The Heart Valves Pacemaker Cells The Electrical Pathway

The Heart Valves Pacemaker Cells The Electrical Pathway of the Heart The Sinus Rhythm Marieb 18 18

Semilunar Valves Ventricle Arteries Smaller than AV valves No cords

The Two Circulations Pulmonary Systemic

The Two Circulations Pulmonary- low volume, low resistance, low pressure Systemic- high volume, high resistance, high pressure

The Cardiac Cycle

Cardiac Cycle Electrical Pattern Muscle Depolarization Pattern (ECG) Muscle Contraction Pattern of Pressure Changes Pattern of Valves Opening/Closing (Sounds) Pattern of Blood Movement

Wiggers Diagram

Cardiac Muscle drives the Cardiac Cycle Pacemaker Conducting Contracting

Automaticity/Pacemaker Function of Heart A subset of cells depolarize and repolarize in an intrinsic pattern!

Pacemaker Cells of the Heart Modified myocardium Intrinsic Firing Pattern Spider Cells in the right atrium Set heart rate

Normal Heart Contractions and the SA Node Sinoatrial Node Intrinsic 100 bpm Vagal Tone Internodal Pathway

AV Node Atrioventricular node Intrinsic 50 bpm Conduction very slow (Atria contract)

Bundle of His/Atrioventricular Bundles Surrounded by fibrous skeleton Quick Splits R/L Branch

Purkinje Fibers Very Fast Activate cardiac bundles in a fixed pattern

Sinus Rhythm 1) SA sets the pace 2) 60 -100 bpm 3) Proper conduction pattern

Timing in the Heart