Forget the songs and the car stickers that equate the heart with love. The organ that beats in every breast has nothing to do with emotions, though it often reacts to them. The heart is phenomenal workhorse, a pump that beats continuously and regularly, about seventy times a minute, every hour of the day and night, for perhaps as long as a century. It is the hardest working muscle in your body, and generates enough power in a day to drive a truck 32 km (20 miles).
Every week it contracts about 700,000 times, in a average life span more than 2500 million times. It drives hard – and it needs to. It operates a delivery service that never stops, sending life-sustaining blood charged with oxygen and nutrients through hundreds of kilometers of the body’s vessels and bringing it back to dispose of wastes. What other machine gives such reliable service with so little care and attention?
For all its power, the hart is quite small – a muscle not much bigger than a closed fist. And for all its importance, most of us know little about it. We ten, for example, to think of it is a single organ, when in fact it is really two pumps, each with tow chambers.
Ask somebody to place a hand on the heart, and almost certainly he or she will indicate the left side of the body. The heart is almost in the center of the chest, with a little more of it to the left than to the right. One reason why we believe it to be on the left is because that is where we feel its beat more clearly. Another mistaken idea, encouraged by car stickers and St. Valentine cards, is about the heart’s shape. More accurately the symbol for the heart should be a pear.
Mistaken ideas about the heart and its functions have a long history. Until the seventeenth century, doctors believed that the liver produced blood, and the heart delivered it once only to various reservoirs in the body. In 1553, Michael Servetus was burned as a heretic for declaring – quite correctly – that blood moves from the right side of the heart to the left via the lungs. His fate undoubtedly deterred other physicians from speaking out, and perpetuated fallacies about the heart’s role. This is not the case today as Guide to Healthcare Schools actually lists numerous heart-related medical degrees as some of the most popular career choices.
The heart works like most pumps, with valves to make sure that the blood flows through it in only one direction. But unlike many water pumps, which work continuously, the heart pumps and then relaxes. Its sequence is controlled by electrical impulses from the heart’s in-built pacmaker, the sinuatrial node, which is situated at the top of the right atrium, one of its chambers.
In three precise phases the heart draws in blood and pumps it out. These three phases are called diastole, atrial systole and ventricular systole, and in a healthy heart are finely tuned. At each stroke, the volume of blood pumped by the two sides of the heart must perfectly matched, even though the force required to drive it through the lungs to be oxygenated is less than that to circulate it to the rest of the body.
The heart is cunningly designed to cope with this delivery problem and avoid a build-up of blood in one place and a shortage in another. The heart’s left side contracts with greater force than the right. That is why the heart is shaped as it is, with more muscular bulk on its left side.
No matter whether you heart beats at 200 times a minute, as it may do if you exercise strenuously, or at a mere third of that when you rest, it must cope with wide variations in its output. When you exercises, you muscles demand more oxygen. To deliver it, the heart pumps more blood, as much as 50 liters (11 UKgal; 13 USgal) a minute, compared with about 6 liters (1.3 UKgal; 1.6 USgal) when it is at rest.
These changes in pace and output are achieved in two ways. Because it pushes out more blood, the heart also receives more. An increase in its intake produces automatic increase in output. In addition, a nucleus of nerve cells located in the brain stem watches over the heart from what is know as the cardiac center. These nerve cells are part of the body’s automatic nervous system, which monitors a number of essential functions without your having to worry about them. If you are at rest, the heart rate automatically slows. If you exercise, a release of two hormones adrenaline and noradrenaline, increases the heart rate and the force of its contraction.
A key measure of a heart’s efficiency is its cardiac output, the amount of blood it pumps in a given time. this depends on how fast the heart beats and the volume of blood ejected with each contraction. On average, cardiac output is about 4.5 litres (1 UKgal; 1.2 USgal) a minute – a staggering 8 tonnes a day.
The heart is a tough muscle of special kind, unlike any other in the body and perfect in design. Despite our command of technology, we have not yet made an artificial heart that compares in performance with the natural organ.
For all its efficiency and resilience the heart is susceptible to disease. So, of course, is the rest of the body. The essential difference is that the heart plays such a vital role. If it stops beating for as little as four minutes, its owner may die or suffer irreversible brain damage.
That is why heart disease is such a killer. Today, it is the number one cause of death, accounting for about one-third of all fatalities in adults, with a rising toll in both the developed and developing countries. Many of these deaths are premature , adults age forty to sixty,with men of this group four times more likely to die than women.
Because so much premature heart disease is directly related to our lifestyle and is preventable, a worldwide campaign aims to the people how to safeguard their hearts. The education programs shows pleasing results. The United States, for example, has cut deaths from coronary heart disease by a third.
If you have a healthy heart and want to keep it, here are some everyday rules that will help you:
Do not smoke. The more you smoke, the greater the risk no only to your heart and cardiovascular system but to your lungs and brain. Even if you have smoked heavily for thirty years, it’s not too late to benefit stopping.
Watch your diet. Ask your doctor to check your cholestertol level. If it’s hgih cut down on fatty meats, eggs and rich dairy foods. Go for low fat and high fibre. It will reduce your weight – easing th strain in your heart – and improve your appearance.
Exercise sensibly. Leave the car at home and walk whenever you can – to the shops, up and down stairs. Forget all those heavy lunches. Have a light healthy snack and take a walk.
Relax. Stress and tension, anxiety and conflict may all contribute to higher blood pressure. Vary your week with some truly relaxing leisure. Play games for enjoyment, not to satisfy a driving desire to win. If you are seriously troubled, take some relaxation therapy.