Because February is Heart Month, I would like to do a two part story. Part 1: How our most important organ/muscle keeps us alive, and Part 2: What we need to do to keep it at optimum working level, less we succumb to heart disease.
Here are some interesting facts about the heart:
(1). This cardiovascular system organ, grapefruit-sized and cone-shaped, is located more centered in the body than most people realize. It is found under the breast bone and between your lungs and is protected by your ribs.
(2). Its main function is to act as a double-pump, in spite of being a single organ. (a)It pumps oxygen-rich blood throughout your body through arteries. Oxygen from your blood reacts with sugar in your cells to make energy; and (b)it pumps oxygen-poor blood through veins back to your lungs, where the waste product of this process, carbon dioxide, is exhaled. Blood only goes one way, either in or out through the four valves that separate the four chambers of the heart: the right and left atriums, and the right and left ventricles. The main artery leaving the left ventricle is the aorta, while the main artery leaving the right ventricle is the pulmonary artery. Blood coming from the lungs to the left atrium is carried through the pulmonary veins, while blood coming from the body to the right atrium is carried through the vena cava and inferior vena cava.
(3). You might have felt your own heart beating; this is known as the cardiac cycle. When your heart contracts, it makes the chambers smaller and pushes blood into the blood vessels. After your heart relaxes again, the chambers get bigger and are filled with blood coming back into the heart. The thump-thump of a heartbeat is the sound made by the four valves of the heart closing, which prevents blood from flowing backwards. Electricity going through your heart makes the muscle cells contract. The heart beats with enough power to shoot blood more than 30 feet away.
(4). The right atrium holds about 3.5 tablespoons of blood. The right ventricle holds slightly more than a quarter cup of blood. The left ventricle holds the same amount of blood as the right, but its walls are three times thicker, making it a much more powerful pump to send oxygenated blood throughout your body. In one day, your heart transports all your blood around your body about 1000 times.
(5). Your heart is an incredibly powerful organ. It works constantly, unlike skeletal muscles that need to be stimulated by nerve impulses. It is made of cardiac muscle that never gets tired. Though weighing only 14 ounces on average, a healthy heart pumps 2000 gallons of blood through 60,000 miles of blood vessels each day. (Your blood vessels are long enough to go around the world 2 times if they were stretched end to end.) A kitchen faucet would need to be turned on all the way for at least 45 years to equal the amount of blood pumped by the heart in an average lifetime. The volume of blood pumped by the heart can vary over a wide range from 5 to 30 liters per minute. The heart pumps oxygen-rich blood through the aorta at about 1 mile (1.6 km) per hour. By the time blood reaches the capillaries (small blood vessels), it is moving at around 43 inches (109 cm) per hour. The heart pumps blood to almost all of the body’s 75 trillion cells. Only the corneas receive no blood supply. When the body is at rest, it takes only six seconds for the blood to go from the heart to the lungs and back, only eight seconds for it to go to the brain and back, and only 16 seconds for it to reach the toes and travel all the way back to the heart. Five percent of blood supplies the heart (blood vessels located outside the heart), 15 to 20 percent goes to the brain and central nervous system, and 22 percent goes to the kidneys. In fact, the heart does the most physical work of any muscle during a lifetime. The power output of the heart ranges from 1-5 watts. While the quadriceps can produce 100 watts for a few minutes, an output of one watt for 80 years is equal to 2.5 gigajoules. Every day, the heart creates enough energy to drive a truck 20 miles. In a lifetime, that is equivalent to driving to the moon and back.
(6). Because the heart has its own electrical impulse, it can continue to beat even when separated from the body, as long as it has an adequate supply of oxygen. The heart begins beating at four weeks after conception and does not stop until death. Without some kind of unifying function, your heart would be an inefficient, uncoordinated pump. So your heart has a tiny group of cells, known as the sinoatrial node, that are responsible for coordinating the heartbeat rate across the heart. It starts each heartbeat and sets the heartbeat pace for the whole heart. However, without nervous system control, your heart would beat about 100 times a minute. When you are relaxed, your parasympathetic nervous system sets a resting heart beat of about 70 to 72 beats per minute: 100,000 times a day; 3,600,000 times a year; and 2.5 billion times during a lifetime. When you exercise or feel anxious or excited, your heart beats more quickly, increasing the flow of oxygenated blood to your muscles. This is triggered by your sympathetic nervous system. Your heart rate also increases in response to hormones, such as adrenalin. (On an average, your max heart rate is 220 beats per minute minus your age.) Plato and Aristotle thought that the heart was the origin of emotions. Such modern expressions as “He thinks with his heart” or “She’s a brave heart” continue observations made by scholars centuries past. Perhaps this is one reason why we associate Valentine’s Day with the human heart and its emotional changes.
We will see in Part 2, next Sun Day Edition (February 23), why former Sun City Stingray Swim Club coach, Jack Bolger, says, “So what you want to do is to keep the ticker ticking—that and the circulation.”
