To mark the occasion, I wore my red hot pants today. They’re a little… tight. So tight that as I held the belt loops and squirmed into them this morning, the belt loop broke right off the pants. Uh well- girl’s gotta do what a girl’s gotta do.
Little hearts littered my inbox and Facebook page this morning. Why is it that the heart is a symbol of love? It bears little resemblance to the organ, which is in function but a muscle, void of any emotional capacity or storage. Seeing as it’s Valentine’s Day, this is a great opportunity to explore where your heart gets its mojo.
The heart beats to it’s own drum, quite literally. Your heart has its very own power supply and time-keeper. That is to say it does not receive signals from the brain telling it to beat. This was surprising to me when I first learned of the heart’s independence, since other autonomic functions- like breathing and digestion- are all orchestrated by signals from the brain.
The heart has two electrical nodes- little groups of specialized cells that initiate and manage your heart’s contractions. The sinoatrial node, located towards the top of the heart, is the big daddy. It initiates the heart beat. If the SA node sparks 60 times a minute, then your heart beats 60 times a minute. Ah lah, your pulse!
The second node, called the atrioventricular node, is located a little farther down than the SA node, to which it is directly wired. The purpose of having this second node is to set up somewhat of a delay system- the AV node contracts the bottom half of the heart about a tenth of a second after the SA node activates. As a result, the cells of the top half of the heart (atria) contract slightly before the bottom half of the heart (ventricles.) This creates more of a wringing motion, rather than the entire heart contracting in on itself at once. That wouldn’t move blood very effectively. But the heart contracting top-down certainly does.
After all, when you listen to someone’s heart you don’t hear “boom… boom…. boom.” Instead, you hear “boom boom…. boom boom….. boom boom.” You’re hearing your atria contract, followed shortly by your ventricles.
So, if you have a honey, I dare you to make your move tonight by asking to “listen to his or her sinoatrial node activate approximately 0.1 seconds before the atrioventricular node.” It will be romantic and s-e-x-y.
What would you do without me to up your Valentine’s Day game?
Bonus question: Which node do artificial pacemakers mimic?