Chapter 3 - GFR and RBF

Question 1

In general, molecules with a radius smaller than ___ Å are filtered freely, molecules larger than ____ Å are not filtered, and molecules between __ - ___ Å are filtered to various degrees

Answer 1

In general, molecules with a radius smaller than 20 Å are filtered freely, molecules larger than 42 Å are not filtered, and molecules between 20 and 42 Å are filtered to various degrees

Question 2

The hydrostatic pressure in the glomerular capillary (PGC) is oriented to promote the movement of fluid from the glomerular capillary into Bowman’s space. _________ is the only force that favors filtration. The hydrostatic pressure in Bowman’s space (PBS) and the oncotic pressure in the glomerular capillary (πGC) _____ (favor/oppose) filtration.

Answer 2

The hydrostatic pressure in the glomerular capillary (PGC) is oriented to promote the movement of fluid from the glomerular capillary into Bowman’s space. Because the reflection coefficient (σ) for proteins across the glomerular capillary is essentially 1, the glomerular ultrafiltrate has a very low concentration of proteins, and the oncotic pressure in Bowman’s space (πBS) is near zero. Therefore PGC is the only force that favors filtration. The hydrostatic pressure in Bowman’s space (PBS) and the oncotic pressure in the glomerular capillary (πGC) oppose filtration.

Question 3

What is the equation for RBF?

Answer 3

RBF is equal to the pressure difference between the renal artery and the renal vein divided by the renal vascular resistance

Question 4

What are the major resistance vessels in the kidneys that determine renal vascular resistance?

Answer 4

interlobular artery
afferent arteriole
efferent arteriole

Question 5

What are the 2 mechanisms that are responsible for the autoregulation of RBF and GFR

Answer 5

One mechanism that responds to changes in arterial pressure and another that responds to changes in the sodium chloride (NaCl) concentration of tubular fluid. Both mechanisms regulate the tone of the afferent arteriole.

Question 6

The tubuloglomerular feedback involves what two ions?

Answer 6

The mechanism responsible for the autoregulation of GFR and RBF is the NaCl concentration–dependent mechanism known as tubuloglomerular feedback. This mechanism involves a feedback loop in which the NaCl concentration of tubular fluid is sensed by the macula densa of the juxtaglomerular apparatus

Question 7

_____ and _________ cause vasoconstriction by binding to α1-adrenoceptors, which are located mainly on the afferent arterioles.

Answer 7

Norepinephrine and epinephrine cause vasoconstriction by binding to α1-adrenoceptors, which are located mainly on the afferent arterioles.

Question 8

Activation of α1-adrenoceptors ______ (decreases/increases) GFR and RBF.

Answer 8

Activation of α1-adrenoceptors decreases GFR and RBF.

Question 9

Angiotensin II is produced systemically and locally within the kidneys. It ______ (dilates/constricts) the afferent and efferent arterioles and _________ (decreases/increases) the RBF and GFR

Answer 9

Angiotensin II is produced systemically and locally within the kidneys. It constricts the afferent and efferent arterioles and decreases the RBF and GFR

Question 10

This hormone does NOT play a major role in regulating RBF in healthy individuals. However, during pathophysiologic conditions such as hemorrhage, this hormone is produced locally within the kidneys, and they increase RBF without changing the GFR.

Answer 10

Prostaglandins

Question 11

Increased production of NO causes ______ (dilation/constriction) of the afferent and efferent arterioles in the kidneys. Whereas increased levels of NO ______ (increase/decrease) the total peripheral resistance, inhibition of NO production _____ (increases/decreases) the total peripheral resistance.

Answer 11

Increased production of NO causes dilation of the afferent and efferent arterioles in the kidneys. Whereas increased levels of NO decrease the total peripheral resistance, inhibition of NO production increases the total peripheral resistance.

Question 12

__________ is a potent vasoconstrictor secreted by endothelial cells of the renal vessels, mesangial cells, and tubular epithelial cells in response to angiotensin II, bradykinin, epinephrine, and endothelial shear stress.

Answer 12

Endothelin

Question 13

Endothelin causes profound _____ (vasodilation/vasoconstriction) of the afferent and efferent arterioles and ______ (increases/decreases) the GFR and RBF.

Answer 13

Endothelin causes profound vasoconstriction of the afferent and efferent arterioles and decreases the GFR and RBF.

Question 14

Kallikrein is a proteolytic enzyme produced in the kidneys. Kallikrein cleaves circulating kininogen to ________, which is a vasodilator that acts by stimulating the release of NO and prostaglandins. It also increases the GFR and RBF.

Answer 14

Kallikrein is a proteolytic enzyme produced in the kidneys. Kallikrein cleaves circulating kininogen to bradykinin, which is a vasodilator that acts by stimulating the release of NO and prostaglandins. Bradykinin increases the GFR and RBF.

Question 15

Adenosine is produced within the kidneys and causes ________ (vasoconstriction) of the afferent arteriole, thereby _________ (increasing/decreasing) the GFR and RBF.

