Heart and Lung

Question 1

The events of one heartbeat, so called cardiac cycle

Answer 1

• The heart releaxes and blood enters both atria from veins.
• Both atria contract to push blood into the ventricles through the atrioventricular valves
• The ventricles contract powerfully
• The atrioventricular valves shut, preventing blood from flowing back into the atria
• The semilunar valves open, allowing blood into the aorta and pulmonary artery
• The ventricles relax
• The atria begin to fill again to repeat the cycle

Question 2

Why do we need a circulation?

Answer 2

Blood is a mass flow or a mass transport system. Large volumes of fluid are pumped rapidly around the body from organs of exchange such as the guts and lungs, to the cells that need them.
The heart is simply a pump. Mammals have a double circulation — there are two circuits that take blood on a return journey to the heart.
1 The pulmonary circulation carries blood to the lungs and back.
2 The systemic circulation carries blood to the rest of the body and back.
We need two circulations because blood goes to the lungs to collect oxygen, but in doing so it loses pressure, so it needs to return to the heart for a boost. In order to pump blood round two circulations at the same time, we need a four-chambered heart:

●Two atria. Their job is simply to fill with the right volume of blood, and pump it into the ventricles. Think of them as ‘loading chambers’.
●Two ventricles, whose job is to create pressure. They contract powerfully, forcing blood into arteries.

The right side of the heart fills with deoxygenated blood, and
pumps blood around the pulmonary circulation.
The left side of the heart fills with oxygenated blood from the lungs, which needs to be pumped around the systemic circulation. This requires more pressure, so the left ventricle has a thicker muscle wall than the right ventricle.

Question 3

How many types of blood vessels are there?

Answer 3

There are three main types of blood vessels: arteries, veins and capillaries.

Question 4

What is coronary heart disease?

Answer 4

It is the most common form of heart disease in which the arteries become narrower due to a build-up of fatty deposits inside them. When the coronary arteries get blocked, not enough oxygen and glucose reaches the heart muscle, part of the heart muscle dies, and a heart attack results.
When coronary arteries narrow, they can be treated by inserting a stent — a tubular wire mesh that keeps the lumen of the artery open to allow the blood to flow freely again.

Question 5

How does gas exchange happened in the capillaries?

Answer 5

• Blood flows from the heart into arteries, then into smaller arteries, which finally branch out into capillaries. These tiny vessels take blood to within a fraction of a millimetre of all the respiring cells.
• All cells are surrounded by tissue fluid, from which cells get the oxygen and nutrients, and into which they secrete their waste and other products. Blood slows down as it flows along a capillary. The walls are one cell thick and permeable (leaky) so that exchange can happen between blood and tissue fluid. Tissue fluid is basically plasma that leaks out of the capillaries.

Question 6

For each of the following blood vessels, state the pressure and the oxygen content of the blood it contains (you could do this as a table):

a) vena cava
b) pulmonary artery
c) pulmonary vein
d) aorta

Answer 6

a) vena cava — deoxygenated, low pressure
b) pulmonary artery — deoxygenated, high pressure
c) pulmonary vein — oxygenated, low pressure
d) aorta — oxygenated, high pressure

Question 7

Blood flow is slowest in capillaries. Suggest an advantage of this slow flow.

Answer 7

There is more time for diffusion/exchange of materials.

Question 8

Arteries carry oxygenated blood. Is this always true? Explain.

Answer 8

No, the pulmonary artery carries deoxygenated blood.

Question 9

Most arteries lie deep under the surface of the skin, while veins run much closer to the surface. Explain the advantage of this arrangement.

Answer 9

There is less chance of an artery being cut. Rapid blood loss would be dangerous/fatal.

Question 10

What is blood made up of?

Answer 10

Blood is a complex fluid containing red blood cells, white blood cells, platelets ( bits of broken cells) and plasma.

