The imagination that is raised in man (or any other creature endued with the faculty of imagining) by words, or other voluntary signs, is that we generally call understanding, and is common to man and beast. For a dog by custom will understand the call or the rating of his master; and so will many other beasts.
The fight or flight response refers to the physiological response to stress. It is the body's automatic response that occurs when we perceive a situation as dangerous or stressful. This sets off a chain of chemical and hormonal reactions so your body can be ready to fight or flee to keep you from harm.
combat stress reaction csr is a term used within the military to describe acute behavioral disorganization seen by medical personnel as a direct result of the trauma of war