Lecture 18 Renal Regulation of Ion Concentrations

Question 1

what is the normal extracellular concentration of potassium?

Answer 1

140 mEQ/L

Question 2

a slight increase in extracellular potassium can lead to

Answer 2

cardiac arrest and arrhythmia

Question 3

an extreme increase in extracellular potassium can lead to

Answer 3

cardiac arrest, fibrillation

Question 4

kidneys and [extracellular potassium]

Answer 4

kidneys are primary regulator of potassium

they excrete it rapidly and precisely in response to wide variations in intake

Question 5

overall effect of aldosterone secretion on [potassium]

Answer 5

increase in extracellular [K] stimulates an increase in aldosterone secretion

Question 6

what part of renal tubules is responsible for K reabsorption?

Answer 6

proximal tubule

ascending limb of henle

Question 7

what part of renal tubules are responsible for K secretion

Answer 7

late tubule, collecting duct

Question 8

mechanism of K excretion by principal cells

Answer 8

Na is moved into cell via ENaC pump (from fluid to cell)

K+ is passively secreted from cell to lumen (due to [ ] gradient created by ATPase Na/K+ pump)

Question 9

what factors stimulate K secretion by principal cells?

Answer 9

[K+] and aldosterone

increase uptake of K cause increase in [K] in plasma
stimulates aldosterone secreiton

Question 10

relationship between tubular flow rate and potassium secretion

Answer 10

increase in tubular flow increase K+ secretion because it continuously flush K out of fluid (low K in fluid = more secretion)

increase in tubular flow also activates high conductance BK channels that rapidly increase K conductance

Question 11

why does high sodium intake have little effect on K secretion

Answer 11

high Na+ decreases aldosterone secretion (decreasing K) but also increases tubular flow rate (increasing K) therefore balancing each other out and causing no net change

Question 12

acidosis

Answer 12

less Ca bound to plasma proteins

pH effect (acidic conditions)

Question 13

alkalosis

Answer 13

more Ca bound to plasma proteins

pH effect (basic conditions)

Question 14

effects of PTH

Answer 14

stimulates bone reabsorption
stimulates activation of vitamin D
indirectly increase tubular Ca reabsorption

Question 15

which factors decrease calcium reabsorption?

Answer 15

increase PTH levels (promotes bone reabsorption by increases [Phosphate]

plasma [phosphate]

metabolic acidosis

Question 16

what effects does insulin have on extracellular potassium?

Answer 16

stimulates potassium uptake by cells

Question 17

what effects do catecholamines have on extracellular potassium (beta adrenergic stimulation)

Answer 17

stimulates potassium uptake by cells

Question 18

what condition is know for an express secretion of aldosterone?

Answer 18

hypokalemia or Conn’s syndrome

Question 19

what condition is know for deficiency in aldosterone secretion?

Answer 19

hyperkalemia or Addison’s disease

high amounts of potassium in the body due to lack of excretion

Question 20

effect of metabolic acidosis on extracellular potassium

Answer 20

increases [K]

increases [H] –> decreases Na/K pump activity –> decreases K uptake

Question 21

effect of metabolic alkalosis on extracellular potassium

Answer 21

decreases extracellular K

Question 22

what is the effect of cell lysis, strenuous exercise, and increase fluid osmolarity have on extracellular potassium

Answer 22

hyperkalemia (increase [K])

Question 23

what is the role of intercalated cells in controlling potassium levels?

Answer 23

reabsorb K during depletion