Consider the following three statements regarding neuronal communication in mammals:

1. Postganglionic sympathetic neurones are unmyelinated, meaning action potential propagation along their axons relies on continuous depolarisation rather than saltatory conduction.
2. The rapid repolarisation phase of an action potential in a myelinated motor neurone is driven by the active transport of sodium ions out of the axon by the sodium-potassium pump.
3. At a cholinergic synapse, the influx of calcium ions into the presynaptic knob triggers the exocytosis of acetylcholine, which then diffuses across the synaptic cleft to bind to receptors on the postsynaptic membrane.

Which of these statements is/are correct?