Either mental or physical, stress activities are a brain network involving most directly hypothalamus, the pituitary gland, and the adrenal cortex which releases stress hormones
Stress hormones are the signals of the deeper impact that chronic stress can have on every organ and system in your body. It goes from the nervous and circulatory system, to the digestive and immune system.
The presence of stress hormones in the body are crucial and survival in danger situations. The physiological reaction of the human body is why our body sensitivity is so important.
In your brain, the hypothalamus gets the ball rolling, telling your adrenal glands the stress hormones adrenaline and cortisol. These hormones go up to your heart and send blood rushing to the areas that need it most in a emergency.