Renal Regulation of Ion concentrations

Question 1

extracellular potassium is normally precisely regulated at

Answer 1

4.2 mEq/L (+0.3 mEq/L)

Question 2

an extracellular potassium increase of __ to __ can lead to cardiac arrhythmias and higher can lead to

Answer 2

3 to 4 mEq/L. cardiac arrest or fibrillation

Question 3

Extracellular fluid contains ___ % of total body potassium

Answer 3

2%

Question 4

intake of potassium form a single meal can be as high as

Answer 4

50 mEq

Question 5

____ must adjust potassium excretion rapidly and precisely in response to wide variations in intake

Answer 5

kidneys (mainly involves distal and collecting tubules)

Question 6

What is mainly involved in kidneys adjusting potassium excretion

Answer 6

distal and collecting tubules

Question 7

What is the normal intracellular concentration of potassium ion

Answer 7

140 mEQ/L

Question 8

Total amount of extracellular potassium

Answer 8

4.2 mEq/L x 14 L = 59 mEq

Question 9

Total amount of intracellular potassium

Answer 9

140 mEq/L x 28 L= 3920 mEq

Question 10

Major factors responsible for potassium excretion

Answer 10

• Direct influence on distal renal tubules and collecting ducts via increase in extracellular potassium ion concentration
• Effect of aldosterone secretion on potassium excretion
  
  • increase in extracellular potassium stimulates increase in aldosterone secretion

Question 11

An increase in extracellular potassium stimulates a _____ in aldosterone secretion

Answer 11

increase

Question 12

potassium daily intake is equal to

Answer 12

100 mEq/day

Question 13

Potassium daily output in urine and feces

Answer 13

urine- 92 mEq/day

Feces- 8 mEq/Day

Question 14

Sites of potassium reabsorption

Answer 14

• proximal tubule

- Ascending limb of Henle

Question 15

Sites for the secretion of potassium in the nephron

Answer 15

• Late tubule

- Collecting duct

Question 16

potassium secretion by principle cells is stimulated by

Answer 16

potassium concentration and aldosterone

Question 17

Treatment of hypertension with Beta-Adrenergic receptor blockers, such as propranolol, causes potassium to

Answer 17

-move out of the cells and creates a tendency toward hyperkalemia

Question 18

What __ % of filtered potassium is reabsorbed in the proximal tubule

Answer 18

65%

Question 19

What % of filtered potassium is reabsorbed in the loop of Henle

Answer 19

25-30% (especially in the thick ascending part where potassium is actively co-transported along with sodium and chloride)

Question 20

Cells in the late distal and cortical collecting tubules that secrete potassium are called

Answer 20

principle cells

Question 21

explain how principle cells excrete potassium into tubular lumen

Answer 21

Sodium-potassium ATPase on the basolateral side exchanges potassium for sodium. The increase in potassium inside the cell leaves to a passive diffusion of potassium from the interior of the cell into the tubular fluid

Question 22

How does aldosterone effect extracellular potassium levels

Answer 22

Aldosterone stimulates active reabsorption of sodium ions by the principle cells of the late distal tubules and collecting ducts

Question 23

as aldosterone levels and extracellular K+ levels increase what happens to the urinary potassium excretion

Answer 23

it increases

Question 24

small changes in serum potassium concentration cause ____ changes in aldosterone by adrenals

Answer 24

large

Question 25

what is the direct and indirect way that high potassium intake raises potassium excretion

Answer 25

- Direct influence on kidneys via high potassium concentration - Indirect via aldosterone secretion

Question 26

high potassium intake _____ the potassium secretion rate even at low tubular flow rates

Answer 26

greatly increases

Question 27

A rise in distal tubular flow rate does what to potassium secretion

Answer 27

stimulates potassium secretion

Question 28

explain how high sodium intake has a counterbalance effect on potassium secretion

Answer 28

High sodium intake leads to a decreased aldosterone secretion and thus decrease potassium secretion. But increased sodium intake also leads to increase in GFR and Decrease in proximal tubular Na reabsorption, which leads to increased distal tubular flow and increased potassium secretion.

Question 29

A High sodium diet leads to ____ change in potassium excretion

Answer 29

little.

