The adrenal medulla and the sympathetic nervous system form the sympathetic adrenomedullary system, or sympathoadrenal system, so the action of hormones is closely linked to the sympathetic nerves. After studying the role of the sympathetic adrenomedullary system, the emergency doctrine was proposed. It is believed that when the body encounters special situations, including fear, severe pain, blood loss, dehydration, hypoxia, extreme cold, extreme heat, and strenuous exercise, this system will immediately mobilize and release noradrenaline, the so-called catecholamines, and the secretion will greatly increase. Catecholamines act on the central nervous system, increasing its excitability, putting the body in a state of alertness, responsiveness, faster breathing, increased pulmonary ventilation, faster heartbeat, increased cardiac contraction, cardiac output will increase, blood pressure rises, blood circulation accelerates, visceral vasoconstriction, skeletal muscle vasodilation, while blood flow increases and blood is redistributed throughout the body to facilitate the blood of vital organs in times of emergency supply. Hepatic glucose catabolism will also increase, blood glucose will rise, lipolysis will increase, free fatty acids in the blood will increase, and glucose fatty acid oxidation processes will be enhanced, all of which are very beneficial to the limbic response in stressful conditions.