Modeling the Human Cardiovascular System

[HPW]

I am doing this experiment: "Modeling the Human Cardiovascular System: The Factors That Affect Blood Flow". In the "Make It Your Own" tab, I found this variation: "Does blood pressure affect the flow rate? Experiment with this variable by changing the starting level of the water in the bucket. The pressure at the valve is equal to the density of water multiplied by the difference in height between the surface of the water and the valve." Is this merely a variable, or not? Also, if I want to do this one, do the procedures change? If so, how do they change. Please tell me what variable I can have for this experiment.

Thank you very much.

[JMP]

Hi HPW,

It's great that you have an experiment that you are interested in and want to make it your own by changing it somewhat. In this experiment, the variable will be the height of the water (used to mimic differences in blood pressure). You would follow the procedures as written, but instead of measuring the difference in flow time for tubes of two different diameters (i.e. the 1/4 and 3/8 inch tubes), you would use only one diameter tubing and run the experiment multiple times, each time changing how much water you start with in the bucket. This will change the pressure, and should affect how long it takes for a 1/2 cup of water to flow through the tubing into the measuring cup.

For more details on what a variable is, you can read this link:
https://www.sciencebuddies.org/science- ... bles.shtml

After reading that, can you tell whether the water level in the bucket is an independent or dependent variable?

I hope this helps you get started. If you need more help, please feel free to post here again.

JMP

[HPW]

Thank you so much for this helpful information!

[HPW]

Hi JMP,
Okay, so your procedures are very helpful to me! I just have some question: how would I test the blood pressure? I don't exactly know how I would recognize it. I know that the water level mimics the blood pressure, but I'm a little confused on that part. So, does a lower water level show low blood pressure and a high water level expresses high blood pressure? Also, I was thinking on whether the water level would be an independent or dependent, and I think it would be dependent because the amount of water put in is the independent. Please correct me if I am incorrect; I would really appreciate it!

Also, do you have any creative ideas for the model itself? I want to have a cool blood flowing model, but I don't know if it will work for this project. Please tell me if you have any cool ideas.

Thank you so much for your help; I really do appreciate it!!! After you explained to me this procedure, I decided to do it and make it more interesting!!

[JMP]

Hi HPW,

According to the procedures, you can calculate the pressure using the following equation:
"Experiment with this variable by changing the starting level of the water in the bucket. The pressure at the valve is equal to the density of water multiplied by the difference in height between the surface of the water and the valve."

Thus, a higher starting level of water in the bucket is going to be higher pressure, while a lower starting level would be lower pressure. This acts to model high and low blood pressure. You are not actually testing the blood pressure: you are adjusting the water level (i.e. blood pressure) and measuring how that affects the flow rate of the water (i.e. blood) through the tubing. You'll measure your pressure using the above formula and compare that to the flow rate (i.e. how long it takes for 1/2 cup of water to flow into the measuring cup). Does that make sense?

As for your variables, you are on the right track thinking of independent variables as being what you change, so the water level you start with is the independent variable. Since we are modeling blood pressure by changing the water level, you can consider them as the same variable, so the pressure is your independent variable. The dependent variable is generally what you are measuring, or in this case how long it takes for the water to flow into the measuring cup. Are you following me?

I don't have any particular exciting ideas for a blood flowing model right now, but I'll keep it in mind, and other experts may be able to come up with something as well. Keep in mind that in the current model, there isn't a pump or anything (like the heart) to keep blood flowing continuously. Once the water runs through the tubing, that is it until you add more. You could obviously add food coloring to it to make it look more like blood if you wanted to, though. Additionally, you could experiment with liquids with different viscosities (i.e. thicknesses) to see how that makes a difference in flow, since blood is more viscous than water. You might try something like liquid detergent in place of water. Just make sure you are only testing one variable at a time (i.e. blood pressure or blood thickness) so that you have all of the correct controls.

I hope this helps, and keep posting if you run into any trouble!
JMP

[Science interest]

I'm doing Modeling the Human Cardiovascular System: The Factors That Affect Blood Flow Rate for my science experiment. According to my grading rubric I must have a total of 5 variations so far I only have 4 variations (1 is using 1/4 inch tubing for 2 ft.. 2 is using 1/4 inch tubing with 3 ft.. 3 is using 3/8 inch tubing 2 feet .. 4 is using 3/8 inch tubing with 3 ft) but that's only 4 variations and I need 1 more variations. I'm conducting my experiment now and ran into this problem Please help me. Any ideas would be greatly appreciated. Thanks for your time!

[Science interest]

If my question above is not clear please let me know so I can explain it again. Thank you!

[JMP]

Hi,

If you just need to add a 5th variation of the same variable, I don't see why you couldn't just incorporate another length (i.e. 4 feet of 1/4 inch tubing in addition to the 2 and 3 feet) or a different diameter tubing. If you are looking to test a completely different variable, you could consider changing the viscosity of the liquid, by running a test with something other than pure water. You could use a different household chemical, or sugar syrup, or anything else that is interesting to you.

I hope this helps!
JMP

[20gstewart]

Hi JMP!
I'm so excited to do this project, but I'm a little confused on how to state my hypothesis without making the conclusion sound obvious (because of common sense). I've done my research on Atherosclerosis (i.e. Coronary Artery Disease/Cardiovascular disease) and I'm testing the difference in blood flow rates of a person with cardiovascular disease and a person without cardiovascular disease, but that would make my hypothesis sound too predictable? Do you have any ideas? Also, measuring the viscosity and blood flow rates sounds very interesting, but I'm confused on how exactly you would test that and how it relates to real life (what exactly would it be modeling, the thickness of blood?) How would I know if the other substance is scaled to the thickness of blood?
Thanks, I really appreciate it!
GLS

[20gstewart]

Also, why do we use a 1/4 inch and a 3/8 inch tubing? Are those the actual diameters of a coronary artery and that same artery with plaque build-up?
Thanks Again!
GLS