The Search for Better Health ANSWERS.pdf

8/19/2019 The Search for Better Health ANSWERS.pdf

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Copyright © 2008 McGraw-Hill Australia. Permission is granted to reproduce for classroom use.

1. Define the terms:(a) health

(b) disease.Answer:

(a) Health is a state of complete physical, mental and social wellbeing, and notmerely the absence of disease or infirmity.

(b) Disease is any condition that adversely affects the normal functioning of anypart of a living thing.

2. DiscussDiscuss the difficulties encountered when trying to define both health anddisease.

Answer: When defining both of these terms, one of the difficulties encountered

is that when these terms are used in everyday conversation their meanings aredifferent.

A problem with the definition of health is that if the WHO definition is tobe taken literally then it would be very difficult to achieve a complete stateof physical, mental and social wellbeing at any one time. Another difficultyencountered is the fact that different individuals have different perceptions of

what is healthy for them. Health is a fluid state that is constantly changing relativeto others and ourselves over a given time.

The definition of disease is very broad and, if followed closely, then somethingas simple as a cut to our writing finger could be said to affect the functioning ofthe body. Also to be taken into consideration is the fact that ‘normal functioning’ isat different levels for different people.

THE SEARCH FOR BETTER HEALTH

Answers to end of chapter revision questions

Health and disease CHAPTER

1

Please note that the following answers are sample answers only. There may be many alternative answers to the same question that are also correct. These are examples of correct answers.


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3. Copy the following table and complete:Answer:

4. Analyse the links between gene expression and the maintenance and repair ofbody tissues. Include an example in your answer.

Answer: Gene expression involves the ‘switching on’ of genes so that the relevantproteins that they code for are produced. Many genes code for proteins that areresponsible for the control of the maintenance and repair of body tissues. If thesegenes are expressed properly then the maintenance and repair of body tissuesoccurs as it should. Problems with the normal maintenance and repair processes

will occur if the relevant genes are not expressed properly due to such things asmutation of the genes.For example, the BRCA1 gene is responsible for coding proteins that repair

the PTEN gene. This PTEN gene controls the cell cycle and mitosis required forthe repair and replacement of dead and damaged cells. When the BRCA1 geneis expressed properly, the damaged PTEN genes are repaired and the cell cycle iscontrolled.

If the BRCA1 gene is mutated, then it is not expressed properly, the PTENgene is not repaired and the cell cycle is not controlled. Rather than the bodytissues being maintained and repaired, the cells undergo uncontrolled divisionand tumours develop.

4. Ana yse he links between gene expression and the maintenance and repair o

Process/structure Definition

Outline of how this process assists in the

maintenance of health

Cell differentiation Cells mature and take on different structural

features, so that they become structurally suited

to perform a specifi c function in the body.

Differentiation and specialisation enable cells

to work together in a healthy body to carry out

complex functions in a controlled and co-ordinated

way in order to maintain and repair tissues.

If differentiation and specialisation of cells do not

occur for any reason, the cells will not be able to

function effectively and processes in the body will

not be co-ordinated.

Cell specialisation Specifi c genes are ‘switched on’ in order to

perform a particular function in the body.

Genes These are hereditary units that control the

production of polypeptides that make up the

proteins in the cell.

The maintenance of health is dependent on the

information stored in the genes. The production

of proteins that are responsible for normal cell

functioning, growth and repair are controlled by

the genes. Genes code for the proteins that are

responsible for the regulation of the cell cycleand mitosis in healthy cells. The information

contained in genes also prescribes how and when

an organism’s body tissues are maintained and

repaired.

Mitosis Mitosis is the process of cell division by which

identical body cells are produced to allow for:

■ growth

■ repair of damaged tissue, replacement of

worn-out cells, and

■ genetic stability in which there is a precise

and equal distribution of chromosomes to

each daughter nucleus, so that all resulting

cells contain the same number and kind of

chromosomes as each other and the parent

cell.

It allows all cells to function normally and tissues

in the body to be repaired and maintained. If cells

are damaged through injury or disease, they are

replaced by the division of healthy cells close to the

injury or disease site.


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1. Distinguish between the terms ‘infectious’ and ‘non-infectious’ and give twoexamples of each type of disease.Answer: An infectious disease is one that has been caused by a pathogen and canbe transferred from one person to another, whereas a non-infectious disease is onethat is not caused by an organism and, with the exception of inherited diseases,cannot be passed from one person to another.■ Infectious disease examples: measles, AIDS■ Non-infectious disease examples: Down syndrome, lung cancer

2. IdentifyIdentify the name given to an organism or infective agent that has the conditionsnecessary to cause a disease and list the different types of these organisms orinfective agents.

Answer: A pathogen is an organism or infective agent that causes disease. Thedifferent types of pathogens are prions, viruses, bacteria, protozoans, fungi andmacro-parasites.

3. DescribeDescribe three ways in which pathogens can be transmitted.Answer: Three ways in which a pathogen can be transmitted are:1. direct , where the pathogens pass directly from person to person2. indirect , where the pathogen is transferred from the environment (e.g. air, food

and water) to the person3. by being carried by another organism (a vector ).

4. DescribeDescribe a first-hand investigation that you carried out to identify microbes infood or in water.

Answer: To investigate the microbes in water we followed these steps. 1. Four different sources of water were collected. These sources were tap water,

bottled water, pond water and water from a bottle that had been used andrefilled constantly over a 1-week period.

2. Five sterile nutrient agar plates were obtained. 3. One plate was left unexposed to act as a control, sealed and labelled. 4. The bench was cleared of unnecessary equipment and then wiped down with

alcohol to sterilise the working area. 5. An inoculating loop was sterilised in the correct manner and a sample from

one of the sources was collected in the loop. 6. This was then spread out on the agar plate while the lid was lifted slightly and

the opening pointed away from any members of the class.

7. The agar plate was then sealed tightly with sticky tape around the edge andlabelled around the edge of the underside of the plate with the group name,the date and the source of the water.

8. Steps 5 to 7 were repeated using each of the other sources of water. 9. The Petri dishes were then stacked upside down and placed in an incubator

set at approximately 30°C for a period of 1 week.10. The dishes were observed on a regular basis and the number of different

bacterial and fungal colonies recorded. Descriptions and diagrams of thecharacteristics of each colony were also recorded.

11. A comparison of the number and types of colonies was made between thedifferent water sources.

12. All Petri dishes and equipment were disposed of safely.

‘ ’ ‘ ’

The importance of hygiene CHAPTER

2


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5. ExplainExplain why precautions such as swabbing the bench with alcohol, sterilising theinoculating loop and lifting the lid of the agar plate away from you at an angle ofno greater than 45°C were all used in the investigation described in the previousquestion.

Answer: These are all sterile techniques designed to reduce the risk of microbesfrom sources other than those being tested from landing on the agar and beingcultured.

By swabbing the bench, any microbes will be killed and therefore the chanceof them contaminating the agar plate is reduced.

Sterilising the inoculating loop kills any microbes already on there and thereforereduces the risk of contamination of the plate.

Opening the lid of the dish at a small angle and not allowing anyone to breatheon it reduces the risk of microbes from the air falling on the agar plate andcontaminating it.

