February 11, 2007

Why your heart is like a toilet…

Posted in Randumb at 1:38 am by Iram

Everybody’s heart functions in the exact same way – an electrical impulse induces a rapid depolarization that travels down the heart and stimulates a muscular contraction that pumps your blood to the rest of your body. The electrical impulses used to stimulate your heart, and for that matter to stimulate every other muscle in your body, are called action potentials. You can find this information in any biology or physiology textbook. So why am I telling you about it? Because the one thing you cannot find in any textbook is the explanation for how these action potentials are exactly like your toilet:

1. Both toilets and action potentials have thresholds. If you don’t give them enough of a push, they will not flush (errrr….propagate).

2. The flush is all or none. You either flush or you don’t. Do I have to get any more specific?

3. Both your toilet and your action potentials have absolute and relative refractory periods. What happens when you try to flush twice in succession without waiting in between for the tank to fill? The darn thing doesn’t work! And that is the exact same mechanism that your heart uses to keep its heart rate steady.

*Inspired by Dr. Nathan and the upcoming cardiovascular physiology exam. Wish me luck!

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