Examples of physiological responses are changes in heart rate, a higher respiration rate, sweating, changes in body temperature and changes in blood pressure. All of these occur in response to pain.
The human body has an integrated defense response, which includes flight or fight. The two key systems are hypothalamic-pituitary-adrenal, or HPA, and sympatho-adrenal, or SA. The HPA system releases cortisol, corticotrophin-releasing hormone and other hormones for relieving a person's emotional or physical stress, according to the Centers for Disease Control and Prevention. The SA system's activation results in the release of adrenaline and noradrenaline, which are catecholamines.