6. ExplainExplain how each of the following assists in the control of disease: (a) cleanliness in personal hygiene practices (b) cleanliness in food practices (c) cleanliness in water practices.Answer:

(a) (i) Personal hygiene practices are important because they involve keeping ourbodies and any openings into them clean to reduce the risk of pathogensentering our bodies, or transmission of these pathogens to others, thuscausing disease. It also inhibits the build-up of micro-organisms on ourbodies.

Good personal hygiene practices that should be followed are the washing of hands with soap before eating and after going to the toilet,

washing the body and hair regularly and cleaning the teeth daily.Coughing or sneezing should also be done into a tissue or handkerchief.

(ii) Community hygiene practices are important as they help to prevent thebuild-up of pathogenic organisms in the community and reduce thespread of disease.

Good community hygiene practices involve the efficient removal of waste and sewage, sterilisation and disinfection of equipment in hospitals,doctors’ surgeries etc., and planning to prevent overcrowding.

(b) The more closely cleanliness in food practices is followed when storing,preparing and serving food, the smaller the chance of bacteria in the foodmultiplying and being transmitted to individuals consuming the food, thus

controlling the occurrence and spread of food-borne diseases.(c) It is important that cleanliness in water is maintained in order to minimise therisk of pathogens multiplying and to reduce the risk of the transmission ofpathogens in contaminated water. The treatment of water to destroy pathogensand prevent further multiplication will reduce transmission of disease and is

very important in the successful control of disease.

7. DescribeDescribe the processes involved in the treatment of water to ensure that it meetsthe guidelines required by the National Health and Medical Research Council tomake it safe for drinking.

Answer: A combination of coagulation, flocculation and sedimentation; filtration(to remove particulate matter); and disinfection (to kill or inactivate microbiological

organisms) is the most widely applied water treatment technology around the world.


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Sedimentation, coagulation and flocculation

Some particles will settle out from still water in the process called sedimentation . When particles are slow to settle or will not settle, a coagulant is added to the

water, causing the particles to stick together and form larger particles called floc .This process is called flocculation . The floc will either sink and be removed assludge, or float and be skimmed off the top.

Filtration

Whatever particles are left in the water are removed by the process of filtration .This occurs in many cases by the water being passed through a bed of finesand particles. Membrane filtration in the form of microfiltration (passing waterat pressure through membranes with a small pore size) is the most widely usedmethod of filtration in Australia.

Disinfection

After all the particulate matter has been removed from the water, it is disinfected,

usually by adding chlorine in some form. Other methods of disinfection includetreating the water with ozone or irradiation with ultraviolet (UV) radiation.

If chlorination is used for disinfection, enough should be added to ensure thatthe water remains free of micro-organisms on its journey to the consumers.

8. ExplainExplain how the methods described in the previous question reduce the riskof infection from pathogens.

Answer: Sedimentation, coagulation and flocculation are very effective at removingfine suspended particles that attract and hold bacteria and viruses to their surface.They can remove up to 99.9% of the bacteria and 99% of the viruses from watersupplies. This reduces the risk of infection from pathogens.

Filtration can remove some of the larger micro-organisms from the water, which

again will reduce the risk of infection from pathogens in the water.Disinfection will kill any remaining pathogens in the water, further reducing the

risk of infection.

CHAPTER

3Infectious disease

1. DescribeDescribe the contributions of: (a) Louis Pasteur (b) Robert Koch

to our understanding of infectious disease.Answer:

(a) Louis Pasteur ■ Found that micro-organisms are responsible for the spoiling of wine and

beer and found that they could be killed by heating them to a certaintemperature, which led to the process of pasteurisation .

■ Disproved the ‘theory of spontaneous generation’ and showed that themicro-organisms that were responsible for causing disease and decaycame from the air and did not just appear out of nowhere. He showed this

with his swan-necked flask experiment.


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■ Produced vaccines that prevented organisms from developing a disease when exposed to the micro-organism that causes it. He developed a vaccine for chicken cholera and anthrax.

■ Was the first to use a vaccine on humans, using the vaccine he haddeveloped for rabies.

(b) Robert Koch ■ Developed many bacteriological techniques, such as the agar plate

technique to grow colonies of micro-organisms, which are still in use today. ■ Showed that there is a specific micro-organism for each type of disease. ■ Developed Koch’s postulates to be used to determine which micro-

organism is responsible for causing a particular disease. ■ Identified the bacteria that were responsible for causing tuberculosis and

cholera .

2. OutlineOutline Koch’s postulates. IdentifyIdentify one of the limitations of these postulates.Answer: Koch’s postulates are:1. The same micro-organism must be present in every diseased host.2. The micro-organism must be isolated and cultured in the laboratory and

accurately described and recorded.3. When a sample of the pure culture is inoculated into a healthy host, this host

must develop the same symptoms as the original host.4. The micro-organism must be able to be isolated from the second host and

cultured and identified as being the same as the original species.Koch’s postulates cannot be used successfully with diseases that are peculiar onlyto humans, as there are ethical guidelines that prevent humans acting as healthyhosts to be inoculated with the micro-organism being tested.

3. DescribeDescribe an experiment to show how you modelled Pasteur’s experiment. ssess Assess the validity of your model.

Answer: When we modelled Pasteur’s experiment, we used the followingequipment:■ beef broth made using beef stock cubes, filtered to remove any cloudiness■ two conical flasks, each with a single-hole stopper to fit■ glass tubing bent into an S-shape fitted into one of the stoppers■ straight glass tubing fitted into the other stopper■ heating equipment.

We carried out the experiment using the following method:1. Add the filtered beef broth to each of the flasks until they are approximately

one-third full.

2. Fit the stoppers, one with the straight tubing and the other with the S-shapedtubing, to the flasks.

3. Heat each flask so that it boils gently for 15 minutes. Ensure that after boilingthere is a small amount of water trapped in the S-bend.

4. Leave both flasks in a warm position out of direct sunlight for several weeks.5. Every 2 or 3 days, observe the contents of each flask. Look for cloudiness,

scum, bubbles and fungal colonies. Record any changes.Our model is valid for the following reasons:■ A nutrient broth was provided to allow the micro-organisms to grow when they

came into contact with it.■ We used flasks that had a bend in them to trap the microbes from the air and

prevented them from reaching the broth, just as Pasteur did.


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■ We also used another flask, with a straight tube that allowed microbes to enter,to show what would happen when the broth was exposed to the air. This actedas a control.

■ We ensured that all flasks, with their broth and their tubing, were heated andthe broth was boiled for at least 15 minutes so that all micro-organisms that

were present in both the broth and the tubing were killed and the equipment was sterile.

■ We also ensured that sterilised water was trapped in the S-bend of the tube inorder to trap the micro-organisms so that they could not reach the broth.

One limitation of our model is that the corks would sometimes become loose, which may compromise the sterile conditions and allow micro-organisms into theflask.

