Lecture 18 - Renal Regulation Of [ion]

Question 1

The normal [K]ecf is _______.

A. 142 mEq/L ( 0.3mEq/L)
B. 4.2 mEq/L ( 0.3mEq/L)
C. 150 mEq/L
D. 5 mEq/L

Answer 1

B. 4.2 mEq/L ( 0.3mEq/L)

Question 2

ECF contains approximately what % of body K?

A. 1%
B. 5%
C. 25%
D. 79%

Answer 2

A. 1%

Question 3

An increase in ECF [K] of _____ may lead to the development of cardiac arrhythmia.

Answer 3

3-4 mEq/L

Question 4

Normal ICF [K] is _______.

A. 140 mEq/L ( 0.3mEq/L)
B. 4.2 mEq/L ( 0.3mEq/L)
C. 150 mEq/L
D. 5 mEq/L

Answer 4

A. 140 mEq/L ( 0.3mEq/L)

Question 5

ECF potassium is directly controlled in what two portions of the nephron?

Answer 5

DCT and collecting ducts

Question 6

Aldosterone is a stimulator/inhibitor of potassium secretion

Answer 6

stimulator (increased aldosterone increases potassium loss)

Question 7

Potassium reabsorption occurs in the:

A. PCT and late DCT
B. Ascending limb of LoH
C. Collecting duct and PCT
D. PCT and ascending LOH

Answer 7

D. PCT and ascending LoH

Question 8

Potassium secretion/sodium reabsorption occurs via the ____ in principal cells.

Answer 8

Na/K ATPase

Na+ is reabsorbed; K+ is secreted

Question 9

K+ flow through ____ on the apical membrane

Answer 9

K+ channel

Question 10

High K+ plasma produces an ____ in aldosterone, as well as direct K+ secretion in the ______.

Answer 10

Increase

cortical collecting tubules

Question 11

Approximately 50% of Ca2+ is found ______ proteins.

Answer 11

bound to transport

Question 12

Changes to ___ will affect the binding of Ca2+ to transport proteins

A. Cell size
B. Blood volume
C. Body temp
D. pH

Answer 12

D. pH (changing pH will change proteins)

Question 13

Acidosis results in a ____ of protein bound Ca2+.

A. Decrease
B. Increase
C. No change

Answer 13

A. decrease

Question 14

Release of _____ causes an increase in blood calcium levels.

Answer 14

PTH

Question 15

PTH works to raise blood [Ca2+] by _____.

Answer 15

increasing bone breakdown; increasing Ca2+ absorption in the GI tract; increased Vit. D3 activation; increased tubular reabsorption (indirectly)

Question 16

What % of Ca2+ is reabsorbed by the PCT?

A. 99%
B. 65%
C. 50%
D. 22%

Answer 16

B. 65%

Question 17

20% of calcium is absorbed in the PCT by what routes?

Answer 17

Transcellular

• Electrochemical gradient “pushes” Ca2+ out of the lumen
• Basolateral Ca2+ ATPase
• Basolateral Na+/Ca2+ exchanger

Question 18

Calcium resorption in the loop of Henle is in the _______.

A. Thick descending
B. Thick ascending
C. Thin descending
D. Thin ascending

Answer 18

B. Thick ascending

Question 19

50% of calcium absorption in the thick ascending loop of Henle occurs by paracellular routes. The remaining 50% occurs through the transcellular route and is stimulated by ______.

A. Calcitonin
B. PTH
C. Aldosterone

Answer 19

B. PTH

Question 20

T/F: Ca2+ reabsorption occurs in all portions of the nephron.

Answer 20

False; Ca2+ reabsorption is relegated to the PCT, DCT, and thick ascending Loop of Henle

Question 21

Ca2+ reabsorption of calcium is accomplished by ____ stimulated by PTH.

A. Sodium/Calcium exchanger on the basolateral side
B. Sodium/Calcium exchanger on the apical side
C. Calcium ATPase on the basolateral side
D. Calcium ATPase on the apical side

Answer 21

C. Calcium ATPase on the basolateral side

Question 22

Phosphate excretion occurs via what mechanism?

Answer 22

overflow (Tmax=0.1mM/min)

Question 23

Resorption of phosphate occurs via a ____cellular route.

