The Cardiac Cycle Flashcards
Diastole
Relaxation of the heart
Atrial Systole
Atria Contract, ventricles relax
Ventricular systole
Ventricles contract, atria relax
What happens as the atria fill?
Pressure increases
What happens due to the atrial pressure being high?
Atrioventricular valves open
What happens when the atrial walls contract?
Blood goes to the ventricles
Why are the muscular walls in the atria thin?
Blood doesnt have to go that far so contractions don’t have to be big
What happens to the ventricles in atrial systole?
they are relaxed
What happens to ventricles in ventricular systole?
They contract
What happens to the AV in ventricular systole?
they close
What happens to the semi lunar valves in ventricular systole?
they open
Why do the semi lunar valves open during ventricular systole?
the pressure behind them is higher
Describe how heart action is coordinated by the SAN & AVN
the SAN starts the wve of excitation which spreads across the walls of the atria until it reaches the AVN
Atria contract
delay between the atria contracting and the ventricles contracting
excitation spreads down the bundle of His and the purkyne fibres
Ventricles contract
