Bio7.Search for Better HealthU

HSC Biology Topic 3 “Search for Better Health”copyright © 2005-22009 keep it simple sciencewww.keepitsimplescience.com.au

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but first, some definitions...

HSC Biology Topic 3

THE SEARCH FOR BETTER HEALTHWhat is this topic about?To keep it as simple as possible, (K.I.S.S.) this topic involves the study of:1. INFECTIOUS DISEASES & PATHOGENS

2. BODY DEFENCES AGAINST DISEASE3. NON-INFECTIOUS DISEASES

4. STRATEGIES TO PREVENT DISEASEIN PLANTS & ANIMALS

What is “Health”?Health is a very difficult thing to define. A simpledefinition is that “Health is the absence ofdisease”.

The World Health Organization (WHO) hasdeclared this definition as too simplistic anddefines “health” as

... and NOT merely the absence of disease.

Does this mean thatif you were physicallyfit, well-fed and sane,but having a bad hairday, (sociallydangerous) that youare not healthy?

Despite the WHO’sdefinition, to reallyunderstand “Health”,you need to study“Disease”, and that’swhat this topic is really all about!

What is “Disease”?Disease can be defined as

By this definition, a broken toe-nail might be adisease, but in this topic you will study somemuch more serious conditions...

The Different Types of DiseaseDiseases can be simply classified as follows

“a state of complete physical, mentaland social well-bbeing”

“any condition that disturbs thenormal functioning of the body”

DISEASES

CCaauusseedd bbyy tthhee iinnvvaassiioonn oofftthhee bbooddyy bbyy aa ddiisseeaassee-

ccaauussiinngg oorrggaanniissmm,, aa

“Paathogen”

DDoo NNOOTT iinnvvoollvvee aappaatthhooggeenn,, aanndd ccaannnnoott bbee

ccoonnttaaggiioouuss..MMaayy bbee dduuee ttoo

Pathogens include:•• PPrriioonnss•• VViirruusseess•• BBaacctteerriiaa•• PPrroottoozzooaannss•• FFuunnggii•• MMaaccrroo-ppaarraassiitteess

•• HHeerreeddiittyy ((iinnhheerriitteedd))•• SSttrruuccttuurraall oorrmmeettaabboolliicc mmaallffuunnccttiioonn•• LLiiffeessttyyllee ffaaccttoorrss•• EEnnvviirroonnmmeennttaall

ffaaccttoorrss•• PPoooorr nnuuttrriittiioonn

...... aanndd ootthheerr tthhiinnggss

MMaannyy iinnffeeccttiioouussddiisseeaasseess aarree

Infectious Non-iinfectious

ContagiousTThhiiss mmeeaannss tthhaatt yyoouu ccaannccaattcchh tthhee ddiisseeaassee ffrroomm

aannootthheerr iinnffeecctteedd ppeerrssoonn,,ffrroomm bbooddyy ccoonnttaacctt,, ffrroommtthhee aaiirr,, ffrroomm ffoooodd aanndd

wwaatteerr eettcc..

SSoommee ddiisseeaasseess ccaann bbeeiinnffeeccttiioouuss,, bbuutt nnoott

ccoonnttaaggiioouuss..

SSoommee aarree ttrraannssmmiitttteedd bbyy aaVector

AA vveeccttoorr iiss aannootthheerroorrggaanniissmm wwhhiicchh ttrraannssmmiittss

tthhee ppaatthhooggeenn ffrroomm oonneeppeerrssoonn ttoo aannootthheerr..

FFoorr eexxaammppllee,, tthhee ppaatthhooggeennwwhhiicchh ccaauusseess MMaallaarriiaa iiss

ccaarrrriieedd ffrroomm oonnee iinnffeecctteeddppeerrssoonn ttoo aannootthheerr bbyy

mmoossqquuiittooeess.. TThhee mmoossqquuiittooiiss tthhee vveeccttoorr ooff tthhee ddiisseeaassee..

Fleas (on rats) werethe vector for

the “BlackDeath” in theMiddle Ages.

