3.1.2f) The cardiac cycle

Question 1

1. Ventricles relax, atria contract

Answer 1

Ventricles relax
Atrias contract - decrease volume of chambers & increase pressure inside chambers pushes blood into the ventricles through the AV valves
Slight increase in ventricular pressure & chamber volume

Question 2

2. Ventricles contract, atria relax

Answer 2

Ventricles contract - decrease volume & increase pressure
Pressure becomes higher than in atria - AV valves shut to prevent backflow
Pressure is higher in ventricles than aorta & pulmonary artery - forces open SL valves & blood is forced out into those arteries

Question 3

3. Ventricles & atria relax

Answer 3

Ventricles & atria both relax
High pressure in pulmonary artery & aorta close SL (semi-lunar) valves to prevent backflow into ventricles
Blood returns to heart & atria fill - higher pressure in vena cava & pulmonary vein
Atria contract & the whole process begins again