Block VII - Renal

Question 1

How does the renin-angiotensin system regulate aldosterone secretion?

Answer 1

When blood volume is low, juxtaglomerular cells in the kidneys secrete renin directly into circulation. Plasma renin then carries out the conversion of angiotensinogen released by the liver angiotensin I, which is subsequently converted to angiotensin II. Angiotensin II stimulates aldosterone secretion from adrenal cortex

Question 2

What is the renal clearance of a substance X that is filtered and secreted but not reabsorbed equivalent to? Example?

Answer 2

Renal plasma flow, PAH

Question 3

What factors are primarily responsible for the whole kidney phenomenon of renal auto regulation?

Answer 3

Intrinsic myogenic response of preglomerular arterioles and the tubuloglomerular feedback mechanism

Question 4

What is the renal clearance of a substance X that is filtered but not secreted or reabsorbed equivalent to?

Answer 4

Glomerular filtration rate (GFR), creatinine is an example

Question 5

How do you calculate GFR from creatinine clearance?

Answer 5

GFR = clearance of creatine = (urine concentration)*(urine flow rate)/(plasma creatine concentration)

Question 6

What is the effect of angiotensin II on vascular resistance?

Answer 6

Increase

Question 7

In a 70 kg pt c hypertension (150/95) who is adequately hydrated, what are GFR and filtration fraction (normally 120 and 20% respectively)? Plasma inulin concentration 0.2, urine inulin 8, plasma PAH 0.04, urine PAH 6, urine flow 1.5

Answer 7

GFR = 60, filtration fraction 24%

Question 8

What is the effect of increased sympathetic stimulation on renal function?

Answer 8

Decrease both renal blood flow and GFR

Question 9

How doe renal arteriole changes regulate GFR?

Answer 9

GFR will be increased with dilation of afferent arteriole and constriction of the efferent arteriole

Question 10

Following an acute increase in renal arterial pressure, what kidney response would be expected under normal conditions?

Answer 10

An increase in afferent arteriolar resistance with minimal steady state changes in renal blood flow and GFR

Question 11

Assume that arterial pressure does not change, what is the effect of a decrease in afferent arteriolar resistance on the GFR?

Answer 11

Increase in GFR

Question 12

If a substance X is freely filtered and not metabolized, but has a clearance greater than that of inulin, what can be concluded about that substance X?

Answer 12

Substance X is secreted into tubular fluid

Question 13

What is the function of kidney?

Answer 13

Regulation of electrolytes balance, also net production of glucose under stress condition such as starvation, net production of hormones, excretion of formal chemicals from the blood

Question 14

What are the major resistance vessels in the kidney?

Answer 14

Arterioles

Question 15

What is the mechanism of Na transport in proximal tubule?

Answer 15

Na transport involves Na/K-ATPase (primary active) on the basolateral membrane and cotransport (secondary active) on the apical membrane

Question 16

If a substance X is freely filtered and not metabolized or synthesized, and has a clearance less that that of inulin, what can be concluded about substance X?

Answer 16

Substance X undergoes net reabsorption by the tubules

Question 17

What is ultrafiltration in the kidney?

Answer 17

High capillary pressure forces small molecules through the filter, from the blood to the glomerular capsule across the basement membrane of the Bowman’s capsule and into the nephron. The fluid formed this way is called glomerular filtrate, which is essentially devoid of high molecular weight proteins

Question 18

What is the fluid’s osmotic and pH conditions at the end of the proximal tubule?

Answer 18

The fluid is iso-osmotic, but its pH is lower than that of plasma

Question 19

What is the function of Na/K ATPase in the proximal tubule?

Answer 19

Na reabsorption. Na/K pump is located at the basolateral membrane, maintaining low intracellular Na, Digoxin inhibits this pump

Question 20

How does whiter transport in the proximal tubule?

Answer 20

Passive reabsorption

Question 21

In what segment of the loop of Henle where Na-K-2Cl is an important electroneutral co-transporter?

Answer 21

In the ascending segment (thick), Na, K, Cl are actively transported out of lumen by this symporter. The drugs that inhibit this are called loop diuretics, which are used as antihypertensive

Question 22

What is the protein at the apical membrane of the Principal cells that is responsible for reabsorption of Na in the collecting duct?

Answer 22

Epithelial Na channel (ENaC), blocked by amiloride

Question 23

Why is NH3/NH4 an effective renal buffer?

