In an experiment the vagus is being stimulated, which results in increased acetylcholine entry to the synaptic cleft and that in turn results in the decreased heart rate due to the following mechanism:

Answer options

1. Depolarization of cardiac cell membrane
2. Increase in AV nodal conduction velocity
3. Decrease of action potential duration
4. Hyperpolarization of cardiac cell membrane
5. Increase of action potential duration