4. DescribeDescribe characteristics that could be used to distinguish between the followingpathogens and name one example of a disease caused by each type of pathogen:

(a) bacteria and viruses (b) fungi and protozoans (c) prions and viruses (d) bacteria and fungi (e) protozoans and macro-parasites.Answer:

(a)

Bacteria Viruses

Cellular—procaryotic—has a cell membrane Non-cellular—genetic material surrounded by a

protein coat

Reproduces by dividing in two Cannot reproduce by itself—must get genetic

material into a cell so the cell can copy it many times

Larger than virus Smaller than bacteria

(b)

Fungi Protozoans

Cell wall Cell membrane—no cell wall

Single or multi-cellular Single cell

Non-motile Most are motile

Reproduce asexually/sexually Reproduce asexually

(c)

Prions Viruses

Protein—no genetic material Genetic material surrounded by protein coat

Reproduce by coming into contact with normal

proteins in brain and changing them into prions

Reproduce by putting genetic material into a cell

and allowing the cell to copy it many times

Much smaller than viruses Size 30–300 nm—larger than prions


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(d)

Bacteria Fungi

Procaryotic cell—no membrane-bound nucleus Eucaryotic cell—membrane-bound nucleus

Cell membrane—no cell wall Cell wall

Size—0.5–100 µm, smaller than fungi Larger than bacteria

Reproduces by splitting in two—asexually Reproduces asexually and sexually

(e)

Protozoans Macro-parasites

Microscopic Macroscopic

Single cell Multicellular

Pathogen Disease

Prion Variant Creutzfeld-Jacob

Virus Infl uenza

Bacteria Meningococcal disease

Fungi Tinea

Protozoa Malaria

Macro-parasite Tapeworm disease

Diseases caused by pathogens

5. SummariseSummarise the historical development of our understanding of the cause andprevention of malaria.

Answer:

Time Development

1000 CE Chinese recognised disease.

240 CE Anti-fever properties of qinghao plant described.

2000 years ago Greeks described symptoms of disease and called it malaria.

2000 years ago Greeks and Romans built drains to take away stagnant water.

Mid-1600s Quinine, extracted from the cinchona tree, used to treat malaria in Europe.

1880 Charles Laveran discovered the pathogen that causes malaria.

1885 Golgi established that there were at least two forms of the disease.

1897 Ronald Ross discovered the main steps in the transmission of malaria and

identifi ed the Anopheles claviger mosquito as the vector of the malaria parasite.

1898 Giovanni Grassi and Guiseppe Bastenelli showed that human malaria is

transmitted in the same way as malaria in birds.

1898 Measures such as draining stagnant water, spraying oil on water to stop

breeding of mosquitoes, and wearing protective clothing were carried out.

continued . . .


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Time Development

1901 Pyrethrum used as insecticide.

1930 Anti-malarial drug called Atebrin developed, but its use was discontinued due

to side-effects.

1944 Synthetic quinine developed.

Late 1940s Chloroquine developed.

Late 1950s WHO implemented a program to try and eradicate malaria.

DDT spraying, protective measures, biological control of mosquitoes.

1970s Use of drugs as prophylactics to try and prevent the disease.

Incidence of malaria decreased.

1971 Chinese isolated artemisinin from qinghao plant.

1970s on Many different anti-malarial drugs used by themselves or in combination.

Mid-1980s on Incidence of malaria increases.

1981 Start of search for malaria vaccine.

2000 to present Combination drug therapy that includes the highly effective artemisinin.

Netting treated with long-lasting insecticide and other protective measures.

Developments in understanding the cause

Developments in understanding the prevention

6. ExplainExplain why the incidence of malaria is increasing.Answer: The main reason for the increase in the incidence of malaria is thatthe malaria parasite is so successful at very quickly building up a resistance

to the drugs that are used to treat it. The mosquito that acts as a vector in thetransmission of malaria also quite quickly builds up a resistance to the insecticidesthat are sprayed to try to control its numbers.

Other reasons include the fact that human populations in susceptible areasare increasing both in numbers and density. Another reason may be thatpharmaceutical companies have not been devoting money to research into malariatreatment because it is primarily a disease of the poor and developing nations.

7. Copy the summary table below and complete it using the infectious disease youhave studied:

Answer:

Disease Influenza

Cause Infl uenza is caused by infection with the infl uenza virus. Infl uenza A and infl uenza

B virus are the two main types of infl uenza viruses that infect humans and each

contain RNA surrounded by a protein coat.

Transmission The transmission of the infl uenza virus can be either direct or indirect:

■ direct contact —the viral particles are inhaled through the nose and mouth in

droplets that have been exhaled by an infected person when they sneeze or

cough.

■ indirect contact —the infected person touches their respiratory tract and then

something else, such as a handrail. A second person touches the handrail

soon afterwards and then places their hand on their nose or mouth.

continued . . .


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Disease Influenza

Host response The immune response is initiated by the presence of the virus in the body. This

produces antibodies and other immune response cells specifi c for the particular

strain of infl uenza virus that has infected the body. The immune response isresponsible for destroying the viral particles that have invaded the body.

Major

symptoms■ Fever

■ Headache

■ Infl ammation of the upper respiratory tract

■ Sore throat

■ Myalgia (muscle pain)

■ Nasal catarrh (infl ammation of the mucous membrane causing excess

production of mucus)

■ Coughing and sneezing.

Treatment The main method of treatment is to relieve the symptoms and get plenty of bed

rest and drink extra fl uids.

Bed rest allows the body to fi ght the disease and then recover. Aspirin or

paracetamol can be given to help alleviate headaches, sore throat and musclepain and to reduce fever.

Antibiotics are ineffective in the treatment of viral diseases, but can be used if

secondary bacterial infections develop.

Prevention The primary method of prevention of infl uenza involves the use of infl uenza

vaccines. New vaccines are produced each year and are derived from infl uenza A

and B viruses that circulated the previous infl uenza season.

Control To reduce the spread of the disease through the population a number of

strategies could be employed. These include:

■ the implementation of immunisation programs along with education programs

to encourage at-risk individuals to be vaccinated.

■ the isolation of infected individuals to reduce the spread of infl uenza

throughout the population—this would include infected individuals remaining at

home to stop the spread of the virus to their work or school colleagues.■ quarantine procedures followed to prevent the spread of the disease from one

country to another.

8. DefineDefine the term ‘antibiotic’.OutlineOutline how different antibiotics work.Answer: Antibiotics are chemicals that are capable of destroying or inhibiting thegrowth of bacteria that cause disease.■ Some antibiotics, for example penicillin, accumulate in the cells of the bacteria

and prevent them from forming a new cell wall when they are dividing.■ Other antibiotics, for example amphotericin, destroy the cell membrane, thus

effectively destroying the bacteria.

■ Still other antibiotics interfere with protein synthesis so the bacteria are unableto make essential compounds, resulting in the death of the cell. Erythromycin isan example of an antibiotic that acts in this way.

9. (a) DescribeDescribe how antibiotic resistance develops. (b) Michael was suffering from a very bad cold and went to the doctor to get

antibiotics to make him feel better. ExplainExplain why the doctor should notprescribe them for him.

Answer:

(a) When antibiotics are administered to treat a bacterial infection, some of thebacteria present may possess a natural resistance to that particular antibioticand survive. They then reproduce and can quickly build up a population that

is resistant to the antibiotic. In conjunction with this, the bacteria are also


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capable of passing this resistance on to other bacteria they come into contact with, further building the population of resistant bacteria.

(b) Colds are not caused by bacteria—they are caused by viruses. Antibioticsare used to treat infections caused by bacteria and therefore would not besuitable to treat a cold. If the doctor were to prescribe them, Michael wouldbe increasing the chance of bacteria developing a resistance to the drug thatis being used.