Plague victims14th century




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CONCEPT DIAGRAM (“Mind Map”) OF TOPICSome students find that memorising the OUTLINE of a topic helps them learn and remember

the concepts and important facts. As you proceed through the topic, come back to this page regularly to see how each bit fits the whole. At the end of the notes

you will find a blank version of this “Mind Map” to practise on.

The History ofour

understandingof infectious

disease

1st Line ofDefence...

the barriers

Epidemiology

The range ofPATHOGENS

2nd Line ofDefence...

Non-sspecificImmunity

Case Study ofan Infectious

Disease

InheritedDisease

NutritionalDeficiency

EnvironmentalDiseaseUse of

Pesticides

GeneticEngineering

Quarantine

THE SEARCHFOR BETTER

HEALTH

BBooddyyDDeeffeenncceessAAggaaiinnsstt DDiisseeaassee

SSttrraatteeggiieess ttooPPrreevveenntt

DDiisseeaassee iinn PPllaannttss && AAnniimmaallss

IInnffeeccttiioouussDDiisseeaasseess &&PPaatthhooggeennss

NNoonn-IInnffeeccttiioouussDDiisseeaasseess

Case Studies

3rd Line ofDefence...Specific

Immunity




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Genes, Differentiation and HealthYou began life as a single cell, and have sincegrown to be made up of billions of cells. Growthoccurs by mitosis which produces geneticallyidentical daughter cells, so every one of yourbillions of cells has exactly the same set of genes.

However, not all your cells are the same... theyhave specialised for different functions; musclecells, nerve cells, blood cells, and so on. If allyour cells are genetically identical, how canthey also specialise and be so different? Theanswer is that, in the embryo stage, your bodyunderwent a process called differentiation.

Every cell in your body contains in itschromosomes, ALL the genes needed tospecify all your body parts, functions and traits.In each cell though, only some of the genes are“switched-on”. Muscle cells have switched onthe genes for building muscle fibres, but havenot switched on the genes for eye-colour, orproduction of saliva. Each specialised type ofcell has switched on just those genes whichallow it to carry out its function, and no others.

Differentiation is essential for the correctfunctioning of your body, and therefore forhealth. If a muscle cell suddenly switched on thegenes appropriate for a blood cell, it would nolonger be functioning properly. This couldcause a loss of body function, and therefore, alack of good health.

Cleanliness is Next to HealthinessGood health is not just about correct cell andbody functioning. It was recognised in ancienttimes that cleanliness in water, food andpersonal hygiene would help prevent disease.At the time, the concept of “germs” was notunderstood.

You may have done laboratory work to growmicrobes on “nutrient agar” in petri dishes.

You probably discovered an amazing numberand variety of microbes in our food and water,and throughout our whole environment.

When Good Guys Turn BadWe are constantly surrounded by millions ofmicrobes. Most of them are harmlessly goingabout their business and cause no problems.However, even “harmless” microbes can causedisease.

If, for example, people are careless with foodstorage then microbes can rapidly multiplywithin the food. If eaten, the food can cause“food poisoning” because of the waste productsand toxins produced by the growing microbes.

Many potentially dangerous microbescommonly live on the skin or in people’s throatsand generally cause no disease because theirpopulation is small. However, if the person isweakened by stress, lack of food or illness,these “resident” microbes can suddenlymultiply rapidly and cause a serious disease.So, quite apart from the B.O. and bad breath, itreally is a good idea to wash yourself and cleanyour teeth!

Water from a river or lake may containpotentially dangerous microbes. This is why ourwater supplies are so carefully treated.

Treatment of Water SuppliesA typical Australian town or city obtains itswater from the local rivers. Generally, before itreaches the consumer:

• the water sits for some time in a large reservoir.This allows time for much of the suspendedmatter (including microbes and the matter theyare feeding on) to settle to the bottom.

• the water is filtered to remove any remainingsuspended solids.

• the water is chlorinated to kill virtually allremaining microbes.

When is a Microbe a Pathogen?Some of the “germs” around us are always “badguys” and their only purpose and way of lifeinvolves invading a person’s body and causingdisease.

Others are “harmless” organisms whichnormally go about their life without affectingpeople. However, many are opportunistic, and ifpresented with a chance to multiply in or on ourbody they will do so, and may cause a disease.

