The stress response refers to how stress influences the body and the brain: moving from basic body signals of “fight or flight”, to feelings, thinking, and actions.
All of us experience stress. Under normal stress or sense of danger, the stress response includes body signals and feelings such as increased heart rate, hyper-vigilance, confusion, rapid breathing, numbness, chills, fear, terror — often described as “fight or flight”. The brain processes sights, sounds, and smells related to the stressful or frightening situation and starts the process of producing stress hormones, including cortisol. This is how we experience our body’s alarm system — signaling a threat of some sort. Under tolerable stress, we can experience enough clear thinking so that we can face the problem and take action toward a solution and stress relief. In fact, tolerable stress can build resilience — when we successfully manage the stress.
Traumatic stress or sense of danger stimulates the stress response so that we feel overwhelmed. It involves sensations from the outside (sights, smells, sounds, etc.) combined with sensations from the inside (physical and emotional sensations — like we can’t breathe, are terrified or panicked can’t think) that are so strong that we feel “frozen” without options to re-establish a sense of calm, control, or make things different. It is the extraordinary nature of the trauma itself, combined with the intensity of the emotional and physical response to trauma that defines traumatic stress.
Chronic or uncontrollable stress associated with ongoing stress over time or response to trauma triggers, causes repeated exposure to stress hormones and a change in the stress response system. The system that produces a cascade of neurobiological chemicals including cortisol will become down-regulated; that is, it will take less in the way of stimulation to turn it on, making the stress response more likely to even the slightest stress and lead to significant long-term effects or difficulties.
(Van Horn, 2008, used with permission)