Question 11

Red blood cells

Answer 11

Red blood cells are basically little bags of haemoglobin. They have no nucleus or any of the other normal cell contents such as mitochondria.
The function of haemoglobin is to collect oxygen where it is abundant — the lungs — and release it where it is needed — the respiring tissues.
As red blood cells pass through the lungs, haemoglobin combines with oxygen to form bright red oxyhaemoglobin. As it passes through the respiring tissues in the rest of the body, the haemoglobin gives up its oxygen, becoming a darker red as it does so.

Question 12

White blood cells

Answer 12

White blood cells defend the body against attack by microbes/pahtogens.

Lymphocytes produce antibodies to destroy microorganisms and memory lympohocytes give us immunity to specific diseases. Phagocytes engulf and digest microorganisms.

About 70% of white blood cells are phagocytes.

Question 13

Platelets

Answer 13

Platelets are cell fragments which help clot the blood.

Question 14

Plasma

Answer 14

Plasma is the yellow liquid which transports dissolved food molecules, carbondioxide, and urea as well as all the blood cells. It’s mainly water.

Plasma also contains other important substances such as hormones, blood clotting factors and heat.

Question 15

Red blood cells do not live very long. Use your knowledge of their structure to suggest why.

Answer 15

They have no nucleus, so are not able to repair themselves and therefore have a short life.

Question 16

The higher the altitude at which people live, the greater the volume of red blood cells in their blood. Suggest an advantage of this adaptation.

Answer 16

At higher altitude, each red cell carries less oxygen. So having more red blood cells compensate for this/allows more oxygen to be carried.

Question 17

Why exchange gas?

Answer 17

● All living things must respire — this is the release of energy from
organic molecules such as glucose.
● Respiration uses oxygen, and produces carbon dioxide.
● So all living things must exchange these gases.
● Large organisms — and especially those with high energy demands, such as mammals — need to exchange lots of gas.
● That is why special gas exchange organs such as lungs and gills have evolved.

Question 18

Explain why we cannot drink seawater to cure dehydration.

Answer 18

Seawater has a high salt concentration, which will draw water out of the blood by osmosis and make dehydration worse.

Question 19

Blood clotting is a relatively fast reaction. Give two advantages of
this fact.

Answer 19

Less blood loss; less chance of infection.

Question 20

The lungs contain no muscle. Explain how they inflate.

Answer 20

The lungs are attached to the ribcage and diaphragm (1 mark). The intercostal muscles and diaphragm contract (1 mark), increasing the volume in the thorax (1 mark) and lowering the pressure (to below atmospheric) (1 mark). So air flows in (1 mark).

Question 21

a) Describe how our breathing pattern changes when we exercise.

b) Explain the need for this change.

Answer 21

a) We breathe more deeply, and more frequently.
b) Any three from:

• Muscles respire.
• So they need more oxygen.
• And they make more CO2
• l So gas exchange must be faster.

Question 22

The young of frogs and toads are called tadpoles and they have gills. Predict what features these gills will have in order to maximise gas exchange.

Answer 22

large surface area, thin membranes, good blood supply

Question 23

Smoking effects and health

Answer 23

• Nicotine in smoke makes your heart beat faster and increases your blood pressure. Your heart then need to work faster.
• Carbon monoxide in smoke lowers the amount of oxygen blood can carry as it binds easily to haemoglobin. In pregnant smoker, the developing foetus gets less oxygen and so grows more slowly.
• Substances in smoke, tar and particulates, damages the cilia (ciliated epithelial cells), that line the airways (trachea, bronchi and bronchioles). And increase the risks that arteries will become narrowed by fatty material (atheroma). This can cause heart attacks and strokes.
• Increases cholesterol which causes coronary artery to narrow and less oxygen gets to heart muscles, more anaerobic respiration. Can increase risk of heart attack.

Question 24

Smoking damage to the lungs

Answer 24

Tobacco smoke has the following effects:

• Cilia are destroyed so dirt and bacteria are not removed.
• Emphysema – the walls of the alveoli are damaged and break down to form large irregular air spaces which do not exchange gases efficiently. These all act to decrease the rate of diffusion of O2 through the alveoli into the blood, and the rate of diffusion of O2 from the blood into the respiring tissues. The same is true for CO2 but in the opposite direction. This makes smokers breathless.
• Lung cancer- tar and other chemicals cause cells to mutate and form cancers in the lungs and throat.
• Carbon monoxide binds to haemoglobin, lowering the oxygen levels in the blood. In pregnant women, this deprives the fetus of oxygen and can lead to smaller babies and stillbriths.
• Smoking also affects the circulatory system and causes an increased risk of heart attacks and strokes.

