It feels to me like you are having some irrg heartbeats that you feel which is setting off a panic attack/anxiety attack and thus the adrenalin rush.
Nonessential systems (like digestion and immune system) shut down to allow more energy for emergency functions of your major organs. I am sure you have heard of people in high anxiety having diarrhea...............I suspect this is the reason why but I am not a scientist.
To give you the long version,
The sudden flood of epinephrine, norepinephrine and dozens of other hormones causes changes in the body that include:
- heart rate and blood pressure increase
- pupils dilate to take in as much light as possible
- veins in skin constrict to send more blood to major muscle groups (responsible for the "chill" sometimes associated with fear -- less blood in the skin to keep it warm)
- blood-glucose level increases
- muscles tense up, energized by adrenaline and glucose (responsible for goose bumps -- when tiny muscles attached to each hair on surface of skin tense up, the hairs are forced upright, pulling skin with them)
- smooth muscle relaxes in order to allow more oxygen into the lungs
- nonessential systems (like digestion and immune system) shut down to allow more energy for emergency functions
- trouble focusing on small tasks (brain is directed to focus only on big picture in order to determine where threat is coming from)
All of these physical responses are intended to help you survive a dangerous situation by preparing you to either run for your life or fight for your life (thus the term "fight or flight"). Fear -- and the fight-or-flight response in particular -- is an instinct that every person possesses.
Remember, if you feel you need to be seen by your Dr. for a medical screening exam, please do so.
Sending you good vibes,