Module 3 Section 2 - The Heart

Question 1

What prevents the back flow of blood

Answer 1

Valves

Question 2

What do the atrioventricular valves link

Answer 2

The atrioventricular valves link the atria to the ventricles

Question 3

What do the semilunar valves link

Answer 3

The semilunar valves links the ventricles to the pulmonary artery (right) or aorta (left)

Question 4

How do valves work

Answer 4

• The valves only open one way
• Whether they’re open or closed depends on the relative pressure of the hearts chambers

Question 5

What is the position of the valve if there’s higher pressure behind it

Answer 5

The valve is forced open

Question 6

What is the position of the valve if there’s higher pressure in front of it

Answer 6

The valve is forced shut

Question 7

What is the cardiac cycle

Answer 7

An ongoing sequence of contraction and relaxation of the atria and ventricles that keeps blood continuously circulating round the body

Question 8

What are the three stages of the cardiac cycle

Answer 8

Atrial systole
Ventricular systole
Diastole

Question 9

What is atrial systole

Answer 9

• Ventricles relax, Atria contract
• The atria contract - decreases volume and increase pressure of the atria
• pushes blood into the ventricles through the AV valves
• Slight increase in ventricular pressure and volume as the ventricles reserve the ejected blood from contracting atria

Question 10

What is ventricular systole

Answer 10

• Ventricles contract, atria relax
• Ventricles contract, decreases volume and increases pressure of ventricles
• pressure becomes higher in ventricles than atria which force AV valves shut to stop back flow
• the high pressure in the ventricles open the semi lunar valves
• blood is forced out into the pulmonary artery and aorta

Question 11

What is diastole

Answer 11

• Ventricles and atria both relax
• higher pressure in pulmonary artery and aorta causes semi lunar valves to close preventing back flow
• the atria fill with blood (increasing atria pressure) due to higher pressure in the vena cava and pulmonary vein
• as ventricles continue to relax, their pressure falls below the pressure in the atria.
• this causes AV valves to open and blood flows passively (without being pushed by atrial systole) into the ventricles from the atria

Question 12

What is cardiac output

Answer 12

The volume of blood pumped by the heart per minute

Question 13

What is cardiac output measured in

Answer 13

It is measured in cm³ min ^-1

Question 14

What is the formula for cardiac output

Answer 14

Cardiac Output = Hear Rate x Stroke Volume