Stress is a word commonly found in today's vocabulary, and is often used to describe modern working and living patterns, especially in big cities. Yet stress has been a part of daily life since time immemorial. Thus it would be more pertinent to define stress as the way in which the human body deals with all kinds of threatening situations, from confrontations with wild, vicious animals, to struggling through a crowded subway station during the early-morning rush hour: the effects on the body being universal. When confronted with a stressful situation the body reacts by releasing a hormone known as ACTH from the posterior pituitary gland situated at the base of the brain. The hormone, traveling through the network of arteries that make up the primary blood supply route, reaches the kidneys, or more specifically, glands situated on the peripheries, where it stimulates the release of adrenaline. This has an antagonistic effect on various bodily functions. That is to say it stimulates a response in certain organs, whilst inhibiting action in others. In other words a type of trade-off is reached, whereby energy saved by shutting down one function is thus used to enhance the performance of a neighbor. In this way, the body can prepare itself fully for the oncoming danger by using, primarily, the same given amount of energy, giving rise to what is known as the fight or flight response. When the fight or flight response is activated, with the release of adrenaline, blood is directed away from non-vital functions such as the skin and digestion, and redirected to the essential organs such as the brain to facilitate thought, the large muscle groups to facilitate speed, and the lungs to increase the amount of oxygen uptake into the bloodstream, whilst the heart beats faster to pump the blood round the body at an increased rate of speed, and raising the blood pressure. Once the stressful situation has passed the opposite occurs, resulting in what is known as the sympathetic rebound. The heart slows down and blood is re-directed away from the lungs, brain and muscles, flowing, once more, to every part of the body, whilst digestion resumes. It is, however, the sympathetic rebound, or more specifically, the effects of the sympathetic rebound that lead to the myriad of modern stress-related diseases. Stress, in fact, has been linked to many more common diseases, such as cancer and even the common cold. The reason for this is that during the fight or flight response the body's immune system that fights disease is also shut down, leaving the person more vulnerable to illness, and is, indeed, one of the commonest forms of stress-related problems. Unfortunately, however, modern life is packed full of stressful situations, and costs industry, thus the economy, millions of dollars each year in lost revenue. Traveling to work in morning, meeting tight deadlines whilst at work, studying to further one's qualifications, paying the mortgage or children's school fees are but a few. Thus, it transpires that stress is a modern day epidemic that urgently needs addressing. The word 'pertinent' in Line 3, Para. 1 can be replaced by ______ .