lecture 18 (T3)- renal regulation of ion concentrations

Question 1

Where does most potassium reabsorption occur

Answer 1

proximal convoluted tubule

Question 2

what cell plays a major role in the secretion of potassium

Answer 2

principal cells

Question 3

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

Answer 3

aldosterone

Question 4

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

Answer 4

99%

Question 5

what does metabolic acidosis due to extracellular potassium concentration

Answer 5

increases it

Question 6

how much of filtered calcium is excreted by the kidneys

Answer 6

1%

Question 7

what cell reabsorbs potassium during potassium depletion

Answer 7

intercalated cells

Question 8

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

Answer 8

potassium excretion would increase with increased tubular flow rate

Question 9

what is extracellular potassium normally precisely regulated at

Answer 9

4.2mEq/L

Question 10

how much of total body potassium is in extracellular fluid

Answer 10

2%

Question 11

what is the normal intracellular concentration of potassium ion

Answer 11

140mEQ/L

Question 12

what does an increase in extracellular potassium do to aldosterone

Answer 12

increases aldosterone secretion

Question 13

where does reabsorption of potassium occur

Answer 13

proximal tubule and ascending limb of henle

Question 14

where does secretion of potassium occur

Answer 14

late tubule and collecting duct

Question 15

what is potassium secretion by principal cells stimulated by

Answer 15

potassium concentration and aldosterone

Question 16

what does blockage of the aldosterone system impair

Answer 16

regulation of potassium concentration

Question 17

how much of plasma calcium is in the ionized form

Answer 17

50%

Question 18

define acidosis

Answer 18

less calcium is bound to the plasma proteins

Question 19

define alkalosis

Answer 19

more calcium is bound to the plasma proteins

Question 20

what are parathyroid glands directly stimulated by

Answer 20

low calcium levels

Question 21

what are the effects of PTH

Answer 21

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

Question 22

how is most of the calcium reabsorption in distal tubule done

Answer 22

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

Question 23

what factors regulate tubular calcium reabsorption

Answer 23

increased level PTH
plasma concentration of calcium
metabolic acidosis

Question 24

what happens if phosphate concentration is less than 0.1

Answer 24

all filtered phosphate is reabsorbed

Question 25

what happens if phosphate concentration is greater than 0.1

Answer 25

excess phosphate is secreted

Question 26

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

Answer 26

transcellular pathway

Question 27

what effect does insulin have on regulating extracellular potassium

Answer 27

stimulates potassium uptake by cells

Question 28

define hypokalemia

Answer 28

excess secretion of aldosterone (conn’s syndrome)

low potassium in blood

Question 29

define hyperkalemia

Answer 29

deficiency in aldosterone secretion (addison’s disease)

high potassium in blood

Question 30

what does aldosterone do in regards to potassium

Answer 30

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+

Question 31

what do catecholamines do in regards to regulating extracellular potassium

Answer 31

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

Question 32

what are things that can cause hyperkalemia

Answer 32

cell lysis
strenuous exercise
increased extracellular fluid osmolarity

Question 33

what is the normal rate of potassium filtration

Answer 33

756 mEq/day

Question 34

what is the normal rate of potassium reabsorption

Answer 34

65% in proximal tubule

25-30% in loop of Henle

Question 35

where are principal cells found

Answer 35

late distal tubule and cortical collecting tubules

Question 36

what does increased tubular flow rate do to K+ secretion

Answer 36

stimulates it

Question 37

how do intercalated cells reabsorb K+ during K+ depletion

Answer 37

possibly through a H+K+ ATPase pump

secrete H+ into tubular lumen

Question 38

what does high levels of angiotensin II do to arterial pressure

Answer 38

increases it and this is necessary to increase sodium excretion

Question 39

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

Answer 39

maintained at reduced arterial pressures