SS3. RAAS system overview

Question 1

What does RAAS stand for?

Answer 1

Renin-Angiotensis-Aldosterone system.

Question 2

Where does the RAAS system begin?

Answer 2

Juxtaglomerular cells (JG)

Question 3

What are JG cells?

Answer 3

Special smooth muscle cells in kidney, releases renin that raises blood pressure.

Question 4

What triggers the release of Renin?

Answer 4

1) Decreased blood pressure sensed by Juxtaglomerular cells (JG)
2) Sympathic nerve which neighbours JG’s, sends out release of nerves that triggers release of Renin
3) Macula Densa cells. Lays in kidneys, sense low sodium rates. If there’s a low BP = low fluid rate = low absorbance of Na. Sense that there isn’t enough salt so they send prostaglandins to JG (local messenger) to produce renin

Question 5

What other organs are involved in blood pressure?

Answer 5

The liver

Question 6

What do liver cells produce?

Answer 6

Angiotensinogen

Question 7

How does the activation of angiotensinogen work?

Answer 7

Angiotensinogen, available but inactive, meets Renin which chops off a part of angiotensinogen –> results in Angiotensin 1, a more awake state.
Angiotensin 1 flows through blood cells lined with endothelial cells where it’s converted to Angiotensin 2, an active hormone.

Question 8

What cells does Angiotensin 2 affect?

Answer 8

1) Smooth muscle cells al over body, causing them to constrict which results in increased resistance
2) Kidney cells, holds on to more H2O, resulting in increased stroke volume
3) Pituitary glands on base of brain which secretes ADH, which works on both smooth muscle cells and the kidney.
4) Adrenal gland. Makes aldosterone, affects stroke volume in the kidney.