Renal Physiology Module 13.3 Questions Spring 2010

Front 1

The ____ efficiently reabsorbs much of the original filtrate.

Back 1

Renal tubule.

Front 2

What substances are reabsorbed in the the Proximal Tubule? How much is absorbed?

Back 2

Glucose. Approx 100%

Sodium. Approx 60%

Water. Approx 60%

Front 3

What substances are reabsorbed in the Loop of Henle? How much is reabosrbed?

Back 3

Sodium, Approx 30%

Water, Approx 20%

Front 4

What substances are reabsorbed in the Distal tubule? How much is reabsorbed?

Back 4

Sodium, approx 10%

Water, approx 10%

Front 5

What substances are reaborbed in the collecting duct? How much is reabsorbed?

Back 5

Sodium, approx 10%

Water, approx 10%

Front 6

How much of filtered water is reabosrbed by the kidneys? Sodium? Potassium?

Back 6

Water: 99.2%

Sodium: 99.4%

Potassium 86.1%

Front 7

How much of filtered Calcium is reasborbed by the kidneys? Bicarb? Chloride?

Back 7

Calcium: 98.2%

Bicarb: 99.9%

Chloride: 99.2%

Front 8

How much of filtered glucose is reabsorbed by the kidneys? Urea?

Back 8

Glucose: 100.0%

Urea: 50.0%

Front 9

True or False:

All of the following are NORMALLY found in urine: Glucose, Amino acids, Protein, Blood, Ketones, Leukocytes, Bilirubin.

Back 9

False!

None of these should be found in normal urine! They should all be reabosrbed or not filtered through.

Front 10

What is the fractional excretion rate? (Fractional clearance?)

Back 10

The percentage of a filtered substance that is ultimately excreted in the urine.

Front 11

How do you determine what the fractional excretion rate is? Why do you use it?

Back 11

FEx= [Ux]/[Px] ? [Ucreatinine]/[Pcreatinine] x 100%

FEx = percent of filtered substance x that is excreted.

Ux= concentration of substance X in urine.

Px= concentration of substance X in plasma.

Front 12

What percentage of most solutes are reabsorbed in the Proximal Tubule?

Back 12

About 60%

Front 13

What are the two MAIN mechanisms of solute transport in the kidney?

Back 13

Passive:

(Spontaneous, down an electrochemical gradient--Diffusion, Facilitated diffusion through channels, uniports, coupled transport and solvent drag)

Active.

(Against an electrochemical gradient, requires energy and includes endocytosis).

Front 14

What pump drives most of the transport of solutes in the Proximal Tubule?

Back 14

Active transport via the Na+/K+ ATPase pump.

Located on the basolateral plasma membrane.

Front 15

What are some substances that are taken up from the Proximal Tubule fluid via secondary active transport caused by the Na/K ATPase pump?

Back 15

Glucose, Amino Acids, Phosphate, Lactate.

Front 16

What are two routes that solutes in the proximal tubule can take during reabosrption.

Back 16

Transcellular pathway.

Paracellular pathway.

Front 17

Describe transcellular transport.

Back 17

Substances are taken up across the epithelial cells most often via a carrier-mediate process.

Na+ reabsorption by the proximal tubule is an example of this.

Front 18

Describe paracellular transport.

Back 18

Substances move from the tubular lumen across the zonula occludens and into the lateral intercellular spaces.

Calcium, Magnesium, Chloride and Potassium are all reabsorbed by the proximal tubule via the paracellular route.

Front 19

What is one paracellular way Na+ can get reabosrbed? One transcellular way?

Back 19

Paracellular: Cl- moves into the lateral intercellular space and creates a positive charge in tubular fluid relative to blood-promotes Na+ diffusion across tight junctions.

Transcellular: NaCl enters cell by parallel operation of Na+/H+ and Cl-/Base- antiporters.

Front 20

What drives the reabsorption of water?

Back 20

Solute transport in the proximal tubule.

Water follows solutes.

Front 21

Dilation of the efferent arteriole increases the hydrostatic pressure in the peritubular capillaries (Pc), whereas constriction of the efferent arteriole decreases Pc. An increases in Pc ______ (inhibits/allows) solute and water reabsorption by increasing the backleak of NaCl and water across the tight junctions.

Back 21

Inhibits.

Front 22

The oncotic pressure in the peritubular capillaries is determined in part by the rate of filtration of the glomerular ultrafiltrate. If plasma flow in the afferent arteriole is constant and less ultrafiltrate is formed (GFR decreases), then the plasma proteins become ____ (less/more) concentrated in the plasma that enters the efferent arteriole and peritubular capillaries and IIc decreases.

Back 22

Less.

Front 23

What is peritubular oncotic pressure directly related to?

Back 23

Filtration fraction.

(FF= GFR/ RPF)

A decrease in FF decreases IIc. This increases backleak of NaCl and water from intercellular space into tubular lumen. Increasing FF has the opposite effect.

Front 24

How are filtered peptides and low molecular weight proteins reabsorbed?

Back 24

Via endocytosis.

Front 25

What are some organic anions secreted by the proximal tubule?

Back 25

Endogenous anions: cAMP, Bile salts, Hippurates, Oxalate, Prostaglandins, Urate.