A. paracellular
B. trans

Answer 23

B. trans

Question 24

____ assists in both resorption of Ca2+ and PO4

Answer 24

PTH

Question 25

PTH causes phosphate to exceed its transport maximum; this results in _____.

Answer 25

phosphate excretion

Question 26

Of insulin, chatecholamines, and aldosterone, which produce potassium uptake?

Answer 26

all three

Question 27

Describe the mechanism of action of aldosterone in regard to potassium reabsorption

Answer 27

1) Aldosterone stimulates Na/ATPase pumps in principal cells 2) Luminal membrane permeability for K+ increases 3) Extracellular [K+] increases

Question 28

Describe the effect of metabolic acidosis on ECF [K+]

Answer 28

Acidosis (decreased pH= increased [H+]) produces changes to the proteins comprising the Na/KATPase pumps. This produces decreased re-uptake of K+ into the cells.

Question 29

Describe the effect of cell lysis on ECF [K+]

Answer 29

Increased, as lysis of cells releases large amounts of the ICF K+

Question 30

Describe the effect of metabolic alkalosis on ECF [K+]

Answer 30

Decreases extracellular K+

Question 31

Principle cells are responsible for (secretion/absorption) of K+.

Answer 31

Secretion

Question 32

Principal cells are located in what portion of the nephron? A. DCT B. Cortical collecting tubule C. Medullary collecting tubule D. DCT & Cortical collecting tubule

Answer 32

D. DCT and cortical CT

Question 33

Principle cells secrete K+ what what mechanism?

Answer 33

Na/K ATPase on the basolateral membrane passive diffusion of K+ into tubular lumen

Question 34

Intercalated cells resorb K+ during what situation? A. Increased ECF K+ B. Decreased ECF K+ C. Decreased tubular K+

Answer 34

B. Decreased ECF K+ (K+ depletion)

Question 35

Intercalated cells move K+ and what other ion during K+ depletion? Is this sym- or anti-port?

Answer 35

H+; anti-port (H+ is secreted)

Question 36

_____ intercalated cells secrete K+

Answer 36

Type B

Question 37

______ of the late distal and collecting tubules reabsorb K+

Answer 37

Type A intercalated cells

Question 38

By what mechanisms are internal [K] regulated?

Answer 38

Decreased ECF [K] 1) insulin - increases cellular K uptake 2) aldosterone - stimulates cellular K uptake 3) beta-adrenergic stimulation - increases cellular K uptake Increased ECF [K] 4) acid/base disturbances - decreased pH can increase [K]ecf. The mechanism is unclear, but it's believed to arise from decreased Na/KATPase function 2/2 acidosis* 5) cell lysis - spills out ICF potassium 6) exercise - myocytes release K with strenuous exercise 7) increased ECF Osmolarity - Complicated! Increased ECF Osmolarity promotes diffusion of water out of cells. This, in turn, raises ICF [K]. When this increase in ICF [K] occurs, K flows down its gradient into the ECF fluid. *Remember that pumps are proteins. A change in pH affects the structure of the protein.

Question 39

Potassium excretion is primarily controlled by the _____ of the late distal and cortical collecting tubules.

Answer 39

Prinicpal (Think "Principal Potassium")

Question 40

Outline the process of potassium excretion by the kidneys.

Answer 40

1) Increased blood [K] occurs 2) K is absorbed into renal tubule cells by basolateral Na/KATPase 3) ICF [K] is raised 4) K flows down its gradient into the tubular lumen - occurs in prinicpal cells - "ROMK"-renal outer medullary potassium channels - "BK"- "Big Potassium" channels

Question 41

In severe K depletion, the ____cells act to resorb K. A. Principle cells B. Type A Intercalated cells C. Type B Intercalated cells

Answer 41

B. Type A Intercalated cells

Question 42

In cases of excess potassium, the _____ act in concert with principal cells to secrete potassium. A. Principle cells B. Type A Intercalated cells C. Type B Intercalated cells

Answer 42

C. Type B Intercalated cells These are under control of aldosterone

Question 43

This hormone sees its secretion increased when ECF [K] begin to rise. A. ADH B. Epinephrine C. Aldosterone D. Erythropoietin

Answer 43

C. Aldosterone