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Electrical Conduction System of the Heart quiz #3 Flashcards

Electrical Conduction System of the Heart quiz #3
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  • Describe the pathway of an action potential through the cardiac conduction system, listing the main structures involved in order.
    The action potential starts at the sinoatrial (SA) node, spreads through the atria via internodal pathways, reaches the atrioventricular (AV) node (where there is a brief delay), travels down the atrioventricular bundle (bundle of His), splits into right and left bundle branches, and finally spreads through the Purkinje fibers to stimulate ventricular contraction.
  • Explain how the autonomic nervous system modulates heart rate and contractility, specifying the roles of the sympathetic and parasympathetic pathways.
    The sympathetic nervous system increases heart rate and contractility by acting on the SA and AV nodes and heart muscle, while the parasympathetic nervous system decreases heart rate by acting on the SA and AV nodes but does not affect contractility.
  • What is the primary function of the intrinsic cardiac conduction system?
    It initiates and conducts action potentials within the heart, enabling coordinated and regular heartbeats without requiring neural input.
  • Where does the action potential that triggers a heartbeat originate in the heart?
    It originates in the sinoatrial (SA) node, which contains pacemaker cells that depolarize at regular intervals.
  • List the main structures in order that an action potential passes through in the cardiac conduction system.
    The action potential travels from the SA node, through internodal pathways, to the AV node, down the AV bundle (bundle of His), into the right and left bundle branches, and finally through the Purkinje fibers.
  • What is the purpose of the delay at the atrioventricular (AV) node during the cardiac conduction process?
    The AV node delays the action potential for about 100 milliseconds to ensure the atria contract and empty blood into the ventricles before the ventricles contract.
  • How do gap junctions contribute to the coordinated contraction of the heart?
    Gap junctions allow action potentials to rapidly spread from cell to cell, enabling the heart muscle to contract as a unit.
  • What is the role of the Purkinje fibers in the cardiac conduction system?
    Purkinje fibers rapidly distribute the action potential throughout the ventricular walls, triggering coordinated ventricular contraction.
  • How does the sympathetic nervous system affect heart rate and contractility?
    The sympathetic nervous system increases both heart rate and contractility by acting on the SA and AV nodes and the heart muscle.
  • What effect does the parasympathetic nervous system have on the heart, and through which nerve does it act?
    The parasympathetic nervous system decreases heart rate by acting on the SA and AV nodes via the vagus nerve, but it does not affect contractility.