Answer 23

Acid-base reaction has a high pKa

Question 24

What is the secretion of H in the PT primarily associated with?

Answer 24

Re-absorption of HCO3. The H secretion is mediated by Na/H exchanger.

Question 25

What happens in primary metabolic acidosis?

Answer 25

Metabolic acidosis is diagnosed with low blood pH (< 7.35) and low bicarb (the inability of the body to form bicarb in the kidney, < 24). There is a net increase in titratable acids

Question 26

What cells of the collecting duct are associated with H secretion in the kidney?

Answer 26

Alpha intercalated cells

Question 27

Where is HCO3 re-absorbed?

Answer 27

PT, thick ascending limb, distal tubule, collecting duct. No HCO3 secreted in the urine.

Question 28

Does an increase in GFR provide pathophysiological evidence for increase in glomerular permeability to large molecules?

Answer 28

No. An in crease in urine albumin excretion would provide such evidence.

Question 29

What are the criteria required for the substance used to measure renal clearance using the clearance technique?

Answer 29

Be readily filtered across glomerular capillaries; not be reabsorbed by tubules, not be secreted, not by metabolized or synthesized

Question 30

Where is most of the glucose and amino acids reabsorbed?

Answer 30

Proximal tubule

Question 31

What is the effect of antidiuretic hormone (ADH) on the kidney?

Answer 31

Increase permeability of distal tubule and collecting duct to water

Question 32

How does kidney use HCO3 to regulate acid-base balance?

Answer 32

Reabsorbing filtered HCO3 and generating new bicarb

Question 33

What is the difference between respiratory and metabolic acidosis?

Answer 33

pH is dependent upon the ration of HCO3/CO2 in the blood. Respiratory is resulted from increasing CO2, whereas metabolic decreases HCO3. Metabolic may b compensated by increasing ventilation to lower CO2

Question 34

How to diagnose primary metabolic acidosis?

Answer 34

Low plasma HCO3 < 24

Question 35

In response to metabolic acidosis, what changes in NH4 will occur?

Answer 35

Secretion of NH4 into tubular lumen

Question 36

What is the major extracellular buffer system in the body?

Answer 36

CO2/bicarb buffer system

Question 37

Why does the movement of solute preferential over water movement in the ascending segment of LH?

Answer 37

Because the thin ascending loop is not permeable to water

Question 38

How does the osmolarity of the filtrate change in the loop of Henle?

Answer 38

The isotonic fluid from the loop looses water to the higher concentration outside the loop and increases in tonicity until it reaches a max at the bottom of the loop. The filtration is the diluted in the ascending

Question 39

What is the overall effect of aldosterone?

Answer 39

Increase reabsorption of ions and water in the kidney – increasing blood volume and, therefore, increasing blood pressure. Aldosterone stimulates Na reabsorption and potassium excretion, activity of aquaporins and the expression of ENaC in the collecting duct

Question 40

What is the effect of blood pressure on aldosterone secretin?

Answer 40

Low BP stimulates aldosterone secretion, the adrenal gland is stimulated by the stretch receptors which are sensitive to low BP to release aldosterone. This will return BP to normal.

Question 41

What is the change in the kidney production of NH3/NH4 during acidosis?

Answer 41

Increases

Question 42

How is bicarb reabsorption achieved?

Answer 42

Binding with H ion to form water and CO2, which then diffuses into brush border cells to form new bicarb and H catalyzed by carbonic anhydrase. H-ATPase and Na/H exchanger transport H to lumen. Bicarb diffuses to blood. Blocking of carbonic anhydrase decreases HCO3 reabsorption and H secretion

Question 43

Can you calculate GF coefficient from GFR?

Answer 43

Yes. GFR = K (Pg - Pb - Posmo,g)

Question 44

What are thiazides?

Answer 44

Thiazides are diuretics commonly used for treating hypertension; the function of thiazides is to bock Na-Cl cotransporter in the distal convoluted tubule.

Question 45

Does the fluid in early distal tubule have the lowest osmolarity during excessive water loss?

Answer 45

Yes. Like the thick ascend limb, cells of the early DT are impermeable to water and reabsorption cannot follow solute reabsorption. When the plasma osmolarity increased (water deprivation), the osmoreceptor stimulates ADH from posterior pituitary, ADH works at late DT and collecting ducts to increase reabsorption of water, thus urine osmolarity