Question 25

Emphysema

Answer 25

This damages the walls of the alveoli and vastly reduces the surface area of the lungs. This means that it may no longer be possible to get sufficient O2 to the rest of the body. Thus a sufferer will be breathless and unable to carry out physical exercise. In extreme cases an oxygen cylinder is needed to increase the availability of oxygen to the respiring tissues in the body.

Question 26

Aerobic and anaerobic respiration

Answer 26

If there is enough oxygen for respiration, aerobic respiration occurs.
However, if there is not enough oxygen an organism can respire using anaerobic respiration . This releases less energy.

Aerobic respiration is much more efficient and releases more energy per glucose molecule (19 times) than anaerobic respiration.

Question 27

The oxygen debt

Answer 27

In humans during vigorous exercise our lungs cannot move enough oxygen to our muscles and anaerobic respiration occurs. Lactic acid builds up in the muscles and causes cramps. This lactic acid needs to be removed and metabolized. It can be respired but this requires oxygen. This is known as an oxygen debt. Thus at the end of the exercise the breathing rate and heart rate stay high as the oxygen necessary for the removal of the lactic acid is obtained.

Question 28

Respiration equation

Answer 28

Respiration equation

Glucose + Oxygen —> Carbon dioxide + Water + Energy Released

In animals, lactic acid is made during anaerobic respiration, but in plants and fungi they make ethanol .

Anaerobic respiration equation in animals

Glucose –> Lactic acid + Energy Released

Anaerobic respiration equation in plants

Glucose —> Ethanol + Carbon dioxide + Energy Released

Question 29

Adaptations of red blood cells that help them to perform their function

Answer 29

• Red blood cells transport oxygen from lungs to the tissues. Red blood cells are small and flexible, so they can pass through narrow blood vessels.
• They don’t have nucleus, so they can be packed with haemoglobin.
• The small size and biconcave shape of red blood cells gives them a large surface area to volume ratio for obsorbing oxygen. When the cells reaches the lungs, oxygen diffuces from the lungs into the blood.
• The haemoglobin modules in the red blood cells binds easily with the oxygen to form oxyhaemoglobin.
• The blood is then pumped around the body to the tissues, where the reverse reaction takes place. Oxygen is released which diffuses into cells.

Question 30

Arteries, 10mm diameter on average

Answer 30

• Arteries carry blood away from the heart.
• Substances from the blood can’t pass through artery walls.
• They have thick, muscular, elastic walls in order to cope with the high pressure created when the heart beats.

Question 31

Veins, 4mm diameter (average)

Answer 31

• Veins return blood to the heart.
• They have thinner walls than an artery and have less elastic muscular fibre because they do not have to cope with high pressure.
• They have valves to prevent blood flowing backwards.

Question 32

Capillaries (0.005mm diameter), very narrow lumen

Answer 32

Capillaries are tiny blood vessels whose walls are one cell thick.
The walls are permeable because their function is to allow exchange of substances between blood and the body cells.

Question 33

Describe and explain the differences between the structures of arteries and veins.

Answer 33

• Arteries have thick muscular and elastic walls, which can withstand the high pressure of blood they carry.
• Veins carry blood at low pressure. They contain valves that prevent the low pressure blood flowing backwards. They also have thinner walls than arteries as they don’t need to withstand high pressure of blood.

Question 34

The Heart

Answer 34

The heart consists of powerful muscles that pump blood around the body. It needs glucose and oxygen for respiration because it never get tired or needs rest, so it has high energy requirements.

