L20: Renal Regulation of Ion Concentrations

Question 1

what is normal [K] extracell?

Answer 1

precisely regulated at 4.2

Question 2

increase of [K] up to 7-8 causes

Answer 2

cardiac arrhythmias
cardiac arrest
fibrillation

Question 3

why must the kidneys be able to rapidly adjust extracellular K

Answer 3

to protect the body from the fatal effects of excess K

Question 4

excess extracell K stimulates the release of

Answer 4

aldosterone

which will stimulate increased urination to rid K

Question 5

small changes in [K], result in large changes in ______ secretion by the _____ .

Answer 5

aldosterone secretion by adrenals

Question 6

what part of renal tubules reabsorb K

Answer 6

proximal tubule

ascending limb

Question 7

what part of renal tubules secrete K

Answer 7

late tubule

collecting duct

Question 8

how do principal cells uptake K

Answer 8

from renal interstitial fluid via Na/K exchange pump

Question 9

secretion of K from principal cells

Answer 9

via BK and ROMK

Question 10

BK

Answer 10

big K channel on apical principal cells

Question 11

ROMK

Answer 11

renal outer medullary K channel on apical principal cells

Question 12

where are principal cells found

Answer 12

late distal tubule

cortical collecting tubules

Question 13

factors that stimulate K secretion

Answer 13

• -increased [K] extracell
• -increased aldosterone
• -increased tubular flow rate

Question 14

conditions that cause increased tubular flow rates

Answer 14

• -volume increase
• -high Na intake
• -high K intake
• -diuretics

Question 15

a high K intake/diet will greatly increase

Answer 15

K secretion rate even if tubular flow rate is low

Question 16

why does high Na intake have _____ effect of K secretion. since a high Na intake = increased urination

Answer 16

little effect on K

because increased Na intake = decreased aldosterone = thus also decreasing K excretion

Question 17

relate increased Na intake and GFR

Answer 17

increased Na intake = increased GFR = decreased reabsorption of Na

Question 18

plasma Ca in ionized form =

Answer 18

biologically active form

50% active - 50% stored

Question 19

changes in plasma pH on Ca binding

Answer 19

acidosis = less Ca in active form

alkalosis = more Ca in active form aka Ca is released from storage

Question 20

low levels of plasma Ca will stimulate the release of

Answer 20

PTH

Question 21

effects of PTH

Answer 21

stim bone reabsorption

stim activation of vit. d

indirectly increase tubular Ca reabsorption

Question 22

where is Ca reabsorption in the renal system

Answer 22

99% of filtered Ca is reabsorbed in the proximal tubule

the rest in thick ascending limb, distal tubule

Question 23

what route does Ca take when being reabsorbed

Answer 23

65% paracellular

20% transcellular

Question 24

PTH indirectly stimulates Ca reabsorption in

Answer 24

thick ascending limb via transcellular

distal tubule via active transport

Question 25

where is phosphate reabsorbed

Answer 25

proximal tubule via transcellular

10% in distal tubule

Question 26

role of PTH in phosphate excretion

Answer 26

PTH increase
= increased [phos] in extracell
= greater loss of phos in urine

Question 27

insulin stimulates

Answer 27

uptake of K

Question 28

aldosterone stimulates active reabsorption of Na by

Answer 28

principal cells

and the uptake of K

Question 29

catecholamines effect on reabsorption

Answer 29

=epinephrine
stim K uptake

-receptor blockers = hyperkalemia

Question 30

hyperkalemia results from

Answer 30

deficiency of aldosterone secretion

resulting in buildup of K in extracell and blood

Question 31

metabolic acidosis

Answer 31

increased extracell [k]

Question 32

metabolic alkalosis

Answer 32

decreased extracell [k]

Question 33

other causes of hyperkalemia

Answer 33

cell lysis
strenuous exercise
increased extracell fluid osmolarity

Question 34

what is the role of intercalated cells in controlled K levels

Answer 34

to reabsorb K during K depletion

Question 35

if you get a question of K, what type of cell should you pick for the answer?

Answer 35

principal cells

if you don’t know the answer