Renal Questions Key

1. Make a map showing how the following are related:

GFR Glomerular Filtration Pressure

afferent arterioles efferent arterioles

macula densa juxtaglomerular cells

renin angiotensinogen

angiotensin I angiotensin II

angiotensin converting enzyme

peripheral vasoconstriction

2. Explain why each of the following diuretics works:

Furosemide - inhibits Cl- pumps in the ascending loop of Henle. – Cl- and Na+ are not moved into the renal medulla, so it becomes less salty. They stay in the urine, so the urine is more salty. When the urine is leaving the kidneys through the collecting duct, there is not much osmotic difference between the urine and the renal medulla, so no water is pulled out of the urine into the medulla. It goes out in the urine instead.

Chlorothiazide - blocks Na+ and Cl- reabsorbtion in the distal convoluted tubule – if these solutes are not reabsorbed, water will not follow them back to the blood.

Spironolactone - blocks aldosterone receptors – the Na+/K+ ATPase on’t turn on and as a result Na+ and H2O will not be reabsorbed.

Mannitol - is filtered into the urine at the glomerulus but cannot be reabsorbed – this will raise the osmolarity of the urine, making water stay in the urine.