Potassium Balance Flashcards
dont be a hoe
What are the most prevalent cations in body fluids?
→ Na+ and K+
Where is potassium found?
→ in leafy vegetables
→ Most fruit and juice
→ potatoes
What is the intra and extracellular concentration of potassium?
→ I : 150mmol/L
→E : 4.5 mmmol/L
What cell types have the most potassium?
→ Muscle cells
What is the internal potassium balance maintained by?
→ Insulin
→ Adrenaline
→ pH
→ Aldosterone
What is the external potassium balance maintained by?
Input
→Diet
Output
→ urine & stools
→ sweat
What is acute regulation of K+?
→The distribution of K+ through ICF and ECF compartments
What is chronic regulation of K+?
→ Kidney adjusting K+ excretion + reabsorption
What are the 2 functions of K+?
- Determines ICF osmolality
- Determines resting membrane potential
- Affects vascular resistance
What does the sodium/potassium pump do?
→ Na+ ions are pumped out of the cell
→ K+ pumped into the cell
→ energy driving the pump is released by ATP hydrolysis
What happens to K+ concentration after a meal?
→ Increase in plasma K+
→ shifted into ICF compartment
What hormones is the ICF K+ shift due to?
→ insulin
→ adrenaline
→ aldosterone
→ pH changes
What is hyperkalaemia defined as?
→ plasma K+ is above 5.5 mM
What is hypokalaemia defined as?
→ plasma K+ is below 3.5 mM
What is resting potential formed from?
→ ionic gradients
What is the normal distribution between IC and EC K+?
→ External - 3.5 mM
→ Internal - 140 mM
What happens to the equilibrium potential when you have hyperkalaemia?
→ Less negative
What happens to the equilibrium potential when you have hypokalaemia?
→ More negative
What happens during hyperpolarization (less K+) ?
→ more negative voltage across the membrane
→ Decreased excitability of neurons
→Longer to reach threshold
→ Longer to reach action potential
What happens during depolarization (more K+)?
→ Less negative voltage
→ Threshold is approached quicker
→ Increased excitability
What is hypokalaemia caused by?
→ Renal or extra renal loss of K+
What are causes of hypokalaemia?
→ Diuretics without KCl
→ Hyperaldosteronism ( Conn’s syndrome)
→ Prolonged vomiting (Increased aldosterone secretion)
→ Profuse diarrhoea
What does hypokalaemia result in?
→ Decrease adrenaline, aldosterone and insulin
What is hyperkalaemia caused by?
→ Prolonged exercise
→ Kidneys excrete K+ easily
What are disease states that cause hyperkalaemia?
→ Insufficient renal excretion
→ Increased release from damage body cells
→ Long term use of potassium sparing diuretics
→ Addisons disease
What happens if plasma K+ is above 6.5 mM?
→ Systolic cardiac arrest
What is used to drive K+ into the cells?
→ Insulin/glucose infusion
What hormones stimulate the Na+-K+ pump?
→ Aldosterone
→ Adrenaline