lecture 18 (T3)- renal regulation of ion concentrations Flashcards Preview

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Flashcards in lecture 18 (T3)- renal regulation of ion concentrations Deck (39):
1

Where does most potassium reabsorption occur

proximal convoluted tubule

2

what cell plays a major role in the secretion of potassium

principal cells

3

what plays a major role in stimulating potassium excretion by the kidney tubule

aldosterone

4

approximately how much of the body's supply of calcium is stored in bone

99%

5

what does metabolic acidosis due to extracellular potassium concentration

increases it

6

how much of filtered calcium is excreted by the kidneys

1%

7

what cell reabsorbs potassium during potassium depletion

intercalated cells

8

what effect would high potassium intake have on potassium excretion associated with increased renal tubule flow rate

potassium excretion would increase with increased tubular flow rate

9

what is extracellular potassium normally precisely regulated at

4.2mEq/L

10

how much of total body potassium is in extracellular fluid

2%

11

what is the normal intracellular concentration of potassium ion

140mEQ/L

12

what does an increase in extracellular potassium do to aldosterone

increases aldosterone secretion

13

where does reabsorption of potassium occur

proximal tubule and ascending limb of henle

14

where does secretion of potassium occur

late tubule and collecting duct

15

what is potassium secretion by principal cells stimulated by

potassium concentration and aldosterone

16

what does blockage of the aldosterone system impair

regulation of potassium concentration

17

how much of plasma calcium is in the ionized form

50%

18

define acidosis

less calcium is bound to the plasma proteins

19

define alkalosis

more calcium is bound to the plasma proteins

20

what are parathyroid glands directly stimulated by

low calcium levels

21

what are the effects of PTH

stimulates bone reabsorption
stimulates activation of vitamin D
indirectly increases tubular calcium reabsorption

22

how is most of the calcium reabsorption in distal tubule done

via active transport (calcium ATPase pump in basolateral membrane that is stimulated by PTH)

23

what factors regulate tubular calcium reabsorption

increased level PTH
plasma concentration of calcium
metabolic acidosis

24

what happens if phosphate concentration is less than 0.1

all filtered phosphate is reabsorbed

25

what happens if phosphate concentration is greater than 0.1

excess phosphate is secreted

26

what pathway is 75-80% of phosphate reabsorbed in proximal tubule

transcellular pathway

27

what effect does insulin have on regulating extracellular potassium

stimulates potassium uptake by cells

28

define hypokalemia

excess secretion of aldosterone (conn's syndrome)
low potassium in blood

29

define hyperkalemia

deficiency in aldosterone secretion (addison's disease)
high potassium in blood

30

what does aldosterone do in regards to potassium

increases potassium uptake by cells
stimulates active reabsorption of Na+ by principal cells via Na+k+ ATPase pump
increases permeability of luminal membrane for K+
increases extracellular K+

31

what do catecholamines do in regards to regulating extracellular potassium

beta-adrenergic stimulation (epinephrine): stimulates potassium uptake by cells
beta-adrenergic receptor blockers: hyperkalemia

32

what are things that can cause hyperkalemia

cell lysis
strenuous exercise
increased extracellular fluid osmolarity

33

what is the normal rate of potassium filtration

756 mEq/day

34

what is the normal rate of potassium reabsorption

65% in proximal tubule
25-30% in loop of Henle

35

where are principal cells found

late distal tubule and cortical collecting tubules

36

what does increased tubular flow rate do to K+ secretion

stimulates it

37

how do intercalated cells reabsorb K+ during K+ depletion

possibly through a H+K+ ATPase pump
secrete H+ into tubular lumen

38

what does high levels of angiotensin II do to arterial pressure

increases it and this is necessary to increase sodium excretion

39

how can normal levels of sodium be maintained when there is reduced angiotensin II levels

maintained at reduced arterial pressures