{"id":2575,"date":"2010-09-16T12:00:40","date_gmt":"2010-09-16T19:00:40","guid":{"rendered":"http:\/\/www.todayifoundout.com\/?p=2575"},"modified":"2012-11-27T21:31:50","modified_gmt":"2012-11-28T05:31:50","slug":"how-the-heart-works","status":"publish","type":"post","link":"http:\/\/www.todayifoundout.com\/index.php\/2010\/09\/how-the-heart-works\/","title":{"rendered":"How the Heart Works"},"content":{"rendered":"
Note: This is a guest article contributed by a paramedic and fire fighter, Scott.<\/div>\n

\"\"<\/a>Today I found out<\/a> how the heart works.<\/p>\n

I know what you’re thinking; I hope by the end of this article I can find out if it really is true that I can MacGyver<\/em> an electrical cord together and shock my heart into restarting should it stop!\u00a0 Quick answer\u2026.. maybe, if you\u2019re an electrical engineer with all the appropriate gear, or go buy an automatic external defibrillator\u00a0 (they\u2019re really not that expensive).\u00a0 Before you budding electricians all rush on out to RadioShack for all the equipment, let\u2019s find out how this beast of an organ works.<\/p>\n

The heart is a two part pump, one part mechanical and one part electrical.\u00a0 The mechanical function of the heart is governed by the electrical system within the heart.\u00a0 That electrical system, in turn, can be affected by neurotransmitters from the brain (or fancy pacemakers created by the Dr. Frankenstein-like minds of the world).\u00a0 But since we\u2019re only talking about the heart today, we will only focus on the ability of the electrical system of the heart.\u00a0 Should you want to know how the brain governs it, I direct you to the many medical schools around the country!<\/p>\n

THE MECHNICAL<\/strong><\/p>\n

\"Heart<\/a>The heart is a four chambered pump.\u00a0 The top two chambers are called Atria<\/em>, the bottom two are called Ventricles<\/em>.\u00a0 They are separated from top to bottom by valves; the right and left sides are separated by a septum.\u00a0 So what makes the pump squeeze?\u00a0 Well the heart is a muscle, and like all muscles, when it gets shocked by electricity, it contracts.\u00a0 If you don\u2019t believe me, just stick a fork in the nearest electrical socket and see if anything tenses up! (DISCLAIMER: Due to our lawyers incessant need to justify themselves, they advised us to say, \u201cDon\u2019t do that. It could cause you harm\u201d). When the hearts muscle gets \u201cshocked\u201d, they contract and force the blood down its path.\u00a0 The valves I just spoke of are one way, and will not allow blood to flow back through the system.\u00a0 If it does, see your nearest physician cause death could be imminent!<\/p>\n

The blood’s path through the heart starts in a vein called the Superior Vena Cava.\u00a0 Then it enters the right atrium, flows through the tricuspid valve into the right ventricle.\u00a0 From there it travels through the pulmonic valve into pulmonary arteries, then the lungs.\u00a0 Take a deep breath. Awe\u2026\u2026 the sweet feeling of oxygen entering the blood! Now let it out, OOUU\u2026.. the halitosis laden Co2 leaving the body!\u00a0 Now back to the heart and into the left atrium, through the mitral valve and Walla!\u00a0 The blood is now in the \u201cstrongest\u201d chamber of the heart, the left ventricle.\u00a0 From there it gets pumped through the aortic valve and into the aorta and out to the rest of the body!<\/p>\n

THE ELECTRICAL<\/strong><\/p>\n

So what causes that infamous electric shock the heart receives, approximately 60-100 times a minute?\u00a0 Short answer: chemistry.\u00a0 Long answer: The exchange of electrolytes across specialized cells within the heart build up a differing electrical potential on either side of the cell.\u00a0 When this electrical potential reaches a certain amount, it discharges and sends a shock down another unique set of cells within the heart, causing a shock and thus the contraction.<\/p>\n

The specific set of cells that regulates the heart rate (in most people) are called the Sinoatrial node or SA node for short.\u00a0 The SA node (pacemaker of the heart) sits in the upper portion of the R atria near the entrance of the superior vena cava.<\/p>\n

When the SA node sends out and electrical shock, it immediately shocks the atria.\u00a0 The pulse then gets \u201cheld up\u201d in another set of cells called the Atrioventricular node, or AV node for short.\u00a0 This then transmits the impulse down to the bundle of His (no, not the bundle of hers, sorry ladies) and then to two pathways called the right and left bundle branches.\u00a0 Then it\u2019s transmitted to the rest of the Ventricles through what are called Purkinje fibers.\u00a0 All together this \u201cshock\u201d causes the atria to contract, then the ventricles.\u00a0 The wonder of a pulse!!<\/p>\n

So what and how do these electrolytes cause this shock?\u00a0 In an attempt not to give a physiology lecture of ungodly like proportion, I will simply say; the main two electrolytes involved are sodium and potassium.\u00a0 Potassium normally sits inside the cell, and sodium outside.\u00a0 Potassium slowly leaks outside of the cell and sodium then goes inside the cell.\u00a0 This creates the differing electrical potential that builds up until the point of discharge.\u00a0 Other electrolytes also help in creating this differential, and they are calcium and magnesium.\u00a0 For how exactly all these electrolytes actually cross the cells membrane I will only say that it would take way too long to explain in this article, so trust me, they do.\u00a0 All together the harmony created by this yin and yang system of electrical and mechanical systems come together to make that wonderfully thumping thing inside your chest!<\/p>\n

Shocking<\/strong><\/p>\n

\"\"<\/a>So let\u2019s talk about this infamous \u201cshocking\u201d business. When the SA node becomes damaged, or simply isn\u2019t working properly, other parts of the heart start to take over to create the heart beat.\u00a0 There are millions of foci in the heart that can make this beat happen.\u00a0 The reason why they normally don\u2019t is that the SA node \u201coverrides\u201d them and they accept the impulse from it, instead of trying to create one on their own.<\/p>\n

When these foci start to beat on their own, they can create an electrical impulse that simply doesn\u2019t create the mechanical squeeze necessary for blood flow, thus no pulse.\u00a0 When this happens if you \u201cshock\u201d, known as defibrillation, all of these foci, you get them all to depolarize at the same time.\u00a0 Then the hope is that the SA node, or some other foci, will take over and create a pulse producing rhythm on its own.<\/p>\n

So should there be no electrical impulse at all, like say when someone is \u201cflat-lined\u201d, called asystole, then shocking is pointless, since you would need an electrical impulse to create a beat.\u00a0 So when you see those heroes on the television shocking someone with a flat-line, be assured that their license to practice medicine will be reviewed after the taping of their show.\u00a0 Unless of course, they just say it looked like a fine V-fib!\u00a0 (don\u2019t ask, electrical physiologists go to school for a long time, and this article shouldn\u2019t go that in depth)<\/p>\n

Bonus<\/span> Facts:<\/p>\n