Circulatory Systems, Heart & Blood Vessels (Cambridge (CIE) IGCSE Biology)
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What is the circulatory system?
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What is the circulatory system?
The circulatory system is a system of blood vessels with a pump and valves.
Why does the circulatory system contain valves?
The circulatory system needs valves to ensure one-way flow of blood.
True or False?
Fish have a single circulatory system. (Extended Tier Only)
True.
Fish have a single circulatory system.
What are the differences between single and double circulation? (Extended Tier Only)
Differences between single and double circulation include:
Single circulation
Double circulation
heart has 2 chambers
heart has 4 chambers (or sometimes 3)
blood passes through the heart once for every circuit of the body
blood passes through the heart twice for every circuit of the body
Why is it beneficial for mammals to have double circulation? (Extended Tier Only)
Mammals benefit from having double circulation because double circulation allows the heart to pump blood around the body at high pressure, so it supplies oxygen and glucose to the cells more quickly
What are the structures labelled A-D in the diagram?
The structures are:
A = right atrium
B = right ventricle
C = one-way valve / atrioventricular valve / bicuspid valve
D = septum
Describe the pathway of deoxygenated blood through the heart as it travels from the body to the lungs.
Deoxygenated blood from the body passes through the heart and to the lungs as follows:
blood enters the right atrium via the vena cava
it flows through a valve into the right ventricle
it is pumped into the pulmonary artery which takes it to the lungs
What role do valves play in the heart?
Valves in the heart prevent the backflow of blood, ensuring that blood flows in only one direction through the heart chambers and vessels.
How does blood return to the heart from the lungs?
Oxygenated blood returns to the heart from the lungs via the pulmonary vein.
How is the cardiac muscle of the heart supplied with oxygenated blood?
The coronary arteries supply the cardiac muscle of the heart with oxygenated blood, ensuring it receives a constant supply of oxygen and glucose for aerobic respiration to release energy for muscle contraction.
True or False?
Deoxygenated blood enters the left side of the heart from the body.
False.
Deoxygenated blood enters the right side of the heart from the body, via the vena cava.
Which vein is the only vein in the body to carry oxygenated blood?
The pulmonary vein is the only vein to carry oxygenated blood, returning blood to the heart after gas exchange has taken place.
True or False?
Arteries carry blood away from the heart.
True.
Arteries carry blood away from the heart while veins carry blood into the heart.
How can the activity of the heart be monitored?
The activity of the heart can be monitored as follows:
ECG
measuring pulse rate, e.g. at the wrist
listening to the valves close, i.e. listening to the heart beat
True or False?
Heart rate increases during exercise.
True.
During physical activity the heart rate increases.
How can the effect of exercise on heart rate be investigated?
The effect of exercise on heart rate can be investigated by:
measuring heart rate at rest, e.g. by recording pulse rate in beats per minute
taking part in exercise for a specified time period
repeating the heart rate measurement
This can be repeated several times at the same level of exercise, and could be extended by taking part in exercise at different intensity levels.
When investigating the effect of exercise on heart rate, what is the dependent variable?
In an investigation into the effect of exercise on heart rate, the dependent variable is heart rate, e.g. in beats per minute
Give examples of variables that would need to be controlled when investigating the effect of exercise intensity on heart rate.
Variables that would need to be controlled when investigating the effect of exercise intensity on heart rate include:
the person whose heart rate is measured
the type of exercise
the time period for which exercise is carried out
the method of measuring heart rate
the rest period between repeats
What is coronary heart disease (CHD)?
Coronary heart disease (CHD) occurs when the coronary arteries narrow due to build-up of fatty deposits; this reduces the flow of blood through the coronary arteries of the heart.
What are some of the risk factors for CHD?
Risk factors for CHD include:
diet
inactivity
stress
smoking
age
biological sex
How can a high quality diet reduce the risk of CHD?
A good diet can reduce blood cholesterol, reduce blood pressure and aid weight loss; these can all reduce the risk of CHD.
True or False?
Exercise can reduce the risk of CHD because it lowers blood pressure and reduces stress.
True.
Exercise can reduce the risk of CHD because it lowers blood pressure and reduces stress.
What are the two types of valve labelled X and Y? (Extended Tier Only)
The valves labelled X and Y are:
X = semilunar valve
Y = atrioventricular valve
Why does the left ventricle have a thicker muscle wall than the right ventricle? (Extended Tier Only)
The left ventricle has a thicker muscle wall so that it can pump oxygenated blood at high pressure throughout the body, while the right ventricle pumps deoxygenated blood at lower pressure to the lungs.
True or False?
The muscle walls of the atria are thicker than those of the ventricles. (Extended Tier Only)
False.
The atria have thinner walls than the ventricles. This is because they only need to pump blood the short distance to the ventricles, so they do not need to generate high pressures.
What is the purpose of the septum in the heart? (Extended Tier Only)
The septum separates the left and right sides of the heart, preventing oxygenated and deoxygenated blood from mixing.
True or False?
