The cardiac cycle

Question 1

What are the 2 phases to the beating of the heart?

Answer 1

Contraction - systole

Relaxation - diastole

Question 2

Why is the wall on the left ventricle thicker than the right?

Answer 2

The left ventricle has to pump blood around the body so it goes over quite a long distance whereas the right ventricle only pumps blood to the lungs so it only has a short distance to travel.

Question 3

What happens during diastole of the cardiac cycle?

Answer 3

• Blood returns to the atria of the heart through the pulmonary vein and vena cava.
• As the atria fill, the pressure increases, when the pressure is higher than the pressure in the ventricle, the AV valve opens to let blood to pass into the ventricles, the passage of the blood is aided by gravity.
• The walls of atria and ventricles are both relaxed at this stage.
• SL valve is shut.

Question 4

What happens during atrial systole of the cardiac cycle?

Answer 4

• Atrial walls contract.
• It pushes all the remaining blood into the ventricle.
• The ventricle walls are relaxed at this stage.

Question 5

What happens during ventricular systole of the cardiac cycle?

Answer 5

• Atria relaxes.
• Ventricles are now filled with blood and their walls contract.
• This increases the blood pressure within so AV valves will shut to prevent backflow.
• With the closing of AV valves, the pressure in the ventricle rises further.
• When the pressure is higher than it is in the aorta or pulmonary artery, SL valve open and blood is forced from the ventricles into the vessels.

Question 6

How to calculate cardiac output?

Answer 6

Heart rate x stroke volume.

Question 7

What direction will blood flow in?

Answer 7

It flows in one direction through the heart due to the pressure created by the heart muscle. Blood moves from a region of high pressure to low pressure.

Question 8

What do valves do?

Answer 8

It prevents backflow of blood, as sometimes there might be regions where there are pressure differences.

Question 9

What is the AV valve?

Answer 9

• Between the left and right atrium and ventricle.
• It prevents backflow of blood when contraction of the ventricles so when the pressure in the ventricle is higher than the atrium.
• Closer of the valves ensure that the blood will flow into the aorta or pulmonary artery.

Question 10

What is the SL valve?

Answer 10

• In the aorta or pulmonary artery.
• It prevents backflow of blood into the ventricles when the pressure in the vessel is higher than in the ventricle.
• When the elastic walls of the vessels recoil, it increases the pressure within them and when the ventricle relaxes it reduces the pressure within the ventricles so there’s a greater pressure difference.

Question 11

What is the pocket valve?

Answer 11

• It’s in the veins and occurs throughout the venous system.
• It ensures when the veins are squeezed e.g. skeletal muscles contract, blood flows back into the heart rather than away from it.

Question 12

What makes up valves?

Answer 12

Numbers of flaps of tough but flexible fibrous tissue, in curve shape.