I keep reading, as a science student, that when blood flow or pressure goes down, arterioles constrict in order to raise blood pressure. But vasoconstriction actually increases resistance, thereby depriving the tissue further of blood flow.
So what is it that I’m not understanding?
In: Biology
Okay, so let’s think about this like we would a pipe. Normally, the pump is able to feed enough water into the pipe for the pressure and output on the other end to be reasonable for the pipe size. But let’s say there’s suddenly not a lot of water coming into the pump, and it’s going to be decades before the original flow rate is returned. Now all of a sudden, the pipe acts like a big resevoir rather than a pipe, and it screws with the output’s pressure, making it vary wildly. That’s gonna result in a lot of pissed citizens. So what’s the sane thing to do? Quickly switch out for smaller pipes. Now water flows roughly as it did before, with roughly the same pressure, just with a lower output. Yes, people are still going to be a bit pissed, but there’s not really anything you can do about the output volume. Because of the way water works, the output rate of a pipe system is the same as the input rate (unless something fucks up like the above). You just have to wait for the old input rate to come back.
Now let’s compare to the cardiovascular system. You’ve lost a good deal of blood. You’re not dead, or close to being dead, but you do feel a bit woozy. The key here is the CONSISTENCY of the input/output rate, just like above. So the arterioles constrict, shrinking the pipes of your system. It has restored normal pressure to the system, and now it can do its job of pushing blood along, even if it’s a smaller amount of blood than before. It may not be the IDEAL blood flow of earlier, but at least it’s a CONSISTENT blood flow, and that counts for a lot.
Does that make sense?
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