Cardiac Cycle

SA Node (Sinoatrial Node)

• RA Wall

• Highest degree of automatically

• Pacemaker of cell

Atrial Internodal Pathways

RA: Anterior, middle, Posterior

LA: Bacmann’s Bundle

AV Node (Atrioventricular Node)

Connects Atria to Ventricle

Impulse slows .05 seconds to allow ventricular filling

Bundle Branches

Right and Left bundle branches

Purkinje Fibers

Penetrates into the ventricular muscle

Rapidly conducts action potential to ventricles

P Wave

Atrial depolarization (discharge)

QRS Complex

Ventricular depolarization (Discharge)

Followed immediately by ventricular systole (Contraction)

T Wave

Ventricular repolarization (recharge)

Isoelectric Line

Represents no conduction or contraction

R to R Interval

Represents 1 complete cardiac cycle

What does the Wiggers Diagram Lines represent (6 Lines)

• Aortic Pressure

• Atrial Pressure

• Ventricular Pressure

• Electrocardiogram

• Phonocardiogram

What happens during Isovolumic Contraction Time (IVCT)

No volume change

Pressure rapidly rises (in preparation for SL valve opening)

Heart volume at largest

What Period does IVCT happen

At Atrioventricular (AV) valve closure (end-diastole) and continues until semilunar (SL) valve opening

What happens during Isovolumic Relaxation Time (IVRT)

No volume change

Pressure decreases rapidly in preparation for AV valve opening

Heart Volume at smallest

What Period does IVRT happen

Begins at semilunar (SL) valve closure (end-systole) and continues until atrioventricular (AV) valve opening