Everyone has their own special recipe for anger: Combine one nagging mother, a traffic jam, and two people with more than 10 items in the express lane; stir until boiling mad. What you may not be able to identify, however, is what's actually happening inside your body.

The portion of the brain known as the neomammalian complex, or the limbic system, controls the entire autonomic nervous system, including heart rate, blood pressure, muscle tension, and all nervous and emotional response patterns, explains Bill DeFoore, Ph.D., author of Anger: Deal With It, Heal With It, Stop It From Killing You. "By stimulating different parts of the brain with electrodes, researchers identified part of the neomammalian complex that specifically governs fear and anger," says DeFoore. This core of anger in the brain is associated with the "fight, flight, or freeze" instinct, and termed the "reptilian brain.

"Reptiles are cold-blooded, solitary, small-brained, and self-centered, and their primary motivators are behavioral options of fight, flight, or freeze," explains DeFoore. Hence the adjective reptilian for the part of the brain that controls aspects of human behavior that mimic those of primitive creatures. "When people experience extreme fear or anger, their blood can literally get cold as a physiological response to activation in specific parts of the brain—a cold-blooded killer or a cold-natured person."

When an external event triggers intense pain or fear, our entire nervous system responds. "Physically our heart rate increases, body temperature either rises or drops dramatically, and muscle tension increases," says DeFoore. While pain and fear are feelings or sensations, anger is an active response. "Since anger is a survival mechanism designed to take care of the matter at hand or an immediate threat," he says, "our bodies help our effort to focus on the matter at hand and 'defeat the opponent.' Adrenaline is released into the bloodstream to increase our strength and energy to meet that goal." When we feel especially threatened or vulnerable, scientists believe that even our vision becomes limited.

If we are "emotionally intelligent," we tend to make conscious and rational choices in reaction to these physical and emotional responses. (Instead of beating the man with 16 items in the express lane over the head with his three loaves of bread, we kindly ask if we can step ahead of him in line.) "An emotionally intelligent person is aware of both the external event and the internal emotion," says DeFoore. "Whereas if we are 'emotionally hijacked,' we go into a reaction pattern and don't consider our own history and don't think until after the event is over and we have already reacted." The emotionally intelligent person will use his or her whole brain (literally) and take all factors into consideration before acting, while the emotionally hijacked person might use only the reptilian brain and realize that there was a better course of action only after reacting.

Once chemicals are released into the bloodstream, if a person does not act out or release that energy, the system can actually become toxic. For example, says DeFoore, "if someone becomes angry and then does not get a full release, he or she can become very tired or even physically ill. Anger requires a high energy output." Not acting on that buildup, he warns, can lead one to internalize bitterness, become sick to the stomach, build up tension in the neck and shoulders, and get headaches.

So what's the healthy way to let loose? "One cannot fully release anger by violently attacking or verbally assaulting someone," says DeFoore. "One good option is exercise. It's readily available, it's socially acceptable, and it helps you to move energy." (This is the theory behind the proverbial walk around the block.) He also points out that there is often a psychological wound at the core of the anger response, and a way to deal with the anger buildup may actually be to examine the unresolved issue underlying the anger.