Renin and RAAS system

Question 1

What cells secrete renin?

Answer 1

juxtaglomerular cells

Question 2

Function of renin

Answer 2

hydrolyses angiotensinogen to produce angiotensin I

Question 3

Factors stimulating renin secretion

Answer 3

hypotension causing reduced renal perfusion
hyponatraemia
sympathetic nerve stimulation
catecholamines
erect posture

Question 4

Factors reducing renin secretion

Answer 4

drugs: beta-blockers, NSAIDs

Question 5

Name the 3 layers of the adrenal cortex and the substances they produce

Answer 5

zona glomerulosa (outside): mineralocorticoids, mainly ALDOSTERONE

zona fasciculata (middle): glucocorticoids, mainly CORTISOL

zona reticularis (inside): androgens, mainly dehydroepiandrosterone (DHEA)

Question 6

What enzyme converts angiotension I to II. Where is this enzyme found?

Answer 6

angiotensin-converting enzyme (ACE) in the lungs converts angiotensin I → angiotensin II

Question 7

roles of Angiotensin II

Answer 7

vasoconstriction + raised BP
vasoconstriction of efferent arteriole of the glomerulus → increased filtration fraction (FF) to preserve GFR.

stimulates thirst (via the hypothalamus)
stimulates aldosterone and ADH release
increases proximal tubule Na+/H+ activity

Question 8

What stimulates aldosterone release?

Answer 8

raised angiotensin II, potassium, and ACTH levels

Question 9

Role of aldosterone

Answer 9

causes retention of Na+ in exchange for K+/H+ in distal tubule