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. (D)</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 (B)</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 (B)</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. (C)</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 (A)</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. (A)</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. (C)</p> Signup and view all the answers

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

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

In which direction does depolarization cause myocardial cells to contract?

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

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

<p>Repolarization (C)</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 (D)</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. (A)</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 (D)</p> Signup and view all the answers

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

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

Flashcards

Conduction System

The electrical system in the heart that controls the heartbeat, comprised of specialized cells that generate and conduct electrical impulses.

Electrical Impulse

The electrical impulse that travels through the heart in a wave-like motion, causing the heart muscle to contract.

Electrical-Mechanical Delay

The delay between the electrical impulse reaching the heart and the mechanical response of contraction, ensuring the heart chambers fill with blood before pumping.

Property of Automaticity

The ability of the heart to generate its own electrical impulses, allowing it to beat spontaneously without external stimulation.

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Sinoatrial Node (SA Node)

The primary pacemaker of the heart, located at the border of the superior vena cava and right atrium, generating electrical impulses at a rate of 60-100 beats per minute.

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SA Node

A specialized group of cells in the right atrium that initiates the electrical impulse for each heartbeat, acting as the heart's natural pacemaker.

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Bachmann's Bundle

A specialized pathway that carries the electrical impulse from the SA Node in the right atrium to the left atrium, allowing synchronized atrial contraction.

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AV Node

Located on the floor of the right atrium, the AV Node receives the electrical impulse from the SA Node and delays its transmission to the ventricles, ensuring coordinated heart contractions.

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AV Node: Secondary Pacemaker

The AV Node acts as a secondary pacemaker, taking over if the SA Node fails. It can generate its own electrical impulses at a slower rate, maintaining a heartbeat.

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AV Node: Gatekeeper

The AV Node prevents excessive atrial impulses from reaching the ventricles, ensuring proper ventricular filling before contraction. This delay allows the atria to finish contracting before the ventricles begin.

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Bundle of HIS

A bundle of specialized conductive tissue located in the basal portion of the interventricular septum (IVS).

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Bundle Branches

The branches of the Bundle of HIS that extend down the interventricular septum, responsible for conducting electrical impulses to the right and left ventricles.

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Purkinje Fibers

A network of specialized conductive fibers that spreads electrical impulses throughout the ventricles, ensuring a coordinated and synchronized contraction.

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Depolarization

The process of electrical activation in a myocardial cell, leading to cell shortening and contraction.

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Repolarization

The state of cellular recovery following depolarization, where the heart muscle relaxes and prepares for the next contraction.

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Electrocardiogram (ECG)

A recording of the electrical activity of the heart, as seen by the movement of ions through a pathway.

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Ventricular Contraction Direction

The direction of ventricular contraction during depolarization, starting from the inner lining of the ventricle (endocardium) and moving outwards towards the outer lining (epicardium) and from the apex to the base of the heart.

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Purkinje Fibers: Tertiary Pacemaker

The back-up pacemaker of the heart, if both SA and AV nodes fail, with a pacing rate of 20-40 bpm.

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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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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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