Chapter 20

Question 1

Explain how the countercurrent multiplier in the loop of Henle is the key to the regulation of urine concentration.

Answer 1

• Transfers solutes by active transport (ascending limb) into the medulla
• Results in greater ECF osmolarities

Question 2

What does the vasa recta do in the renal countercurrent multiplier?

Answer 2

removes water

Question 3

what does the osmolarity of urine represent?

Answer 3

how much water is excreted in the urine

Question 4

what does low osmolarity represent?

Answer 4

high water

Question 5

what does high osmolarity represent?

Answer 5

low water

Question 6

What does the medullary interstitial osmolarity allow?

Answer 6

allows urine to be concentrated

Question 7

Fluid in descending loop of Henle _________________ to the medulla.

Answer 7

loses water by osmosis

Question 8

Cells in thick portion of the ascending limb of the loop are impermeable to water and ______________________.

Answer 8

actively transport Na+ out of the lumen into the medulla

Question 9

Fluid leaving loop of Henle is _____ dilute than fluid entering.

Answer 9

more

Question 10

Describe what happens in the distal nephron.

Answer 10

• water permeability is under control of hormones
• Permeable to water, filtrate becomes concentrated

Question 11

What does the collecting duct do?

Answer 11

can reabsorb additional solute, filtrate can become even more dilute

Question 12

Map in detail the reflex pathway through which vasopressin (aka ADH) controls water reabsorption in the kidney.

Answer 12

look on whiteboard

Question 13

Diagram the cellular mechanism of action of vasopressin on principal cells.

Question 14

What does vasopressin cause?

Answer 14

insertion of water pores into the apical membrane –> makes collecting duct epithelium permeable to water

Question 15

Map the homeostatic responses to salt ingestion.

Answer 15

look at whiteboard

Question 16

Diagram the cellular mechanism of aldosterone action at principal cells.

Answer 16

look at whiteboard

Question 17

Map the renin-angiotensin-aldosterone system (RAAS), including all the responses initiated by ANG II and aldosterone.

Answer 17

look at whiteboard

Question 18

Describe the release of natriuretic peptides and their effects on sodium and water reabsorption.

Answer 18

whiteboard

Question 19

Diagram the appropriate homeostatic compensations for different combinations of volume and osmolarity disturbances.

Answer 19

whiteboard

Question 20

Compare and contrast the three mechanisms by which the body copes with minute-to-minute changes in pH.

Answer 20

1) Buffers –> Moderate changes in pH by combining with or releasing H+
- include proteins, phosphate ions, and
HCO3-
2) Lungs –> Ventilation can compensate for pH disturbances
3) Kidneys –> buffers urine
- Proximal tubule secretes H+ and
reabsorbs HCO3-
- Distal nephron can secrete or reabsorb
H+ and HCO3- to regulate pH of
extracellular fluid

Question 21

Diagram the reflex pathways and cellular mechanisms involved in respiratory compensation of pH changes.

Answer 21

whiteboard

Question 22

Diagram the mechanisms by which the kidneys compensate for pH changes.

Answer 22

whiteboard

Question 23

what is the normal pH of plasma?

Answer 23

7.38 - 7.42

Question 24

Describe acidosis.

Answer 24

Neurons become less excitable –> CNS depression

Question 25

Describe alkalosis.

Answer 25

Neurons become hyperexcitable –> severe can lead to muscle tetanus

Question 26

Describe a respiratory acidosis disturbance.

Answer 26

Hypoventilation –> PCO2 increases –> pH decreases

Question 27

Describe a respiratory alkalosis disturbance.

Answer 27

Hypoventilation –> PCO2 decreases –> pH increases

Question 28

Describe a metabolic acidosis disturbance.

Answer 28

Dietary and metabolic input of H+ exceeds excretion –> pH decreases

Question 29

Describe a metabolic alkalosis disturbance.

Answer 29

Loss of H+ through excessive vomiting or excessive ingestion of bicarbonate-containing antacids –> pH increases