Any organism is a “pathogen” if it causes a disease.

1. INFECTIOUS DISEASES & PATHOGENS

Fungicolonies

PETRI DISH

inoculatedbytouchingwith fingers

Bacteriacolonies


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We have only known about the role ofpathogens (especially microscopic “germs”) asthe cause of infectious diseases for about 150years. Diseases were previously thought to becaused by “evil spirits” or were due to “bad air”,or similar ideas. The man recognised as thediscoverer of the “Germ Theory of Disease”was:

Louise Pasteur (1822-1895)Pasteur came to suspect that infectious diseaseswere caused by microbes after proving thatmicroscopic yeast was responsible for thefermentation involved in making beer and wine,and also showing that it was the growth of bacteriain wine that caused it to go sour.

His famous experiment of 1862 did 3 things:

• disproved the generally-held idea of“spontaneous generation” of life, and helpedestablish “Cell Theory”.

• proved that decay was caused by air-bornemicrobes, and not just due to contact with air.

• stimulated scientists to start looking formicrobes that were causing diseases... and, ofcourse, they found them!

You may have repeated Pasteur’s experiment inyour laboratory work.



EEaacchh ffllaasskk ccoonnttaaiinnss aa ““bbrrootthh””,,bbooiilleedd uunnttiill sstteerriilliizzeedd

CClloosseedd ffllaasskkrreemmaaiinnss

sstteerriillee...... nnoommiiccrroobbeessggrrooww iinn iitt..

OOppeenn ffllaasskk ggrroowwssmmiiccrroobbeess && rroottss..IItt wwaass bbeelliieevveeddtthhee lliiffee ccaammee

ssppoonnttaanneeoouussllyyffrroomm ccoonnttaacctt

wwiitthh aaiirr..

TThhiiss ffllaasskk iiss ooppeenn ttoo tthheeaaiirr,, bbuutt tthhee ““ggoooosseenneecckk””pprreevveennttss aaiirrbboorrnnee ssppoorreess

ggeettttiinngg ttoo tthhee bbrrootthh..IItt rreemmaaiinneedd sstteerriillee,, aannddpprroovveedd ““ssppoonnttaanneeoouussggeenneerraattiioonn”” iiss wwrroonngg..

A Brief History of Our Understanding of Infectious DiseasePasteur’sExperiment

Robert Koch (1843-1910)One of the scientists who followed up onPasteur’s work was the German Robert Koch. Heisolated the bacterium responsible for theserious disease anthrax, but more importantlyhe developed a general system for identifying apathogen.

The problem is that there are always manydifferent microbes present in the body of aperson with a disease. It can be very difficult tobe certain which one is causing the disease, andwhich are just “innocent by-standers”.

Koch developed a set of procedures to follow,which will definitely and scientifically identifythe pathogen. These procedures are known as“Koch’s Postulates” and are still used todaywhen previously unknown infectious diseasesare discovered.

Historical Case Study: Understanding MalariaMalaria is a tropical disease caused by a protozoanpathogen which is carried by a vector... themosquito. The symptoms are attacks of shivering,fever, headaches, nausea and extreme tiredness.Without treatment, about 10% of patients die, butsurvivors keep having re-occurrence of symptoms,perhaps for many years.

The history of human attempts to understand it,and cure or prevent it, is a good example of howdifficult this process can be.

The name “malaria” means in Italian “bad air”and it was believed since ancient times that itwas caused by the smelly gases from swamps.

In ancient Rome the occurrence of malaria wasreduced by draining swamps. (The realconnection to swamps was mosquitoes... butno-one thought of that)

After the work of Pasteur and Koch, a scientificsearch for a microscopic pathogen began. In1880, Charles Laveran discovered a protozoanPlasmodium in the blood of malaria patients, butthe method of transmission could not be found.

In 1898-9 Ronald Ross found the pathogen inmosquitoes and, using human volunteers, wasable to prove the transmission of the disease viathe mosquito vector. Throughout the 20thcentury many strategies were tried against thedisease:

• Anti-malarial drugs, such as “Chloroquine”, seemed effective to cure the disease until the pathogen evolved resistance.

