Feel the Rhythm – How the Human Heart Works

The human heart is the most important muscle in the body. From before you’re born until the end of your life, it works tirelessly to supply every organ in your body with oxygen-rich blood to keep them healthy and functioning normally.  As the core functioning muscle that keeps the rest of our body going, it seems like we should have a strong understanding of what the heart is and how it works; but at times it feels like we’re grossly undereducated and take this little muscle for granted. At the center of the most complex organism on Earth, there’s a lot of complicated science to the heart’s functionality, but let’s do a quick crash-course on the basics to better understand our own bodies!

At A Glance

Your heart is a muscle about the size of your fist, and sits just to the left of center behind your ribcage. It is protected by a double-walled sac called the pericardium, which contains pericardial fluid to lubricate the heart during contractions. The heart’s sole function is to pump blood throughout the body, carrying oxygen and nutrients to every extremity.

Bloody Good Work

Your body, at any given time, has approximately 1.2 to 1.5 gallons of blood, according to Mental Floss, which for the average person “equates to about eight to 10 percent of their body weight.” While we can (and should) donate about a pint of blood at a time, more than about 3 or 4 pints of blood loss is a “class 3 hemorrhage, and a blood transfusion is in order.” Since the heart is a pump, it requires a certain amount of pressure to suck and pull blood through the body, and losing too much volume (more than 4 pints) will cause the heart to lose function.

Heart Parts

While the heart’s function is basically “in with the bad, out with the good,” it is actually divided into four chambers, not just two. Cardiosmart.org describes it as “a duplex apartment that is made up of a right and a left unit, separated from each other by a partition wall known as a septum.” Each of those duplexes is divided into an upper “atrium” and lower “ventricle”. While the ventricle pushes blood out into the body, the atrium serves as a holding room, effectively increasing the heart’s ability to forcefully push and pull blood through the body. The four chambers work together to circulate oxygen through the body via red blood cells, in a complex but perfectly coordinated pattern:

1. The right atrium receives oxygen-poor blood from the body and pumps it to the right ventricle through the tricuspid valve.
2. The right ventricle pumps the oxygen-poor blood to the lungs through the pulmonary valve.
3. The left atrium receives oxygen-rich blood from the lungs and pumps it to the left ventricle through the mitral valve.
4. The left ventricle pumps the oxygen-rich blood through the aortic valve out to the rest of the body.

Shockingly Perfect

The heart’s contract-and-release system of pumping blood through the body is coordinated by electrical signals generated by the sinoatrial node (or SA node, or sinus node). This remarkable group of cells is located at the top of the right atrium, and generates an electrical current which travels through the heart to the atrioventricular node (or AV node). The AV node delays the electrical signal until the Right and Left Atria have finished their contraction before stimulating the Right and Left Ventricles to take their action. Getting complicated? Well you can thank your autonomic nervous system for handling all this work for you. That’s the part of the nervous system that regulates the body’s functions that you don’t have to consciously think about! 

All in all, the work the human heart does is incredibly complex and fascinating. This is why cardiologists spend years training specifically on this muscle and its surrounding systems, and why even today we are learning more about how the heart works and how to heal (or replace) it in cases of disease or damage. 

But fortunately, the heart is in some ways basic enough of a machine that we can manually assume its duties for a short time in case of emergency. In the case of Sudden Cardiac Arrest, the heart’s usual function can be supplemented by cardiopulmonary resuscitation, or CPR. While commonly thought to be a method to restart the heart, CPR is actually a method of manually moving oxygen and blood through the body until an automated external defibrillator (AED) can shock the heart into resuming its rhythm. CPR consists of repeatedly pushing on the heart, effectively forcing blood to pump through its normal course, and blowing into the lungs, replenishing the oxygen for red blood cells to absorb on their path through the circulatory system.

CPR is an effective way to save lives in several emergencies where the circulatory system’s behavior is suspended. In cases of drowning, electrical shock, high impact trauma, or other instances that may have affected the heart’s ability to circulate blood, CPR can provide a vital opportunity for survival while waiting for emergency services to arrive. That’s why Safety & Health Solutions provides high-quality CPR training to individuals and groups, as creating a nation of informed, educated, and certified citizens is the most vital step towards saving lives in these cases. Check out our schedule or give us a call to find the class that’s right for you, your family, your coworkers, or staff!