• The coronary artery supplies the heart itself with glucose and oxygen.
• The pulmonary vein carries oxygenated blood from the lungs to the heart.
• The aorta carries oxygnated blood from the heart to the rest of the body.
• The vena cava carries deoxygenated blood from the parts of the body back to the heart.
• The pulmonary artery carries deoxygenated blood from the heart to the lungs.

Question 35

How does the body control heart rate?

Answer 35

The heart beat is controlled by groups of cells called the **pacemaker ** (or sino-atrial node, SAN)

The SAN produces impulses that spread across the atria to make them contract.

The atriventricular node (AVN) relays impulses that spread over the ventricles to make them contract.

Nerves connecting the heart to the brain can increase or decrease the pace of the SAN in order to regulate the heart beat. During exercise, muscles demand more energy so the pacemaker fires more frequently. This makes the heart rate speed up to supply oxygen and glucose to respiring muscles more efficiently.

Adrenaline is also secreted during exercise. Adrenaline acts on the pacemaker making it fire more frequently.

Question 36

Explain why microorganisms reproduce very rapidly once inside the body.

Answer 36

The body provides ideal conditions for microorganisms to grow - warmth, moisture, and plently of nutrients.

Once in your body, harmful microorganisms reproduce very rapidly - some populations can double as fast as every 20 minutes. e.g. Salmonella poisoning.

Question 37

Name two types of white blood cells that are important in the immune response.

Answer 37

Phagocytes and lymphocytes.

Question 38

Describe how anitbodies help to destroy pathogens.

Answer 38

Some antibodies make microorganisms clump together and this makes it easier for phagocytes to digest them.

Question 39

Explain how vaccinations prevent illness.

Answer 39

A vaccination causes production of memory cells to a specific disease-causing microorganism. If a person is later infected with that organism the memory cells stimulate very rapid production of antibodies to the organism. The organism is destroyed before it makes the person ill.

Question 40

Microorganisms and Infection

Answer 40

Infections are caused by microorganisms damaging the body cells or producing poisons (toxins) that harm cells. Infections can be treated with drugs called antimicrobials (e.g. antibotics).

Microorganisms that cause infections are called pathogens and include:

• bacteria, which cause bubonic plague, tuberculosis(TB) and cystitis - treated by antibiotic
• fungi, which cause athlete’s foot, thrush and ringworm - treated by anti-fungal medicine and antibotics
• viruses, which cause Asian bird flu, common cold, HIV, measles and smallpox - very difficult to treat; antibiotics don’t work on viruses.

Question 41

The Immune Response

Answer 41

If the microorganisms get into your body, your immnue system is activiated.

Two types of white blood cell are important in this response - phagocytes and lymphocytes.

Phagocytes

• Phagocytes is activiated when the microorganism gets into the body.
• The phagocyte finds the microorganisms and engulfs them.
• The phagocytes ingests the microorganisms.
• The microorganisms have been digested and destroyed.

Lymphocytes

• Lymphocytes make antibodies. Antigens are markers on the surface of the microorganism.
• The lymphocyte becomes sensitised to the antigens and produces antibodies.
• The antibodies then lock onto the antigens.
• This cause the microorganism to clump together, so that phagocytes can digest them.

Question 42

Specialisation of Antibodies

Answer 42

Different microorganisms cause different diseases. e.g. Antibodies to fight TB will not fight Cholera.

Microorganisms have unique markers, called antigens, on their surface. White blood cells produce antibodies specific to the marker they need to attack. After infection, some white blood cells act as memory cells as they ‘remember’ the antigens and are able to produce antibodies quicker if the body is re-infected. This is natural immunity and it protects that particular individual in the future.

Question 43

How does vaccination helps the body develop immunity?

Answer 43

• Vaccine contain antigens that are the same as those found in the microorganism that causes a disease.
• When the vaccine containing weakened/dead strain of the microorganism is injected, the antigens on the modified microorganism’s surface cause the lymphocytes to produce specific antibodies
• The microorganisms is destroyed before they can cause infection.
• The lymphocytes that are capable of quickly producing the specific antibody, memory cell, remain the bloodstream.