10. DiscussDiscuss some problems related to antibiotic resistance.Answer: Antibiotics were hailed as a miracle cure when they were first introduced.

As bacteria began to develop a resistance to these first antibiotics, more weredeveloped. Strains of bacteria resistant to many of the antibiotics that are in usetoday have now developed. One problem with the resistance of bacteria to themore common antibiotics is that the diseases will be more severe and, becausethey take longer to cure, there is a greater chance of them spreading throughoutthe community. Another problem is that, in order to destroy the bacteria, moretoxic and expensive antibiotics have to be used. If the individuals or countriescannot afford to use this more expensive cure, the disease will spread throughoutthe population. For example, a multi-resistant strain of the bacteria that causestuberculosis is very hard to treat and many countries cannot afford the antibioticsrequired to cure this disease. This leads to a large increase in the incidence of theresistant strain of the disease.

There are now several infectious bacteria that are resistant to vancomycin,one of our strongest antibiotics. Vancomycin-resistant enterococci (VRE) and

vancomycin-resistant Staphylococcus aureus are ‘superbugs’ that resist all treatmentand if they were to become widespread in the community it would cause greatproblems.

The current trend indicates that, unless there is a breakthrough in thedevelopment of more effective drugs, our inability to successfully treat antibiotic-resistant bacteria could lead to the spread of the diseases they cause throughoutpopulations.

Factors that are increasing the development of antibiotic-resistant bacteria are:■ the overuse of antibiotics for many diseases and not just bacterial diseases■ not completing the course of antibiotics when they are prescribed■ feeding antibiotics to food-producing animals such as pigs and chickens to

enhance their growth■ using cleaning products that contain antibacterial substances.

CHAPTER

4Defence of the body I

1. (a) dentifyIdentify the barriers in the human body that make up the first line ofdefence.

(b) DescribeDescribe how cilia and mucous membranes work together to prevent theentry of pathogens into the respiratory system.

(c) ExplainExplain why most pathogens do not survive in the digestive tract.Answer:

(a) The barriers are: ■ skin


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■ mucous membranes ■ cilia ■ chemical barriers ■ other body secretions.(b) The mucous membranes produce mucus, which traps the pathogens, and

the cilia beat in an upwards direction to move the mucus containing thepathogens out of the respiratory tract.

(c) If a pathogen makes its way past the saliva in the mouth and enters thestomach, it will most likely be destroyed by the concentrated acid in thestomach. If the acid in the stomach doesn’t kill it then the alkaline conditionsof the intestine may destroy it.

2. Copy the following table and complete it to summarise the first line of defence.

Barrier Location in the body

Mechanism by which the barrier prevents

the entry of the pathogen

Skin Covering the surface of the body ■ It forms a tough outer barrier that covers the

body and prevents penetration by microbes.

■ It is fairly dry, helping to prevent the growth

of pathogens.

■ It contains its own population of harmless

bacteria that help to stop the invading

microbes from multiplying.

■ Oil and sweat glands in the skin produce

antibacterial and antifungal substances

that further inhibit the growth of invading

pathogens.

Mucous

membranes

Digestive, respiratory,

reproductive and urinary tracts■ They produce a thick layer of viscous mucus

which traps the entering pathogens.

■ Pathogens are held in the mucus until theyare removed by processes such as coughing

and sneezing.

■ The mucus can contain a chemical that

prevents bacteria and viruses from attaching

to the surface layer.

■ The mucus also provides a moist, nutritious

layer in which the harmless microbes live and

produce substances that inhibit the growth

and entry of pathogens.

Cilia Tiny ‘hairs’ that line the

respiratory surfaces of the

trachea and bronchial tubes.

■ They constantly beat in an upwards direction

to move the mucus containing the trapped

pathogens towards the throat where they are

removed by coughing, sneezing or swallowing.

Chemical

barriers

Alimentary canal

Urinary and vaginal openings,

surface of skin

■ Pathogens entering with food or drink, or

swallowed with mucus, will be destroyed by

the acidic conditions of the stomach or the

alkaline conditions in the intestines.

■ These are acidic, which inhibits the growth

of pathogens.

continued . . .


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3. Draw a flow chart to show how the disease candidiasis can develop from an

imbalance of microflora.Answer:Normal balance of microflora in the mucous membranes of the vagina

Numbers of Candida albicans kept in check by competitionfrom other micro-organisms

Antibiotics used to fight an infection

Some of the ‘good’ microflora are destroyed

Increase in numbers of Candida albicans

Development of the disease candidiasis

4. (a) DescribeDescribe what makes it possible for the body to identify cells that belongto it.

(b) DefineDefine an antigen. (c) ExplainExplain why organ transplants trigger an immune response.Answer:

(a) Cells in the body have on their surface chemical ‘marker’ molecules that allowthe body to identify them as belonging to it.

(b) An antigen is any molecule that is identified as being foreign and triggers theimmune response.

(c) When a person has an organ transplant, the new organ they are receiving fromsomebody else has on the surface of its cells ‘marker’ molecules (antigens)that are different to the marker molecules on their own cells. The transplantedorgan is therefore identified as foreign and the immune response is activatedto attack the organ in order to defend the body.

3. raw a flow chart to show how the disease candidiasis can develop from an

Barrier Location in the body

Mechanism by which the barrier prevents

the entry of the pathogen

Other body

secretions

Urine

Tears

Saliva

■ It is sterile and slightly acidic and fl ushes and

cleans the ureters, bladder and urethra. Ithelps to prevent the growth of microbes.

■ They contain lysozymes that destroy the cell

walls of some bacteria. As the tears are

produced and the eyelid blinks, the surface

of the eye is cleaned and the pathogens are

washed away.

■ It contains lysozymes and washes micro-

organisms from the teeth and the lining of

the mouth.


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5. DescribeDescribe how each of the following defence adaptations help to protect the bodyagainst invasion by foreign particles:

(a) the inflammation response (b) phagocytosis (c) the lymph system (d) cell death to seal off pathogens.Answer:

(a) Inflammation response: ■ The inflammation response is non-specific and occurs at the site of

infection. ■ When the cells are infected or injured in some way, they release chemical

alarm signals such as histamines and prostaglandins. ■ These chemicals cause the blood vessels to dilate, increasing the blood flow

to the site of infection or injury and causing the area to become red and warm.

■ These chemicals also increase the permeability of the blood vessels,allowing the movement of phagocytes from the blood into the tissues sothey can attack the invading pathogens.

■ Plasma also moves into the tissues, bringing more phagocytes andproducing swelling in the area of the infection, thus forcing tissue fluid intothe lymph and taking debris with it.

■ Other chemicals that increase the temperature, which inhibits the growth ofbacteria, are released.

■ When the pathogens are destroyed, they are removed along with any toxinsand the tissues are repaired.

(b) Phagocytosis:

■

White blood cells called neutrophils and macrophages are two types ofphagocytes. ■ They are capable of changing their shape so that they can surround any

foreign particle, such as a bacterium, and completely enclose it within theircell.

