Cardiovascular | Electrophysiology | Extrinsic Cardiac Conduction System

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Ninja Nerds!
In this cardiovascular physiology lecture, Professor Zach Murphy presents an overview of the extrinsic cardiac conduction system, focusing on how the autonomic nervous system (ANS) modulates heart rate, conduction velocity, and contractility to adapt cardiac output to the body’s changing demands.

We begin by breaking down the two key branches of the ANS—the sympathetic and parasympathetic nervous systems—and their innervation of the SA node, AV node, and ventricular myocardium. You’ll learn how sympathetic stimulation via β1-adrenergic receptors increases heart rate, conduction velocity, and contractility. In contrast, parasympathetic stimulation through the vagus nerve and muscarinic M2 receptors slows the heart and prolongs AV nodal delay.

This lecture also explores the neurotransmitters and second messenger systems involved—norepinephrine activates cAMP pathways in sympathetic signaling, and acetylcholine reduces cAMP through inhibitory G-protein signaling during parasympathetic tone.

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