Question 30

Explain how low sodium intake has a counterbalance effect on potassium secretion

Answer 30

-increase in aldosterone---> increase potassium secretion also decreases GFR and distal tubular flow rate thus decreased potassium excretion between the two there is now change in potassium secretion

Question 31

about 50% of total plasma calcium is in the ___ form

Answer 31

ionized form (ionized has biological activity at cell membraes)

Question 32

Acidosis has what changes on calcium binding

Answer 32

less calcium is bound to the plasma proteins

Question 33

Alkalosis has what changes on calcium binding

Answer 33

more calcium is bound to the plasma proteins

Question 34

A large amount of calcium is excretion occurs in the

Answer 34

feces; therefore, GI tract is important in calcium homeostasis

Question 35

Almost all calcium in the body is stored in

Answer 35

the bones

Question 36

____ is one of the most important regulators of bone uptake and release of calcium

Answer 36

PTH (parathyroid hormone)

Question 37

Parathyroid glands are directly stimulated by

Answer 37

low calcium levels

Question 38

Low calcium levels increase the secretion of

Answer 38

PTH (parathyroid hormone)

Question 39

Parathyroid hormone effects

Answer 39

- stimulates bone reabsorption - stimulates activation of Vitamin D - Indirectly increases tubular calcium reabsorption

Question 40

About __% of filtered calcium is reabsorbed in the proximal tubule.

Answer 40

99%

Question 41

What percentage of filtered calcium is reabsorbed in the proximal tubule through the paracellular route

Answer 41

65%

Question 42

What percentage of filtered calcium is reabsorbed in the proximal tubule through the transcellular route

Answer 42

20%

Question 43

How is calcium reabsorbed in the proximal tubule by the transcellular route

Answer 43

- electrochemical gradient | - Basolateral calcium-ATPase and sodium-calcium counter-transport

Question 44

Calcium reabsorption in the loop of Henle is restricted to the

Answer 44

thick ascending limb

Question 45

of the calcium reabsorbed in the thick ascending loop of Henle what percent is through the paracellular route

Answer 45

50% (passive diffusion and slight positive charge of tubular lumen)

Question 46

of the calcium reabsorbed in the thick ascending loop of Henle what percent is through the transcellular route and is stimulated by

Answer 46

50% stimulated by PTH (parathyroid hormone)

Question 47

Calcium reabsorption in the distal tubule is almost entirely via _____ transport in the ____ membrane

Answer 47

active transport (calcium-ATPase pump) in the basolateral membrane

Question 48

Calcium reabsorption in the distal tubule is stimulated by

Answer 48

PTH (parathyroid hormone)

Question 49

Factors that regulate tubular calcium reabsorption

Answer 49

- PTH - plasma concentration of calcium - metabolic acidosis

Question 50

Factors that increase calcium excretion

Answer 50

- decrease in PTH - Increase in extracellular fluid volume - increase in blood pressure - decrease in plasma phosphate - Metabolic acidosis

Question 51

Factors that decrease calcium excretion

Answer 51

- Increase in PTH - Decrease in extracellular fluid volume - decrease in blood pressure - increase in plasma phosphate - metabolic alkalosis - Vitamin D3

Question 52

compensatory responses to decrease plasma ionized calcium concentration is mediated by

Answer 52

PTH

Question 53

Vitamin D3 is activated by

Answer 53

increase in PTH

Question 54

Vitamin D3 functions in

Answer 54

increasing intestinal calcium reabsorption

Question 55

who does the calcium exhanger in the proximal tubular cells work

Answer 55

3 sodium in and 1 calcium out (into the renal interstitial fluid)

Question 56

phosphate transport maximum for reabsorption equals

Answer 56

0.1 mM/min

Question 57

phosphate excretion by the kidneys is controlled primarily by an

Answer 57

overflow mechanism

Question 58

phosphate normally begins to spill into the urine when its concentration in the extracellular fluid rises above a threshold of about

Answer 58

0.8 mM/L

Question 59

When less than .1mmol of phosphate is present in the glomerular filtrate than

Answer 59

essentially all the filtered phosphate is reabsorbed

Question 60

When more than .1 mmol of phosphate is present in the glomerular filtrate than

Answer 60

the excess (over .1mmol) is secreted

Question 61

____ % of phosphate is reabsorbed in the proximal tubule via what pathway

Answer 61

75%-80%, transcellular

Question 62

___% fo phosphate is reabsorbed in the distal tubule

Answer 62

10%

Question 63

how does PTH effect phosphate concentrations

Answer 63

- PTH promotes bone reabsorption and thus an increase in phosphate in the extracellular fluid- - PTH decreases transport maximum for phosphate by renal tubules ---> greater loss of phosphate in urine

Question 64

Whenever plasma PTH is ____ , tubular reabsorption is decreased and more phosphate is excreted.

