Even Arteries Need a Sabbath

How the heart sustains itself over the 2.5 billion beats of a lifetime. /

It is perhaps the most famous sound in all of human history: lubdub, lubdub.

The beating of a heart is the soundtrack of life: lulling every infant and narrating our most glorious and ordinary days alike. It races with our fear, slows in our rest, skips with our joy, and pounds with our passions. While that muted double thump has sustained every human that has ever lived, it is the pause in between—that forgotten, expectant silence between beats—that sustains the heart itself. In this silence, our hearts are renewed; without this silence, they stop.

A single heart will have 2.5 billion beats over a lifetime, each one sending a rush of blood to our brains and bodies and giving us a few more seconds of life. Our dependence upon the function of the heart is much more immediate than on that of any other tissue. If the liver or kidneys fail, we may have days. If the lungs give up, we may have minutes or hours. But the moment the heart stops, we are gone, and only dramatic action can reverse it. So instead of recharging during long, languid periods of sleep like other organs, the heart takes its only break in the quick half second between pulses.

The word diastole comes from the Greek word for separation or expansion. It is the return to baseline—the rest—of the heart in between each contraction (systole). The heart has two pairs of chambers: the smaller atria (lub) that receive blood from the venous system and push it into the larger chambers called the ventricles (dub), the workhorses that pump blood out to the body. With each beat of the heart, the muscular walls of the ventricles squeeze together, forcing blood through the unidirectional valves and into the large-caliber aorta and pulmonary ...

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Also in this Issue

Issue 23 / May 28, 2015
  1. Editors’ Note

    Issue 23: When the heart stops, poetry by Luci Shaw, the glory of an orchestra, and Harriet Tubman.

  2. The Precise Magic of the Symphony

    The modern orchestra produces order out of chaos, and something beautiful for the heart. /

  3. Black Moses

    The mystical faith and no-nonsense tactics of the Underground Railroad’s most famous leader. /

  4. What Secret Purple Wisdom

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  5. Wonder on the Web

    Issue 23: Links to amazing stuff

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