The Circulatory System

Question 1

Atrial systole

Answer 1

• the ventricles are relaxing and the atria contracts
• this increases the pressure and decreases the volume in the atria, pushing the blood into the ventricles
• the atrioventricular valves are open

Question 2

Ventricular systole

Answer 2

• the atria relaxes and the ventricles contract
• there is now more pressure in the ventricles so the atrioventricular valves close to prevent back flow
• the pressure is also higher in the ventricles than in the aorta and the pulmonary artery which forces the semilunar valves open as blood is forced into the arteries

Question 3

Atrial and ventricular diastole

Answer 3

• the atria and ventricles both relax
• the higher pressure in the both the aorta and pulmonary artery (from elastic recoil) force the semilunar valves open lunar valves closed
• blood returns to the heart as the pressure in the vena cava and pulmonary vein is greater than in the atria
• as the ventricles continue to relax, there is a higher pressure in the atria so the atrioventricular valves open and blood trickles into the ventricles

Question 4

Diastole

Answer 4

• during diastole there is a drop in blood pressure and the blood in the veins is particularly affected
• the contraction of leg muscles in conjunction with the valves (preventing back flow) facilitates the return of blood to the heart

Question 5

Cardiac Output

Answer 5

stroke volume x heart rate

Question 6

Cardiac Output

Answer 6

volume of blood pumped by heart in 1 min

Question 7

Stroke Volume

Answer 7

volume of blood pumped in single heartbeat

Question 8

Heart Rate

Answer 8

number of heart beats per min