1
Q
What are the main phases of the cardiac action potential?
A
Phase 0 (depolarisation), phase 1 (initial repolarisation), phase 2 (plateau), phase 3 (repolarisation), phase 4 (resting potential).
2
Q
Which ions are involved in phase 0 depolarisation in atrial/ventricular cells?
A
Rapid sodium influx through voltage-gated sodium channels.
3
Q
What causes the plateau phase (phase 2)?
A
Balance between calcium influx and potassium efflux.
4
Q
Why is the plateau phase important?
A
It prolongs contraction and prevents tetany of the heart.
5
Q
What determines automaticity in pacemaker cells?
A
Gradual depolarisation during phase 4 driven by funny (If) channels.
