BPK 142 Lecture Notes - Lecture 13: Premature Ventricular Contraction, Ventricular Tachycardia, Ventricular Fibrillation

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Anatomy of the Circulatory System
Composed of the heart, blood vessels, and blood
Transport essential materials (oxygen, fuel, molecules, hormones, etc.) throughout
the body to cells where they are needed and to collect waste materials (carbon
dioxide, lactic acid, urea, etc.) generated by the body's metabolic activity.
Divided into two sections:
Pulmonary circuit: Blood vessels going to and from the lungs
Systemic circuit: Blood vessels going to and from the rest of the tissues of
the body
Heart: Four chambered muscular pump which propels blood through the blood
● Atria: Two upper chambers
● Ventricles: Two lower chambers
● Septum divides the left and right sides of the heart (two pumps)
Right ventricle pumps blood through the pulmonary circuit
Left ventricle pumps blood through the systemic circuit.
The wall of the left ventricle is thicker than the wall of the right ventricle because
the systemic circulation is a much higher pressure system than the pulmonary
The direction of blood flow through the heart is controlled by unidirectional valves.
Heart murmur: Valve is damaged or does not close properly ---> blood regurgitates
causing a noise.
The heart muscle (myocardium) is a specialized type of muscle (cardiac muscle)
Unlike skeletal muscle, all of the fibers or cells in cardiac muscle are anatomically
interconnected (Functional syncytium: When one fiber contracts, all fibers contract)
The fibers of the atria are separate from the fibers of the ventricles.
Conduction System of the Heart
The heart's inherent contractile rhythm originates in an area of specialized tissue
located in the posterior wall of the right atrium: The S-A node, the normal
pacemaker of the heart.
Pathway of conduction of the wave of depolarization (cardiac impulse) across the
Atrial muscle fibers to contraction S-A node
A-V node to A-V bundle to left and right bundle branches to Purkinje
fibers which travel throughout the ventricular myocardium to simultaneous
contraction of the left and right ventricles.
The wave of depolarization is delayed in the A-V node for approximately 0.10
seconds in order to give the atria time to contract and empty their contents
into the ventricles.
○ Electrocardiography: Record the wave of depolarization as it passes across
the heart using electrodes on the surface of the body.
Components of a normal ECG waveform:
P wave - represents atrial depolarization
QRS wave - represents ventricular depolarization
T wave - represents ventricular repolarization
○ Arrhythmia: An irregularity in the rhythm of the heartbeat
Diagnosing arrhythmias: Look at heart rate, amplitude and shapes of the
components of the EKG waveform, and time intervals.
Examples of arrhythmias:
Atrial: Tachycardia
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