Under stressful or dangerous situations, organisms enter into the "flight-or-fig

The sympathetic division of the nervous system becomes very active in response to stressful or startling stimuli. While the animal's motor neurons are stimulating skeletal muscles to contract in running away or fighting, the sympathetic drive is increasing heart rate and breathing rate. Additionally, blood vessels going toward skeletal muscles will dilate to ensure an adequate supply of oxygen and nutrients. At the same time, the sympathetic drive stimulates the adrenal medulla to release epinephrine into the bloodstream. This will also increase heart and respiratory rates. The nervous system also stimulates glucagon release and inhibits insulin release to maintain high plasma levels of glucose. The high plasma glucose levels will be enhanced by the release of glucocorticoids from the adrenal cortex.