Renal Regulation of Ion Concentrations

Question 1

You encounter a patient who is experiencing symptoms of cardiac arrest. Would you expect their extracellular potassium levels to be high or low?

Answer 1

High

Question 2

How much of the total body potassium is located in the extracellular fluid?

Answer 2

2%

Question 3

What is the normal intracellular concentration of potassium ions?

Answer 3

140 mEq/L

Question 4

An increase in extracellular potassium stimulates an increase in the secretion of what molecule?

Answer 4

aldosterone

Question 5

Where does reabsorption occur in the nephron?

Answer 5

proximal tubule and the ascending limb of Henle

Question 6

Where does secretion occur in the nephron?

Answer 6

late tubule and collecting duct.

Question 7

How are principle cells stimulated to secrete potassium and aldosterone?

Answer 7

They are dependent upon potassium concentration and aldosterone.

Question 8

Is there an inverse or direct relationship between aldosterone secretion and extracellular potassium secretion?

Answer 8

direct

Question 9

Potassium concentration is indirectly affected by what molecule?

Answer 9

aldosterone

Question 10

If the aldosterone system is blocked, how will potassium regulated be affected?

Answer 10

Potassium will not be as regulated; the aldosterone system imparis regulation of potassium concentration.

Question 11

A high potassium diet is usually correlated with what?

Answer 11

A high secretion of potassium.

Question 12

How does a in increased sodium diet affect potassium excretion?

Answer 12

It does not affect potassium excretion.

An increased intake of sodium decreases aldosterone (decreases K+ secretion) and increases distal tubular flow rate (increases K+ secretion). These counteract each other and there is not net change in potassium excretion.

Question 13

Approximately what percentage of total plasma calcium is in the ionized form?

Answer 13

50%.

Question 14

You encounter a patient who is experiencing acidosis. Do you expect high or low levels of calcium to be bound to the plasma proteins?

Answer 14

low

Question 15

You encounter a patient with alkalosis. Do you expect high or low levels of calcium to be bound to the plasma proteins?

Answer 15

high

Question 16

Almost all of the calcium in the body is stored where?

Answer 16

In the bones

Question 17

What hormone is one of the most important regulators of bone uptake and release of calcium?

Answer 17

Parathyroid hormone

Question 18

Vitamin D is activated by what hormone?

Answer 18

Parathyroid hormone

Question 19

How much of the filtered calcium is reabsorbed, and what region of the nephron absorbs most of it?

Answer 19

99%; the proximal tubules absorb the most through paracellular (65%) and transcellular (20%) routes.

Question 20

How is calcium reabsorbed in the proximal tubules?

Answer 20

Through paracellular (65%) and transcellular (25%) routes.

Question 21

What region of the loop of henle absorbs calcium?

Answer 21

thick ascending limb.

Question 22

How is calcium reabsorbed in the distal tubule?

Answer 22

via active transport.

Question 23

What factors regulate tubular calcium reabsorption?

Answer 23

increased PTH

Plasma concentration of calcium

metabolic acidosis

Question 24

Reabsorption in the distal tubule is stimulated by what hormone?

Answer 24

PTH

Question 25

Calcium excretion is decreased by what factors?

Answer 25

Decreased PTH Plasma concentration of phosophate Metabolic acidosis

Question 26

When parathryoid hormome is increased, what three regions of the body will subsequently increase calcium reabsorption?

Answer 26

intestines, kidneys and bones.

Question 27

What is the phosphate transport maximum for reabsorption?

Answer 27

0.1 mM/min. If it is above this value, excess is secreted. If it is below this value, all filtered phosphate is reabsorbed in the proximal tubule.

Question 28

What is the relationship between PTH and phosphate?

Answer 28

An increase in PTH causes an increase of extracellular phosphate, which is eventually lost in the urine.

Question 29

During a fed state, insulin is released. What is the relationship of insulin and potassium?

Answer 29

Insulin stimulates potassium uptake by cells.

Question 30

You encounter a patient who is experiencing Conn's Syndrome (hyporkalemia). You order a blood test. Do you expect aldosterone levels to be high or low?

Answer 30

high

Question 31

You encounter a patient who has Addison's disease (hyperkalemia). You order a blood test. Do you expect aldosterone levels to be high or low?

Answer 31

low

Question 32

What is the function of aldosterone?

Answer 32

It increases potassium uptake by cells. It also stimulates active reabsorption o Na+ by principal cells via Na/K ATPase pump.

Question 33

As extracellular potassium increases, what substance is secreted?

Answer 33

aldosterone

Question 34

What is the function of catecholamies?

Answer 34

They stimulate potassium uptake by cells.

Question 35

You encounter a patient who has metabolic acidosis. You order a blood test. Do you expect plasma (extracellular) concentrations of potassium to be high or low?

Answer 35

high

Question 36

You encounter a patient who has metabolic alkalosis. You order a blood test. Do you expect their plasma (extracellular) levels to be high or low?

Answer 36

low

Question 37

You perform a study on rats that have undergone strenous excercise and are experiencing hyperkalemia. What physiological symptoms do you expect the rats to have?

Answer 37

cell lysis and increased extracellular fluid osmolarity.

Question 38

What are the major cells found in the late distal tubule and collecting tubules?

Answer 38

principal cells.

Question 39

What type of pump is important in controlling K+ secretion?

Answer 39

Activity of the Na/K ATPase pump.

Question 40

What three factors control K+ secretion?

Answer 40

Activity of the Na/K ATPase pump Electrochemical gradients Permeability of luminal membrane.

Question 41

What three factors stimulate K+ secretion?

Answer 41

Increased extracellular K+ concentration Increased aldosterone Increased tubular flow rate

Question 42

What is the function of intercalated cells?

Answer 42

To reabsorb potassium during potassium depletion. They reabsorb through a H/K ATPase pump. H+ is secreted into the lumen.

Question 43

In order to excrete high levels of sodium, what must happen to blood pressure?

Answer 43

It has to increase.

Question 44

At reduced angiotensin II levels, ____ levels of sodium can be maintained at reduced arterial pressures.

Answer 44

normal

Question 45

At what concentration is extracellular potassium maintained?

Answer 45

4.2 mEq/L (+/- 0.3 mEq/L)