Answer 15

Adenosine is produced within the kidneys and causes vasoconstriction of the afferent arteriole, thereby reducing the GFR and RBF.

Question 16

Both ANP and BNP ____ (constrict/dilate) the afferent arteriole and (constrict/dilate) the efferent arteriole. Therefore ANP and BNP produce a modest _____ (decrease/increase) in the GFR with little change in RBF.

Answer 16

Both ANP and BNP dilate the afferent arteriole and constrict the efferent arteriole. Therefore ANP and BNP produce a modest increase in the GFR with little change in RBF.

Question 17

Administration of therapeutic doses of glucocorticoids _____ (increases/decreases) the GFR and RBF.

Answer 17

Administration of therapeutic doses of glucocorticoids increases the GFR and RBF.

Question 18

Histamine ______ (increases/decreases) the resistance of the afferent and efferent arterioles and thereby __________ (increases/decrease) RBF without elevating the GFR.

Answer 18

Histamine decreases the resistance of the afferent and efferent arterioles and thereby increases RBF without elevating the GFR.

Question 19

Dopamine is a vasodilator that is made by what part of the kidney?

Answer 19

The proximal tubule

Question 20

Name the five factors that stimulate the production of NO (which increases the GFR and RBF)

Answer 20

Shear stress, acetylcholine, histamine, bradykinin, and ATP stimulate the production of NO, which increases the GFR and RBF.

Question 21

Finding which of the following substances in the urine would indicate damage to the glomerular ultrafiltration barrier? and why?

• RBC
• Glucose
• Protein
• Sodium

Answer 21

Normally, the urine contains essentially no protein. The glomerulus prevents the filtration of plasma proteins. However, when the glomerulus is damaged, large amounts of plasma proteins are filtered. If the amount filtered overwhelms the reabsorptive capacity of the proximal tubule, protein appears in the urine (proteinuria).

Question 22

Explain why the use of NSAIDs does not affect GFR or RBF in patients with normal renal function and why administration of NSAIDs is not recommended for patients with severe reductions in GFR and RBF.

Answer 22

Normally, renal prostaglandin production is low, and NSAIDs do not have an appreciable effect on prostaglandin production. However, during reductions in GFR and RBF, elevated prostaglandin levels cause vasodilation of the afferent and efferent arterioles. This effect prevents excessive decreases in RBF and GFR. Administration of NSAIDs to patients with low GFR and RBF inhibits prostaglandin production and further reduces GFR and RBF.

Question 23

What are the 3 basic processes of urine formation? (RL)

Answer 23

1. Ultrafiltration of plasma by glomerulus
2. Reabsorption of water and solutes from the ultrafiltrate
3. Secretion of select solutes into the tubular fluid

Question 24

Define Passive Transport (Diffusion). (RL)

Answer 24

Passive transport of uncharged solutes occurs form an are of higher concentration to one of lower concentration (down chemical gradient) or for ions affected by electrical potential difference (down electrical gradient)

Question 25

Define Facilitated Diffusion (RL)

Answer 25

Facilitated diffusion or transport depends on the interaction of solute with a specific protein in the membrane that facilitates its movement across the membrane.

Question 26

Define Active transport (RL)

Answer 26

Active transport coupled directly to energy derived from metabolic processes (consumes ATP) - usually takes place from an area of lower concentration to an area of higher concentration.

Question 27

Endocytosis is a form of active transport, because it require ATP. True or False? (RL)

Answer 27

True

Question 28

Reabsorption of water and NaCl can only occur through cells (transcellular pathway) not between cells (paracellular pathway) True or False? (RL)

Answer 28

False.

Question 29

Define solute drag and list 2 solutes that are frequently involved (RL)

Answer 29

Solute drag is when solutes dissolved in water are also carried along with the water during osmosis. 2 solutes are K and Ca

Question 30

Reabsorption of HCO3 and secretion of H+ is the major function of the nephron (RL)

Answer 30

False. Reabsorption of water and NaCl is the major function of nephron.

Question 31

In the proximal tubule, what % of filtered Na is reabsorbed? What % of filtered water is reabsorbed? (RL)

Answer 31

67% ; 67%

Question 32

In the Loop of Henle, what % of filtered Na is reabsorbed? What % of filtered water is reabsorbed? (RL)

Answer 32

25% ; 15%

Question 33

In the Distal Tubule, what % of filtered Na is reabsorbed? What % of filtered water is reabsorbed? (RL)

Answer 33

~5% ; 0

Question 34

In the late distal tubule and collecting duct, what % of filtered Na is reabsorbed? What % of filtered water is reabsorbed? (RL)

Answer 34

~3% ; ~8-17%

Question 35

What is the key pump in the proximal tubule (the pump that everything is linked to in one way or another) and where on the membrane is it located? (RL)

Answer 35

Na-K-ATPase pump on the basolateral membrane