Question 44

List diseases caused by smoking

Answer 44

Smoking can lead to several diseases, including cancer of the mouth, throat, oesophagus and lungs, heart disease, emphysema and bronchitis.

Tar in cigarettes contains chemicals that are irritants and carcinogens ( cancer-causing chemicals).

Particulates in cigarette smoke accumulate in living tissue (e.g. lungs) and can cause cancer.

Question 45

Simple experiment to investigate the effect of exercise on breathing rate

Answer 45

1. Sit still for five minutes and then count your breaths for one minute.
2. Now do some exercise for four minutes. e.g standing on and off a step, skipping or jogging on the spot, etc.
3. Immediately after you’ve finised exercising, count how many breaths you take in one minute
4. Record the change in number of breaths per minute before and after exercise.
5. Repeat the experiment a few times with different people.

Variables that you should keep the same include the time spent exercising and the type of exercise you do.

You should find that number of breath per minute increase during exercise. You’ll also find that the breathing rate stays higher than normal for serveral minutes after the exercise stops.

Question 46

Aerobic respiration

Answer 46

• Respiration is one of the seven signs of life. It’s a process that goes on in all cells, in all organisms, all of the time.
• Animals, plants, fungi and bacteria respire all the time, all day and all night.
• The only cells that do not respire are either dead or dormant (such as seeds in winter).
• Respiration releases energy from organic molecules such as glucose and lipid(fat). Humans normally use glucose, and resort to respiring fat when glucose runs out.
• Aerobic respiration uses oxygen. It can be thought of as the complete breakdown of glucose, to get all energy out.
• Most of the reactions of aerobic respiration take place inside the mitochondria.

Question 47

The energy released in respiration can be used for many different things

Answer 47

The energy released in respiration can be used for:

• the contraction of muscles
• keeping a stable body temperature in mammals and birds
• growth - building up small molecules into larger ones, e.g, building amino acids up into proteins
• movement of substances in or out of cells by active transport

Question 48

Anaerobic respiration

Answer 48

Anaerobic respiration is respiration without oxygen.

It can be thought of as incomplete breakdown of glucose. Some of the energy in glucose is released, but to get it all out requires a supply of oxygen.

The incomplete breakdown of glucose produces lactic acid.

Question 49

Respiration and exercise

Answer 49

The energy to move our muscles comes from respiration. When muscles are working hard:

• a lot of oxygen and glucose gets used up
• a lot of carbon dioxide and heat gets produced

So, during exercise, the brain can detect increased carbon dioxide levels and responds by:

• increasing the heart rate
• increasing the ventilation(breathing) rate - we breathe deeper and more frequently

The increased blood flow to the muscles delivers more oxygen and glucose (or ‘blood sugar’) and takes away the excess carbon dioxide and heat.

When we are short of glucose we can instantly get more by breaking down a storage substance called glycogen.

• Glycogen is stored in the liver and muscles.
• It’s smply a large molecule made from thousands of glucose molecules bonded together.
• When required, enzymes break down the glycogen and release more glucose for the muscles to keep working.
• We build up our glycogen stores again when we eat carbohydrate food such as starch.

Question 50

List three harmful substances found in tobacco smoke

Answer 50

Tar, carbon monoxide, nicotine

Question 51

Explain why carbon monoxide causes breathless

Answer 51

Carbon monoxide is picked up by blood instead of oxygen. The body then doesn’t get sufficient oxygen, so breathes faster to try to get more.

Question 52

Explain why it is necessary for the heart rate to increase during exercise.

Answer 52

During exercise, the muscle cells are respiring faster. They need more oxygen to do this and produce more cabon dioxide as a result. The heart rate increases to speed up the flow of blood and deliver oxygen faster, and to remove the extra carbon dioxide more efficiently.

Question 53

The Human Thorax

Answer 53

Thorax is a chest cavity that contains:

the trachea - a flexible tube, surrounded by rings of cartilage to stop it collapsing

bronchi - branches of the trachea

bronchioles - branches of a bronchus

lungs - to inhale and exhale air for gas exchange

alveoli (air sacs) - microscopic air sacs at the ends of bronchioles, where gases are exchanged

intercostal muscles - to raise and lower the ribs

pleural membranes - to protect and lubricate the surface of the lung

the diaphragm - a muscular ‘sheet’ between thorax and abdomen

Question 54

What is Gas Exchange?

