K+ and Ca2+ Regulation--Muster

Question 1

98% of K⁺ is located

Answer 1

intracellularly

Question 2

Insulin’s effect on [K⁺]_serum

Answer 2

decreases [K⁺]_serum by bringing K⁺ into cells

activates Na⁺/K⁺ ATPase

eat food → increase in K⁺ is coming → let’s make insulin and get ready for it

Question 3

Catecholemine’s effect on [K⁺]_serum

Answer 3

decreases [K⁺]_serum

β₂ receptor stimulation increases activity of Na⁺/K⁺ ATPase

Question 4

Exercise and [K⁺]_serum

Answer 4

increases [K⁺]_serum

muscle cells release measureable amounts of K⁺ during exercise

insignifigant physiologically

Question 5

pH effect on K⁺

**know this**

Answer 5

K⁺ acts as H⁺ charge buffer

in acidotic situations:

H⁺ enters cells to buffer pH

K⁺ leaves cell, enters serum to buffer charge gradient

acidosis → hyperkalemia

up to 60% buffering of serum pH in this manner

Question 6

Long-term control of K⁺ excretion

where

what

how

Answer 6

RAAS system

hyperkalemia → RAAS system activation

SRE activation

increased transcription of ROMK and additional BK channel, moving K+ out into lumen

as well as increase Na⁺/K⁺ ATPase and ENaC

occurs in collecting duct: principle cells

Question 7

K⁺ reabsorbtion mechanism

how

where

what

Answer 7

in collecting duct intercalated cells

PAY ATTENTION

• to reabsorb K⁺, we need to secrete H⁺ via K⁺/H⁺ antiporter
• HCO₃^- must also be made in endothelial cell
• HCO₃^- carried into interstitium via HCO₃^-/Cl^- antiporter

Question 8

1˚ means of Ca²⁺ control

Answer 8

PTH

Question 9

Ca²⁺ distribution in blood

Answer 9

40% bound to albumin

10% bound to other things

50% as free ionic Ca²⁺

iCa²⁺ (that’s really all we care about)

Question 10

PTH effect on kidney

Answer 10

distal convoluted tubule

PTH receptor increases calbindin protein

Ca²⁺ from filtrate binds calbindin

Ca²⁺ pumped into interstitium via Ca²⁺ ATPase

Question 11

PTH mechanisms in Ca²⁺

Answer 11

bone

release Ca²⁺ and phosphorus from cortical > trabecular bone

kidney

increase production of activated vitamin D

increase Ca²⁺ reabsorption

increase renal phosphorus absorption (increase excretion)