The cortisol then triggers the classic fight or flight response in the man's brain, and at the same time, cortisol gives him heightened awareness and a sudden burst of energy. (supernaturalacnetreatment.com)
This is sometimes described as fight or flight responses. (verywellfit.com)
The problem with fear in dogs is that the fear may lead to aggression when your dog's fight or flight response kicks in. (professorshouse.com)