Flashcards in The Cardiac Cycle Deck (11):
What is a normal stroke volume?
Which direction does contraction spread from and to in the heart?
Contraction spreads from the inner endocardial cells to the outer epicardial cells.
Name the 7 stages of contraction in the heart.
Describe the stage of Atrial contraction
Atrial contraction accounts for the final 10% of ventricular filling. Mitral and tricuspid valves are open whilst the Aortic and pulmonary valves are closed.
Describe the stage of Isovolumetric contraction
Mitral and tricupsid valves shuts as ventricles contract and causes C wave in atrial pressure. 1st heart sound heard.
Describe the stage of Rapid Ejection
Aortic and pulmonary valves open and there is a small decrease in atrial pressure as it is pulled downwards by ventricular contraction.
Describe the stage of Reduced Ejection
Ventricles begin to repolarise and pressure drops. Atrial pressure begins to rise in V wave from venous filling.
Describe the stage of Isovolumetric relaxation
Aortic and Pulmonary valves close causing small peak in aortic pressure (dicrotic notch), large drop in ventricular pressure but note volume remains the same. 2nd heard sound heard.
Describe the stage of Rapid filling
Mitral and tricupsid valves open causing drop in atrial pressure. Sometimes a third heart sound is heard here especially in children.
Describe the stage of Reduced Filling
As ventricles reach their relaxed volume any further filling is driven by venous pressure and atrial contraction.