Disorders of Cardiac Conduction Flashcards
What is Dysrhythmia?
Abnormality of the cardiac rhythm.
How does cardiac conduction affect the SNS?
Stimulates the heart.
Epinephrine and norepinephrine increase heart rate, contractility, automaticity, and atrioventricular (AV) conduction.
How does cardiac conduction affect the PNS?
Stimulation of vagus nerve slows heart rate and AV conduction.
What are the properties of cardiac cells?
Cardiac cells are of 2 types: electrical and myocardial
Electrical cells compose the cardiac conduction system
What is the definition of Automaticity?
ability to generate and discharge an electrical impulse.
What is the definition of Excitability?
ability of the cell to respond to an electrical impulse.
What is the definition of Conductivity?
ability to transmit an electrical impulse.
What is the definition of Contractility?
ability to change force of contraction without changing length of cardiac muscle fibers while in “resting” state of diastole.
What is cardiac impulse?
Movement of electrolytes across the cardiac cell membrane generates an electrical impulse, also called action potential.
The impulse is carried through the cardiac conduction system within the myocardial and some endocardial tissue.
Stimulation of the myocardial muscle by the electrical impulse produces the heart’s contraction, also called systole.
What are electrical cells in conduction determined by?
interaction between actin and myosin in myocardial cells
What is action potential? (Cardiac Impulse)
movement of electrolytes across the cardiac cell membrane which generates an electrical impulse
What is the cardiac impulse carried through?
the cardiac conduction system within the myocardial and some endocardial tissue
What does the stimulation of myocardial muscle by electrical impulse produce?
the heart’s contraction (systole)
What causes the cell to lose positive charges (repolarize)?
loss of intracellular potassium ions
What is extracellular space composed of?
-low potassium
-high sodium
What causes the cells to gain positive charges (depolarize)?
an increase in intracellular sodium ions
What does intracellular space consist of?
-high potassium
-low sodium
What are the primary carriers of electrical charge in cardiac muscles?
-sodium (intracellular)
-potassium (extracellular)
-calcium (extracellular)
How do sodium ions move through channels in the cells membrane?
into cell via FAST channel
How do calcium ions move through channels in the cells membrane?
into cell via SLOWER channel
How do potassium ions move through channel in the cells membrane?
moves OUT of cell
During cardiac contractibility what does ion movement create?
an electrical current across the cell membrane
What do electrical impulses stimulate in cardiac contractibility?
cardiac muscle cell to shorten (contract)
What happens in the SA node?
impulses BEGIN
What are Cardiac Conduction System Major Landmarks?
SA (sinoatrial) node – impulse begins
AV (atrioventricular) node
Bundle of His
AV junction – between the atria and ventricles
Left and right bundle branches
Purkinje fibers – impulse ends
What is inherent rate?
Inherent rate is the rate at which the SA node or another pacemaker site normally generates electrical impulses.
What are the components of the SA nodes?
Pacemaker of the heart in the upper wall of right atrium where the normal impulse originates.
Inherent rate 60 – 100
Once an impulse is initiated, it usually follows a specific path through the heart, and usually does not flow backward.
What are the components of the AV nodes?
Located in lower right atrium near the septum
Temporarily delays the impulse to allow for atria to empty and ventricles to fill to achieve peak cardiac output
What are the components of AV junction?
Contains some pacemaker cells that fire if the impulse doesn’t fire normally from higher in the conduction system.
(AV node and bundle of his)
What is “bundle of his?”
Resumes rapid conduction of the impulses through the ventricles
What are the components of Purkinje fibers?
Conduct impulses rapidly through the muscle to depolarize and contract.
Can also serve as a pacemaker with an inherent rate of 20 – 40.
Extends from the bundle branches into the endocardium and deep into the myocardial tissue
What is Depolarization and Repolarization?
Depolarization and repolarization are electrical activities that cause muscular activity – contraction of the heart.
What are polarized cardiac cells?
-cells at rest
-no electrical activity takes place
What are electrical cells generate by?
automaticity of specialized cardiac cells
What happens once and electrical cell generates an impulse?
the electricity crosses the cell membrane and results in depolarization
What is the drive that causes contraction of the cardiac cells?
the movement of electrolytes across the cell membrane through specific sodium, potassium, and calcium channels
What is depolarization?
electrical event that produces contraction
What is repolarization?
the return to the previous resting state or relaxation
What is Ventricular systole?
Ventricles contract
What is ventricular diastole?
Ventricles relax and fill with blood
What is Atrial Filling and Contraction?
Atrial filling occurs during systole and diastole.
What is the main function of atria?
to store blood as it enters the heart’s upper chambers
What is the definition of cardiac contractility?
The contraction function of the heart is one of the reasons why having normal electrolyte levels is so important.
What is an electrocardiogram for cardiac contractility?
Graph of the electrical activity of the heart that results in the mechanical function (contraction).
