Aldosterone, Angiotensin II/III, etc

[tncekm]

Edit: I mean Aldosterone, not ADH.

Okay, so these cause vasoconstriction and an increase in blood pressure. Vasoconstriction and increasing blood pressure are incongruous with conservation of energy as stated by Bernoulli's equation. What's the deal? Is the increase in blood pressure just a result of increased Na+ absorption leading to increased blood volume and people tend to report the reason for increased BP incorrectly?

Thanks

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[Doctor Bagel]

Edited your thread title for you. Also, I have to admit I'm not at all up on Bernoulli's equation, but yes, the bp is increased because of increased Na and consequently increased fluid volume. Also, Angiotensin II has 2 effects -- it directly causes vasoconstriction, and it stimulates release of aldosterone. The vasoconstriction and the increased uptake of Na are separate processes.

 

[tncekm]

Thanks a lot!

I was also reading that there is a difference in the effects of ATII on the afferent and efferent arterioles leading to a net increase in fluid volume of the systemic arteries, or something like that--I read it an hour or so ago. Could that be a contributing factor as well?

 

[Doctor Bagel]

Thanks a lot!

I was also reading that there is a difference in the effects of ATII on the afferent and efferent arterioles leading to a net increase in fluid volume of the systemic arteries, or something like that--I read it an hour or so ago. Could that be a contributing factor as well?

Angiotensin II preferentially constricts efferent arterioles in the kidney over afferent arterioles. That causes an increase in GFR. From my understanding, that by itself isn't really a blood pressure action -- it's just to improve kidney functioning.

I'll also say that unless they changed the MCAT a lot recently, the details of this are probably beyond the scope of the MCAT.

 

[tncekm]

Thanks again

I know its probably more detail than I need to know for the MCAT, but I was reviewing some of my notes from my Bio readings and it was driving me nuts, so I had to ask

 

[Doctor Bagel]

Thanks again

I know its probably more detail than I need to know for the MCAT, but I was reviewing some of my notes from my Bio readings and it was driving me nuts, so I had to ask

Well, you will have to know it for phys in medical school, so hey it's not wasted info.

 

[tncekm]

Yeah, definitely not wasted info. The more I know now, the less I learn then ∴ I get more sleep!