Renal - Pt 3 Nephron in Numbers

Question 1

What method is used to measure the GFR?

Answer 1

Orange dot - Inulin method.

Question 2

[] is a term that refers to the ability of the kidneys to clear a substance from the blood.

Answer 2

Clearance

Question 3

Orange dot- Inulin

• Freely []
• Not [] or []

Answer 3

• Freely filtered
• Not reabsorbed or secreted

Question 4

Renal clearance is [] a measurement of the concentration of a solute in the plasma or urine.

Answer 4

NOT

Question 5

What is the clearance of inulin calculation? What does each variable stand for?

Answer 5

C_inulin = U_inulin x V/ P_inulin

• C_inulin - Clearance of inulin (mL/min)
• U_inulin - Urine [inuline] (mg/mL)
• P_inulin - Plasma [inulin] (mg/mL)
• V - Urine flow rate (mL/min)

Question 6

What is the clearance calculation for Creatinine? What does each variable stand for?

Answer 6

C_Cr = U_Cr x V/ P_Cr

• C_Cr - Clearance of creatinine (mL/min)
• U_Cr - Urine [creatinine] (mg/mL)
• P_Cr - Plasma [creatinine] )mg/mL)
• V - Urine Flow rate (mL/min)

Question 7

• Creatinine in the urine is slightly [] due to secretion. This would lend to an [] of GFR
• Creatinine in the plasma is measured artifically [] due to modern techniques. This would lend to an [] of GFR

Answer 7

• Creatinine in the urine is slightly higher due to secretion. This would lend to an overestimation of GFR
• Creatinine in the plasma is measured artifically higher due to modern techniques. This would lend to an underestimation of GFR

Question 8

Blue dot - PAH

• Freely []
• Not []
• Fully [] in on e pass through peritubular capillaries in low [PAH]
• C_PAH = [] mL/min = []

Answer 8

• Freely filtered
• Not reabsorbed
• Fully secreted in one pass through peritubular capillaries in low [PAH]
• C_PAH = 625 mL/min = RPF

Question 9

Renal Plasma FLow of a patient can be found by calculating the clearance of a substance called []-[] acid (PAH)

Answer 9

Renal Plasma FLow of a patient can be found by calculating the clearance of a substance called para-aminohippuric acid (PAH)

Question 10

What are the 3 Filtration Fraction equations we learned?

Answer 10

FF = GFR/RPF

FF = C_inulin/C_PAH

FF = C_creatinine/C_PAH

Question 11

What is the equation for Renal Blood Flow?

Answer 11

RBF = C_PAH/1-HCT

• Normal HCT is .5

Question 12

What is the equation for Renal Plasma Flow? What does each variable stand for?

Answer 12

C_PAH = U_PAH x V / P_PAH

• C_PAH - Clearance of PAH (mL/min)
• U_PAH - Urine [PAH] (mg/mL
• P_PAH - Plasma [PAH] ( mg/mL)
• V - Urine flow rate (mL/min)

Question 13

T/F

Potassium, under normal conditions, experiences a net secretion.

Answer 13

TRUE!

Question 14

Even though Reabsorption and Secretion happen throughout the renal duct system…

1. Reabsorption happens mainly at the [] and []
2. Secretion happsn mainly at the [] and []

Answer 14

1. Reabsorption happens mainly at the PCT and TAL
2. Secretion happens mainly at the DCT and Collecitng Duct

Question 15

What are the 2 ways that solutes are reabsorbed in the PCT? What mechanisms are used in each method?

Answer 15

• Paracellular
  
  • Small molecules like Na, Cl move through tight junctions between cells via diffusion. High concentration to low concentration.
• Transcellular
  
  • Molecules move across tubular cells from potential urine to the blood via active transport mechanisms.