■ Once inside the cell, enzymes are released to destroy the foreign material. ■ This process is known as phagocytosis.(c) Lymph system: ■ The lymphatic system is made up of the lymph vessels, lymph nodes,

lymph and spleen, the thymus, the tonsils and the adenoids. ■ As the blood circulates around the body, some of the plasma moves out

of the capillaries into the tissues, especially at the site of infection, and

becomes part of the tissue fluid. ■ The lymph vessels form a one-way drainage system from all parts of the

body back to a point near the heart where clean lymph fluid is drainedstraight into the blood. The muscles that surround the vessels squeeze thefluid in a one-way direction. Valves prevent the fluid moving backwards.

■ If there is an infection in the tissues, the foreign particles, along with deadcells and other debris, move with the tissue fluid into the lymph vessels.

■ At different points along the lymph vessels, there are structures calledlymph nodes where the waste particles are filtered and the foreign particlesare destroyed by macrophages.


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(d) Cell death to seal off pathogens: ■ Sometimes cells die to seal off an area of tissue that is infected and is not

being successfully defended by the body. ■ If the infected cells are surrounded by a wall of dead cells, it prevents the

infection from spreading to other areas and infecting them. Macrophagesalso surround the dead cells.

■ This wall of dead cells forms a capsule or cyst. The cells inside will thendie, causing the destruction of the pathogens that are infecting them.

■ The debris inside the capsule or cyst will be destroyed by the macrophages.

CHAPTER

5

Defence of the body II

1. MacFarlane Burnet developed the clonal selection theory which allowed us tobetter understand the functioning of the immune system.

(a) DefineDefine the clonal selection theory. (b) OutlineOutline two other areas of research that he undertook to increase our

understanding of the immune system.Answer:

(a) The clonal selection theory states that all the B cells and T cells for all thepossible antigens are already present in very small amounts in the immunesystem of the body. When an antigen is present in the body, the B cell orT cell that is specific for that antigen is activated, and then cloned so that theantigen can be destroyed.

(b) MacFarlane Burnet studied viruses and how the body defends itself against

invasion by viruses. He also investigated the way in which the body canrecognise cells that are foreign and cells that are ‘self’, and how it can defenditself without attacking itself.

2. OutlineOutline some of the features of each of the following components of the immuneresponse:

(a) T cells (b) B cells (c) antibodies.Answer:

(a) T cells are produced in the bone marrow and mature in the thymus gland.From here they move to the blood, lymph nodes, spleen and tonsils. Each

T cell has a surface receptor protein that recognises only one type ofantigen. T cells are involved in the cell-mediated immune response in whichcytotoxic T cells move to the site of the infection and release chemicals thatdestroy the infected cell and the antigens contained within it.

(b) B cells are produced and mature in the bone marrow and then move to theblood, lymph nodes, spleen and tonsils. Each B cell has, on its surface, itsown unique antibody that will identify only the antigen that matches it. B cellsare involved in the antibody-mediated immune response and, once activated,produce plasma cells that make antibodies specific to the antigen. Theseantibodies move to the infection site and combine with the antigen to renderit harmless.


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(c) Antibodies are proteins, called immunoglobulins, that are produced by theplasma cells in the antibody-mediated immune response. Each antibody hasthe shape that corresponds to the antigen that it is specific for, and joins withthat antigen to render it harmless by forming the antigen–antibody complex.

3. IdentifyIdentify the different types of T cells and outlineoutline the role of each type.Answer: The four main types of T cells are:1. helper T cells2. cytotoxic T cells3. memory T cells4. suppressor T cells.

Helper T cells: Each helper T cell will recognise only one type of antigen and when it is present the helper T cell becomes activated. It then releases a cytokinechemical called interleukin-2, which activates the cytotoxic T cells and B cells.

Cytotoxic T cells: When the helper T cells activate the cytotoxic T cells, theyare stimulated to produce many copies of themselves. These activated cytotoxicT cells then move to the site of the infection, bind with the infected cells andrelease chemicals that destroy the antigen-infested cell, stimulate the inflammatoryresponse and increase phagocytic activity.

Memory T cells: These cells are produced at the same time as the cytotoxicT cells and are specific for the antigen that stimulated their production. Theyremain in the body so that the body can respond more quickly the next time thesame antigen enters.

Suppressor T cells: When the infection has been defeated, the suppressor T cellsare responsible for stopping the immune response.

4. Interactions between the B cells and T cells are important for the correctfunctioning of the immune system.

(a) ExplainExplain how the helper T cells are activated in the immune response. (b) DescribeDescribe how the activated helper T cells interact with both the B cells and

the cytotoxic T cells. (c) OutlineOutline the process by which the immune system is ‘turned off’.Answer:

(a) Helper T cells can be activated in two ways. One of these involves themacrophage attaching a portion of the antigen to its surface and transportingit to the lymph nodes. When this antigen-presenting macrophage encountersa helper T cell that has a receptor that corresponds to the particular antigenbeing presented, the helper T cell is activated.

Helper T cells can also be activated when a B cell that has encountered an

antigen and has attached it to the surface of their cell presents it to the helperT cell that has a receptor that matches the antigen.

(b) The activated helper T cells release chemicals called cytokines, which activatemore helper T cells and cause the production of clones of the B cells that arespecific to the particular antigen. The cytotoxic T cells that are specific to theantigen are also activated to produce clones of themselves.

(c) Suppressor T cells suppress the activity of the B cells and the T cells when theinfection has been defeated.


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5. MHC molecules are an important part of the mechanisms that allow interactionbetween the B and T cells.

(a) OutlineOutline the structure and function of the MHC molecules. (b) dentifyIdentify the two different types of MHC molecules and outline the function

of each. (c) dentifyIdentify two other mechanisms that allow for interactions between B and

T cells.Answer:

(a) MHC molecules are glycoprotein molecules composed of a carbohydratemolecule and a protein molecule. These molecules occur on the surface of thecells and allow the B and T cells to recognise that they belong to the body andprevent them from attacking each other. This system allows the identificationof foreign cells, as these cells will have different MHC molecules.

(b) MHCI molecules are present on all cells that have a nucleus and are involvedin the recognition of antigens by T cells. MHCII molecules are present only on

B cells and macrophages; they are involved in the recognition of antigens onmacrophages by helper T cells and the recognition of antigens by B cells. Thisthen leads to the activation of the B and T cells by the helper T cells.

(c) Two other mechanisms that allow for interactions between B and T cells are: ■ the close proximity of the cells to each other ■ the regulation of their activities by the secretion of chemicals by the helper

T cells.

6. ExplainExplain, with the aid of a flow chart, how each of the following types of immuneresponse destroy the invading antigens:

(a) cell-mediated immunity (b) antibody-mediated (humoral) immunity.

Answer:(a) Cell-mediated immunity: Foreign material is engulfed by macrophages, which then display the antigen

attached to their MHCII molecules. The antigen-presenting macrophages move to the lymph nodes, where

they are inspected by the helper T cells that have the antigen receptor thatcorresponds to the antigen being presented.

These helper T cells then activate the cloning of millions of cytotoxic T cells

and memory T cells that are specific for this antigen.

The cytotoxic T cells leave the lymph nodes and migrate to the site of theinfection, where their antigen receptors bind with the antigen displayed on theinfected cell.

They then release chemicals that destroy the cell and any pathogens within it. These chemicals also increase the inflammation and attract more macrophages

that carry out phagocytosis to help destroy the pathogens and clear up anydebris.