Answer 54

Carbon dioxide diffuses from the blood into the alveolus, and oxygen diffuses from alveolus into the blood. This is called gas exchange.

All gas exchange surfaces are moist because they are permeable to small molecules, so water will always pass out of the cells.

Question 55

How are lungs are adapted fro gas exchange?

Answer 55

There are millions of alveoli, surrounded by a dense network of blood capillaries, which provide an enormous surface area for gas exchange. Both the alveolar epithelium and the capillary wall (called the endothelium) are very thin, so the distance between air and blood is tiny and diffusion of gases in and out is very rapid.

Question 56

Name the structures air passes through as it is breathed in.

Answer 56

Nose, trachea, bronchi, bronchioles, alveoli

Question 57

Explain why cartilage rings are needed around the trachea.

Answer 57

The cartilage rings keep the airways open.

Question 58

Describe what happens to oxygen and carbon dioxide at the gas exchange surface of the alveolus.

Answer 58

Oxygen diffuses across the wall of the alveolus and through the capillary wall into the blood. Carbon dioxide diffuses from the blood into air in the alveolus.

Question 59

Name the muscles used in ventilating the lungs.

Answer 59

diaphragm and intercostal muscles

Question 60

Describe how air is:

a) move into the lungs
b) pushed out of the lungs

Answer 60

a) Breathing in: The diaphragm and intercostal muscles contract, so the ribs rise and the diaphragm flattens. The pressure inside the thorax falls and so air enters the lungs.
b) Breathing out: The diaphragm and intercostal muscles relax, so the ribs move down and the diaphragm moves up in the thorax. This increases the pressure inside the thorax, which pushes air out of the lungs.

Question 61

Describe how particles of dust are removed from the lungs.

Answer 61

Some cells lining the trachea and bronchi secrete mucus. Most of the lining cells have cilia. The particles stuck in the mucus. The mucus is moved up out of the lungs by the waving action of the cilia.

Question 62

Chemicals in cigarette smoke cause mutations in cells which can lead to cancer. What is meant by term mutation?

Answer 62

The term mutation means that the cells randomly genetically change.

Question 63

Explain the effect of emphysema on gas exchange

Answer 63

The alveolus of the smoker lungs has less surface area than non-smoker which can lead to less diffusion of oxygen and carbon dioxide.

Question 64

The coronary artery supplies blood to heart muscle cells. A heart attack may occur if the coronary artery is blocked by a blood clot.

Suggest what happens in heart muscle cells when the coronary artery is blocked.

Answer 64

When the coronary arteries get blocked, not enough oxygen and glucose reaches the heart muscle cells. So, there will be less aerobic respiration and more anaerobic respiration resulting build up of lactic acid. Heart muscle cells become acidic, low pH, and part of the heart muscle dies, and a heart attack results.

Question 65

Making yoghurt

• Put milk in a saucepan and heat the milk to 80 degree celcius
• Pour the hot milk into a bowl and leave to cool to 46 degree celcius
• add the organisms needed to change the milk into yohurt
• pour yoghurt into glass jars and put them into a warm place for 8 hours
• pour the yoghurt into a sterile, airtight container and put it in the fridge.

Answer 65

Name an organism added to change the milk into yoghurt.

• Lactobacillus/Streptococcus

Explain why the milk must be heated to 80 degree celcius

• to kill the bacteria in the milk

Explain why the milk must be cooled to 46 degree celcius

• to avoid killing the Lactobacillus organisms that make yoghurt
• it’s the optimum temperature for the enzymes before they can be denatured

Explain why yoghurt is kept in a warm place for 8 hours

• during this time, lactic acid is produced
• warm temperature is optimum condition for enzymes and bacteria reproduction

Changes take place to the pH of the yoghurt when it is kept warm for 8 hours. Describe and explain how the change in pH helps to preserve the yoghurt.

