The cardiovascular system T1

Question 1

How do you calculate heart rate?

Answer 1

60/time taken for one cardiac cycle

Question 2

Why do the atrioventricular valves need to close during ventricular systole?
(2)

Answer 2

• Ventricles need to contract and force blood into the aorta/pulmonary arteries/arteries.
• So valves need to close to prevent back flow into atria on contraction.

Question 3

Which is the heart blood vessel transporting blood with the highest pressure?

Answer 3

-Aorta

Question 4

As levels of activity increase, the heart can respond to the changing demand for oxygen.
During the cardiac cycle there are pressure changes in the chambers of the heart.
Explain how pressure differences in the heart ensure efficient pumping of the blood into the arteries.
(3)

Answer 4

• Pressure increases in the ventricles.
• Greater pressure in the ventricles than the atria.
• This causes atrioventricular valves to close.
• Causing the semi-lunar valves to open/forcing blood into the arteries.

Question 5

Explain the difference in thickness of the wall of the right atrium and the wall of the right ventricle.
(3)

Answer 5

• Right atrium has less muscle.
• This thickness is related to blood pressure required.
• Right atrium pumps blood to right ventricle.
• Right ventricle pumps blood to lungs.

Question 6

Explain how the structure of an artery is related to its functions.
(3)

Answer 6

• Elastic fibres:
• Allow stretching so the artery can accommodate to higher pressure/recoil to maintain.
• Folded endothelium:
• Allows stretching to accommodate high pressure.
• Smooth muscle:
• So muscle can contract.
• Smooth (lining/endothelium):
• Reduces friction due to blood flow.
• Narrow lumen:
• To maintain high blood pressure.
• Collagen:
• Avoiding rupture or damage.

Question 7

Why do only small animals have an open circulatory system?

Answer 7

Movement of oxygen, carbon dioxide and other products carried by the blood relies on diffusion with an open CS, diffusion is only fast enough for small organisms.

Question 8

What are the advantages of having a double circulatory system?

Answer 8

Blood can pass slowly through the region where gaseous exchange takes place; maximising the transfer of oxygen and carbon dioxide; and then be pumped vigorously around the rest of the body, Allowing the organisms to be very active.