Release of stress hormones.
Step-by-step explanation:
Stress hormones include adrenalin and cortisol.
Adrenaline which is commonly known as the fight or flight hormone is produced by adrenal glands after they receive a message from the brain that a stressful occasion occurs. Adrenaline's role, along with norepinephrine, is to respond and react immediately, when a person is stressed. Adrenaline also gives a big amount of energy, which is the best thing if you're in a life-threatening situation, where you need to run as fast as you can, but still remained focused.
Cortisol is a steroid hormone or the stress hormone, and it is produced by the adrenal glands. It takes a little time until you can feel the effects of the cortisol during stressful time, because it involves additional two hormones. The part of the brain, that's called amygdala has to recognize a threat first. Then, it sends a message to the hypothalamus, which will release corticotropin, which releases hormone named CRH. Then, CRH tells hypophysis to release ACTH, and then they tell adrenal glands to produce cortisol. If a person is suffering tremendous stress and is fighting for her/his life, the amounts of cortisol can be life-savers. On the other hand, too much cortisol can increase blood pressure, make a disbalance in the immune system, contribute to obesity and many more.