Renal Physiology

Question 1

Reflection coefficient

Answer 1

0 - all particles pass

1 - membrane impermeable to that particle

Question 2

Extracellular fluid volume determined by:

Answer 2

[Na] concentration

Question 3

plasma osmolality calculation:

Answer 3

osmolality ≈ 2[Na] + [Glucose]/18 + [BUN]/2.8

Question 4

osmolar gap

Answer 4

measured - calculated osmolality. alerts to toxins in blood (methanol, ethylene glycol)

Question 5

Fluid compartments as percentage of body weight:

Answer 5

Total body water: 60%
ICFV: 40%
ECFV: 20%

Question 6

If GFR increases by 50%, oxygen consumption by the kidney will increase by:

Answer 6

50%. increases in parallel.

Question 7

Glomerular Capillary hydrostatic pressure —– (drives/opposes) filtration while glomerular oncotic pressure — filtration.

Answer 7

glomerular hydrostatic drives filtration; glomerular oncotic opposes filtration.

Question 8

GFR equation:

Answer 8

GFR = Kf [(PGC – PBS) – πGC]

Question 9

filtration fraction equals:

Answer 9

GFR/RPF. GFR related most to glomerular hydrostatic pressure.

Question 10

Loss of negative charge on the filtration barrier in the Bowman’s space would lead to:

Answer 10

appearance of albumin (anionic) in the tubular fluid, and if the reabsorptive capacity of the proximal tubule is exhausted, in the urine (proteinuria)

Question 11

renal clearance is defined as:

Answer 11

volume of plasma that would be completely cleared of the substance per unit time.

Question 12

A good measurement of RPF is:

Answer 12

PAH, because it is almost entirely excreted (urine excretion rate = rate of infusion).

Question 13

tubuloglomerular feedback:

Answer 13

macula densa senses increased solute arriving as increased GFR and RBF, signals to constrict afferent arteriole to bring down GFR and RBF.

Question 14

what kind of transporter is on the macula densa?

Answer 14

Na/Cl/K co transporter.

Question 15

AII primarily effects which arterioles?

Answer 15

efferent, with less strong effect on afferent. Causes increased GFR, alters macula dense sensitivity, decreases renin release.

Question 16

Inhibition of carbonic anhydrase by acetazolimide would result in:

Answer 16

diuretic and treatment of respiratory or metabolic alkalosis. The inhibition of carbonic anhydrase &raquo_space; decreased reabsorption of bicarbonate, resulting in urinary bicarbonate wasting. This leads to a decreased ability to exchange Na+ for H+ in proximal convoluted tubules&raquo_space; mild diuresis.

Question 17

glomerotubular balance:

Answer 17

changes in GFR are responded to be corresponding changes in reabsorption by the proximal tubule.

Question 18

Loop diuretics act on what kind of transporter in the thick ascending limb of henle/

Answer 18

Na/Cl/K co transporter (also present on macula densa).

Question 19

Where do thiazide diuretics act? what kind of transporter?

Answer 19

distal tubule; Na/Cl cotransporter.

Question 20

Plasma [Na] is regulated by altering:

Answer 20

WATER! not Na. ADH is secreted in response to increased [Na]. Thirst is also stimulated by increased [Na] but NOT in response to ADH. ADH&raquo_space; decreased thirst b/c it effects water reabsorption in kidney.

Question 21

free water clearance:

Answer 21

rate at which water needs to be added to, or subtracted from urine to render it isoosmotic with plasma. idneys excrete excess water: CH2O is positive.
• Kidneys excrete excess solute: CH2O is negative

Question 22

ECFV is regulated via:

Answer 22

kidneys altering salt content. sensed via low & high pressure stretch receptors.

Question 23

aldosterone impacts which areas of the kidney?

Answer 23

distal tubule and collecting duct

Question 24

Main effects of ANP:

Answer 24

dec afferent tone&raquo_space; Increased GFR
dec renin
dec ADH sensitivity in CD

Question 25

if the body wants to decrease blood pressure, it would want a higher or lower GFR?

Answer 25

higher

Question 26

which region of the kidney will increase reabsorption in response to decreased total NaCl in tubular fluid?

Answer 26

proximal tubule

Question 27

rate of Na/K ATPase in cells is determined by Na or K?

Answer 27

turnover rate of Na+/K+ ATPase and thus K uptake is determined by the rate of Na entry.

Question 28

what impact does insulin have on Na/K ATPase?

Answer 28

increases; therefore&raquo_space; hypokalemia

Question 29

Epinephrine acts via B2 receptors on cells, which has what effect on K?

Answer 29

increases Na/K ATPase&raquo_space; hypokalemia.

Question 30

norepinephrine acts via alpha receptors on cells to have what effect on K?

Answer 30

inhibits Na/K ATPase&raquo_space; hyperkalemia

Question 31

what effects do organic acids have on potassium?

Answer 31

little to no effect: h2CO3 diffuses across cell therefore respiratory acidosis does not have big impact on K directly.

Question 32

Decreased flow has what impact on K secretion?

Answer 32

decreased flow&raquo_space; decreased potassium secretion.

Question 33

What impact does ADH have on K secretion?

Answer 33

K secretion remains same due to decreased flow paired with stimulation of K secretion..

Question 34

alkalosis/acidosis effect on potassium secretion:

Answer 34

alkalosis stimulates potassium secretion in collecting duct; acidosis inhibits potassium secretion (via stimulated of K/H+ exchanger)

Question 35

metabolic acidosis is buffered by: —- while respiratory acidosis is buffered by:

Answer 35

metabolic&raquo_space; respiratory (exhale C02)

respiratory&raquo_space; proteins (kidneys days, long term)

Question 36

the anion gap in URINE gives a measure of:

Answer 36

NH4+. The UAG becomes neGUTive if the GUT is the culprit (diarrhea), but remains positive in renal tubular acidosis

Question 37

K depletion has what effect on acid/base balance?

Answer 37

K depletion&raquo_space; metabolic alkalosis. K leaves cell, H+ enters, cells become acidotic&raquo_space; acid secretion in kidney. K+ and NH4+ also compete on transporters so in order for K+ to be increasingly reabsorbed, NH4+ remains in tubular fluid.

Question 38

Which diuretics are Ca sparing?

Answer 38

Thiazide: inhibit Na/Cl transporter in distal tubule. essentially, decreased positive charge inside cell allows Ca to be reabsorbed more readily (overly simplified).

Question 39

What is the relationship of acid/base balance to Ca2+?

Answer 39

Respiratory alkalosis results in symptoms of
hypocalcemia bc H+ and Ca2+ compete for binding to calbindin. Less acid means more Ca2+ bound, less active Ca available.

Question 40

Effect of acidosis on bone:

Answer 40

bone dissolution to buffer acid w/Ca salts.

Question 41

Ca/Mg sensing receptors are where:

Answer 41

TAL and collecting ducts

Question 42

Low urine osmolality combined with an increase in plasma osmolality suggests:

Answer 42

lack of ADH action

Question 43

The main regulator of plasma sodium concentration is:

Answer 43

ADH