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Cardiac action potential
Cardiac action potential
Cardiac action potential
| Phase | Description | Mechanism |
|---|---|---|
| 0 | Rapid depolarisation | Rapid sodium influx These channels automatically deactivate after a few ms |
| 1 | Early repolarisation | Efflux of potassium |
| 2 | Plateau | Slow influx of calcium |
| 3 | Final repolarisation | Efflux of potassium |
| 4 | Restoration of ionic concentrations | Resting potential is restored by Na+/K+ ATPase There is slow entry of Na+ into the cell decreasing the potential difference until the threshold potential is reached, triggering a new action potential |
NB cardiac muscle remains contracted 10-15 times longer than skeletal muscle
Conduction velocity
| Site | Speed |
|---|---|
| Atrial conduction | Spreads along ordinary atrial myocardial fibres at 1 m/sec |
| AV node conduction | 0.05 m/sec |
| Ventricular conduction | Purkinje fibres are of large diameter and achieve velocities of 2-4 m/sec, the fastest conduction in the heart. This allows a rapid and coordinated contraction of the ventricles |
+PassMedicine Notes
Cardiac action potential
swb006.png#http://en.wikipedia.org/wiki/Cardiac action potential
Phase_ Description _ Mechanism| 0 _ Rapid depolarisation _ Rapid sodium influx These channels automatically deactivate after a few ms| 1 _ Early repolarisation _ Efflux of potassium| 2_ Plateau _ Slow influx of calcium| 3_ Final repolarisation _ Efflux of potassium| 4 _ Restoration of ionic concentrations _ Resting potential is restored by Na+/K+ ATPase There is slow entry of Na+ into the cell decreasing the potential difference until the threshold potential is reached, triggering a new action potential|NB cardiac muscle remains contracted 10-15 times longer than skeletal muscle
