Fight Or Flight Response
When faced with a life-threatening danger it often makes sense to run away or , if that is not possible, to fight. The fight or flight response is an automatic survival mechanism which prepares the body to take these actions. All of the body sensations produced are happening for good reasons - to prepate your body to run away or to fight - but may be experienced as uncomfortable when you do not know why they are happneing.
Quicker thinking helps us to evaluate danger and make decisions. It can be very difficult to concentrate on anything apart from the danger (our escape routes) when the right or flight response is active.
Dizzy or Lightheaded
If we don't exercise (e.g. run away or fight) to use up the extra oxygen then we can quickly start to feel dizzy or lightheaded.
Changes to Vision
Vision can become acute so that more attention can be paid to danger. You might notice tunnel vision or vision becoming "sharper".
The mouth is part of the digestive system. Digestion shuts down during dangerous situations as energy is diverted towards the muscles.
Heart Beats Faster
A faster heart beat feeds more blood to the muscles and enhances your ability to run away or fight.
Breathing Becomes Quicker and Shallower
Quicker breathing takes in more oxygen to power the muscles. This makes the body now able to fight or run away.
Adrenal Glands Release Adrenaline
The adrenaline quickly signals other parts of the body to get ready to respond to danger.
Muscles in the bladder sometimes relax in response to extreme stress.
Nausea and "Butterflies" in the Stomach
Blood is diverted away from the digestive system which can lean to feelings or nausea or "butterflies".
Palms Become Sweaty
When in danger the body sweats to keep cool. A cool machine is an efficient machine, so sweating makes the body more likely to survive a dangerous event.
Hands Get Cold
Blood vessels in the skin contract to force blood towards major muscle groups.
Muscles all over the body tense in order to get you ready to run away or fight. Muscles may also shake or tremble, particularly if you stay still, as a way of staying "ready for action".