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Some of these cytotoxic T cells produce a chemical, interferon , which protectsthe cells around an infected cell from viral invasion.

Once the infection has been defeated, the suppressor T cells release other

chemicals to stop the production and action of the cytotoxic T cells. The memory T cells that are produced at the time and are specific to that

particular antigen remain in the body in the lymph nodes and, on re-exposureto the same antigen-containing pathogen, cause the rapid production of moreof the same cytotoxic T cells. This prevents the body from developing thesymptoms of the disease again.

(b) Antibody-mediated immunity: Antigen-presenting B cells or macrophages move to the lymph nodes.

They are inspected by helper T cells that have the antigen receptor thatcorresponds to the antigen being presented.

These helper T cells release interleukin-2 to stimulate the cloning of millions

of the B cells that are specific to the antigen being presented. At the same time, millions of memory B cells that are specific for that antigen

are cloned. The activated B cells produce plasma cells that remain in thelymph nodes.

These plasma cells secrete antigen-specific antibodies that then move via the

blood and lymph to the infected areas. The antibodies then combine with the antigens to form the antigen–antibody

complex that inactivates the pathogen or its toxin. The pathogen is then destroyed in a variety of ways, depending on its type. The inflammatory response is also activated, attracting phagocytes and leading

to the clearing of the debris. The memory B cells produced can lead to short-term immunity (where

antibodies are secreted for 20–30 days) or long-term immunity (where the

memory cells remain in the lymph nodes). On re-exposure to the same antigenthere is a rapid division to produce plasma cells that secrete a large quantity ofantibodies very quickly and prevent the re-infection of the body.

7. DescribeDescribe the difference between each of the following: (a) vaccination and immunisation (b) naturally induced and artificially induced active acquired immunity.Answer:

(a) Vaccination is the process of introducing a vaccine into the body, whereasimmunisation is the process by which the vaccine causes the body toundergo the immune response in order to produce memory cells for that


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particular antigen. This confers immunity on the body so that the next time theantigen enters the body, the secondary response will occur and the body willnot suffer the symptoms of the disease.

(b) Active acquired immunity is the process by which the immune responseoccurs and memory cells are produced.

It is naturally induced when an antigen enters the body, causes symptomsof the disease and produces memory cells for that antigen.

Artificially induced acquired immunity is produced when a vaccine isintroduced into the body, causing the production of memory cells without thebody experiencing the symptoms of the disease.

8. Figure 5.16 is a graph that shows the amount of antibodies produced as a resultof the immune system’s first exposure to a particular antigen. This person wasagain exposed to the same antigen at six weeks. Complete the graph by drawingin the expected shape to show the number of antibodies produced as a result ofthis secondary exposure. ExplainExplain this process.

Answer:

When the antigen first enters the body, the process involved in fighting thedisease is quite lengthy as it takes some time for the numbers of B and T cells toincrease. Time is also required for the plasma cells to produce enough antibodiesto successfully fight the infection. In the process of the immune response, memory

cells specific to the antigen are also produced and remain in the body. This is theprimary response. When the same antigen enters the body two weeks later, the memory cells react

quickly to its presence. Appropriate B cells, which form many plasma cells thatsecrete a large quantity of antibodies very quickly, are produced. This destroysthe antigen before any symptoms of the disease are produced in the body. This isknown as the secondary response. See Figure 5.16a.

0 2 4 6 8 10

Concentration

of antibodies

in blood

first exposureto antigen

Time (in weeks)

Figure 5.16

The primary

response to

the exposure

to an antigen


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9. OutlineOutline the way in which vaccinations prevent infection.Answer: Vaccination is a process that introduces vaccines into the body. A vaccinecan contain cultures of micro-organisms that may be living but attenuated, ordead. Vaccines may also contain toxoids. The introduction of a vaccine causes thebody to undergo the immune response and produce memory cells for a particularantigen without suffering any symptoms of the disease.

When the antigen enters the body at a later date, the memory cells producedafter vaccination will cause its destruction before any symptoms of the disease areproduced.

10. EvaluateEvaluate the effectiveness of vaccination programs in preventing the spread andoccurrence of once-common diseases, including smallpox, diphtheria and polio.

Answer: Many diseases, including smallpox, diphtheria and polio, were once verycommon and caused widespread suffering and many deaths. Vaccination programshave been one of the most successful methods used in preventing the spreadand occurrence of these diseases. Since the introduction of vaccination programssuch as the Expanded Program on Immunisation launched by the WHO in 1974,the percentage of the world’s infants immunised against six target diseases hasincreased from 5% in 1974 to 80% in 1997. This has prevented approximately threemillion deaths per year. Mass immunisation programs are not only effective inreducing the occurrence of disease in the individual, but have also decreased thespread of disease through the population.

Vaccination programs have been very effective in preventing the spread andoccurrence of the disease smallpox . The program has been so successful that it hastotally eradicated the disease from the world.

Smallpox has killed more people than any other infectious disease and wasresponsible for one-tenth of all deaths in Europe in the nineteenth century andmore than 300 million deaths in the twentieth century. Each year until 1968, there

were 10–15 million cases of smallpox, resulting in two million deaths. A vaccine for smallpox was developed by Edward Jenner in 1796, but it was not

widely used. In 1967 there were still 33 countries in the world where smallpox wasa major health problem. The WHO carried out a worldwide immunisation programthat involved routine mass immunisations, with supplementary doses given on

0 2 4 6 8 10

Concentration

of antibodies

in blood

first exposureto antigen

Time (in weeks)

second exposureto antibodies

Figure 15.6a

The primary and

secondary response

to an initial exposure

to antigen and then

a second exposure to the same antigen

six weeks later


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special immunisation days. People who missed out on the routine immunisations were then targeted and special surveillance teams were sent out to all possiblecases of smallpox infection.

In 1979, WHO declared that it had eliminated the virus from the worldpopulation and eradicated the disease smallpox.

Diphtheria is a deadly disease, often killing its sufferers within a week. Mortalityrates were very high, with two-thirds of the deaths being children under 5 yearsof age. In 1921, there were 206 000 cases with 15 500 deaths in the United Statesof America. Immunisation programs introduced in Australia, Europe and otherdeveloped countries in the 1930s and 1940s resulted in a rapid decrease in theincidence of diphtheria.

When the WHO introduced the EPI program in 1974, only 5% of children inthe world were immunised against diphtheria. By 1990, the percentage of childrenimmunised had increased to 80% and this resulted in a greatly decreased mortalityrate worldwide.

Polio is an extremely serious disease with death occurring in 50% of the casesand nerve damage and paralysis in 50% of sufferers. After a safe vaccine wasdeveloped by Albert Sabin, and following widespread immunisation, there wasa 60–70% reduction in the incidence of the disease. Polio had become very rarein industrialised nations, and the incidence further decreased after the EPI wasintroduced in 1974.

A global Polio Eradication Initiative was launched in 1988 by the World Health Assembly. When this program began there were 350 000 cases in 125 countriesof the world, with more than 1000 children being paralysed each day. In 1997,almost 450 million children under 5 years of age were immunised during NationalImmunisation Days.

By 2000, there were only 719 cases of polio, a 99% reduction in cases. At theend of 2006, only four countries that have experienced uninterrupted transmissionof polio remained and fewer than 700 cases were reported.

