Sodium regulation

Question 1

What are the two hormone systems that regulate body levels of sodium?

Answer 1

• renin-angiotensin-aldosterone system (RAAS) - for when sodium is low
• atrial natriuretic peptide (ANP) - when sodium is high

Question 2

What secretes renin?

Answer 2

• juxtaglomerular cells

Question 3

Two receptor types that detect low sodium

Answer 3

• baroreceptors - carotid sinus baroreceptors signal to JG cells (JG cells are also intrarenal baroreceptors)
• chemoreceptors - Macula densa cells detect low Na and signal to JG cells through paracrine signalling

Question 4

What is angiotensin ll?

Answer 4

• produced from angiotensin l
• stimulus is renin release
• causes increased reabsorption of Na in the proximal tubule
• also causes vasoconstriction of the afferent and efferent arterioles, therefore decreasing GFR

Question 5

What is Aldosterone?

Answer 5

• steroid hormone that increases reabsorption of Na and secretion of K in principal cells of the collecting duct

Question 6

What is the atrial natriuretic peptide (ANP)?

Answer 6

• peptide hormone made by the atrial cells of the heart
• stimulus is high blood pressure (will cause an increase in excretion of Na)
• reduces reabsorption of Na by inhibiting aldosterone release and by vasodilation of the afferent arteriole