How will you react? Will you even be able to react, or will you be paralyzed with fear? Even the best combat trained police officers and soldiers have experienced “freezing” when faced with moral danger.
When faced with mortal danger, the human body instinctively reacts by releasing an enormous surge of adrenaline, the most powerful hormone in the body, which causes certain predictable physiological and psychological responses within the body. This reaction is often called the “fight-or-flight reflex." Although these effects may be lessened by intensive training, they are occur involuntarily and cannot be consciously prevented.
Therefore, the fight-or-flight reflex is not a matter of courage or lack thereof, it is an instinctive response controlled mostly by the autonomic nervous system. When the brain sense mortal danger, your sympathetic nervous system instantly dumps a variety of hormones into your body that cause a high arousal state known as fear. In this state, your body operates differently than it normally does and sometimes you have no control over its actions. These changes take effect immediately and may last for a long time, so their effects may linger long after the actual threat is removed. One common effect precipitated by these effects is the distortion of perceived time, called tachypsychia.