The WHO aims to completely eradicate polio by the year 2010.It can be seen from the success of the vaccination programs introduced for

smallpox, diphtheria and polio that vaccinations programs are one of the mosteffective methods of reducing the spread and occurrence of diseases.

11. Our understanding of how the immune system functions led to thedevelopment of vaccination programs to prevent infectious disease. ssess Assess theimpact of the use of vaccination programs on society (include the financial,health and social justice impacts on society).

Answer: Historically, infectious disease has been a major cause of death in ourcommunities. There was no treatment for these diseases until the development ofantibiotics, used to treat diseases caused by bacteria. The monetary cost of treatingthese diseases was quite high for both the individual and the public health system.The effect of these diseases on the sufferers and their families was in many casesdevastating. The burden on the public health system was very high. Inhabitantsof developing countries and poorer areas were disadvantaged in terms of havinga greater chance of contracting the diseases and a lesser chance of being able toaccess any available treatments or cures.

As our understanding of how the body develops immunity to a diseaseincreased, methods of producing artificial immunity were investigated. Vaccines


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that conferred immunity to the body without the body suffering symptoms of thedisease were developed.

Due to the success of vaccines in preventing the occurrence of disease, vaccination programs were implemented to ensure that all children wereimmunised against many once-common diseases, such as measles, diphtheria,

whooping cough and polio. These programs have had a positive impact on societyin many ways. They have decreased the incidence of diseases in the community.This has led to a much higher level of overall health in society and decreased thedeath rates from these diseases. Individuals do not have to suffer the symptomsof these diseases and have a much better quality of life, free of any possible sideeffects.

Vaccination programs have prevented many diseases. This has dramaticallyreduced the financial burden for the treatment of these diseases and for thecontinued support of individuals who have suffered side effects from the disease.Families have a reduced financial burden, as does the public health system. Money

does not have to be spent on costly treatments for these diseases as the diseasehas been prevented in the first place.

The WHO has implemented vaccination programs in many developingcountries so that all individuals, regardless of their socioeconomic status, areprovided with immunity to many diseases. This reduces the incidence of diseasein areas that are more susceptible to the spread of infectious disease because oftheir crowded, unhygienic conditions. This also decreases the costs associated withtreating disease in the communities that can least afford it.

There have been many positive impacts on society due to the introductionof vaccination programs. These impacts include a lowering of the incidence anddeath rate of a disease, a decrease in the financial burden on individuals and the

public health system and providing equality across all levels in society in terms ofimmunity to disease.

12. OutlineOutline reasons why drugs are given to suppress the immune response in organtransplant patients.

Answer: When a donated organ is transplanted into a recipient, the organ has, onits surface, ‘marker’ molecules that are different to the ‘marker’ molecules on thecells of the recipient. The immune system recognises that the donated organ isnot ‘self’ and treats the organ as a foreign invader. It mounts an immune responseinvolving the T cells and, if drugs are not given to suppress the action of cytotoxicT cells, the transplanted organ will be rejected.

CHAPTER

6Non-infectious disease

1. DefineDefine epidemiology.Answer: Epidemiology is the study of the patterns of disease in the populationand the factors that affect these patterns. It not only describes the disease and itspatterns, but also statistically analyses these patterns and then suggests reasons asto the cause of the disease.


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2. DefineDefine the following terms: (a) incidence (b) prevalence (c) morbidity (d) mortality.Answer:

(a) Incidence—the number of new cases of a disease in a given time period(b) Prevalence—the number of people in a population affected by the disease

at a specific time(c) Morbidity—the number of cases of a disease(d) Mortality—the percentage of the population that dies from the disease

3. IdentifyIdentify and describedescribe the three main types of epidemiological studies.Answer: The three main types of epidemiological studies are:(1) descriptive studies , which provide information about the frequency of the

disease, which section of the population is affected, whether the diseaseoccurs in a particular area and if there was a particular time period in whichthe disease occurred

(2) analytical studies , which are used to collect data and analyse it to try to work out the likely cause(s) of the disease. There are two types of analyticalstudies—case control and cohort studies.

Case control studies compare people with the disease and people withoutthe disease to try and find differences in their lifestyle, including differences intheir exposure to the likely causes of the disease.

Cohort studies follow groups of similar people who initially do not have thedisease. The only difference between the groups is that one group is exposedto the risk factor that may cause the disease and the other group is not

exposed. These two groups are followed for an extended period of time andthe resulting incidences of the disease in question are compared.

(3) intervention studies , which are used to carry out clinical trials of new drugs orevaluate the success of public health campaigns.

4. IdentifyIdentify and describedescribe the main features of epidemiology using lung cancer as anexample.

Answer: The main features of epidemiological studies are:■ There are large study numbers—many studies have been completed on lung

cancer; one of these by Hill followed 40 000 doctors.■ The study should be carried out over a long time period—Hill’s study was over

10 years.

■ A large amount of information from sufferers of the disease and those whoare free of the disease is collected. This information should be from a broadrange of people. Doll collected information from a large range of lung cancerpatients and those free of lung cancer. He established that there could be a linkbetween smoking and lung cancer.

■ Two large groups of similar individuals who do not have the disease are studiedfor a long period of time. The only difference between the groups is that onegroup is exposed to the potential cause of the disease and the other is not. Hillstudied 40 000 doctors, half of which smoked while the others did not.

■ Data is collected and analysed at the end of the study. Hill’s data showed thatthe doctors who smoked had a much higher incidence of lung cancer than


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those who did not smoke. His study also showed that the higher the numberof cigarettes smoked per day, the greater the chance of dying from lung cancer.

■ The possible cause of the disease is identified. From Doll and Hill’s studies, as well as many others, it has been found that smoking causes lung cancer.

5. The rates of a certain type of cancer are much higher in a particular area of a bigcity. IdentifyIdentify the main features you would have to include in an epidemiologicalstudy to try to determine why this is the case.

Answer:

■ A large study group from a broad range of people both in the area of concernand outside the area should be used. Information concerning all aspects of theirlives should be collected.

■ From this a pattern of the disease could be formed.■ Two large groups of similar people should be followed over a long period of

time (e.g. 10 years). One of these groups should be exposed to the possiblecause of the disease and the other group should not.

■ Large amounts of data should be collected and statistically analysed.■ The possible cause of the disease is then suggested.

6. Refer to Figure 6.10 and identifyidentify the relationship between each of the following: (a) smoking and the death rate from lung cancer (b) the number of cigarettes smoked per day and the death rate from lung

cancer (c) age and the death rate from lung cancer.Answer:

(a) Smoking causes an increase in the death rate from lung cancer.(b) The more cigarettes smoked per day, the higher the risk of dying from lung

cancer.(c) As age increases, the death rate from lung cancer increases.

45

30

15

10

5

35–44 45–54 55–64 65–74 75–84

A n n u a l d e a t h r a t e f r o m l

u n g c a n c e r ( x 1 0 3 )

Age

40

20

Key heavy smokers (> 1 pack per day) all smokers

never smoked

25

35

Figure 6.10 Annual

death rate from lung

cancer


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7. DistinguishDistinguish between infectious and non-infectious disease.Answer: An infectious disease is caused by a pathogen, while a non-infectiousdisease is not caused by a pathogen.

8. Copy the following table and complete to summarisesummarise information about thedifferent types of non-infectious disease.

