Welcome to Straight Talk on Health. I’m your host Dr. Chet Zelasko. Straight Talk on Health is a joint production with WGVU in Grand Rapids MI. I examine the practical application of health information. Nutrition. Exercise. Diet. Supplementation. I look at the science behind them, and let you know whether it’s something to consider or not. You can check out other things that I do on my website Drchet.com and sign up for my free emails.
I miss teaching exercise physiology. There are many reasons but one of them is having the privilege of showing someone the cool way the body works—and then getting to show them how exercise can modify those things for the better. In this podcast, I’m going to explain a few qualities your heart has that no other organs in the body have. Why focus on that?
I have no P-wave. There. I said it. Don’t worry. I haven’t lost my mind quite yet. It means I’m in constant atrial fibrillation. I thought it best I explain a few things about the heart as there is a reason I don’t appear to be all that concerned about it. That leads me to what I really miss at times: teaching to an audience there to learn about the mysteries of how our bodies works.
The heart muscle is similar to skeletal muscle in the way it contracts, but that’s where the similarity ends. While skeletal muscles are laid out in parallel fashion and independent of one another, the heart muscle splits and connects to other fibers. In that way, every heart muscle cell connects to every other heart muscle cell. That allows signals to be transferred very quickly. It’s referred to as a syncytium in that the heart can act as a single unit.
But the heart must contract in specific locations at the correct time in order for blood to be pumped. The heart has to contract at the upper chambers first, the atria, and then the bottom of the lower chambers called the ventricles. That allows the blood to be pumped from the upper chambers to the lower, then from the lower chambers through arteries to the body. Pretty cool, isn’t it? What’s really amazing is that it all happens so fast. Think about it. If the heart beats more than once per second, all of those events have to happen very quickly. That depends not only on the syncytial arrangement of the heart muscle but also the electrical system of the heart.
Your heart can beat over 200 times per minute during maximal exercise—give or take, depending on your age. Yet every beat is a succinct event made up of many steps with every one of those beats controlled by the electrical system of your heart. While that’s incredible in and of itself, the real story is one of the most amazing features of your heart called autorhythmicity.
Your heart has a special area in one chamber that stimulates it to beat; it’s called the sino-atrial node or the pacemaker. Think of that as the command center. It takes information and sets the pace for your heart. On an EKG, the first line that indicates the heart is preparing to beat is the P-wave. As I suggested, I don’t have one and neither do thousands of others. If there is nothing to start the beating process, how does the heartbeat? There are a couple of electrical back-ups but when all is said and done, the fail-safe mechanism is the heart muscle cells themselves.
What you may not have known is that some cells of the heart can stimulate themselves to beat. If something goes wrong with the electrical system for some reason, your heart can go right on beating because of the muscle make-up I just talked about and this autorhythmic feature. Think of it as the ultimate fail-safe system. Makes you sleep a little easier, doesn’t it?
One of the coolest things I ever saw was a little film on autorhythmicity. Researchers took a single cardiac cell from a mouse heart and put it in a petri dish with the right blend of nutrients. The heart cell continued to beat. Then, they placed another heart cell close to it—not touching—but close. They beat independent of each other, each at their own pace. But within a few minutes, they were beating in unison. In other words, one set the pace and the other matched it. How cool is that?
The logical question is this: is that what is happening with my heart? More than likely—yes—but there is no way to tell for sure. It can get freaky when your resting heart rate can be as low as 40 beats per minute but while the internal electrical system may be off normal, the nerves controlling HR are still there and may be impacting the process so let’s look at the nerves that control HR.
We think it just happens but in reality, it’s a very complicated process. Let’s take a look. If you live to 80 years, your heart will beat an average of three billion times. That’s right: billion with a b. Faster when you exercise, slower when you’re at rest, it does its job 24 hours a day, seven days a week. What’s even more amazing is how your heart rate is controlled by the nervous system. I’ve always found it fascinating and here’s why.
The pacemaker of the heart we just talked about gets signals from nerves that tell it to slow down and nerves that tell it to speed up. The Vagus nerve is inhibitory, to slow it down, while the Accelerator nerve is stimulatory to speed it up, but they’re both sending signals at the same time. The point where they balance is called tone and sets your resting heart rate. Now, here is the really cool thing.
Start to exercise and more stimulatory impulses speed up your heart rate. Stop exercising and more inhibitory are sent until you reach your resting heart rate again. Exercise regularly and you reset the balance at a lower HR by increasing the inhibitory and decreasing the stimulatory. You don’t even have to think about it.
There are other mechanisms that control heart rate such as the fight-or-flight hormones but most of the time, the tone you set by your lifestyle is the heart rate you’re going to have. Want to do something special for your heart? Exercise.
That’s why I never take more than one day off from doing aerobic exercise. Over the years of running and now walking and using other forms of exercise, I’ve built up collateral circulation. Small blood vessels have sprung from my coronary arteries to pick up the slack to make sure my heart gets enough blood and oxygen. I can’t be certain of the status of that collateral circulation but I want to make sure I do all I can to challenge my heart with exercise to keep the blood flowing. I think that has helped keep me around.
On the other hand, the lack of a P-wave could also be limiting how high my heart rate can go, sort of like a governor. But as I continue to increase my fitness level and my weight continues to drop, I may be able to push things a little harder. We’ll see. One more thing? Maybe at some point, I’ll need a pacemaker to keep a higher basic rhythm. I’ll travel that road when I get there because I’ve got a lot of teaching left in me.
I hope you know more about your heart, and my heart as well, than you did before. The most important thing is to take care of it as best you can. If your heart stops beating, well, you can see the problem with that. Take care of it and it will take care of you! If you want to learn more details about the heart and how it works, do a search for the words lumen learning, SUNY, anatomy and physiology, module 3. Let me repeat that.
That’s all the time I have for this episode. If you like this podcast, please hit the share button and tell your friends and colleagues about it. Until next time, this is Dr. Chet Zelasko saying health is a choice. Choose wisely today and every day.
