Many years ago Dr. Walter Cannon began describing how refusal to deal with anger and fear can trigger physical illness. He discovered this by measuring the physical changes in a cat exposed to a barking dog. The emotion of fear stimulates us to take flight and the emotion of anger stimulates us to fight. These trigger our autonomic nervous system causing physical changes. For instance, digestion, assimilation, and elimination halt as blood vessels to the stomach and intestines shut down.
Blood increases in the brain, heart lungs and external muscles.
These areas are important in carrying out the decision to either fight or flee. The heart and lungs pump faster, while the bronchial tubes relax so more oxygen can enter. A number of changes occur in the blood. The spleen releases more white blood cells in case they are needed to combat infection in a wound. The number of platelets increase thus insuring a quicker blood clot if a wound is inflicted.