Kidney Overview

Question 0

What is colloid osmotic pressure (COP)? Why does it increase along the length of the glomerular capillary?

Answer 0

Osmotic pressure caused by solutes in the blood (esp proteins).
As water, but not proteins, move into the filtrate, the concentration of proteins in the blood increases -> increased COP -> reduced filtration rate.

Question 1

What are the three pressures that drive glomerular filtration?

Answer 1

Glomerular capillary pressure (GCP) - promotes.
Colloid osmotic pressure (COP) - opposes.
Capsular pressure (CP) - opposes.

Question 2

Why do we measure urea?

Answer 2

It isn’t itself toxic, but it’s a marker for the build of other toxic products.

Question 3

Describe the shape of the relationship between renal arterial pressure and glomerular filtration rate.

Answer 3

Over normal pressures (80mmHg - 160ish mmHg), the GFR stays pretty constant - it plateaus.
When pressure drops below 60mmHg, GFR rapidly declines (which is bad).

Question 4

What structure governs autoregulation of GFR? (3 components of it?)

Answer 4

The juxtaglomerular apparatus - which includes the juxtaglomerular cells, macula densa, and mesangial cells.

Question 5

What’s the point of all the salmon discussion?

Answer 5

The kidney and it’s molecular components can be up/downregulated to adjust to different levels of salt intake.

Question 6

What’s the normal level of sodium output?

Answer 6

Depends on intake.

Question 7

Where in the nephron is most of the water reabsorbed?

Answer 7

In the proximal convoluted tubule.

Question 8

What drives water resorption in the proximal tubule?

Answer 8

The Na+ gradient.

Question 9

What creates the Na+ gradient across the proximal convoluted tubule?

Answer 9

Na+/K+ pumps on the basolateral membrane - makes interstitial Na+ high, and intracellular Na+ low.

Question 10

How is glucose resorption in the proximal convoluted tubule driven?

Answer 10

Cotransport with Na+

Question 11

Where in the nephron is Na+ resorption regulated? What hormone mediates regulation? What is the molecular mechanism of regulation?

Answer 11

In the distal tubule, aldosterone increases Na+ expression by upregulating ENaC.

Question 12

What’s a molecule that ADH upregulates to increase H2O resorption?

Answer 12

Aquaporin-2

Question 13

Where is the “diluting segment” of the nephron? Why is it called this?

Answer 13

The ascending loop of Henle is impermeable to H2O, but allows ions to be transported out of the lumen, diluting the urine.

Question 14

What’s Liddle’s syndrome? What’s the genetic basis for this disease? Where in the nephron is affected?

Answer 14

Liddle’s syndrome: Way too much Na+ retention -> hypertension.
Mutation in ENaC such that it always allows Na+ through.
This causes greatly increased Na+ resorption in the distal convoluted tubule.

Question 15

Cardio review: 2 ways angiotensin II increases BP?

Answer 15

Increased Na+ and H2O retention (via several mechanisms).

Vasoconstriction.

Question 16

Normal pH of blood?

Answer 16

7.4

At 6.8, you’re pretty much dead. At 7.8, you’re in bad shape too

Question 17

4 sources of H+ ions?

Answer 17

Cell metabolism (CO2).
Food intake.
Medications.
Metabolic byproducts (e.g. lactic acid, ketones - not really a byproduct, but whatever).

Question 18

What ions does kidney change the secretion/retention of to maintain acid/base homeostasis??

Answer 18

H+ and bicarb.

Question 19

What vitamin will you be deficient in if you have severe kidney disease?

Answer 19

Activated vitamin D.

Kidneys have enzyme that converts 25-OH-D3 to 1,25-(OH)2-D3

Question 20

How does the kidney talk to the bone marrow?

Answer 20

EPO -> increased RBC synthesis.