• Widespread spraying of swamps, forests andvillages with insecticides to try to eradicate themosquito vector may have reduced the incidenceat times, but overall this strategy failed.

• All attempts to develop a vaccine against thepathogen have been unsuccessful, but research is stillgoing on, and recent developments are promising.

Malaria remains one of the world’s greatesthealth problems. Several hundred millionpeople are affected by it, and 2-3 million dieeach year... mostly children.

Anopheles MosquitoVector for Malaria




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The Variety of PathogensThere are 6 different categories of pathogen known to cause human diseases.

Macro-ParasitesThese are the larger, macroscopic parasites.

Ectoparasites are thosewhich are parasites onthe outside of the body,usually sucking blood.

Examples are fleas,ticks, leeches, mites,lice, mosquitoes, andso on. Some caninject toxins whilefeeding, causinginflammation, allergicreactions and sometimespartial paralysis.Generally, ectoparasites only become majorthreats to health if they are vectors formicroscopic pathogens.

Endoparasites are those parasites which liveinside the body. The most common pathogensare either flatworms (e.g. tapeworms and flukes)or roundworms.

Disease Example: Taeniasis (Tapeworm disease)

Pathogen: Taenia saginata(tapeworm)

Comment: Tapeworm lives in intestine. Can cause weight loss and abdominal pain.

ProtozoansProtozoans are single-celled organisms. Thecell is animal-like; eucaryotic and lacking a

cell wall. Billions of protozoans live inswamps, rivers and oceans where they formpart of the “plankton” and are a vital link inthe food chains. Only a few cause disease.

Disease Example: MalariaPathogen: Plasmodium species

Comment: Mosquito vector. Affects many millions of people. Major health problem.

FungiThe Fungi include the various moulds and

yeasts. Some are very useful (yeast for bread& beer) or are eaten for food (mushrooms).Most fungi live in soil and are important as

decomposer organisms in nature. Only a few cause disease.

Disease Example: Tinea (Athlete’s foot)Pathogen: Tinea pedis (a mould-like fungus)

Comment: Highly contagious. Feeds onskin, causing itchy, smelly, flaking of feet.

BacteriaBacteria are an enormously varied group of single-celled, procaryotic organisms.

The vast majority are decomposer organisms in soil and water environments, or make their own food by photosynthesis or chemosynthesis.

Some, however, are disease pathogens and caused many of the great “plagues” of history, such as the “black death” of the Middle Ages.

Tick

In the 20th century, most of the seriousbacterial diseases were brought under control

by the use of antibiotics and programs ofmass immunization.

Disease Example: TetanusPathogen: Clostridium tetani

(a rod-shaped bacterium)Comment:Detailed case-study in this section.

More pathogens next page...

VARIETY OF BACTERIABacteria have very small cells, in many shapes

Rod ShapedBacteria




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The Variety of PathogensContinued

AntibioticsOne of the great success stories of disease control in the20th century was the discovery of the class of drugs calledantibiotics. The first and most famous was Penicillin, firstextracted from a mould fungus Penicillium, in 1928. Otherantibiotics were discovered in various fungi, and some have been synthesised chemically.

Antibiotics are selectively toxic to living cells. They kill or inhibit the cells of microbes such asbacteria, but do not harm human cells. Antibiotics are mainly effective against bacteria. Some will killfungal pathogens (these are usually called “fungicides”) and others work against protozoans. It should be noted that antibiotics DO NOT work on viruses.

During the 20th century the use of antibiotics wasresponsible for helping to bring under control a rangeof diseases (mostly bacterial) which had been healthproblems for centuries... tuberculosis, leprosy,syphilis, pneumonia, cholera, to name just a few. Forthe first time in history, these serious diseasesbecame curable, and some have been virtuallyeradicated.

Also, antibiotics are widely used to treat infection inminor wounds, sore throats, eye and ear infections, andso on. This speeds recovery from minor ailments andimproves everyone’s quality of life. Antibiotics arefrequently prescribed for those suffering viral infectionsalso. This prevents “secondary infections” of bacterialdisease that might strike a person weakened by the virus.