Answer 64

increased

Question 65

extracellular fluid potassium concentration normally is maintained at

Answer 65

4.2 (plus or minus 0.3 mEq/L)

Question 66

only ___ % of the total body potassium is in the extracellular fluid

Answer 66

2%

Question 67

____ must be able to adjust potassium excretion rapidly

Answer 67

Kidneys

Question 68

____, ____, and _____ stimulate potassium uptake by cells

Answer 68

Insulin, aldosterone, beta-adrenergic stimulation (epinephrine)

Question 69

What is conn's syndrome. What does it lead to

Answer 69

increased secretion of aldosterone. Leads to hypokalemia

Question 70

What is Addison's disease?

Answer 70

is adrenal insufficiency | decreased levels of aldosterone leads to hyperkalemia

Question 71

Aldosterone stimulates active reabsorption of Na+ by _____ cells via sodium-potassium-ATPase pump

Answer 71

principle cells

Question 72

Can beta-adrenergic receptor blockers lead to hyperkalemia

Answer 72

yes

Question 73

____ potassium intake stimulates aldosterone secretion

Answer 73

increase

Question 74

metabolic acidosis has what effect on extracellular potassium concentration

Answer 74

increases extracellular potassium concentration

Question 75

metabolic alkalosis has what effect on extracellular potassium concentration

Answer 75

decreases extracellular potassium concentration

Question 76

Cell lysis, strenuous exercise, and increased extracellular fluid osmolarity have what effect on extracellular potassium concentration

Answer 76

hyperkalemia

Question 77

increased H+ concentration ----> reduction in activity of ________ pump ----> decrease in cellular uptake of potassium

Answer 77

Na+-K+ ATPase pump

Question 78

What is the rate of potassium filtration

Answer 78

Normal= 180 L/day x 4.2 mEq/L= 756 mEq/day

Question 79

what is the rate of potassium reabsorption in the proximal tubule (%)

Answer 79

65%

Question 80

What percent of potassium is reabsorbed in the loop of Henle

Answer 80

25-30%

Question 81

90% of the cells in the late distal tubule and cortical collecting tubules are

Answer 81

principle cells

Question 82

Principle cells in the late distal tubule and cortical collecting tubules have what function

Answer 82

Secrete potassium into tubular fluid - have Na+-K+-ATPase pump in basolateral membrane - passive diffusion of K+ into tubular lumen

Question 83

What factors stimulate potassium secretion in the principle cells

Answer 83

- increase in extracellular fluid potassium concentration - stimulates Na+-K+-ATPase - increase potassium gradient from ECF to cellular fluid - stimulates aldosterone secretion - increase aldosterone - tubular flow rate

Question 84

What are the controls of Potassium secretion

Answer 84

- activity of Na+-K+ ATPase pump - electrochemical gradients - permeability of luminal membrane

Question 85

What is the role of intercalated cells

Answer 85

- Reabsorb K+ during K+ depletion: - possibly through a H+-K+-ATPase - secrete H+ into tubular lumen

Question 86

Most of the potassium reabsorption occurs at

Answer 86

proximal convoluted tubule

Question 87

what type of cells play a major role in the secretion of potassium

Answer 87

principle cells

Question 88

Approximately how much of the body's supply of calcium is stored in the bone

Answer 88

99%

Question 89

how much of the filtered calcium is secreted by the kidneys

Answer 89

1%

Question 90

What cells reabsorb potassium during potassium depletions

Answer 90

intercalated cells

Question 91

a high potassium intake would have what effect on potassium excretion associated with increased renal tubular flow rate

Answer 91

-potassium excretion would increase with an increase in tubular flow rate

Question 92

which of the following describes a valid change in potassium distribution due to an acid-base abnormality? A.) metabolic acidosis decreases extracellular K+ concentration B.) Metabolic alkalosis increases extracellular K+ concentration C.) metabolic acidosis increases extracellular K+ concentration D. both A and B are valid

Answer 92

C.) Metabolic acidosis increases extracellular K+ concentration

Question 93

At high levels of angiotensin II greater _______ in arterial pressure are necessary to ______ sodium excretion

Answer 93

increases, increase

Question 94

at reduced angiotensin II levels, normal levels of sodium can be maintained at ______ arterial pressures

Answer 94

reduced

Question 95

Blood volume ___________ in normal range of daily fluid intakes

Answer 95

remains relatively normal