Ask Dr. Universe – Human Hearts

Dr. Universe: How do human hearts beat? -Jacob, 12, Forney, Texas
Dear Jacob,
You have a heart that beats every single day—even when you aren’t thinking about it. It likely beats about 6o to 100 times per minute. That adds up to more than a billion beats in a lifetime.
To find out how exactly how it all works, I talked to my friend Garry Smith, a researcher at Washington State University.
Smith told me the heart has its own electrical system which helps it beat. We can find the source of electrical signals in the upper right part of the heart called the sinus node.
Now, let’s imagine your fist is a heart. Squeeze your fist and let your muscles contract. Now stop squeezing and the hand will relax. The heart also contracts and relaxes in a similar way.
Before the heart contracts, the upper part of the heart fills with blood. The electrical signals from the sinus node make their way down into the top chambers of the heart. When this happens, the heart contracts, or beats.
This movement can also help squeeze the blood down into the bottom chambers of the heart. Next, the bottom part of the heart contracts, or beats. It brings blood down from the top of the heart and pumps it out to the rest of the body.
Smith said that when your heart contracts, that also means every individual cell, or building block, that makes up the heart also pulls in on itself and gets smaller.  
“All of those cells doing that together is what creates the whole contraction in the heart,” Smith said.
One way we can measure how well a heart beats is with a machine that can sense those electrical signals. These machines are called electrocardiograms, or EKGs.
The number of waves per minute that show up on the graph tells us a person’s heart rate. The distance between those waves is the rhythm. EKGs can also let us know if there might be some damage inside the heart.
You know, there is still a lot to learn about how human hearts work. Smith’s research is helping us improve human health and learn new things about the innerworkings of this important organ.  
By getting a better look at certain cells and molecules in the heart, Smith and the team at WSU are improving our understanding of how the human body works. Their research could one day help treat heart conditions that are passed down through generations.
Perhaps, you can do a little research into your own heartbeat. Place two fingers on the right side of your wrist down below the thumb. Count the number of beats you feel in 15 seconds. Now, multiply that number by four and calculate how many times your heart beats a minute.
As you go about your day, think about all the electrical signals that help make your heart beat. Yes, it’s true our hearts keep beating even when we aren’t thinking about it, but when you do stop to think about it, you sure can learn a lot.
Dr. Universe