Under stress or emergency conditions, the preganglionic neurons of the sympathetic division release acetylcholine. Acetylcholine stimulates secretion and release of epinephrine and norepinephrine from the adrenal medulla. These hormones enhance the effects of the sympathetic division of the autonomic nervous system (ANS) during stress. Epinephrine and norepinephrine augment the fight-or-flight response as they increase the heart rate and force of contraction, the output of the heart, and blood pressure. They also increase blood supply to the heart, liver, and adipose tissue. The airways to lungs become dilated and there are increase blood levels of glucose and fatty acids.
