Organisms Exchange Substances with their Environment: Mass Transport in Animals - Cardiac Cycle

Question 1

Define the term systole

Answer 1

• When the heart contracts

Question 2

Define the term diastole

Answer 2

• When the heart relaxes

Question 3

How does blood move along a pressure gradient?

Answer 3

• Blood moves from an area of higher pressure to an area of lower pressure

Question 4

Describe what happens during atrial systole

Answer 4

• The atria contract

• This decreases volume of atria
• This increases pressure of atria

• Atrioventricular valves open

• The ventricles are relaxed
- Blood moves from atria to ventricles down a pressure gradient

• The semi-lunar valves close
- To prevent blood in ventricles moving to arteries

Question 5

Describe what happens during ventricular systole

Answer 5

• The ventricles contract

• This decreases volume of ventricles
• This increases pressure of ventricles

• Semi-lunar valves open
- Blood moves from ventricles to arteries down a pressure gradient

• The atria are relaxed and atrioventricular valves close
- To prevent backflow of blood from ventricles to atria

Question 6

Describe what happens during diastole

Answer 6

• Atria and ventricles are relaxed

• Blood re-enters atria via vena cava / pulmonary vein
• Atria fill with blood, increasing pressure

• Atrioventricular valves open
- Blood enters ventricles

• Semi-lunar valves close
- To prevent backflow of blood from arteries to ventricles