6 Questions
What initiates the normal heart rhythm by causing the atria to contract and pushing blood into the ventricles?
SA node
What is the primary function of contractile cells in the heart?
Produce force for heart contractions
Which type of arrhythmias are deviations from normal heart rhythm based on heart rate classification?
Tachyarrhythmias
What is the primary mechanism of action for Class 2 antiarrhythmic drugs?
Preventing the action of catecholamines
Which of the following substances is classified as an antiarrhythmic agent but does not fit into Class 1 to 4 categories?
Digoxin
What is the main role of the SA node in the heart's electrical system?
Serving as a natural pacemaker
Study Notes
- The heart's electrical system controls its pumping action
- Five elements make up the cardiac conduction system: SA node, AV node, bundle of His, bundle branches, and Purkinje fibers
- Normal heart rhythm begins with electrical signals from the SA node, causing atria to contract and pushing blood into ventricles
- Cardiac cells are divided into contractile and conducting cells
- Contractile cells generate force for heart contractions, while conducting cells initiate electrical impulses
- The SA node is the heart's natural pacemaker due to its fastest automaticity
- The action potential of pacemaker cells differs from heart muscle cells, particularly in their membrane potentials and ion channels involved
- Tachyarrhythmias are deviations from normal heart rhythm, classified based on heart rate as bradyarrhythmias or tachyarrhythmias
- Tachyarrhythmias can be caused by abnormal automaticity, triggered activity, or reentry mechanisms
- Antiarrhythmic drugs are classified based on their dominant mechanism of action as Class 1, 2, 3, or 4 agents
- Class 1 drugs block sodium channels, inhibiting the depolarization process and slowing conduction velocity
- Class 2 drugs are beta blockers, preventing the action of catecholamines on the heart and decreasing heart rate and contractility
- Class 3 drugs block potassium channels, prolonging the action potential and refractory period
- Class 4 drugs block calcium channels, slowing conduction in the SA and AV nodes and reducing heart contractility
- Other antiarrhythmic agents, such as Digoxin, Adenosine, and Magnesium Sulfate, do not fit neatly into these classes and have unique mechanisms of action
Test your knowledge on the cardiac conduction system and antiarrhythmic drugs. Learn about the SA node, AV node, bundle of His, Purkinje fibers, and different classes of antiarrhythmic agents.
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