Tubular Transport of NaCl and Water

Question 1

Carnivore urine is more _________ than herbivore urine.

Answer 1

acidic

Question 2

Normal GFR is ___________.

Answer 2

125 ml/min

Question 3

What four parts of homeostasis does the kidney control?

Answer 3

pH
Electrolytes
Osmolarity
Fluid volume

Question 4

The tubules are lined with polarized cells. Which side is the apical surface facing?

Answer 4

The lumen

Question 5

Differentiate transcellular and paracellular transport.

Answer 5

Transcellular means passing through the cell–that is, through both the apical and basolateral membranes–and paracellular means passing between cells.

Question 6

The kidney is second only to the ________ in terms of oxygen needed per gram of tissue.

Answer 6

heart

Question 7

Which side of the tubular epithelium is the Na/K pump on?

Answer 7

The basolateral

Question 8

The sodium-potassium pump drives the gradient into the cells, which pulls ____________ along co-transporters.

Answer 8

chloride ions, glucose, and amino acids

Question 9

In what section of the tubule are glucose and amino acids resorbed?

Answer 9

100% in the proximal convoluted tubule for both

Question 10

The proximal convoluted tubule is responsible for ____________.

Answer 10

bulk resorption of water, ions, and macromolecules

Question 11

What acid-base functions take place in the proximal convoluted tubule?

Answer 11

H+ secretion and HCO3- absorption

Question 12

The ____________ is impermeable to water.

Answer 12

thick ascending loop of Henle

Question 13

The thick ascending loop of Henle ________ the urine.

Answer 13

dilutes, by absorbing Na, K, and Cl in a lumen that is impermeable to water; also, Mg and Ca get pulled along in paracellular transport

Question 14

Where do thiazides work?

Answer 14

The distal convoluted tubule

Question 15

In what section of the tubule are magnesium and calcium reabsorbed?

Answer 15

The distal convoluted tubule and the thick ascending limb

Question 16

What force drives re-entry of ions into the peritubular capillaries?

Answer 16

Oncotic pressure of the interstitial area (where the tubules send material) drives ions and fluid into the capillaries.

Question 17

Why is the peritubular capillary oncotic pressure so high?

Answer 17

Because the large proteins and cells remain unfiltered, so the blood is relatively concentrated

Question 18

How much sodium is filtered and reabsorbed by the kidneys each day?

Answer 18

1,500 g

Question 19

What three properties does the collecting duct fine tune?

Answer 19

Potassium
Water
Acid/base balance

Question 20

Organic anions are secreted in the ____________.

Answer 20

proximal tubule

Question 21

The collecting duct has two types of cells. What are they and what do they do?

Answer 21

Principal cells: secrete K and reabsorb Na; fine tune water

Intercalated cells: acid/base balance

Question 22

What cells does vasopressin act on?

Answer 22

Principal

Question 23

What does vasopressin do?

Answer 23

It stimulates the release of aquaporins in principal cells of the collecting duct, thereby inducing reabsorption of water.

Question 24

Regardless of filtered load, the proximal tubule still absorbs ___________.

Answer 24

65% of the NaCl and water

Question 25

Macula densa cells are part of the ____________.

Answer 25

ascending limb of the loop of Henle

Question 26

The macula densa cells secrete paracrine signals in response to __________.

Answer 26

changes in distal-tubule flow; with decreased NaCl they stimulate renin release (from JGA) that induces efferent-arteriole vasoonstriction