How does the renin-angiotensin-aldosterone system cause vasoconstriction?

[Penelope61]

I’ve been reading about how the body regulates blood pressure, and I keep seeing references to the renin-angiotensin-aldosterone system. I understand it’s a hormone cascade, but I’m struggling to picture how exactly renin release from the kidneys translates into vessels constricting and blood pressure going up.

[Abigail_D]

I picture the kidney as a pressure sensor. When blood pressure or salt delivery is low, the juxtaglomerular cells release renin into the blood. Renin cuts a hormone called angiotensinogen into angiotensin I, then ACE in the lungs makes angiotensin II. Ang II tightens the small vessels a bit, with a bigger effect on the efferent arteriole of the kidney, and it also tells the adrenal glands to make aldosterone. Aldosterone makes the kidneys hold onto salt and water, so blood volume rises. Put together, the pressure goes up and the cycle can keep feeding itself until something changes. This whole chain is the renin-angiotensin-aldosterone system.

[MasonD]

I tried to memorize it as a flowchart, but in practice I keep tripping over which part actually does the constricting first. Angiotensin II seems to do several jobs at once, so the picture gets muddy fast.

[DennisM]

I actually watched my clinic BP numbers and my doctor started me on an ACE inhibitor; over a couple of weeks my systolic numbers drifted down by 5-10 points and stayed there. It felt like the cascade was being damped.

[SavannahJM]

Could it be that the real problem isn’t the hormones alone but how sensitive the vessels are to Ang II, or how well the kidneys respond to aldosterone?

[Camila_M]

Sometimes I drift to thinking about salt intake and stress and how those crank up the whole system, even if the hormones are behaving.

[Scott.G]

I’m not confident I have the steps right, but what stuck is that a signal from the kidneys starts a chain that affects vessels and volume, and that’s enough to push BP higher until something rebalances.