3.3.4.1 Mass transport in animals - CIRCULATION

Question 1

What happens in diastole?

Answer 1

-blood enters atria, causing pressure in atria to rise
-pressure in atria exceeds pressure in ventricles
-pressure difference causes blood to flow into ventricles
-atrioventricular valves OPEN
-walls of atria and ventricles are relaxing

Question 2

What happens in atrial systole?

Answer 2

-atrial muscles contract, increasing the pressure in atria
-ventricle walls recoil
-pressure in atria exceeds pressure in ventricles
-blood is forced from atria to ventricles
-atrioventricular (tricuspid) valves are open
-semi-lunar valves are closed
-volume of atria decreases and volume of ventricles increases

Question 3

What happens in ventricular systole?

Answer 3

-muscular walls of ventricles contract
-pressure in ventricles increases
-pressure in ventricles exceeds the pressure in atria + arteries
-atrioventricular valves close to prevent backflow of blood
-semi-lunar valves open to allow blood to flow into arteries
-atrial walls are relaxed and recoiling
-volume in ventricles increases and volume in arteries increases