Snapshot A 30-year-old man presents to the emergency room for palpitations and a syncopal episode. His blood pressure is 140/95 mmHg, pulse is 180/min, and respirations are 20/min. An electrocardiogram is ordered and reveals a supraventricular tachycardia. Vagal maneuvers are attempted with no effect. An intravenous medication that slows conduction through the atrioventricular node is started. (Adenosine) Introduction Two types of muscle cells exist in the heart contractile cells working cells of the heart that contract conducting cells tissues sinoatrial (SA) node generate action potentials spontaneously atrioventricular (AV) node atrial intermodal tracts bundle of His Purkinje system rapidly spread action potentials except for the SA node, all other tissues’ ability to generate action potentials are suppressed Spread of Excitation SA node → atrial intermodal tracts → left and right atria → AV node → bundle of His → Purkinje system → ventricles SA node serves as the pacemaker, generating the action potential AV node slows conduction velocity ensures ventricles have enough time to relax and fill with blood before contraction rapid conductions through AV node can lead to decreased stroke volume and cardiac output His-Purkinje system is very rapid low-resistance pathways essential for efficient contraction Relative conduction velocities Purkinje fibers > atria > ventricles > AV node
QUESTIONS 1 of 3 1 2 3 Previous Next Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (M1.CV.12.13) A researcher measures action potential propagation velocity in various regions of the heart in a 42-year-old Caucasian female. Which of the following set of measurements corresponds to the velocities found in the atrial muscle, AV Node, Purkinje system, and venticular muscle, respectively? QID: 100529 Type & Select Correct Answer 1 2.2 m/s, 0.3 m/s, 0.05 m/s, 1.1 m/s 5% (10/185) 2 1.1 m/s, 0.05 m/s, 2.2 m/s, 0.3 m/s 56% (104/185) 3 0.5 m/s, 1.1 m/s, 2.2 m/s, 3 m/s 9% (17/185) 4 0.3 m/s, 2.2 m/s, 0.05 m/s, 1.1 m/s 17% (32/185) 5 0.05 m/s, 1.1 m/s, 2.2 m/s, 3.3 m/s 5% (10/185) M 1 Question Complexity E Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 2 Review Tested Concept Review Full Topic
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