• the bacteria produce and feed on the lactose sugar in the milk, producing lactic acid which changes the yoghurt to low pH. The lactic acid in the yoghurt also stops the growth of the bacteria and preserves it. The low pH denature the enzymes that caused the respiration.

Question 66

Describe how the levels of blood glucose are kept constant in human plasma after eating a meal.

Answer 66

• The pancreas is the key organ responsible for monitoring and controlling the blood glucose.
• The liver receives all of the glucose from the gut, and stores a lot of it as glycogen.
• If blood glucose levels are too high, the pancreas will detect the change and respond by releasing insulin into the blood. This hormone - like all hormones - travels to all parts of the body, and works by allowing cells to take up more glucose. So, glucose enters cells and the blood glucose levels get lower.
• If blood glucose levels are too low, the pancreas also detects the change and release another hormone, glucagon, into the blood. Glucagon causes the breakdown of glycogen into glucose.

Question 67

Statement about blood cells

Answer 67

Statement Red blood cells White blood cells

• transport oxygen Yes No
• contain a nucleus No Yes
• produce antibodies No Yes
• biconcave shape Yes No
• ingest pathogens No Yes
• numbers may increase following infection No Yes

Question 68

Some athletes preparing for a long distance race train at high altitude for several weeks. The availability of oxygen at high altitude is lower so the body responds by increasing the number of red blood cells. The number of red blood cells remains high when the athletes return to lower altitude to compete.

Explain how having more red blood cells is an advantage to athletes who take part in long distance races.

Answer 68

Having more red blood cells allow more oxygen to be carried to respiring muscles, and less chance of obtaining energy from anaerobic respiration; thus, less built up of lactic acid meaning less muscle cramp. The athlete can run faster, longer, further and is less tired.

Question 69

At 100m sprint race takes less than 10 seconds to complete.

Suggest why sprint athletes gain no advantage from training at altitude.

Answer 69

It’s a short race and having more red blood cells to carry oxygen is not needed as anaerobic respiration is less likely.

Question 70

The longest race that is classed as a sprint is 400m. Suggest why.

Answer 70

This is because there is a build-up of lactate (= lactic acid) which is painful/interferes with muscle contraction. So athlete cannot continue beyond this distance at full speed.

Question 71

The effect of fear on human heart rate

Answer 71

When frightend, the adrenaline hormone, from adrenal glands, increases the heart and breathing rate, the blood sugar level and the rate of respiration. More energy is released in the muscles, so the body is ready for ‘action’.

Question 72

Describe two difference between the heart of a fetus and an adult heart.

Answer 72

connection between atria, connection between arteries, pulmonary atery and aorta.

Question 73

Name two of the blood vessels that carry blood away from the heart.

Answer 73

aorta; pulmonary artery

Question 74

What is meant by the term intraventricular?

Answer 74

in ventricle

Question 75

What are the consequences of having too few platelets in the blood.

Answer 75

Too few platelets in the blood mean there will be less or no clotting resulting in blood loss and also, allowing microorganisms to enter the blood stream and cause infection.

Question 76

Phagocytes.

Answer 76

They ingest bacteria or viruses, then digest them using enzymes. They have an irregular shaped nucleus.

Question 77

Lymphocytes

Answer 77

Lymphocytes produce antibodies which bind to antigens on invading bacteria ( like Pneumococcus that causes pneumonia) causing them to stick together so that phagocytes can digest them.

Question 78

Vaccination causes the body to produce memory cells.

Describe the advantages to the human body of producing memory cells.

Answer 78

In vaccination memory cells are produced and they make antibodies faster and in larger numbers when reinfected with the same disease. They remain in the body for years. These cells form the antibodies that will bind to specific bacteria. Vaccination can produce faster response to infection.

Question 79

Describe how bacteria are used to make yoghurt.

Answer 79

Lactobacillus bacteria are added to the boiled and cooled milk where they feed on the milk sugars and produce lactic acid.

Question 80

Name four useful products of industrial fermentation.