The Bugs Fight Back... Antibiotic Resistance

Unfortunately, there is a down-side to the use ofantibiotics; Natural Selection. Among the billions ofindividual pathogen cells there may be a few whichhave some natural resistance to an antibiotic. Whenthe antibiotic kills all the others, the resistant cellssurvive and reproduce and evolution takes place.

Many pathogens have evolved resistance to theolder antibiotics and new ones need to bedeveloped or discovered, in order to keep winningthe war against the germs.

The danger is that, by using antibiotics, we have causedthe evolution of resistant strains. This could lead to futureepidemics of diseases that we cannot control.

PrionsPrions are a mysterious type of pathogenonly discovered about 20 years ago andstill not fully understood. They are NOT

living things, and are not cellular.

Prions are proteins molecules whichreproduce themselves and cause

infectious disease, especially of nervetissue such as the brain. They seem to beproteins that are folded and twisted intothe wrong shape, and are able to cause

more proteins to re-arrange to the wrongshape, thus spreading from cell to celland causing malfunctions to the brain.

Disease Example: CJD (Creutzfeldt-Jakob disease)

Pathogen: BSE prion(causes “Mad Cow Disease” in cattle.)

Comment: Incurable, 100% fatal, braindegeneration. Transmitted by eatingnerve tissue from infected animals.

VirusesViruses are all “bad guys”. Every virus is a pathogen which causes disease in some organism or other... plants, animals, even bacteria all suffer virus diseases.

The lifestyle of every virus is to invade a living cell and “hijack” its genetic machinery. The cell is taken over and forced to make more virus particles to infect more cells.

Viruses are NOT cellular. Each is a very small capsule ofprotein containing either DNA or RNA.

Many serious and common human diseases are caused byviruses, including AIDS, influenza (flu), measles, polio, rabies

and the common cold. Some, such as polio, have been broughtunder control by immunization programs.

FLU VIRUS RABIES VIRUSNNuucclleeiicc aacciiddss

PPrrootteeiinn ccaappssuullee aanndd aattttaacchhmmeennttss ffoorr eenntteerriinngg hhoosstt cceellll




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Case Study of an Infectious Disease: Tetanus

Tetanus, also known as “Lock-jaw”, has beenknown since ancient times, but only

understood since about 1890 when the causeand method of infection was discovered.

Since early in the 20th century it has become curable and preventable

by the use of immunization.

Host ResponseThe infected person’s defence mechanisms react inall the usual ways:

Inflammation of the wound, serves to partly seal off theinfected area and raise the temperature to try to speedhealing and inhibit heat-sensitive pathogens.

Phagocytes (white blood cells which “eat” bacteria) areattracted to the wound area and destroy bacteria andclean up dead tissue. However, they can only operateat the edges of the wound where conditions areaerobic. Further in, the C. tetani can be thriving in theanaerobic areas.

The immune system reacts to the exotoxin bybeginning the process of producing an antibody todestroy the toxin molecules. However, this processmay take weeks, and the disease is likely to kill theperson well inside this time, if untreated.

CausePathogen: Clostridium tetani ,

a rod-shaped bacterium.

This bacterium is common in soil, especially ifthere is a lot of animal manure, such as around

farmyards. The bacterium is anaerobic (liveswhere there is no oxygen) and normally feeds

on dead organic matter in the soil.

C. tetani produces heat-resistant spores which can survive in soil for many years.

Major SymptomsThe tetanus exotoxin affects nerve cellscausing them to keep “firing” when they

shouldn’t. This stimulates muscles to go intospasms and seizures.

Jaw and throat muscles are usually the first affected... hence “Lock-jaw”.

High temperature, elevated blood pressure andheart rate. Sudden, powerful and painful

muscular seizures may be so strong as tobreak bones and tear muscles in the abdomen

and chest. Seizures can interrupt breathing,causing brain damage and suffocation.

Untreated, between 30-60% of patients will die,and survivors may take months to recover.

Prevention and ControlTetanus is completely preventable by immunization. The vaccine contains tetanus “toxoid”;

tetanus toxin which has been treated chemically to render it harmless, but it still sets off the immune system to actively produce antibodies. Immunity lasts about 12 years,

so “booster” shots are recommended every 10 years.