Contraction of the muscle of the atrial walls pumps blood into the ventricles. (Extended Tier Only)
True.
The muscular contractions of the atrial walls force blood downwards into the ventricles.
How do the heart valves enable forward flow of blood while preventing backflow? (Extended Tier Only)
The heart valves enable forward flow of blood while preventing backflow as follows:
high blood pressure in front of a valve forces the valve open, enabling forward flow of blood
high blood pressure behind a valve forces it closed, preventing blood from flowing backwards
Why does heart rate change during exercise? (Extended Tier Only)
During exercise the heart rate increases because:
increased blood flow increases the supply of oxygen and glucose to the muscles
muscle cells can respire faster and release more energy for muscle contraction
waste products of respiration (e.g. carbon dioxide) can be removed from the cells faster
What is the function of arteries?
Arteries carry blood away from the heart.
Which features in the diagram show that the blood vessel is an artery?
The blood vessel in the diagram is an artery because:
the wall is thick
the lumen is narrow
no valves are present
What is the function of veins?
Veins carry blood at low pressure towards the heart.
Which features in the diagram show that the blood vessel is a vein?
The blood vessel is a vein because:
the wall is thin
the lumen is wide
Which key feature of veins is not visible in the diagram?
The key feature of veins that is not visible in the diagram is the presence of valves.
What is the function of capillaries?
The function of capillaries is to transport oxygenated blood from the arteries to the cells, and deoxygenated blood from the cells to the veins.
In doing so they supply the cells with oxygen and nutrients, and remove waste products from the cells.
What are the names of the blood vessels labelled A-D in the diagram?
The blood vessels are:
A = pulmonary artery
B = vena cava
C = aorta
D = pulmonary vein
Which blood vessel carries deoxygenated blood to the lungs from the heart?
The blood vessel that carries deoxygenated blood to the lungs from the heart is the pulmonary artery.
True or False?
The pulmonary vein carries oxygenated blood to the lungs from the heart.
False.
The pulmonary vein carries oxygenated blood to the heart from the lungs.
True or False?
The renal vein carries oxygenated blood away from the kidneys.
False.
The renal vein carries deoxygenated blood away from the kidneys.
How are arteries adapted to their function? (Extended Tier Only)
Arteries are adapted for their function as follows:
thick, muscular walls can withstand high pressure
elastic fibres in the walls allow them to stretch
a narrow lumen maintains high blood pressure
How are veins adapted to their function? (Extended Tier Only)
Veins are adapted to their function as follows:
a wide lumen increases the volume of blood that flows at any one time
the wide lumen reduces friction between blood and the blood vessel walls
valves prevent the backflow of blood
What capillary adaptations are shown in the diagram? (Extended Tier Only)
Capillary adaptations shown include:
walls that are one cell thick, and that are made of flattened cells to reduce diffusion distance
a narrow lumen to increase contact between blood and the capillary walls, increasing diffusion
Note that while capillaries also have gaps between the cells in their walls to increase permeability, this feature cannot be seen in this image.
Which blood vessels are labelled A-C in the diagram? (Extended Tier Only)
Blood vessels A-C are:
A = hepatic vein
B = hepatic artery
C = hepatic portal vein
What are the main components of blood?
The main components of blood are:
red blood cells
white blood cells
platelets
plasma
What cell types are indicated by X and Y in the diagram of blood components?
Structures X and Y are:
X = red blood cell
Y = white blood cell
What is the role of red blood cells?
The function of red blood cells is to transport oxygen (via haemoglobin) to tissues and organs.
What is the function of white blood cells?
White blood cells are involved in the immune response; they carry out:
phagocytosis
antibody production
True or False?
Platelets transport oxygen around the body in the blood.
False.
Platelets are involved in the blood clotting process. Red blood cells transport oxygen.
What substances are transported in the blood plasma?
Substances transported in the plasma include:
blood cells
ions
nutrients
urea
hormones
carbon dioxide
Why is blood clotting important?
Blood clotting is important because it:
prevents significant blood loss from wounds
seals wounds with a scab, preventing entry of microorganisms that could cause infection
What are the blood cell types indicated by labels A-C? (Extended Tier Only)
Blood cell types A-C are:
A = lymphocyte
B = phagocyte
C = red blood cell
True or False?
Lymphocytes engulf and destroy pathogens. (Extended Tier Only)
False.
Lymphocytes produce antibodies. Phagocytes engulf and destroy pathogens.
What is the function of phagocytes? (Extended Tier Only)
The function of phagocytes is to engulf and destroy pathogens during phagocytosis.
True or False?
Soluble fibrin proteins are converted to insoluble fibrinogen proteins during the blood clotting process. (Extended Tier Only)
False.
Soluble fibrinogen proteins are converted to insoluble fibrin proteins during the blood clotting process.
What is the role of insoluble fibrin during blood clotting? (Extended Tier Only)
Fibrin forms an insoluble mesh across the wound, trapping red blood cells to form a clot, which eventually dries to become a scab.