To our cave-dwelling ancestors, the fight/flight response was an essential tool for survival, evolved over many thousands of years living in wild and dangerous places. To us, living in today's technological twenty-first century, it is often an ineffective response, which can actively prevent us from responding usefully to a problem situation.

This response to anything which is perceived as a threat, or potential threat begins when certain primitive parts of the brain send a message to the adrenal glands. These begin a process involving a number of hormones including adrenaline, whose purpose is to prepare the body for vigorous emergency action. The main changes that follow are below.

Non-essential processes are immediately switched off. In particular, if the body is digesting food, that is stopped immediately, and people notice a feeling of churning or 'butterflies' in the stomach, or feeling nauseous or sick. A number of other changes follow, to make the muscles as strong as possible.

The liver releases glucose into the bloodstream. Fats are released into the bloodstream from the fat stores in the body. These are fuel for the muscles, so oxygen is needed to burn them - so the breathing increases, and those under stress may notice feeling breathless.

Having Fuel and oxygen in the bloodstream, the body needs to get it to the muscles as soon as possible - (remember, the body thinks this is a life or death emergency). So to pump the blood quickly, the heart begins beating far faster - and some people notice palpitations. Blood pressure rises, and some people notice feeling hot or cold - even breaking into a sweat, as the body seeks to dissipate the heat that will be generated by the vigorous muscular activity for which the body is preparing.

Becoming ready for instant action, muscle tension increases, and a person may notice shaking, or becoming restless - fidgeting. If the pattern in continued for long enough, chronic headaches or backache may result.

As all this is happening in the body, there are two important changes in the neurology. First, reflexes are speeded up. At the same time, so is the thinking, and some notice racing thoughts.

Second, the blood supply to the frontal parts of the brain, responsible for higher levels of reasoning is reduced, while the blood supply to the more primitive parts, near the brain stem, is increased. These parts are responsible for automatic, or instinctive, or impulsive decision making and behaviour, and a person undergoing a stress response may be prone to impulsive thinking and behaviour - which they may thoroughly regret later.

These responses, while they are often experienced as automatic and out of conscious control, can be brought under a person's control, and clients usually experience the first beneficial effects of such learning within mere weeks of beginning therapy here.