Final: Lecture 18

Question 0

Factors that shift K+ into cells (decrease extracellular K+)

Answer 0

• Insulin
• Aldosterone
• ß-adrenergic stimulation
• Alkalosis

Question 1

What is the normal intracellular concentration of K+ ion?

Answer 1

•140 mEQ/L

Question 2

Factors that shift K+ out of cells (Increase extracellular K+)

Answer 2

• Insulin and aldosterone deficiency
• ß-adrenergic blockade
• Acidosis and cell lysis
• Strenuous exercise
• Increased extracellular fluid osmolarity

Question 3

Major factors responsible for K+ excretion?

Answer 3

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

Question 4

What are the two sites of K+ reabsorption?

Answer 4

•Proximal tubule and Ascending limb of Henle

Question 5

What are the two sites of K+ secretion?

Answer 5

•late tubule and collecting duct

Question 6

Mechanisms of K+ secretion and Na+ reabsorption and secretion are by?

Answer 6

•Principal cells

Question 7

Small changes in K+ concentration cause ______ changes in aldosterone secretion by adrenals.

Answer 7

•Large

Question 8

Acidosis, _______ Ca is bound to plasma proteins, while in Alkalosis ______ Ca is bound.

Answer 8

• Less

* More

Question 9

Almost all the Ca in the body is stored in the _______.

Answer 9

•bone

Question 10

________ is one of the most important regulators of bone uptake and release of Ca.

Answer 10

• PTH (parathyroid hormone)

* Parathyroid glands are directly stimulated by low Ca levels

Question 11

PTH effects

Answer 11

• Stimulates bone reabsorption
• Stimulates activation of vitamin D
• Indirectly increases tubular Ca+ reabsorption

Question 12

Reabsorption in the proximal tubule

Answer 12

•99% of filtered Ca reabsorbed, 65% through paracellular, 20% through transcellular

Question 13

Ca Reabsorption in loop of Henle

Answer 13

• Restricted to thick ascending limb
• 50% thought paracellular, passive diffusion and slight positive charge of tubular lumen
• 50% via transcellular, stimulated by PTH (pumps Na/Ca)

Question 14

Ca reabsorption in distal tubule

Answer 14

• Almost entirely via active transport
• Ca-ATPase pump in basolateral membrane
• Stimulated by PTH

Question 15

Factors that regulate tubular Ca reabsorption

Answer 15

• Increase levels of PTH
• Plasma concentration of Ca
• Metabolic acidosis
• All decreases Ca excretion

Question 16

Phosphate Excretion

Answer 16

• Controlled by overflow mechanism, all filtered reabsorbed excess is secreted
• 75-80% reabsorbed in proximal tubule, transcellular
• 10% in distal tubule

Question 17

_______ stimulates K+ uptake by cells

Answer 17

•Insulin

Question 18

________ increases K+ uptake by cells

Answer 18

• Aldosterone
• Stimulates active reabsorption of Na by principal cells via Na-K-ATPase pump
• Increase permeability of luminal membrane K+
• Increase extracellular K+—> aldosterone secretion

Question 19

Hypokalemia is _________ secretion of aldosterone.

Answer 19

•Excess

Question 20

Hyperkalemia is _______ in aldosterone secretion.

Answer 20

•Deficiency

Question 21

Catecholamines

Answer 21

• ß-adrenergic stimulation (epinephrine), stimulates K+ uptake by cells
• ß-adrenergic receptor blockers–> hyperkalemia

Question 22

What 4 things can result in hyperkalemia?

Answer 22

• Metabolic alkalosis–>decrease extracellular K+
• Cell lysis
• Strenuous exercise
• Increased extracellular fluid osmolarity

Question 23

Principal Cells

Answer 23

• Found in late distal tubule and cortical collecting tubules, 90% of cells in these regions
• Secrete K+, passive diffusion of K+ into tubular lumen, could end up in urine

Question 24

Intercalated cells

Answer 24

• Reabsorb K+ during K+ depletion
• possibly through a H+-K+-ATPase pump
• Secrete H+ into tubular lumen