Vertebrate regulatory hormones play a critically important role in mobilizing the body to respond to emergencies . many neural and endocrine systems but specially the hormones secreted by the adrenal glands participate in these response. In humans the hormones cortisol is secreted into the blood by the adrenal cortex whenever the individual is stressed because of illness or injury . extreme physical effort pain radical changes in body temperature or intense emotion. Cortisol stimulate the breakdown of body proteins into sugars to provide energy liberates vital amino acids for use in tissue repair combats inflammatory reactions that accompany inures increases the capacity of muscles to remain contracts and is involves in a variety of other life protecting functions.

Another reactions to stress is the fight or flight response in which more sugar is released into the blood , blood pressure, breathing rate and hear rate are increased blood is shunted form the digestive tract to the skeletal muscles blood clotting time is reduced. And a variety of other changes occur that prepare the animal and norepinephrine from the adrenal medulla. The secretion of these two hormones is stimulated by the sympathetic division of the autonomic nervous system on response to intense physical exertion pain fear anger . they prepare the body for fighting or for running away from the environmental threat.