Adrenaline production is part of the body-wide network of the fight or flight response stimulated by your sympathetic nervous system. The conscious mind detects a threat, and the subconscious sympathetic system responds – ready for battle. The sympathetic system alerts the whole body via nerve pathways. Included in the body-wide alert are signals that race along nerves of cells of the adrenal medulla that secrete adrenaline and norepinephrine.

The body was designed to produce adrenaline in direct response to an immediately threatening physical encounter. Signals from any of the five senses alert the whole body through the autonomic nervous system of immediate danger to life and limb. The big deal about adrenaline is that man has learned to stimulate its production with his mind when no actual physical danger exists. Remember, both fear of the future and fear of a charging tiger cue adrenaline production.

Adrenaline has much the same effect on the body as the sympathetic nervous system. But its effects are more far-reaching. Adrenaline can affect the metabolic rate of every cell of the body. Although the sympathetic system can control body-wide functions such as arterial pressure or metabolic rate, the nerve connections of the sympathetic system directly affect only a small portion of cells of the body. And since adrenaline and norepinephrine are delivered into the blood, adrenaline effects last five to ten times as long as sympathetic nerve stimulation. When you become excited in your conscious mind, your subconscious activates sympathetic and parasympathetic responses, and epinephrine and norepinephrine flood your body. The result is defense physiology.

For example, there you are in front of your trusty computer chaffing under the pressures of the job. What’s happening in your body is that your sympathetic system is responding to a job stress “threat” and adrenaline is coursing through your body. But you don’t run. You don’t fight. And the adrenaline with its residual effects keeps coming. Unless you do something to “burn off” the adrenaline your body will stay uptight. You could scream, jump up and down, or put your fist through the wall, but none of those responses is socially acceptable.

What many of us end up doing is gritting our teeth, clenching our fists, and knotting our stomachs. We go on with our bodies working faster and harder. But we don’t “work off” the adrenaline. Then, at the end of the day, we wonder why we are tired when we haven’t done much in the way of physical exercise. How can sitting at a desk all day be so tiring? Now you know. It’s not your imagination. The body has been working hard even though it hasn’t moved around much.