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Question 1

Na+ antiporters reabsorb Na+ and secrete H+

• PCT cells produce the H+ & release bicarbonate ion to the peritubular capillaries
• important buffering system

Answer 1

Reabsorption of Bicarbonate, Na+ & H+ Ions

Question 2

on test as fill in the blank

Reabsorption of Bicarbonate, Na+ & H+ Ions

Answer 2

For every H+ secreted into the tubular fluid, one filtered bicarbonate eventually returns to the blood

Question 3

• Electrochemical gradients produced by symporters & antiporters causes passive reabsorption of other solutes
• Cl-, K+, Ca+2, Mg+2 and urea passively diffuse into the peritubular capillaries
• Promotes osmosis in PCT (especially permeable due to aquaporin-1 channels

Answer 3

Passive Reabsorption in the 2nd Half of PCT

Question 4

secretion=

Answer 4

blood to tubule

Question 5

reabsorption=

Answer 5

tubule to blood

Question 6

Ammonia (NH3) is a poisonous waste product of protein deamination in the liver
–most is converted to urea which is less toxic

Answer 6

secretion of NH3 and NH4 in PCT

Question 7

Both ammonia & urea are filtered at the

–PCT cells deaminate glutamine in a process that generates both NH3 and new bicarbonate ion.

Answer 7

glomerus and secreted in the PCT

Question 8

Bicarbonate diffuses into the bloodstream during __ where more bicarbonate is generated

Answer 8

acidosis

Question 9

• -Tubular fluid

- -Sets the stage for independent regulation of both volume & osmolarity of body fluids

Answer 9

Reabsorption in the Loop of Henle

Question 10

–PCT reabsorbed 65% of the filtered water so chemical composition of tubular fluid in the loop of Henle is quite different from plasma

–since many nutrients were reabsorbed as well, osmolarity of tubular fluid is close to that of blood

Answer 10

tubular fluid in Reabsorption in the Loop of Henle

Question 11

–Thick limb of loop of Henle has Na+ K- Cl- symporters that reabsorb these ions

–K+ leaks through K+ channels back into the tubular fluid leaving the interstitial fluid and blood with a negative charge

–Cations passively move to the vasa recta

Answer 11

symporters in the loop of henle

Question 12

–Removal of Na+ and Cl- continues in the DCT by means of Na+ Cl- symporters

–Na+ and Cl- then reabsorbed into peritubular capillaries

Answer 12

Reabsorption in the DCT

Question 13

major site where parathyroid hormone stimulates reabsorption of Ca+2
—not very permeable to water so it is not reabsorbed with little accompanying water

Answer 13

DCT

Question 14

–By end of DCT, 95% of solutes & water have been reabsorbed and returned to the bloodstream

–Cells in the collecting duct make the final adjustments

Answer 14

Reabsorption & Secretion in the Collecting Duct

Question 15

two types of cells in the collecting duct make the final adjustments

Answer 15

principal cells

intercalated cells

Question 16

reabsorb Na+ and secrete K+

Answer 16

principal cells

Question 17

reabsorb K+ & bicarbonate ions and secrete H+

Answer 17

intercalated cells

Question 18

actions of principal cells

**micro essay?

Answer 18

1. Na+ enters principal cellsthrough leakage channels
2. Na+ pumps keep theconcentration of Na+ inthe cytosol low
3. Cells secrete variableamounts of K+, to adjustfor dietary changes in K+intake
   - -down concentration gradient due to Na+/K+ pump
4. Aldosterone increases Na+ and water reabsorption & K+ secretion by principal cells by stimulating the synthesis of new pumps and channels

Question 19

Secretion of H+ and Absorption of Bicarbonate by Intercalated Cells

actions of intercalated cells
**micro essay

Answer 19

1. Proton pumps (H+ATPases) secrete H+ into tubular fluid
   –can secrete against
   a concentration
   gradient so urine
   can be 1000 times
   more acidic than
   blood
2. Cl-/HCO3- antiporters move bicarbonate ions into the blood
   –intercalated cells
   help regulate pH of
   body fluids
3. Urine is buffered by HPO4 2- and ammonia, both of which combine irreversibly with H+ and are excreted