Lecture 18: Renal Regulation of Ion Concentrations

Question 1

What are the major factors responsible for K+ excretion?

Answer 1

1. Increase in extracellular potassium ion concentration

2. Increase in extracellular K+ stimulates increase in aldosterone secretion

Question 2

Where in the kidney tubule is K+ reabsorbed?

Answer 2

Proximal tubule, ascending limb of Henle

Question 3

Where in the kidney tubule is K+ secreted?

Answer 3

Late distal tubule, collecting duct

Question 4

What is the relationship between a high K+ diet, K+ secretion, and tubular flow rate?

Answer 4

Under high K+ dietary conditions, K+ is secreted at high levels, even at low tubular flow rates due to the effects of increased aldosterone secretion

Question 5

Why does Na+ have little effect on K+ excretion?

Answer 5

Na+ both lowers aldosterone secretion and increases GFR and tubular flow rate; these events counteract each other and cause no net effect on K+ excretion

Question 6

What is the extracellular fluid concentration of potassium?

Answer 6

4.2 mEq/L

Question 7

Which substances stimulate potassium uptake by cells?

Answer 7

Insulin, aldosterone, catecholamines

Question 8

Hypokalemia + associated pathological condition

Answer 8

Low K+, high aldosterone = Conn’s syndrome

Question 9

Hyperkalemia + associated pathological condition

Answer 9

High K+, low aldosterone = Addison’s disease

Question 10

What effect do beta-blockers have on extracellular potassium concentration?

Answer 10

Cause hyperkalemia because cells can not take up any K+

Question 11

Which of the following does NOT increase extracellular potassium concentration?

A. metabolic acidosis
B. metabolic alkalosis
C. cell lysis
D. strenuous exercise
E. increased extracellular fluid osmolarity

Answer 11

B. metabolic alkalosis

Question 12

Most K+ reabsorption occurs at which of the following sites?

A. Ascending loop of Henle
B. Distal convoluted tubule
C. Proximal convoluted tubule
D. Collecting duct

Answer 12

C. Proximal convoluted tubule

Question 13

Which of the following cells play a major role in the secretion of potassium?

A. Intercalated cells
B. Principal cells
C. Chief cells
D. Podocytes

Answer 13

B. Principal cells

Question 14

Which of the following plays a major role in stimulating potassium excretion by the kidney tubules

A. Aldosterone
B. Angiotensin II
C. Sodium ion
D. PTH

Answer 14

A. Aldosterone

Question 15

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

A. 1%
B. 47%
C. 78%
D. 99%

Answer 15

D. 99%

Question 16

How much of filtered calcium is excreted by the kidneys?

A. 1%
B. 47%
C. 78%
D. 99%

Answer 16

A. 1%

Question 17

Which of the following cells reabsorb potassium during potassium depletion?

A. Intercalated cells
B. Principal cells
C. Chief cells
D. Podocytes

Answer 17

A. Intercalated cells

Question 18

High K+ intake would have which of the following effects on K+ excretion associated with increased renal tubular flow rate?

A. K+ excretion would increase with increased tubular flow rate
B. K+ exretion would decrease with increased tubular flow rate
C. There would be little effect
D. Tubular flow rate would be decreased

Answer 18

A. K+ excretion would increase with increased tubular flow rate

Question 19

Which of the following describes a valid change in K+ 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 19

C. Metabolic acidosis increases the extracellular K+ concentration