Beating Hearts & Flexing Muscles (“You and Your Body” Series, Part 1)

Hey all, it’s been a long (and busy!!!!!!) time, good to be back.

In this post, I’m going to share with you some information that will hopefully begin to transform how you think about your body, and secondary to that how you think of yourself.

The world we inhabit is an extraordinary place.  We, as human beings, are arguably the most extraordinary of its features.  Recently, I was engaged in some intensive review of the human biology as I do from time to time because I’m a healthcare professional.  Let me just say that there are no words in existence to describe how phenomenal the human body is.  As a healthcare professional, I see the body as a machine.  It is a truly wondrous machine–in fact, the single most sophisticated machine that has ever graced this universe.

For those who claim there is no proof of the existence of God, the great irony is that they need not look any farther than the nearest mirror.

I’ll give two examples of why I believe this.  Let’s start with our muscles.

Look at your palm for a moment.  Now move your thumb around, back and forth.  Back and forth.  Back and forth.  It is so easy, isn’t it?  You barely have to think about it, you just do it and your thumb moves.  Effortless.  Look at the base of your thumb, where it meets your palm.  The muscle that flexes to move your thumb back and forth with such effortless grace and convenience is actually composed of billions of microscopic cells called myocytes.  Within each of these cells lies an apparatus made of proteins that visually resembles and physically behaves like a hydraulic press.  Instead of being powered by fuel of some sort, however, you might think of it as being a bio-organic electrohydraulic press.  Each of the billions of myocytes contains this protein electrohydraulic system, and each and every time you flex that thumb like we just practiced above, those BILLIONS of cells, with their BILLIONS of microhydraulic systems are SIMULTANEOUSLY flexing with PERFECT SYNCHRONIZATION.

I hope you can join me in my awe at this.  Remember how effortless it is for you to make that motion.  That motion required the perfect coordination of BILLIONS of hydraulics.  And every single time you want it to happen, your body makes certain it does.  What other machine in existence can possibly be said to share this degree of sophistication?  It is not simply sophisicated… is PERFECT.

The second example is the human heart.

The human heart beats roughly 60–100 times per minute, on average, although this varies in some individuals and depends on degrees of relaxation or stress.  Put your hand to your heart for a second and feel that beat.  Beat.  Beat.  Beat.  Beat.  It is such a spontaneous phenomenon; you feel the beat as it announces its presence by pressing against your fingertips, and by the time you acknowledge its arrival it is already gone and replaced by the next beat.  Let’s take a closer look at what a heart beat really is for a moment.

Every time our heart beats, it completes what is called a cardiac cycle.  In the tiny and brief interval of time when our fingers detect that pulse blip, a 5-stage cardiac cycle has completed a revolution.  5-stages.  What can happen that quickly, that we can fit 5 different stages into each and every beat of our heart?  Let’s take a closer look at the heart to find out.

Your heart houses four chambers, 2 atria and 2 ventricles.  There is a right and left side to your heart, and each side has its own atrium and ventricle.  The wall that partitions the left and right sides off from one another is referred to as the septum.  Let’s talk about that heartbeat now, and for the sake of simplicity, consider just the right half of the heart for just a second.

The right half of the heart contains two chambers, with atrium on top and below it is the larger ventricle.  Blood enters the heart through valves leading into the atrium.  When those valves open, blood flows in and the atrium fills up with and stores this blood.  Then the heart beats.

