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47 Cards in this Set
- Front
- Back
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What is the rule for ion coupling with sodium?
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Same- Cl, water
Opposite- K |
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What is the rule for ion coupling with HCO3-?
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Opposite- Cl- and H+
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What is the rule for ion coupling with Ca?
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Same- Na in the proximal tubule
Opposite- Mg2+, HPO3-, and Na+ in the early distal tubule |
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What is the rule for ion coupling with Na?
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Same- Glucose, AA, HCO3-, HPO3-, Cl-
Opposite- H+, K+ |
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What is the main effect of Angiotensin II on the nephron?
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It increases sodium and water reabsorption and is the most potent hormone to do this?
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By which 2 pathways does it do this?
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1. Constricts efferent arterioles to increase GFR and filtration fraction and decrease peritubular hydrostatic and oncotic pressure ---> increased proximal reabsorption
2. Stimulates Na transporters in proximal tubule directly |
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Why are these Na/water effects mainly in the proximal tubule?
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This is where most of reabsorption (65%) happens so this is the most effective site to act on.
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What is Angiotensin II's effect on acid/base balance?
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Increases the Na/HCO3- basolateral cotransport and the Na/H+ apical antiport at the basolateral membrane.
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Why are electric potentials so important in the kidney?
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You want to reabsorb ions that will balance out to be neutral.
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What quality must be present in a membrane to drive water movement through osmosis?
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The membrane must be more permeable to water than it is to the solutes.
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Is most reabsorption in the kidney hypo, hyper, or iso osmotic? Why?
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Isosmotic. Think about it. You filter through 180L/day, but want the blood to stay at the same osmolality.
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What is osmolality?
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mOsm/kg
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What is osmolarity?
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mOsm/L
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Which one do we measure and which one do we want? Why?
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We measure osmolarity, but want osmolality because it isn't influenced by nonideal solutes.
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Does osmolarity overestimate or underestimate osmolality? Why?
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It over estimates it because the volume shrinks when you add ionic solutes to it, making it seem like there is less solvent.
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What is the least cleared substance in the kidney? (most reabsorbed)
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Bicarbonate
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If GFR suddenly increases, what happens to reabsorption at the proximal tubule?
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It will increase. There will be proportionately less hydrostatic pressure and more oncotic pressure in the capillaries.
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Does the same compensation happen when you have volume contraction and expansion? Why?
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No because then you are working with a larger or smaller pool of plasma overall instead of just redistributing it.
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Which components of the starling forces are most powerful in tubular resorption?
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Oncotic and hydrostatic pressure of the peritubular capillaries. (mostly oncotic)
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Describe the starling forces in volume contraction.
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Oncotic pressure of capillary goes up because you have a larger hematocrit.
Hydrostatic pressure goes down because there is less overall blood. |
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Where are all the basolateral ion transporters in the proximal tubule?
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In the lateral intercellular space between cells
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Why are they there?
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because they can create a huge osmotic gradient through which solvent drag can act.
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Why do carbonic anhydrase inhibitors cause kidney stones?
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It makes the urine more alkaline, which tend to precipitate Calcium Phosphate stones.
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Which are the only diuretics that do not cause K wasting?
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Triamterene, Spironolactone, and Amiloride/Benzamide.
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Why don't these diuretics cause K wastting?
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Becasue they act either at or after the principle cells so that the increased fluid volume passing by the principle cells don't drag large amounts of K out.
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What will K wasting diuretics also waste? Why?
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They will waste H+ from intercalated cells in much the same fashion.
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What does the macula densa sense and what does it do in response?
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It senses low Na in the distal tubule and send prostaglandin signals to the afferent arteriole to release renin.
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Why does low Na in the distal tubule mean low RBF?
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Since you have decreased RBF, you have less hydrostatic pressure in the peritubular capillaries and thus more Na and water resorption there. This means less of both in the distal tubule.
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What is the difference between glycation and glycosylation?
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glycation doesn't need an enzyme.
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What are the two big ways in which serum K levels are managed?
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Between cells and blood and then renal regulation.
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How does high blood osmolality affect intra/extra cellular K exchange?
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water rushes out of the cell and brings K along it. (remember this too because the osmogenic Na/K pumps are not pumping it in also)
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How does insulin affect K?
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It pulls it into cells along with glucose.
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Why does DKA not really affect K like other types of acidosis would?
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Because the H+ enters the cells along with it's keto anion, it doesn't need to go through the H/K exchanger.
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Why do loop and thiazide diuretic make more dilute K in the late distal tubule?
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Because those areas don't really resorb K (thick ascending a little, but still leaves a lot and ED not at all) so amount of K stays the same and the drugs only change the water/Na amount.
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Why does spironolactone and amil/triam need to be used with a loop or thiazide diuretic?
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To prevent hyperkalemia.
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What kind of luminal charge drive K excretion?
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If there are a lot of anion in the lumen, it WILL drive K secretion by attracting those cations in the principal cells.
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What happens to K in the proximal and ascending tubules vs the late distal and collecting?
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In the first part of the nephron, K is reabsorbed. In the later part, it can be either reabsorbed or secreted based on demand.
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What percentage of K is reabsorbed in the proximal vs thick ascending?
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Almost the same as sodium. 67% in proximal and 20% in thick ascending.
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How is K secreted in the later part of the nephron?
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By a H/K ATPase
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What are the two ways in which H+ is secreted in the a-intercalated cells on the apical membrane?
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An aldosterone stimulated H+ ATPase
A K/H+ antiport ATPase |
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How widely can renal excretion of K+ vary?
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Anywhere from 1% to 110% of the filtered load depending on K intake, aldosterone, and acid/base balance
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What will B andrenergic drugs do to K balance? Why?
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They stimulate the Na/K pumps so they will move K into cells.
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What is the definition of being in potassium (or any ion) balance?
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How much you take in and how much you excrete.
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Can you have hyperkalemia and be in negative K balance? HOW?
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YES! You can have more movement of K from cells to blood than renal K secretion, but still be secreting more than you eat.
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What units are ions usually measured in?
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mEq/L
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What units are proteins usually measured in? Why
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mOsm/L because they are actually able to exert osmotic pressure
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How does diarrhea contribute to metabolic acidosis?
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You don't have enough time in the intestines to reabsorb the HCO3- secreted by the pancreas.
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