Questions and Answers
The cardiac conduction system includes three populations of pacemaker cells: 1.________________ 2.________________ 3.________________
Cardiac conduction system includes three populations of pacemaker cells: 1.________________ 2.________________ 3.________________
Sinoatrial node, Atrioventricular node, Purkinje fiber system
Where is the sinoatrial (SA) node located?
In the upper right atrium, slightly inferior and lateral to the opening of the superior vena cava.
What intrinsic rate of depolarization does the SA node have?
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What is the intrinsic rate of the atrioventricular (AV) node?
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What is the depolarization rate of the Purkinje fiber system?
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What does the atrioventricular bundle (AV bundle) penetrate?
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What are the right and left bundle branches responsible for?
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What are terminal branches also known as?
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What is the SA node known as?
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Under normal conditions, _____ node generates an action potential that spreads rapidly via gap junctions to surrounding atrial cells.
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Which nodes normally conduct action potentials?
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If SA node ceases to function, _________ can successfully pace the heart, albeit somewhat slowly.
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What is an electrocardiogram (ECG)?
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What does an ECG depict?
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Electrical changes are shown on ECG as deflections, or waves that show ____________.
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One of the most obvious changes in the heart revealed by an ECG is a disturbance in electrical rhythm known as a _______________.
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An ECG recording generally consists of _________, each of which represents active depolarization or repolarization of different parts of the heart.
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The small, initial __________ represents depolarization of all cells within atria except SA node.
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P wave nearly always registers as an _________ on ECG.
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A large ________ represents ventricular depolarization in an ECG.
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QRS complex actually consists of three separate waves: _____ is first downward deflection, _____ is large upward deflection, and _____ is following downward deflection.
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A small __________ occurs after the S wave of the QRS complex, representing ventricular repolarization.
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The T wave is an ________ deflection under normal conditions.
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Study Notes
Cardiac Conduction System
- Comprises three populations of pacemaker cells: Sinoatrial node (SA node), Atrioventricular node (AV node), Purkinje fiber system.
Sinoatrial Node (SA Node)
- Located in the upper right atrium, near the opening of the superior vena cava.
- Fastest intrinsic rate of depolarization, generating approximately 60 or more action potentials per minute.
- Known as the heart's "Pacemaker," influenced by both sympathetic and parasympathetic nervous systems.
Atrioventricular Node (AV Node)
- Positioned posterior and medial to the tricuspid valve.
- Intrinsic pacing rate is slower than the SA node, approximately 40 action potentials per minute.
Purkinje Fiber System
- Comprises the slowest group of pacemaker cells, depolarizing around 20 times per minute.
- Sometimes referred to as atypical pacemakers due to their reliance on different ion channels.
Atrioventricular Bundle (AV Bundle)
- Penetrates the heart's fibrous skeleton, located in the inferior interatrial septum and the superior interventricular septum.
Right and Left Bundle Branches
- Course along the right and left sides of the interventricular septum, guiding electrical impulses.
Terminal Branches (Purkinje Fibers)
- Extend into the ventricles and make contact with contractile cardiac muscle cells.
SA Node Function
- Acts as the normal pacemaker for the entire heart, maintaining sinus rhythms through electrical activity.
AV Node and Purkinje Fiber System Coordination
- Typically conduct action potentials generated by the SA node, ensuring synchronized heartbeats.
AV Node Backup Role
- In the event the SA node ceases functioning, the AV node can take over pacing the heart, although at a slower rate.
Electrocardiogram (ECG)
- A crucial clinical tool for assessing the heart's health.
- Provides a graphic representation of overall electrical activity happening in cardiac muscle cells.
Electrical Activity Visualization
- Changes in electrical activity appear as deflections (waves) on an ECG; absence of net difference results in no deflection.
Dysrhythmia or Arrhythmia
- Disturbances in the heart's electrical rhythm can be identified using an ECG.
Waves in ECG Recording
- Generally consists of five waves, each indicating depolarization or repolarization of different heart parts.
P Wave
- A small, initial upward deflection representing the depolarization of all atrial cells, excluding the SA node.
QRS Complex
- A large deflection on the ECG representing ventricular depolarization, consisting of three distinct waves (Q, R, S).
- Q wave: first downward deflection.
- R wave: large upward deflection.
- S wave: following downward deflection.
T Wave
- A small upward deflection following the S wave in the QRS complex, which represents ventricular repolarization.
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Description
Test your knowledge on the cardiac conduction system with these flashcards. Learn about the Sinoatrial node, Atrioventricular node, and Purkinje fiber system, their locations, and functions. Perfect for students studying anatomy and physiology.