Question 16

Transcellular PCT Reabsorption:

1. [] Active transporters reside in the tubule apical in order to pull Na+ from the potential urine. These can be [] or [] transport mechanisms.
2. [] pumps reside on the basolateral surface of the tubule cells in order to keep the concentration gradient of Na+ inside the cells []

Answer 16

1. Secondary Active transporters reside in the apical side of the tubule, in order to pull Na+ from the potential urine. These can be symport or antiport transport mechanisms.
2. Na+/K+ pumps reside on the basolateral surface of the tubule cells in order to keep the concentration gradient of Na+ inside the cells low

Question 17

Early PCT Reabsorption: Apical side

1. You can find Na+/Glu [] transporters (or []) and Na+/H+ [] transporters
   
   1. These use the energy created by Na+ going down its concentration gradient to power the movement of Glu and H+ []their concentration gradients
2. We get the H+ ions form the hydration of Co₂ by the enzyme [] [] , which creates carbonic acid. This disassociates into [] and [].

Answer 17

1. Apical side - you can find Na+/Glu symport transporters (or SGLT) and Na+/H+ Antiport transporters
   
   1. These use the energy created by Na+ going down its concentration gradient to power the movement of Glu and H+ against their concentration gradients
2. We get the H+ ions form the hydration of Co₂ by the enzyme carbonic anhydrase, which creates carbonic acid. This disassociates into bicarbonate and H+

Question 18

Early PCT Reabsorption: Basolateral Side

1. [] diffusion allows [] (via GLUT transporters) and [] to move down their concentration gradients.
2. []/[] pumps keep the cellular concentration of Na+ low by pumping it out into the [] [].

Answer 18

1. Facilitated diffusion allows Glucose (via GLUT transporters) and Bicarbonate to move down their concentration gradients.
2. Na+/K+ pumps keep the cellular concentration of Na+ low by pumping it out into the interstitial space.

Question 19

In early PCT reabsorption, the [] ions are secreted into the [] fluid and the [] is reabsorbed across the [] membrane.

Answer 19

In early PCT reabsorption, the hydrogen ions are secreted into the tubular fluid and the bicarbonate is reabsorbed across the basolateral membrane.

Question 20

Late PCT Reabsorption: Apical Side

1. [] Shuttle
   
   1. Chloride - Anion [] system brings Cl- into the cell
   2. Anion-H+ [] down its concentration gradient into the cell
   3. Na+/H+ [] transporter brings [] into the cell and [] out of the cell.
      
      1. This allow H+ to bond to the anions in the [] fluid.
2. Chloride is kept at a []centration inside the cell because it must diffuse into the [] [] for reabsorption.

Answer 20

1. Anion Shuttle
   
   1. Chloride - Anion antiport system brings Cl- into the cell
   2. Anion-H+ diffuses down its concentration gradient into the cell
   3. Na+/H+ antiport transporter brings sodium into the cell and H+ out of the cell.
      
      1. This allow H+ to bond to the anions in the tubular fluid.
2. Chloride is kept at a high centration inside the cell because it must diffuse into the interstitial fluid for reabsorption.

Question 21

Late PCT Reabsorption: Basolateral Side

1. []/[] pumps keep tubular cell Na+ concentrations low by pumping Na+ into the i[] fluid
2. K+/Cl- [] transporters pulls K+ and Cl- into the [] fluid.

Answer 21

1. Na+/K+ pumps keep tubular cell Na+ concentrations low by pumping Na+ into the interstitial fluid
2. K+/Cl- symport transporters pulls K+ and Cl- into the intersitial fluid.

Question 22

The transport of sodium ions across the tubular wall facilitates the transport of [] ions and [].

Since these ions are reabsorbed in the same concentration found in the tubule, this is referred to as [] [].

Answer 22

Chloride ions and water

Isosmotic reabsorption.

Question 23

Glomerulotubular balance is a process by which an [] in filtration leads to an [] in the reabsorption….(to a point).

Answer 23

Increase; increase

Question 24

Glomerulotubular Balance:

• Increase FF —> [] in GFR —> [] in filtration of H₂O and solutes —> [] H₂O and solutes in Peritubular Capillaries —> [] BCOP in peritubular capillaries –> [] Reabsorption of H₂O and solutes into peritubular capillaries

Answer 24

Increase FF —> increase in GFR —> increase in filtration of H₂O and solutes —> decrease H₂O and solutes in Peritubular Capillaries —> increased BCOP in peritubular capillaries –> increased Reabsorption of H₂​O and solutes into peritubular capillaries