SPEC POINT 1.4

Question 1

Why do double circulatory systems enable mammals to carry out effective gas exchange?

Answer 1

1. One side of heart pumps blood to lungs, the other to the body
2. separation of oxygenated and deoxygenated blood
3. maintained concentration gradient
4. transport system for mass flow, supplying O2 to cells
5. need a good supply of oxygen as mammals are very active

Question 2

What is the cardiac cycle?

Answer 2

The series of events that take place within one heartbeat

Question 3

What happens to pressure when volume increases/decreases within a chamber of the heart?

Answer 3

Volume increase = pressure decrease

Volume decrease = pressure increase

Question 4

When do valves open/close in the heart?

Answer 4

Valves open when the pressure of the blood behind them is greater than the pressure in front of them
Valves close when the pressure behind them is less than the pressure in front of them

Question 5

What happens during diastole?

Answer 5

1. Heart relaxes so heart has a lower pressure than major blood vessels
2. So blood moves from high pressure in VENA CAVA and PULMONARY VEIN into ATRIA
3. SEMI LUNAR VALVES in AORTA and PULMONARY ARTERY prevent blood moving back into VENTRICLES

Question 6

What happens during atrial systole?

Answer 6

1. ATRIA contract so ATRIA pressure is higher than ventricles
2. This causes the ATRIOVENTRICULAR VALVES to be open
3. Blood moves from ATRIA to VENTRICLES

Question 7

What happens during ventricular systole?

Answer 7

1. VENTRICLES contract slightly after ATRIA so VENTRICULAR pressure is higher than ATRIA
2. So the ATRIOVENTRICULAR VALVES close
3. VENTRICULAR pressure is higher than ARTERIES, so SEMILUNAR VALVES open
4. Blood moves into ARTERIES
5. (diastole begins)

Question 8

How do pressure differences in the heart ensure efficient pumping of the blood into the arteries?

Answer 8

1. Greater pressure in VENTRICLES than ATRIA
2. This causes ATRIOVENTRICULAR VALVES valves to shut
3. The SEMILUNAR VALVES are then forced open and blood is pushed into the ARTERIES

Question 9

Why is there a difference in thickness between the right atrium wall and right ventricle wall?

Answer 9

The right atrium wall is thinner because of the higher blood pressure required in the ventricles. The right atrium only pumps blood to the ventricle but the ventricle pumps blood to the lungs (pulmonary artery)

Question 10

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

Answer 10

It has to pump blood further around the body, and therefore has to withstand higher pressure