Vagal M2 Bradycardia — FRCA Primary MCQ
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Correct answer: A — Bradycardia and reduced AV conduction velocity via M2 muscarinic receptors
Vagal (parasympathetic) stimulation of the heart via M2 muscarinic receptors causes: decreased heart rate (negative chronotropy — slows SA node) / decreased AV conduction velocity (negative dromotropy) / shortened atrial refractory period / and minimal effect on ventricular contractility (sparse vagal innervation of ventricles). The neurotransmitter is acetylcholine.
Reference: Power Kam 2018 Principles of Physiology for the Anaesthetist