cardiovascular and respiratory system (topic 2).

Question 1

explain how the human circulatory system is adapted to provide oxygen and remove waste products from our tissues (6)

Answer 1

humans have a double circulatory system:
- double circulatory system
- which means there is greater flow of blood to the tissues (higher blood pressure)
the heart is a muscle:
- heart made of muscle cells which have long protein filaments
- which slide past each other to shorten the cell
- to bring about contraction for pumping blood
blood is oxygenated in the lungs:
- heart pumps blood to lungs in pulmonary artery so that oxygen can diffuse into blood from air in alveoli
- blood returns to heart via pulmonary vein where muscles pump blood to the body via aorta
oxygenated blood is taken to the body cells in red blood cells:
- oxygen carried by RBCs
- which contain haemoglobin to bind oxygen
- and have no nucleus so there is more space available to carry oxygen
blood vessels transport blood throughout the body:
- arteries carry oxygenated blood to tissues where capillaries deliver oxygen to cells
- for respiration and energy release
- thin walls of capillaries allow for easy diffusion to cells
- large surface area of capillaries maximises exchange
- waste products removed / diffuse from cells into the blood plasma
- blood goes back to the heart in veins
- which have valves to prevent backflow

Question 2

explain how the human lungs are adapted for efficient exchange of gases by diffusion (6)

Answer 2

alveoli:
- lungs have many alveoli
- which provide a larger surface area (to volume ratio)
capillaries:
- capillary walls are thin
- capillaries are close to the alveoli
- short diffusion path (for oxygen and carbon dioxide)
capillary network:
- large capillary network around alveoli (or good blood supply)
- to remove oxygenated blood quickly
- to bring carbon dioxide to the lungs quickly
- to maintain a concentration gradient

Question 3

suggest why an emphysema (lung disease that damages the alveoli in lungs, shortness of breath) sufferer may not be able to engage in physical activities (2)

Answer 3

• less oxygen is taken in
• less oxygen available for respiration
• less energy released

Question 4

what are the main components of the blood, name each component and describe its function in the human body (6)

Answer 4

red blood cells:
- contain haemoglobin (which binds to oxygen)
- carry oxygen from the lungs to the bodys tissues
white blood cells:
- are part of the immune system (help the body fight against infection)
- engulf pathogens
- produce antibodies
- produce antitoxins
platelets:
- are small cell fragments
- involved in blood clotting
plasma:
- is the liquid component of blood
- carries various substances like hormones and antibodies
- and clotting factors to different parts of the body

Question 5

predict the differences between blood collected from an artery and blood collected from a vein (2)

Answer 5

arterial blood has:
- more oxygen
- more glucose
- more amino acids / fatty acids
- less carbon dioxide
- less lactic acid

Question 6

how do platelets contribute to the process of blood clotting (6)

Answer 6

• platelets in the blood carry a chemical
• which is released into the plasma when the platelets come into contact with air/damaged cells
• the chemical changes the soluble plasma protein fibrinogen into the insoluble fibrin
• fibrin forms long threads which traps some red blood cells
• making a plug called a blood clot
• phagocytes engulf the pathogens
• the clot hardens protecting the wound as the skin heals beneath

Question 7

Answer 7

A = aorta
B = pulmonary vein
C = left atrium
D = left ventricle
E = right ventricle
F = right atrium
G = vena cava
H = pulmonary artery

Question 8

pathway of blood (6)

Answer 8

• deoxygenated blood enters the right atrium of the heart from the vena cava
• blood moves into right ventricle
• blood is pumped into the pulmonary artery
• the pulmonary artery carries deoxygenated blood to the lungs
• the blood becomes oxygenated in the lungs
• oxygenated blood leaves the lung via the pulmonary vein
• blood enters the left atrium
• blood moves into the left ventricle
• blood is pumped into the aorta which carries oxygenated blood around the body

Question 9

suggest why it is more common that a stroke is caused by an artery than a vein

Answer 9

blood in arteries is under higher pressure

Question 10

describe the sequence of events that can lead to a heart attack (6)

Answer 10

• increase in levels of cholesterol in the blood
• causes fatty deposits to build up in the coronary arteries
• a blood clot forms on a fatty deposit
• blocks a coronary artery
• some heart muscle cells do not get enough oxygen
• if left untreated then the cells start to die leading to a heart attack

Question 11

(6)

Answer 11

fatigue (max 2 marks):
- fewer red blood cells
- so less haemoglobin
- so less oxygen transported around the body
- so less aerobic respiration can take place
infections (max 2 marks):
- fewer white blood cells
- fewer antibodies produced or less phagocytosis
- fewer pathogens killed
bleeding:
- fewer platelets
- so blood does not clot as easily

Question 12

amphibians have a three-chambered heart that has two atria and only one ventricle rather than the four-chambered heart of mammals, suggest why the circulatory system of amphibians is less efficient than that of mammals (2)

Answer 12

• oxygenated and deoxygenated blood mixes
• so less oxygen reaches the tissues (and body)