Answer:

Type of non-

infectious disease Description Examples of diseases

Inherited These are diseases that are caused by

errors in genetic information and are

transmitted genetically.

Down syndrome, cystic fi brosis,

haemophilia

Nutritional Diseases that are caused by diets

lacking in vital nutrients

Scurvy, beri-beri, anaemia

Environmental These are diseases that can be caused

by:■ lifestyles that increase the risk of

certain diseases, e.g. lack of exercise

■ exposure to factors in the

environment, e.g. too much sunlight

■ exposure to chemicals in the

environment.

Cardiovascular disease,

melanoma, lead poisoning

9. IdentifyIdentify the non-infectious disease that you have studied and provide informationabout its:

■ occurrence ■ symptoms

■ cause ■ treatment/management.Answer: Scurvy Occurrence:■ Previously in sailors■ Now in developing nations where diet is lacking in vitamin C■ Also found in elderly people and those (such as alcoholics) whose diet is

unusual.Symptoms:■ Pain and tenderness in the legs■ Swelling of the long bones■ Swollen, purplish and spongy gums■ Gangrene (degeneration of tissue)■ Reopening of old wounds■ Spontaneous haemorrhaging■ Purple/black spots on the skin, indicating haemorrhaging■ Separation of once-healed broken bones■ Bleeding of the membrane covering the front of the eyes or the eyelidsCause:■ Lack of a sufficient amount of vitamin C in the dietTreatment:■ Inclusion of sufficient amounts of vitamin C in the diet


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CHAPTER

71. Identify the role of quarantine in preventing the spread of disease and plants andanimals: (a) into Australia (b) across regions of Australia. In your answer describedescribe some of the procedures used in quarantine.Answer:

(a) The role of quarantine in preventing the spread of disease and plants andanimals into Australia is to protect the native flora and fauna, agriculturalindustries, the environment and our health. It does this by:

—having a strict policy of inspection at all entry points to Australia —isolation of all plants and animals that are permitted entry into Australia

so that any diseases or pests that enter with them can be identified

—isolation of any people entering Australia with notifiable symptoms —having a specially developed policy governing northern Australia, as this

is the area that is most vulnerable to incursions by pests and diseases fromclose neighbours

—large fines and prison terms issued to those caught flouting our strictregulations.

(b) Quarantine prevents the spread of plants and animals and diseases acrossregions of Australia in order to protect areas that are pest and disease free.This protects our agricultural industry and helps make our products attractiveto those countries where these diseases and pests are prevalent. It alsoprotects the native flora and fauna, our environment and our health. The ways

in which this is achieved are: —legislation by governments and territories that prohibits the movement ofcertain items across borders or into exclusion zones

—checkpoints to inspect goods being taken across borders — warning signs and quarantine boxes for the dumping of items that are

prohibited —large fines and prison terms.

2. DefineDefine the terms: (a) prevention (b) control.Answer:

(a) Prevention—stopping the development of a disease in an organism(b) Control—involves regulating the incidence of disease.

Prevention and control of disease


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3. DescribeDescribe the quarantine measures you would have to follow or be subjected toand explainexplain how these measures protect Australia, if you:

(a) were bringing a horse into Australia to compete in a show-jumpingcompetition

(b) were returning to Australia from a holiday to an overseas destination and had wooden beads and dried pork products in your luggage

(c) were a ship’s captain entering a port in Australia and you had on boardpassengers who were showing the symptoms of a notifiable disease

(d) were entering the fruit fly exclusion zone in Australia and had some bananasin the boot of your car.

Answer:

(a) The horse would be placed in an animal quarantine station for a period oftime. It would be inspected on a regular basis to monitor whether any diseaseshave developed. The horse would not be released until quarantine officers

were satisfied that it was not harbouring any pathogens or pests. This process

prevents the entry of unwanted diseases and pests into Australia.(b) The items that were being carried in your luggage would have to be declared

and your bag would be inspected by a quarantine officer. The pork would beconfiscated and the wooden beads may be allowed entry after treatment. Thisensures that no unwanted pathogens or pests are brought into Australia.

(c) The ship’s captain must notify quarantine officers of the presence on theirship of individuals with symptoms that could be due to diseases that arenot present in Australia. The boat would be required to anchor offshore andquarantine officers would board and inspect the passengers and the ship. They

would then determine the best course of action to prevent the disease fromentering Australia. This prevents the entry of diseases into Australia.

(d) The bananas would have to be dumped in the quarantine bins that aresituated on all roads into the exclusion zones. This prevents the spread of fruitflies into the exclusion zone.

4. DescribeDescribe the early warning systems that are in place in northern Australia andexplainexplain their function.

Answer: The early warning systems that are in place in northern Australia include:■ the use of ‘sentinel animals’ such as pigs and cattle, which are regularly

checked for the occurrence of any diseases that are not present in Australia. Ifany diseases develop, responses are quickly put in place to control their spreadand eradicate the disease before it becomes established.

■ insect traps for the early detection of exotic pests, which are used in the same

way as the sentinel animals■ public education programs, which encourage the reporting of any differentpests or any diseases that have not been seen in Australia before. This againallows swift responses to be carried out to control and eradicate the pest ordisease.

5. DescribeDescribe two different types of evidence exhibited by: (a) plants infected by a pathogen (b) plants infested by an insect pest.Answer:

(a) Plants infected by a pathogen will show symptoms such as blight, spots andmosaic patterning on the leaf.


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(b) Plants that have been infested by pests may show holes where they have beeneaten, and webbing or trails left by burrowing insects.

6. DescribeDescribe the quarantine measures that are in place to prevent the spread of foot-

and-mouth disease into Australia and evaluateevaluate the effectiveness of these measures.Answer: The normal quarantine measures that involve inspection of cargo,passengers, containers and ships at all entry points to Australia are followed.

X-rays, detector dogs and quarantine officers are used to inspect all entries into Australia. Animal quarantine is also carried out. In addition to these measures, allcloven-hoofed animals and their products are banned from entry into Australia.People entering Australia from infected areas are subject to thorough processingand may even have their shoes washed to remove any traces of soil. Mail frominfected areas is checked and travellers to infected areas are asked to be especially

vigilant when travelling to rural areas in the infected countries.These measures have proved to be very effective, as Australia has been free of

foot-and-mouth disease since 1872.

7. ExplainExplain how the different strategies used in public health programs can controland/or prevent disease.

Answer:

■ Regulations that govern hygiene practices in the food and health industriesensure that pathogens are not transferred from one person to another. Thisprevents disease.

■ Regulations governing the maintenance of a disease-free community bytreatment of drinking water, removal of rubbish and removal and treatment ofsewage all prevent the movement of pathogens throughout the community andtherefore prevent disease.

■ The notification of the occurrence of certain diseases enables swift responsesto be put in place in order to control the spread of disease throughout thepopulation.

■ Public education programs that encourage regular monitoring for diseasessuch as breast cancer and prostate cancer allow for the early detection of thesediseases so that the chance of recovery from the disease is increased.

■ Childhood immunisation programs prevent the development of these diseasesin the population.

■ Public awareness programs attempt to educate the public about the dangersof some activities and encourage a change in lifestyle in order to prevent thedevelopment of the disease associated with the risk activity.

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