Lecture 8: Regulation of Potassium Balance Flashcards
Where is most K+ located?
ICF
How is ICF K+ controlled?
Na+/K+ pump
Internal K balance
Distribution of K+ across cell membranes
External K Balance
Renal mechanisms to manage variations in K+ intake
What pump helps with internal K+ balance and with buffering when needed?
H+/K+ pump
Alkalemia is accompanied by what condition
Hypokalemia
What is the mechanism that causes Alkalemia
Hydrogen in blood decreases, so H+ leaves to enter ECF and K+ enters cells
Acidemia is accompanied by what condition
Hyperkalemia
What is the mechanism that causes acidemia?
Hydrogen in blood increases, so H+ enters and K+ leaves the cell exchange
Do acid-base disturbances always cause a K+ shift across membranes?
No (particularly if disturbance is respiratory acidosis or respiratory alkalosis)
Hyperkalemia leads to what kind of cells
Hyperexcitable
Hypokalemia leads to what in cells
Hyperpolarization
Why does hyperkalemia lead to hyperexcitable cells?
More potassium outside of cell and concentration of K more equal than between inside and outside. Decreased concentration gradient so less driving force for K+ to leave inside of cell –> RMP more positive/closer to threshold
Why does Hypokalemia lead to hyperpolarization
K+ shifts into cells, so have more K inside than normal. Concentration gradient increases even more, so K leaves via channels because driving force is increase, so RMP even more negative and harder to reach threshold
Insulin increases what pump activity
Na+/K+ ATPase activity
Insulin increases uptake of what into cells
K+
What condition does insulin prevent?
Hyperkalemia
What happens if insulin is deficient (Type 1 diabetes)?
Decreases K intake after meals –> Hyperkalemia
What are the 6 major factors that disturb internal K+ balance?
Catecholamines
Osmolarity
Cell lysis
Exercise
Insulin
Acid-base abnormalities
Beta-2 adrenergic agonists increase activity of what
Na+/K+ ATP (increase potassium in cell, hypokalemia)