The Conduction System of the Heart
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Questions and Answers

What role does the AV Node play concerning the SA Node?

  • It regulates blood flow to the heart.
  • It completely replaces the SA Node.
  • It amplifies the impulses from the SA Node.
  • It serves as a secondary pacemaker if the SA Node fails. (correct)

    • How does the AV Node act as a gatekeeper?

  • It permanently blocks all atrial impulses from reaching the ventricles.
  • It increases heart rate by sending multiple impulses to the ventricles.
  • It delays electrical conduction to prevent rapid ventricular response. (correct)
  • It generates electrical impulses independently of the SA Node.

    • What is the primary function of Bachmann's Bundle?

  • To increase heart rate under stress conditions.
  • To moderate conduction speed based on blood oxygen levels.
  • To carry impulses from the SA Node to the left atrium. (correct)
  • To serve as a secondary pacemaker.

    • How does the autonomic nervous system affect the SA and AV Nodes?

    <p>It allows for fluctuations in heart rate based on physiological needs.</p> Signup and view all the answers

    What is the pacing rate of the AV Node if the SA Node fails?

    <p>40-60 bpm</p> Signup and view all the answers

    What is the primary role of the sinoatrial (SA) node in the heart's conduction system?

    <p>To initiate a self-generated impulse into the atrial muscle fibers</p> Signup and view all the answers

    Which statement accurately describes the electrical impulse process in the heart?

    <p>There is an electrical-mechanical delay where the impulse precedes the muscle contraction.</p> Signup and view all the answers

    What unique property of myocardial cells allows them to generate impulses independently?

    <p>Automaticity, which refers to their ability to spontaneously fire</p> Signup and view all the answers

    What happens if the SA node fails to initiate impulses?

    <p>Other pacemakers can take over to maintain heart rhythm.</p> Signup and view all the answers

    What is the primary characteristic of the conduction pathways in the heart?

    <p>They contain specialized, high-speed conductive pathways for effective pumping.</p> Signup and view all the answers

    Which structure is primarily responsible for receiving impulses from the AV Node?

    <p>Bundle of HIS</p> Signup and view all the answers

    What is the function of the Purkinje Fibers in the cardiac conduction system?

    <p>To spread impulses through the ventricles</p> Signup and view all the answers

    In which direction does depolarization cause myocardial cells to contract?

    <p>From endocardium to epicardium</p> Signup and view all the answers

    The state of cellular recovery that occurs after myocardial contraction is known as?

    <p>Repolarization</p> Signup and view all the answers

    What is the role of the right and left bundle branches in the heart's conduction system?

    <p>To divide the impulse towards the apex</p> Signup and view all the answers

    Which of the following statements about ventricular contraction is true?

    <p>It occurs from the apex to the base.</p> Signup and view all the answers

    If both the SA and AV nodes fail, which part of the conduction system acts as the tertiary pacemaker?

    <p>Purkinje Fibers</p> Signup and view all the answers

    During which phase of the cardiac cycle do the chambers refill with blood?

    <p>During repolarization</p> Signup and view all the answers

    Study Notes

    The Conduction System

    • The heart has an electrical conduction system
    • This system is the source of electricity in the heart
    • Electrical impulses travel through the heart in a wave-like motion
    • These impulses signal the muscles to contract (mechanical response)
    • The electrical and mechanical responses do not happen at the same time
    • There is a delay, the electrical impulse sends the signal, the heart then reacts with a mechanical action

    3 Ways Myocardial Cells Differ from Skeletal Muscle

    • Contain specialized, high-speed conductive pathways which ensures a smooth, effective pump
    • Possess a long refractory period. This ensures the signal stops once it has traversed the heart, not continuing to circle
    • Do not require an external stimulus. They spontaneously fire at periodic intervals, known as the Property of Automaticity

    Conduction Pathway

    • SA Node
    • AV Node
    • Bundle of HIS
    • Right & Left Bundle Branches
    • Purkinje Fibers

    Sinoatrial Node (SA Node) - Location & Role

    • Located at the border of the SVC & RA
    • Initiates a self-generated impulse into the atrial muscle fibers
    • Initiates atrial contraction

    SA Node: Primary Pacemaker

    • Primary pacemaker of the heart
    • Paces at 60-100 bpm
    • If it fails, other pacemakers can take over

    SA Node - Communication

    • Impulse from the SA Node in the RA travels to the LA via the interatrial tract
    • Known as Bachmann's Bundle

    AV Node - Location & Role

    • Located on the floor of the RA
    • Receives the impulse from the SA Node
    • Via 3 internodal tracts

    AV Node: Secondary Pacemaker

    • Secondary pacemaker of the heart
    • Backs up the SA node if it fails
    • Paces at 40-60 bpm

    AV Node: Gate / Gatekeeper

    • Serves as a gatekeeper from the ventricles
    • Delays electrical conduction
    • Prevents excessive number of atrial impulses from entering the ventricles
    • Allows ventricles to contract after the atria have
    • Allows electrical impulses through to the ventricles at the appropriate time
    • Think of the AV Node as the bouncer!

    Fun Fact

    • Both the SA Node & AV Node have sympathetic & parasympathetic fibers
    • These fibers allow the heart rate to change in response to physiological changes

    Bundle of HIS - Location

    • Located in the basal portion of the IVS (interventricular septum)

    Bundle of HIS - Conduction

    • Receives impulse from the AV Node
    • Conducts the wave down the IVS toward the apex
    • Divides into 2 branches:
      • Right Bundle Branch
      • Left Bundle Branch

    Bundle Branches - Location

    • Located in the IVS
    • Right Bundle Branch is on the right side of the IVS
    • Left Bundle Branch is on the left side of the IVS
    • Course down toward the apex

    Purkinje Fibers - Location

    • Complex network that develops from bundle branches
    • Spreads the impulse through the ventricles like a web

    Purkinje Fibers: Tertiary Pacemaker

    • Backup pacemaker of the heart if both SA & AV Nodes fail
    • Paces at 20-40 bpm

    Depolarization

    • State of cellular stimulation (Electrical activation)
    • Causes myocardial cells to shorten & contract

    Repolarization

    • State of cellular recovery that follows each contraction
    • Myocardial relaxation
    • Heart relaxes & allows chambers to refill in order to repeat the cycle
    • Myocardial relaxation occurs in the opposite direction of contraction (epicardium → endocardium, base → apex)

    Electrocardiogram (ECG/EKG)

    • Aka EKG or ECG
    • Test that detects & records electrical activity of the heart

    Wigger's Diagram

    -(Diagram showing the electrical and mechanical events of the cardiac cycle)

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    Related Documents

    The Conduction System PDF

    Description

    This quiz explores the electrical conduction system of the heart, highlighting the key components such as the SA Node, AV Node, and specialized pathways. Understand the unique properties of myocardial cells and their differences from skeletal muscle. Test your knowledge on how electrical impulses affect heart contractions and the rhythm of the heart.

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