Cardiac Conduction and Rhythm - (part of chapter 17) Flashcards
What makes the heart muscle unique from other muscles?
It is capable of generating and rapidly conducting its own action potentials.
What are the parts of the cardiac conduction system?
Sinoatrial (SA) node Internodal pathways Atrioventricular (AV) node AV bundle Left and right bundles of the Purkinje system
What is the function of the SA node?
This is where the rhythmic impulse is generated.
What is the function of the internodal pathways?
They conduct the impulse from the SA node to the AV node.
What is the function of the AV node?
This is where the impulse from the atria is delayed before passing to the ventricles.
What is the function of the AV bundle?
This conducts the impulse from the atria to the ventricles.
What is the function of the left and right bundles of the Purkinje system?
They conduct the impulses to all parts of the ventricles.
What is the “pacemaker” of the heart?
The SA node.
What would happen if transmission of impulses through the AV node were blocked?
The atria and ventricles would beat independently of each other.
How does the delay of impulse conduction in the AV node provide a mechanical advantage to the heart?
It allows the atria to complete their ejection of blood before ventricular contraction begins.
What other parts of the cardiac conduction system (besides the SA node) have the ability to control the rhythm of the heart?
The AV node and the Purkinje system.
Why does the SA node control the heart under normal circumstances (even though other parts of the cardiac conduction system can do so)?
The discharge rate of the SA node is considerably faster than those of the AV node and the Purkinje system.
What are the three parts of an action potential (and what occurs during each)?
The resting - unexcited state during which the membrane is polarized (positive on the outside, negative on the inside).
Depolarization - a change in the direction of polarity (negative on the outside, positive on the inside).
Repolarization - reestablishment of polarity of the resting membrane potential.
Which three ions are the major charge carriers in cardiac muscle cells?
Sodium, potassium, and calcium.
What role do the charge carrying ions play in the generation of cardiac arrhythmias and conduction disorders?
Disorders of the ion channels along with disruption in the flow of these current-carrying ions are increasingly being linked to the generation of cardiac arrhythmias and conduction disorders.