Cardiac Cycle

Question 1

What happens when pressure is greater in front of the valve

Answer 1

The valve closes

Question 2

What happens when pressure is greater behind the valve

Answer 2

The valve opens

Question 3

What causes the valves to open and close

Answer 3

The valves are forced open and closed by pressure of the blood in the heart

Question 4

What prevents the atrioventricular valves from inverting

Answer 4

Heart tendons (chordae tendinae)

Question 5

What holds the atrioventricular valves in place

Answer 5

Papillary muscles

Question 6

What is the cardiac cycle

Answer 6

This is the complete cycle of events in the heart from the beginning of one heart beat to the beginning of the next

Question 7

What is the contraction of the heart called

Answer 7

Systole

Question 8

What are the two divisions of the systole

Answer 8

The atriole systole (the atria contract) and the ventricular systole (the ventricles contract)

Question 9

What follows the contraction in the cardiac cycle

Answer 9

A period of relaxation known as diastole

Question 10

What are the three stages that the cardiac cycle can be split into

Answer 10

Diastole- the heart relaxes and blood enters the atria
Atria systole- the atria contract and push blood into the ventricles
Ventricular systole- the atria relax, the ventricles contract and blood moves out of the arteries

Question 11

Describe what occurs during diastole

Answer 11

The atria and ventricular walls are in diastole (relaxed). Blood moves into the heart via the pulmonary vein and vena cava. The atrioventricular valves are open (due to the pressure of the blood against them) and the semilunar valves are closed as the pressure is higher in the arteries than in the ventricles.

Question 12

Describes what happens during atrial systole

Answer 12

The atria walls contract, because they are in systole while the ventricular walls are still in diastole; they are relaxed. The atrioventricular valves are still open and the semilunar valves are closed. Therefore, blood moves to the ventricles.

Question 13

What happens when ventricular systole occurs

Answer 13

The atria are relaxed and the atrioventricular valves close due to the pressure of blood against the valve flaps.

Question 14

During ventricular systole why does the semilunar valves open

Answer 14

They open due to pressure being higher in the ventricles than in the arteries

Question 15

How does blood move during ventricular systole

Answer 15

Blood moves out of the ventricles to the arteries and then to the lungs or body. Then the cycle starts again

Question 16

Explain why the wall of the left ventricle is thicker than the wall of the left atrium

Answer 16

This gives it more muscle to create more force as it needs to create higher higher pressure to push blood with greater force. This way the left ventricle is able to pump blood further to all parts of the body

Question 17

Explain how pressure changes in the heart bring about the closure of the atrioventricular (bicuspid valve)

Answer 17

Ventricular systole contracts, this contraction raises ventricular pressure. This pressure becomes higher than atrial pressure. This higher pressure closes the atrioventricular valves.