CVS 4 Electrical + Molecular Mechanims In Heart + Vasculature Flashcards
What sets the the resting membrane potential?
K+ permeability
How does K+ permeability set the resting membrane potential?
- K+ move out down conc. gradient until Ek is reached
- negative charge inside
- build up of charge creates an electrical gradient
What is the Ek?
Equilibrium potential for K+ ions
-95mV
What is the resting membrane potential valve?
-80 to -90mV
What do you get if the action potential fires too slowly?
Bradycardia
What do you get if the action potential fires too quickly?
Tachycardia
What do you get if the action potential fires randomly?
Fibrillation
What do you get if the action potential fails to fire?
Asystole
Explain the process of ventricular action potential
1- influx of Na+ - opening of VGNC - depolarisation
2- short efflux of K+ - transient outward K+ current - initial repolarisation
3- influx of Ca2+ - opening of VGCC- plateau
4- efflux of K+ - opening of VGKC- repolarisation
Hyperkalaemia meaning + value
High plasma K+ conc.
> 5.5mol/L
Hypokalaemia meaning + value
Low plasma K+ conc.
<3.5mol/L
Normal plasma K+ conc
3.5-5.5mmol/L
What is the effect of hyperkalaemia on ventricular AP?
- Some VGNC are inactive- slow upstroke
- Shorter AP?
- can stop heart if K+ conc is too high
Risks of hyperkalaemia
Asystole - heart stops if too high
Initial increase in excitability
Treatment of hyperkalaemia
Calcium gluconate
Insulin + glucose - control cell uptake of K+