Edit: The first version of this post had the winner being (a), due to an incredible failing of my proofreading skills :) Aargh!
That's a nice question.
Though there are complications, it is roughly correct to state that the muscle in both ventricles is equally stimulated by the heart's conduction system. In both the right and left ventricle's cases, they contract in response - yet the pressure they generate is different. Why?
I think the best way of looking at it is as follows. Let's say I have a puny right biceps muscle (hypothetically speaking, of course) compared with an Olympic shot put athlete's right biceps. What could I do to best challenge his dominance with the shot put?
Option (a): Electrically stimulate my muscle to an increased degree.
Option (b): Get a bigger muscle (i.e. work out).
And the winner is... (b).
You see, the electrical stimulation that the heart's conduction system sets up obviously doesn't do the work of lifting heavy objects, etc. All it does is tell the muscle to contract - it has more or less the same effect as shouting at me to lift something harder would. At the end of the day, the only thing that is capable of doing the work (or failing to do it!) is my muscle. And if my muscle isn't big enough, it just won't be able to do it, no matter how strong the stimulation is.
The right ventricle is a bit like my (hypothetical) right biceps, and the left ventricle is closer to the Olympic athlete's one. There's simply more muscle that can contract in the left ventricle than there is in the right ventricle. And so the pressure that the left ventricle is capable of generating is correspondingly much higher.
And why does it have to be so much higher on the left side? Well, to get blood moving, each ventricle only has to be strong enough to generate more pressure than there is in the artery leading from that ventricle. In the right ventricle's case, it has only to pump against the low pressure pulmonary trunk (i.e. main pulmonary artery), and so it can get away with pressures as low as, say, 10 mm of mercury. The poor left ventricle, on the other hand, has to pump against the aortic (diastolic) pressure, and so needs at least about 80 mm Hg to do the trick.
Hope that made sense...!
Though there are complications, it is roughly correct to state that the muscle in both ventricles is equally stimulated by the heart's conduction system. In both the right and left ventricle's cases, they contract in response - yet the pressure they generate is different. Why?
I think the best way of looking at it is as follows. Let's say I have a puny right biceps muscle (hypothetically speaking, of course) compared with an Olympic shot put athlete's right biceps. What could I do to best challenge his dominance with the shot put?
Option (a): Electrically stimulate my muscle to an increased degree.
Option (b): Get a bigger muscle (i.e. work out).
And the winner is... (b).
You see, the electrical stimulation that the heart's conduction system sets up obviously doesn't do the work of lifting heavy objects, etc. All it does is tell the muscle to contract - it has more or less the same effect as shouting at me to lift something harder would. At the end of the day, the only thing that is capable of doing the work (or failing to do it!) is my muscle. And if my muscle isn't big enough, it just won't be able to do it, no matter how strong the stimulation is.
The right ventricle is a bit like my (hypothetical) right biceps, and the left ventricle is closer to the Olympic athlete's one. There's simply more muscle that can contract in the left ventricle than there is in the right ventricle. And so the pressure that the left ventricle is capable of generating is correspondingly much higher.
And why does it have to be so much higher on the left side? Well, to get blood moving, each ventricle only has to be strong enough to generate more pressure than there is in the artery leading from that ventricle. In the right ventricle's case, it has only to pump against the low pressure pulmonary trunk (i.e. main pulmonary artery), and so it can get away with pressures as low as, say, 10 mm of mercury. The poor left ventricle, on the other hand, has to pump against the aortic (diastolic) pressure, and so needs at least about 80 mm Hg to do the trick.
Hope that made sense...!
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