Cannon taught that activation of the sympathetic nervous system and adrenal gland in
emergencies helps maintain homeostasis, a word he invented. Since then, other
neuroendocrine systems have been described that are closely linked to components of the
ANS. These include the hypothalamic-pituitary-adrenocortical (HPA) system, the renin-
angiotensinaldosterone system (RAS), and the arginine vasopressin system. Across a
variety of stressors, responses of plasma epinephrine (EPI) levels are more closely tied to …