RAAS

Question 1

What stimulates renin release?

Answer 1

1. Decreased tubular flow sensed by macula densa.
2. Low afferent arteriolar pressure. (Internal renal baroreceptors)
3. Sympathetic nervous system stimulation (B1)

Question 2

What is the rate-determining step in the RAAS?

Answer 2

The renin mediated proteolysis of angiotensinogen determines rate.

Question 3

Where does angiotensin II target/ stimulate?

Answer 3

1. Smooth muscle in vasculature- vein/vaso constrict. Increase SVR.
2. Adrenal gland - secrete aldosterone
3. Pituitary- ADH release (posterior lobe pituitary) and sympathetic nervous system
4. Kidneys- vasoconstriction both afferent + efferent arteriolar, but maintain GFR. Increase SVR of kidneys.

Question 4

Where does angiotensingen and renin originate?

Answer 4

Angiotensinogen found in the liver and released to circulate blood.

Renin is secreted by granular cells, juxtaglomerular apparatus in the kidney.

Question 5

Where can the macula densa be located?

Answer 5

At the junction of DCT and thick ascending limb of Loop of Henle.

Question 6

What is aldosterone and where is it produced?

Answer 6

It is a steroid hormone, produced in the zona glomerulosa in the adrenal gland.

It accounts for 95% of the bodies mineralocorticoid activity.

Question 7

What are the layers of the adrenal gland and what do they produce?

Answer 7

Layers: GFR
Zona glomerulosa - aldosterone
Zona fasiculata - cortisol
Zona reticularis - testosterone precursors

Hormones: ACTH

Question 8

What is the effect of Aldosterone?

Answer 8

Promotes Na and water reabsorbtion.

K+ and H+ excretion.

Question 9

What is the main trigger for renin release?

Answer 9

Decreased renal blood flow

Question 10

What directly and indirectly stimulates aldosterone secretion?

Answer 10

Directly:

1. Hyperkalaemia
2. Acidosis
3. ACTH

Indirectly:
1. Renin via RAAS