The "plumbing" A normal, healthy heart is a strong, muscular pump a little larger than your fist. It pumps blood continuously through the circulatory system. Each day the average heart beats 100,000 times and pumps about 2,000 gallons of blood. In a 70-year lifetime, an average human heart beats more than 2.5 billion times.   The circulatory system is the network of elastic tubes that carries blood throughout the body. It includes the heart, lungs, arteries, arterioles (small arteries), and capillaries (very tiny blood vessels). These blood vessels carry oxygen- and nutrient-rich blood to all parts of the body. The circulatory system also includes venules (small veins) and veins. These are the blood vessels that carry oxygen- and nutrient-depleted blood back to the heart and lungs. If all these vessels were laid end-to-end, they'd extend about 60,000 miles. That's enough to encircle the earth more than twice.   The circulating blood brings oxygen and nutrients to all the body's organs and tissues, including the heart itself. It also picks up waste products from the body's cells. These waste products are removed as they're filtered through the kidneys, liver and lungs.   The heart has four chambers through which blood is pumped. The upper two are the right and left atria. The lower two are the right and left ventricles. Four valves open and close to let blood flow in only one direction when the heart beats. Each valve has a set of flaps (also called leaflets or cusps). The mitral valve has two flaps. The others have three. Under normal conditions, the valves let blood flow in just one direction. Blood flow occurs only when there's a difference in pressure across the valves that causes them to open.   "The electrical"   Your heart's four chambers must beat in an organized manner. This is governed by an electrical impulse. A chamber of the heart contracts when an electrical impulse moves across it. Such a signal starts in a small bundle of highly specialized cells in the right atrium -- the sinoatrial node, also called the sinus node. (You've probably heard the term normal "sinus rhythm" on more than one television show where doctors use the paddles to shock a patient!) A discharge from this natural "pacemaker" causes the heart to beat. This pacemaker generates electrical impulses at a given rate, but emotional reactions and hormonal factors can affect its rate of discharge. This lets the heart rate respond to varying demands.

People who suffer heart attacks often experience symptoms before the onset of crushing pain in the chest. Awareness of these "warning signs" will help you seek help sooner, improving your chances of survival and limiting damage to your heart. • Mild discomfort or nagging ache in the center of your chest
• Recurring discomfort that feels like indigestion
• Chest pain upon exertion, subsiding with rest
• Shortness of breath
• Discomfort in the neck, jaw, arm or back
• Flu-like symptoms such as nausea, dizziness, weakness and sweating   Women often have different symptoms, including: • Stomach pain
• Unexplained anxiety
• Extreme fatigue
• Cold sweats
• Paleness   If you experience any of these "warning signs," call 9-1-1 immediately. Do not  drive yourself. Emergency crews are trained to access your condition on the spot and begin immediate life-saving treatment. Exercise your preference with your emergency crew. Tell them you want to come to St. Mary's of Michigan. For more information, click on any of the following links: www.americanheart.org
www.webmd.com
www.heartinfo.org
www.heartcenteronline.com