Answer 80

food, insulin, enzymes, antibiotics

Question 81

Explain why fermenters must be sterlised.

Answer 81

So that no microorganisms are allowed to grow other than the ones you are trying to culture.

Question 82

Blood clotting

Answer 82

Blood clotting involves several stages:

injury -> platelets arrive -> platelets break open -> if calcium ions present thrombin is formed -> thrombin acts on fibrinogen to turn it to fibrin-> fibrin forms mass of insoulble protein threads which forms a clot and then a scab as red blood cells become trapped in it.

Question 83

Immune Response

Answer 83

The white blood cells protect the body against pathogens.

Pathogens have antigens on their cells surface. Lymphocytes make antibodies in response to these antigens. The antibodies stick to the antigens and destroy the pathogen in one of several ways:

• making the pathogen stick together so that phagocytes engulf them easily
• acting as a label so that phagocytes recognise the pathogen more easily
• causing bacterial cells to burst open
• neutralising toxins produced by bcateria

Some lymphocytes form memory cells so that if the pathogen gets into your body again it can be dealt with quickly before your are affected by the symptoms of illness. This secondary immune response is much faster and stronger than the first one.

Question 84

lymph

Answer 84

Tissue fluid becomes lymph. It travels around the body in the lymph system. When it returns to the blood it is rich in antibodies against disease.

Question 85

Some babies are born with a ‘hole in the heart’- there is no gap in the central dividing wall of the heart. They may look blue in colour and have very little energy. Surgeons can close up the hole and the child can lead a normal life.

Explain how the treatment may help.

Answer 85

If there is a ‘hole in the heart’, oxygenated and deoxygenated blood are no longer kept separate.
They can mix, so the level of oxygen in the blood going round the body is not as high as it should be. This explains the blue colour and the lack of energy. If surgeons close up the hole,
the heart works perfectly normally and the blood no longer mixes.

Question 86

The blood vessels supplying blood to the heart muscle itself may become clogged with fatty material. The person affected may get chest pain when they exercise or even have a heart attack. Doctors may able to replace he clogged blood vessels with bits of healthy blood vessels taken from other parts of the patient’s body or open them up with a special metal tube called a stent.

Explain how this treatment helps.

Answer 86

The heart muscle itself is starved of oxygen and so cannot work properly. This is why the chest pain develops. If the damaged blood vessels are replaced with healthy ones or opened using a
stent, the blood flow to the heart muscle is restored, and the muscle is no longer starved of oxygen and can work properly again.

Question 87

The plasma is very important for transporting substances round the body. Three of the main substances are carbon dioxide, urea and digested food.

a) For each substance, say where in the body it enters the plasma.
b) For each substance, say where it is transported to, and what happens to it when it gets there

Answer 87

a) Carbon dioxide – the cells; urea – the liver (cells); digested food – the gut
b) Carbon dioxide is transported to the lungs, from where it diffuses out into the air. Urea is removed from the blood in the kidneys and passes out of the body in the urine. Digested food is transported in the plasma to the liver and then to the cells where it is needed.

Question 88

Phagocytes and lymphocytes both help defend your body against disease. Explain the different ways in which they work.

Answer 88

Phagocytes extend their cytoplasm (pseudopodia) around pathogens and enclose them in a vacuole. They secrete digestive enzymes into the vacuole and break down and digest the pathogen. Lymphocytes respond to antigens on the surface of a pathogen. They make antibodies which destroy the pathogen or make it more likely to be digested by a phagocyte. Also some lymphocytes form memory cells, which gives rise to a very rapid secondary immune response if the pathogen gets into the body again. Large numbers of the right antibody are released very rapidly, so the pathogen is destroyed before it can cause the symptoms of disease.

Question 89

How does vaccination use your immune system to protect you against a disease you have not had?

Answer 89

Vaccination introduces a weakened or dead strain of a pathogen. Your immune system responds to the antigen and produces the right antibodies and memory cells without being exposed to a serious disease. If you then meet the live pathogen, the immune system is ready and a rapid secondary immune response makes sure you don’t become ill.