. Even fear doesn't hurt me. There is nothing to be afraid of now. I will not fear fear anymore. I will face fear and process what my body wants me to process, so I can be clear, current and forward thinking.
To answer your question, now, regarding what happens to your body, it saves the fear-alarm experience, putting itself on "hold", to be continued later. Perhaps you were rescued, and you jumped from alarm to gratitude. Whatever happened, your body is on standby.
Many physicians prescribe pills, because they, too, believe that we shouldn't have to feel fear or anxiety. They almost act as if there isn't a cause underlying the feeling. Instead the focus is on a belief that we shouldn't have to suffer these negative emotions.
When we are traumatized, the amygdala records and saves the trauma, so we can remain on alert, if need be. Remember, our bodies were designed over time by evolution, where threats to survival sometimes lasted and we shouldn't drop our guard.
Even when we don't specifically remember the threat, the amygdala does. The amygdala never forgets. However, the amygdala can let go of a fully processed experience. It is just that if we have put our process on hold (with medication, denial or stoicism), and the amygdala will keep our feelings at the ready for us, on a hyper-vigilant standby, alert mode. So, when we are triggered, the rest of the body goes into that alarmed state of fight or flight, as if we could die. Not only do we have the chemical release of the amygdala, but we have adrenaline and cortisol coursing though our body, because he brain believes we are revisiting our life-threatening experience again, and we have to save ourselves. It's up to you to finish the process and reassure yourself that it's over.