Drugs: Acetazolamide, Chlorothiazide, Furosemide, Penicillin, Probenecid, Salicylate (Aspirin), Hydrochlorothiazide, Bumetanide

Front 26

What are some organic cations secreted by the proximal tubule?

Back 26

Endogenous cations: Creatinine, Dopamine, Epinephrine, Norepinephrine.

Drugs: Atropine, Isoproterenol, Cimetidine, Morphine, Quinine, Amiloride, Procainamide

Front 27

What are some practical applications of knowing how tubular secretion works, and what is secreted?

Back 27

Tubular secretion provides a way of urine testing for hormones and foreign substances as a reflection of blood levels that may only be transiently elevated.

To determine which antibiotics can reach high concentrations in the urine for more effective UTI treatment.

Secretion of diuretics enhances delivery of these drugs to their site of action downstream.

Tubular secretion of drugs determines their excretion rate and affects the dosage of renally excreted drugs, which is important if renal function is compromised.

Front 28

The _____ segments reabsorb salts and dilutes the tubule fluid.

Back 28

Distal tubules.

Front 29

What do the distal tubule segments include?

Back 29

TALH (Thick Ascending limb of Henle's Loop)

DCT (Distal Convoluted Tubule?)

Front 30

The Thick ascending limb of Henle's loop reabsorbs 20% of these filtered substances ___ and 80% of this one ___.

Back 30

20%: Na+, Cl-, Ka+, Ca++

80%: Mg++

The key element in solute reabsorbtion is the Na/K ATPase system.

Front 31

True or False:

The Thick ascending limb of Henle's Loop and the Distal Convoluted Tubule are IMPERMEABLE to water so while salt is reabsorbed, water is not.

Back 31

True!

This is why these are the diluting segments!

Front 32

What are the two main cell types throughout most of the Collecting Duct system?

Back 32

Principal cells. (NaCl reabsorption and K+ secretion)

Intercalated cells. (H+ secretion/ HCO3- reabsorption. Important in regulating acid-base).

Front 33

Name three substances that promote uptake of K+ into cells.

Back 33

Epinephrine.

Insulin.

ADS (Aldosterone)

Front 34

What are some pathophysiologic problems that upset K+ concentrations from normal?

Back 34

Acid-base balance.

Plasma osmolality.

Cell lysis.

Exercise.

Front 35

Where in the kidney is the main control of K+ balance?

Back 35

Distal Tubule and Collecting Ducts

(This is where K+ can be both secreted and reabsorbed).

Front 36

True or False:

In the PT, there is an ability to regulate the excretion of electrolytes (Na+, K+ and Ca++) and water in order to maintain homeostasis, while in the DT and CD solutes and water are generally reabsorbed regardless of the animal's overall needs.

Back 36

False!

It's actually the opposite...

PT= solutes and water reabsorbed regardless of overall needs.

DT/CD= regulates rate of excretion of electrolytes and water in order to maintain homeostasis in the body.

Front 37

ADS (Aldosterone) acts on the _____ to enhance Na+ reabsorption.

Back 37

Principal cells.

Front 38

What stimulates the release of ADS? Aldosterone.

Back 38

The Renin/Angiotensin system, and Hyperkalemia.

Front 39

What are three physiologic regulators of K+ balance?

Back 39

Plasma K+ concentrations.

Aldosterone.

ADH/Vasopressin.

Front 40

An increase in Sodium concentrations in the tubular fluid ____ secretion, whereas a fall ____ secretion.

Back 40

Increase Na+ stimulates secretion.

Decrease Na+ decreases secretion.

Front 41

What are three things that regulate Ca2+ reabsorption in the Distal nephron and connecting segments?

Back 41

Parathyroid hormone (PTH)

Vitamin D

Calitonin.

Front 42

Normally, how much of filtered calcium is reabsorbed by the kidney?

Back 42

99%

Front 43

In the proximal tubule, Ca++ is reabsorbed by ____ and ____ pathways.

IN the DT and CD it is reabsorbed entirely by ____ transport.

Back 43

PT: Transcellular and Paracellular pathways.

DT/CD: Active transport due to large electrochemical gradient.

Front 44

Of the following: PTH, Calcitonin, Calcitriol, which has the most powerful control on Ca++ excretion??

Back 44

PTH (Parathyroid Hormone)


It actually acts to decrease excretion and increase reabsorption in response to hypocalcemia.

Front 45

Vitamin D ____ Ca++ excretion, and calcitonin ___ Ca++ excretion.

Back 45

Both decrease excretion as a response to hypocalcemia.

Front 46

Will acidosis increase or decrease calcium excretion?

Back 46

It increases calcium excretion.

The mechanism is unknown.

Front 47

What factors increase excretion of PO4?

Back 47

Increase PTH

Pi loading

ECV expansion

Acidosis

Glucocorticoids

Front 48

What factors decrease excretion of PO4?

Back 48

Decrease PTH

Pi depletion

ECV contraction

Alkalosis

Growth hormone.

Front 49

Where do factors that affect the excretion of PO4 work in the kidney?

Back 49

On the proximal tubule.

PTH has the greatest effect on this.