Decrease V is decrease P

[laczlacylaci]

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Just to clarify:

In ideal gases, as volume increases, pressure decreases.
In liquid, ie. plasma, as volume increases, pressure also increases? (got this from Qpacks Bio #80)

 

[betterfuture]

Are you sure you have the right question?

 

[laczlacylaci]

Are you sure you have the right question?

oops sorry, here it is:

My thought process:
aldosterone deficiency=decreases Na+reabsorption by the kidneys into the plasma=decrease blood volume. I am asking that if in fluids, you have decreases volume, you have decreased pressure, which is what the key said. If not, how did you reason the pressure part?

 

[theonlytycrane]

Not sure if it applies to fluids in general, but one of the reasons aldosterone is secreted is to increase blood pressure. So an aldosterone deficiency would do the opposite, likely due to the reason you mentioned.

 

[betterfuture]

You see, blood volume and blood pressure go hand in hand. So if you increase blood volume you can increase the pressure as well. Just think of a heart like a balloon if you fill it with water. The water is analogous to blood. When you increase the amount of water filling the balloon, you exert more pressure on the balloon walls. Same goes for the elastic arteries in the body and the heart ventricles.

However, ideal gases are just that. They are gases and have different properties than solids and liquids. When we talk of ideal gases we are assuming that they dont react with each other, have negligible volume, etc., etc.

 

[aldol16]

Blood pressure = cardiac output x resistance. Cardiac output is the product of stroke volume and heart rate. If you have a lower stroke volume, you're going to have a lower blood pressure. Since the circulatory system can be approximated as a closed circuit, if you lower the blood volume, you're bound to have a lower stroke volume.

 

[NextStepTutor_2]

oops sorry, here it is:
View attachment 207719
My thought process:
aldosterone deficiency=decreases Na+reabsorption by the kidneys into the plasma=decrease blood volume. I am asking that if in fluids, you have decreases volume, you have decreased pressure, which is what the key said. If not, how did you reason the pressure part?

For the body, a loss of blood volume must result in a drop in blood pressure, and vice versa. It is simply the way the body is designed. The rule of ideal gases (PV= constant) are not applicable here.

Aldosterone acts to increase Na+ reabsorption in the kidneys, resulting in increased water reabsorption and more solute AND fluid in the circulatory system (thus why you will see the AAMC state that aldosterone will not significantly change blood osmolarity) which causes an increase in systemic blood pressure.

Hope this helps, good luck!