Tag Archive for: sino-atrial node

Your Heart: Autorhythmicity

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Your heart can beat over 200 times per minute during maximal exercise, 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 the 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 (SA node) or the pacemaker. Think of that as the command center: it takes information coming from your body and sets the pace of your heart rate.

What you might not know 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 we talked about in Saturday’s Memo on syncytium. It lends itself to this autorhythmic feature. Think of it as the ultimate fail-safe system—makes you sleep a little easier, doesn’t it?

One more cool feature I’ll talk about on Saturday.

What are you prepared to do today?

        Dr. Chet

Aging Stressor: The Cardiovascular System

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The next three Memos before Christmas will identify the three major stressors of aging as I see them and the general solution to them. The first stressor of aging is the changes to the cardiovascular system (CV). Cells wear out in all systems at all ages, but there are some that stop replacing and repairing themselves in the CV. A few examples:

  • The sino-atrial node is the pacemaker of the heart. As we get older, some of the specialized nerve cells of this area are not replaced. That can cause abnormal heart rhythms such as atrial fibrillation.
  • The arteries can become less pliable, called arteriosclerosis, which can cause an increase in blood pressure. (Atherosclerosis, the buildup of plaque in arteries, can be considered a special type of arteriosclerosis and can happen at any age depending on genetics and lifestyle.)
  • The heart muscle can get damaged and be replaced with scar tissue. That automatically weakens the heart, which pumps less blood (called the ejection fraction) and reduces fitness levels.

The solution? CV exercise, also called aerobic exercise: walking, riding an exercise bike, swimming or water aerobics, or pulling a sleigh (just checking to make sure you’re reading.) It doesn’t matter which mode you choose as long as you move your body for 30 to 45 minutes per day most days of the week. You can’t reverse every effect of aging on the CV and other systems, but nothing impacts every system of the body like exercise does. Aging with a vengeance requires aerobic exercise within the limitations you currently have, and the younger you start, the more successful you’ll be.

What are you prepared to do today?

        Dr. Chet