The world-wide death toll from tetanus is approximately 200,000 per year, but only a few hundred of these are in “developed” countries like Australia because of the immunization programs.

Virtually all Australian cases occur in older people who have forgotten to get a booster shot, or from self-tattooing, or drug-users using dirty needles.

Treatment• Antibiotics to kill bacteria in the wound.• Surgical exploration and cleaning of the wound.• Treat spasms with muscle-relaxant drugs.• The major treatment is the use of tetanusantitoxin. The “Antitoxin” is Tetanus ImmuneGlobulin (TIG). Basically this is a concentrate ofantibodies from a person (or other animal) who hasdeveloped immunity to tetanus. TIG binds to thetetanus toxin in the bloodstream so it becomesharmless and is destroyed by phagocyte cells.

TransmissionThe disease is not contagious. You cannot catchit from someone else.

The normal manner of infection is from a deepwound, such as when someone steps on a nail,but even being pricked by a plant thorn could beenough. The essential requirement is that thewound is deep enough to provide anaerobicconditions in dead tissue.

If spores of C. tetani enter the wound, they maygerminate and the bacteria grow, feeding on thedead cells within the wound. If that’s all thathappened, it would not be a serious problem,but C. tetani produces an “exotoxin” whichhappens to be one of the most potent nervepoisons ever discovered.

In the human body it is life-threatening!

“Health” is a state of a)..................................................................... “Disease” is anycondition b)....................................................Infectious disease is caused by ac)............................... If the disease can be caughtfrom another infected person then it is said tobe d)............................. Some infectious diseasesare transmitted by another organism, called ae)...........................

“Differentiation” is the process by which bodycells become f)............................. Every cell in amulticellular organism is geneticallyg)..............................., but differentiated cellshave “switched on” different h)........................ inorder to function correctly.

Microscopic organisms are found in every partof our environment. This is why it is essential tofollow i)............................. procedures for storageof j).................... and personal k)...........................Water supplies are routinely l)...............................and m)........................ to remove or kill microbes.Any organism can become a n)............................if it causes o)...........................

The man most responsible for helping usunderstand the “Germ Theory of Disease” wasp)..................... .............................

Tetanus Case Study.The pathogen is called v)...................................Tetanus w)....................... (is or is not) contagious.Transmission usually occurs by x)................................................. The pathogen grows iny)....................... conditions in a wound, feeding onz).................... It produces a powerful aa)..................which affects ab)........................ cells.

The host reponses include inflammation, whichattempts to ac)............................... Also, white cellscalled ad)............................... gather at the woundsite. The immune system begins makingae).................................. but the disease progressesfaster than this.

The major symptom is sudden, violentaf)........................ which can break bones, and eveninterrupt ag).......................... leading to braindamage and suffocation.

Patients are treated with an antitoxin containingah)....................... from an immune person or animal. Prevention of tetanus is achieved byai)............................ This involves a “toxoid” whichis aj)............................................................ Boosterinjections are needed every ak)............. years.

Antibiotics are especially effective againstal)........................... but have no effect onam)........................ A modern problem is pathogensthat have an)......................................................

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Copying is permitted according to the Site Licence Conditions onlykeep it simple science®


COMPLETED WORKSHEETSBECOME SECTION SUMMARIES

Worksheet 1 Basic Definitions & HistoryFill in the blank spaces Name....................................

Worksheet 2 Pathogens & Disease Name....................................

His famous experiment of 1862 proved thatdecay was caused by q)........................... and notjust due to r).................................... His workstimulated others to begin searching formicroscopic pathogens. The great Germanscientist s)................................. discovered thebacteria which caused t).............................., butmore importantly he developed a set ofprocedures which allow u)............................................... .....................................

Malaria is caused by a v)....................... pathogen,transmitted by a vector, the w)..........................The pathogen, called x).................................., wasdiscovered in patients’ blood in 1880. The link tomosquitoes was proven by y)................................in 1898. Many strategies have been used againstMalaria, including drugs such asz)................................ These were successful, butthe pathogen has evolved aa)...............................to drugs in many places. Attempts to kill themosquito vector have failed, and attempts todevelop a ab).............................. have not yetsucceeded. Malaria remains a major worldhealth problem, killing ac).....................................people each year.

