The Stress Response System is a system to get you energy when you need it.
As mentioned in the last post, the sympathetic nervous system (SNS) tells your organs to get busy and respond to a demand for action, such as extra heart activity and respiration so your muscles can get more energy when climbing a flight of stairs for example.
In order to have the energy you need for this to happen, you need some chemical assistance from hormones. Adrenalin and Cortisol are two hormones needed for stress and they travel through the bloodstream. This makes the body release glucose and fat (or stores of fuel) that your muscles will use while burning energy when having to work hard.
"Cortisol is one of nature's most powerful anti-inflammatory drugs. In "The Mind-Body Interaction in Disease," Sternberg describes this hormone and the role it plays in managing stress in the body: "Cortisol is a steroid hormone that increases the rate and strength of heart contractions, sensitizes blood vessels to the actions of norepinephrine (an adrenalinelike hormone) and affects many metabolic functions — actions that help the body meet a stressful situation. In addition, cortisol is a potent immunoregulator and anti-inflammatory agent. It plays a crucial role in preventing the immune system from overreacting to injuries and damaging tissues. Furthermore, cortisol inhibits the release of CRH by the hypothalamus — which keeps this component of the stress response under control. Thus, CRH and cortisol directly link the body's brain-regulated stress response and its immune response."
The stress response can work for any length of time. Small little releases of energy or short powerful bursts of energy or long extended periods of stress response when you are in an emotional situation or under the burden of high expectations.