A heartbeat is initiated by a very unique node of cells at the top of the septum, referred to as the sinoatrial, or SA, node.  This node is like a natural pacemaker for your body.  It spontaneously generates electrical impulses, and the rate at which it does this becomes the rate of your heart beats (your heart rate).  Anyhow, the SA node fires, initiating your heart beat.  The electrical impulse that it fires then travels a very specific path.  It travels down along the atrial septum.  As it does so, its electrical activity causes what is called “depolarization” of the muscle tissue, leading to muscle contraction.  So, the atrial muscle contracts as the pulse moves further down along that muscle.  Just as the electrical pulse begins at the top of the septum and travels towards the bottom, so too does the contraction of the muscle begin up high and and squeeze on down.  It’s a good thing it does it this way because doing so ensures that the entire volume of blood will be ejected into the ventricle.  If the full volume is not ejected into the next chamber, then that chamber will deliver a deficient volume of blood into the rest of the body.  Blood carries oxygen, critical for so many things.  If cells are deprived of oxygen for even an extremely short time, damage begins to occur.  This damage is called ischemia.  We don’t like ischemia. Deprivation of oxygen can occur when bloodflow is compromised, which in turn occurs under circumstances of inadequate ventricular filling.  We’re getting ahead of ourselves here.

So the electrical impulse continues traveling down until it hits the halfway point, now between the atrium (top) and ventricle (lower).  Somehow, your body is designed to appreciate this need for full filling.  To ensure that the atrium fully transfers its blood load into the ventricle it is connected to, your heart actually seizes that pulse and HALTS it for 0.1 seconds.  Just long enough to make sure safe ventricular filling takes place.

WTF?  I read this in my textbook and just stopped for a second, awe-stricken.  The efficiency of this system, to the minutia of stopping that contraction-generating electrical pulse so briefly yet importantly, is really breath taking.

This takes place at the atrioventricular (AV) node.  And then, just like that, the pulse continues moving downward, depolarizing ventricular muscle cells so that they squeeze in the blood out through the exit valves of the ventricle.  Note that the muscle surrounding the atrium is smaller than that of the ventricle.  This is because the atrium need not squeeze so hard–it only has to push the blood into the ventricle, the chamber downstairs.  The ventricle needs to have a larger muscle, however, because it pushes that blood out of the heart and through our arteries then eventually through the veins and back into the heart.  In order for that blood to return to the heart, it needs a powerful push, and so it needs a large (but not too large!) ventricular muscle.

So the blood that leaves the right half of the heart goes makes two stops before returning to the heart: the lungs and the brain.  It hits the lungs first because it needs to pick up a few fresh cases of oxygen, right?  After all, when it goes on its tour of the human body, every organ is looking for oxygen handouts.  It comes back empty handed, and this is when it recharges.  But the walls of arteries it flows through are too thick and it can’t reach the blood.  It’s okay because once it hits your lungs, it enters a network of extremely delicate tubes called capillaries, with walls so thin the blood can just snatch tons of oxygen as it passes through without stopping.  So the blood is rich again in oxygen, and it stops at the most important customer–the brain.  The brain takes its share, and then the blood takes an express route back to the heart, but this time into the left side’s atrium.  SA node fires again (2nd heartbeat now) and blood ejected into the ventricle, fills it up, then it is ejected through ventricular exit valves.  It tours the body, comes back, and repeats this entire process.

In the tiny span of time your it takes your heart to beat, all of this happens.  Imagine, every single time your heart beats, a cascade of PERFECTLY SYNCHRONIZED steps is carried out.  Now think of how many times this happens per day?

60-100 beats/min = Average of 80 beats/min = 4800 beats/hour = 115,200 beats/day

Take a moment and absorb that.  That entire cascade of perfectly synchronized yet highly complex interrelated processes happens 115,200 times per day, without screwing up.  Your heart pumps roughly 42.048 MILLION times per year, without screwing up.  My heart has pumped roughly 1.135 BILLION times, and it has never screwed up.  Not even once.

What other machine can do this?  Even if you do not believe in God in the religious sense, I think we can agree that whoever engineered our bodies has engineering capabilities so far beyond our own that they DESERVE to be called God.

Wait till you hear about the brain next time.

The point I want to make with this series is to help you realize how amazing your body is.  It is unlike anything else in this world; nothing else can even approach its complexity.

And it is all yours.

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