9- circulatory system

Question 1

what are the advantages of double circulation

Answer 1

1. blood returning from the lungs has a much higher pressure to go around the body
2. more oxygen can be delivered faster

Question 2

why and how does physical activity increase heart rate

Answer 2

1. as you exercise, the more energy you need, so respiration increases
2. therefore more oxygen is needed to be moved to the muscles and CO2 away from the muscles
3. pH of the blood increases so the brain signals to the heart to beat more frequently

Question 3

what are arteries and what are their adaptations

Answer 3

1. vessels that carry blood from heart to other organs
2. they have thick, collagen-rich walls and a narrow lumen for high blood pressure

Question 4

what are capillaries and what are their adaptations

Answer 4

1. the branches of arterioles
2. tiny, and very close to the cells
3. carries glucose and O2 to the cells and removes CO2
4. one cell thick permeable membrane

Question 5

what are veins and what are their adaptations

Answer 5

1. thin walls and wide lumen; so lower pressure
2. one ways valves

Question 6

how do platelets stop bleeding

Answer 6

1. soluble protein fibrinogen is present in the blood
2. enzyme thombrin turns fibrinogen into insoluble fibrin