I'M CERTAINLY no beauty. I weigh 12 ounces, am red-brown in color and have an unimpressive shape. I am your dedicated slave. I am, your heart.
I hang by ligaments in the center of your chest. I am about six inches long and at my widest point, four inches across more pear-shaped than valentine. Whatever you may have heard about me from poets, I am really not a very romantic character. I am just a hardworking four chambered pump - actually two pumps, one to move blood to the lungs, the other to push it out into the body. Every day, I would say, I pump blood through 60,000 miles of blood vessels. That's enough pumping to fill a 4OOO-gaIlon tank.
When you think of me at all, you think of me as fragile and delicate. Delicate! When so far in your life I have pumped more than 300,000 tons of blood? I work twice as hard as the leg muscles of a dash runner, or the arm muscles of a heavyweight boxing champ. Let them try to go at my pace and they would turn to jelly in minutes. No muscles in the body are as strong as I am - except those of a woman's uterus as she expels a baby. But uterine muscles don't keep at it day and night for 70 plus years as I am expected to do.
That, of course, is a slight exaggeration. I do rest - between beats. It takes about three tenths of a second for my big left ventricle to contract and push blood out into the body. Then I have a rest period of half a second. Also, while you sleep, a large percentage of your capillaries are inactive; this means that I don't have to push blood through them, and my beat slows from a normal 72 down to 55.
You almost never think of me - which is good. I don't want you to become one of those heart neurotics and worry us both into real trouble. When you do worry about me it is almost always about the wrong things. It might have been one night, as you where drifting off to sleep, that you where listening to my quiet thumping - that's the opening and closing of my valves - and thought you heard me "skip" a beat, that could be quite Worrying, but you need not of worried I wasn't about to let you down.
From time to time, my ignition system gets momentarily out of whack - just like the ignition system on your car. I generate my own electricity, and send out impulses to trigger contraction. But occasionally I will misfire; piling one beat on top of another. It sounds as if I have "skipped" - but I haven't. You would be surprised how often this happens when you are not listening.
After a nightmare you sometimes wake up and worry because I am racing. That's because when you run for your life in your dreams, I run too. Your worries actually aggravate things - making me go still faster. If you would calm down, so would I. But if you can't, there is a way to slow me down. The vagus nerves act as a brake. They pass up through the neck - behind the ears, at the hinge of the jaw. Gentle massage here will slow my beat.
You blame almost everything on me - fatigue, dizzy spells and such. But I have little to do with your fatigue, and those occasional dizzy spells usually trace to your ears. From time to time you will be doing deskwork, and will get a sharp pain in the chest. You may fear that you are about to have a heart attack. Don't worry. That pain comes from your digestive tract - payback for the heavy meal eaten a couple of hours earlier. When I am in trouble, I usually send out a pain signal only after undue exertion or emotion. That's the way I tell you I am not getting enough nourishment to carry out the work you are loading on me.
How do I get my nourishment? From the blood of course, although I represent only 1/200 of the body weight, I require about 1/20 of the blood supply. That means I consume about ten times the nourishment required by your body's other organs and tissues.
My Heartbeat patterns number close to 40 and vary with age and the state of health of the various vital organs. The life supporting blood I pump reaches every part of every cell in your body and in so doing I gather valuable information about your state of fitness, health and emotions which are passed on to the Brain for storage and compiling a most comprehensive well-being evaluation of your entire self.