Lecture 1

Question 1

What is the pathway for urine through the kidney?

Answer 1

nephron -> collecting duct -> papillary duct -> renal pelvis

Question 2

What are the main functions of the nephron?

Answer 2

-filtration via glomerulus
-reabsorption and secretion via tubules

Question 3

What are the two types of nephrons?

Answer 3

-cortical
-juxtamedullary

Question 4

What is the importance of juxtamedullary nephrons?

Answer 4

-closer to cortex/medulla border with longer LOH
-most important in animals that need to conserve a lot of water

Question 5

What are the characteristics of the glomerulus?

Answer 5

-membrane filtration barrier
-molecules filtered based on molecular weight
-formed of negatively charged glycoproteins; positive charges more readily filtered

Question 6

How do different forces impact GFR?

Answer 6

-hydrostatic pressure in glomerular capillaries favors filtration
-oncotic pressure in glomerular capillaries opposes filtration
-hydrostatic pressure in Bowman’s space opposes filtration

Question 7

What are the autoregulation mechanisms of GFR?

Answer 7

-myogenic mechanism
-tubuloglomerular feedback

Question 8

How does the sympathetic nervous system impact the kidneys?

Answer 8

vasoconstriction in times of fear/stress reduces renal blood flow and GFR

Question 9

How does the renin-angiotensin cascade impact the kidneys?

Answer 9

-triggered by decreased GFR and flow to tubules
-increases GFR initially but eventually decreases blood flow to tubules

Question 10

What is the effect of prostaglandins on the kidneys?

Answer 10

locally produced vasodilators that dampen the vasoconstrictor effect of sympathetic nervous system and angiotensin II

Question 11

Why can COX 1 inhibitors cause kidney damage?

Answer 11

block prostaglandin production

Question 12

What are the characteristics of the proximal convoluted tubule?

Answer 12

-responsible for 60-80% of NaCl reabsorption
-NaCl reabsorption linked to glucose, AA, and HCO3 reabsorption
-site where PTH works

Question 13

What are the consequences of proximal convoluted tubule damage?

Answer 13

-hyponatremia
-hypochloremia
-glucosuria
-metabolic acidosis
-hyperphosphatemia (cannot excrete)
-decreased GFR

Question 14

What are the characteristics of the Loop of Henle limbs?

Answer 14

*descending limb:
-permeable to water
-passive water reabsorption

*ascending limb:
-passive NaCl reabsorption in thin limb
-active reabsorption of NaCl in thick limb via K+ coupled co-transporter

Question 15

What are the consequences of Loop of Henle damage?

Answer 15

-inability to concentrate urine as needed
-inability to dilute urine as needed

Question 16

What are the characteristics of the distal convoluted tubule?

Answer 16

-begins at juxtaglomerular apparatus
-contains macula densa cells that sense NaCl levels
-contains juxtaglomerular cells that store and release renin
-reabsorption of Na via NaCl symporter
-PTH stimulates active Ca reabsorption here
-contains late distal tubular cells and collecting ducts

Question 17

What are the effects of angiotensin?

Answer 17

-arteriolar vasoconstriction
-increases NaCl reabsorption by proximal tubule; water follows
-stimulates aldosterone and vasopressin (ADH) secretion

Question 18

What are the effects of aldosterone?

Answer 18

-stimulates NaCl reabsorption by thick ascending LOH limb, distal tubule, and collecting duct
-leads to potassium secretion in exchange

Question 19

What is the role of principle cells in the collecting ducts?

Answer 19

respond to aldosterone to reabsorb Na and secrete K

Question 20

What is the role of intercalated cells in the collecting ducts?

Answer 20

reabsorb HCO3 and secrete H

Question 21

What is the function of the collecting duct aside from K and H secretion?

Answer 21

reabsorption of water and urea as controlled by ADH

Question 22

What are the consequences of distal convoluted tubule and/or collecting duct damage?

Answer 22

-impaired HCO3 reabsorption; renal tubular acidosis type 1
-impairment of K secretion/hyperkalemia
-inability to concentrate urine
-nephrogenic diabetes insipidus

Question 23

What are the other functions of the kidney besides urine formation?

Answer 23

-erythropoietin production
-vitamin D/calcium homeostasis

Question 24

What is the primary action of a diuretic?

Answer 24

cause excretion of Na that water follows

Question 25

What is physiologic diuresis?

Answer 25

water loss without increased solute loss

Question 26

What is the consequence of ingesting/administering too much water?

Answer 26

-increase in vasa recta blood flow leads to loss of osmotic gradient and medullary washout -concentrating ability is lost until gradient is re-established; around 24h

Question 27

What are the characteristics of osmotic diuretics?

Answer 27

-strong diuretics -alter osmotic driving forces along the nephron -typically mannitol

Question 28

What are the indications for osmotic diuretics?

Answer 28

-anuric/oliguric acute renal failure -cerebral edema

Question 29

What are the contraindications for osmotic diuretics?

Answer 29

-diseases with volume overload -severe dehydration -uncontrolled hemorrhage -diseases already associated with osmotic diuresis

Question 30

What are the characteristics of carbonic anhydrase inhibitors?

Answer 30

-weak diuretics -work at proximal tubule only -other segments in kidney can compensate for effects at proximal tubule

Question 31

What are the indications for carbonic anhydrase inhibitors?

Answer 31

-fluid retention and alkalosis -preventative for cystine or uric acid stone formation -preventative for horses with hyperkalemic periodic paralysis

Question 32

What are the characteristics of thiazide diuretics?

Answer 32

-moderate strength -inhibit NaCl symporter at early distal tubule -compensation in late distal tubule and collecting ducts increases Ca reabsorption and K and H secretion

Question 33

What are the indications for thiazide diuretics?

Answer 33

-hypertension and congestive heart failure -prevention of Ca urinary calculi not associated with hypercalcemia -nephrogenic diabetes insipidus (opens the water channels)

Question 34

What are the charactersitics of loop diuretics?

Answer 34

-block Na/K/Cl at medullary thick ascending limb -can increase sodium excretion by 25% -greater potential for side effects -rapid onset and short duration of action -stimulate prostaglandin secretion to increase blood flow to cortex

Question 35

Which side effect of loop diuretics is especially important to monitor for?

Answer 35

hypokalemia

Question 36

What are the indications for loop diuretics?

Answer 36

-cardiac failure with volume overload -hepatic fibrosis with secondary ascites -nephrotic syndrome -acute pulmonary edema -acute renal failure -hypercalcemia secondary to: *pseudohyperparathyroidism *primary hyperparathyroidism *vitamin D intoxication

Question 37

What are the characteristics of potassium sparing diuretics?

Answer 37

-weakest diuretics -used in combination with other diuretics to prevent hypokalemia -mild potential to cause hyperkalemia

Question 38

What are the indications for potassium sparing diuretics?

Answer 38

-congestive heart failure -hepatic fibrosis/cirrhosis -nephrotic syndrome

Question 39

What are the two types of potassium sparing diuretics?

Answer 39

-aldosterone antagonists -sodium channel blockers

Question 40

How do aldosterone antagonists work?

Answer 40

competitive inhibition on the action of aldosterone at the principal cell

Question 41

How do sodium channel blockers work?

Answer 41

direct interaction with Na-selective channel in apical membrane of principal cell