The Heart

Question 1

Describe the cardiac cycle focusing on the left side

Answer 1

• Blood enters heart through pulmonary vein
• Bicuspid valves are shut so blood remains in the atrium
• Pressure increases in atrium, forcing bicuspid valve open
• Walls of the atrium contract pushing blood into ventricle
• Walls of ventricle contract forcing shut bicuspid valves and open semilunar valves
• Blood exits via aorta

Question 2

What do valves do

Answer 2

Prevent the backflow of blood

Question 3

Single circulatory system

Answer 3

Blood enters the heart once in a complete cycle
Fewer chambers and vessels
Less efficient
Less active organism (e.g. fish)
Can’t release energy as quickly

Question 4

Double circulatory system

Answer 4

Blood enters the heart twice in a complete cycle
Allows separation of oxygenated and deoxygenated blood
More efficient gas exchange
More respiration
More ATP released

Question 5

Unicellular organisms - how do they obtain nutrients

Answer 5

Larger SA:V
Diffusion can occur at a fast enough rate to meet demand of organism
(e.g. enough O2 to all body cells to meet metabolic demands)
Remove waste products at a fast enough rate that it won’t be problematic
No circulatory system

Question 6

Multicellular organisms - how do they obtain nutrients

Answer 6

Smaller SA:V
Not able to obtain enough nutrients (O2 and glucose) to all cells via diffusion at a quick enough rate to sustain life
Circulatory system required instead - would not be able to remove waste products quickly enough