Kidneys

Question 1

Aldosterone

• where does it act?
• what does it cause?
• net effect?

Answer 1

Aldosterone acts on the DCT, where it makes it permeable to Na+ and K+ via Na and K channels and Na/K ATPase.

Results in an increase in Na+ uptake by the blood. This causes water to flow out of the filtrate into the cells.

Net effect = water retention and increased BP

Question 2

ADH -

• where does it act?
• by what mechanism?
• result?
• net effect?

Answer 2

ADH acts on the CD. It acts via insertion of aquaporins into the CD, where the CD is normally (in the absence of ADH) impermeable to water.

However, with the insertion of these, and the fact that the CD plummets down into the very “salty” medulla of the kidney, water will flow out of the CD into the cells out of the filtrate.

Net effect = water retention and increased BP

Question 3

Describe all the important parts of the nephron

Answer 3

Glomerulus - where filtrate leaks out of
Bowman’s capsule- catches the filtrate
Proximal convoluted tubule- where Na+, glucose, HCO3-, and AA reabsorption by the blood occurs
Descending loop of Henle- permeable to water due to the environment being hypertonic (water flows out of the nephron)
Ascending Loop of Henle- impermeable to water, location of NaKCl transporters. Makes the bottom of the medulla very salty
Distal convoluted tubule- where final reabsorption of important solutes into the blood occurs. Ex: Ca++, some water
Collecting duct: plummets back into the medulla. With high levels of ADH, the insertion of aquaporins can cause water to diffuse out of the CD into the blood

Question 4

Describe what a kidney should look like

Answer 4

Capsule
Medulla
Cortex
Renal calyx
Renal pyramids
Renal papilla
Renal pelvis