There are 6 different categories of pathogen:Macro-parasites include the a).................-parasiteswhich feed on the outside of the body, such asb)..................... These rarely cause any serious problemsthemselves, but can be c)...................... for otherpathogens. Endoparasites live d)................... the body.An example is e)....................... (tapeworm disease)caused by the flatworm f).......................................

Fungi are responsible for some diseases of the skin,such as the highly contagious g)...................... caused bythe fungus h)........................................... (scientific name)

i)............................ are single-celled, eucaryoticorganisms. Not many cause disease, but Malaria,caused by various species of j)............................... is oneof the world’s greatest health problems.

Bacteria are a varied group of k).........................organisms with very l)................ (size) cells of variousshapes. They are responsible for many diseasesincluding m).................... caused by n)................................

Viruses are non-cellular. Each is a capsule ofo)................... containing p)....................... A virus invadesliving cells and forces the cell toq)............................................ Examples of virus diseasesinclude r)....................and ..........................

s)...................... are non-cellular protein molecules whichcause diseases of the t)................................. system. Ahuman example is u)................................

Multiple Choice1. A disease could NOT ever be:A. infectious and contagiousB. hereditary and carried by a vectorC. non-infectious and hereditaryD. pathogenic and contagious

2. “Differentiation” occurs when cells becomespecialized because:A. they contain different genetic information.B. they contain the same genes, but mutations

occur.C. new combinations of genes have been

produced by meiosis.D. they follow different parts of the same total

set of genes.

3. The scientist responsible for developing asystem for positively identifying the pathogenresponsible for a disease was:A. PasteurB. LaveranC. KochD. Ross

4. A pathogen was described as:“Non-cellular and microscopic. Composed of aprotein capsule containing nucleic acid”This pathogen is a:A. FungusB. BacteriaC. VirusD. Prion

5. The pathogen responsible for the diseaseMalaria, and its vector would be classified(respectively) as:A. protozoan and insect.B. bacterium and macro-parasite.C. insect and virus.D. macro-parasite and bacterium.

6. Antibiotics are not an effective treatment for adisease caused by a:A. fungusB. bacteriumC. protozoanD. virus

Longer Response QuestionsMark values given are suggestions only, and are togive you an idea of how detailed an answer isappropriate. Answer on reverse if insufficient space.

7. (5 marks)Write a brief definition for each of the following.a) Infectious disease

b) Non-infectious disease

c) Pathogen

d) Contagious

e) Vector

8. (3 marks) It is essential for public health that watersupplies are made as safe as possible. Outlinethe processes that are typically used to treat ourwater supplies.

9. (3 marks)Give a brief account of the main strategies thathave been made to control the disease malaria,commenting on the effectiveness of each.

10. (6 marks)List the 6 categories of pathogen responsible forinfectious disease. For each, name a diseasecaused by a pathogen of that type.

11. (8 marks)For a named, infectious disease you havestudied:a) give the name of the pathogenb) describe the major symptomsc) describe how the disease is transmittedd) describe the host response to the infectione) outline the treatment given to a patient withthe diseasef) outline any measures to control & prevent thedisease

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Worksheet 3 Test Questions section 1 Name....................................




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2. BODY DEFENCES AGAINST DISEASE

Flushing Mechanisms• Regular emptying of the bladder

flushes microbes from the bladder and urethra.

• Production of tears, and regular“blinking” wash and wipe microbes from the eyes.

Reflex ActionsCoughing and sneezing reflexes move dust,mucus and trapped pathogens, etc out of thebreathing passageways.

Vomiting removes stomach contents that aremaking you nauseous, removing pathogens whichhave been swallowed.

SkinThe outside surface of skin is layers ofdead, dry cells, virtually impossible for

microbes to penetrate.

It is a difficult environment for a pathogento grow on (no water).

Skin constantly flakes off, carryingmicrobes away.

Your body is not defenceless against invadingpathogens. You are equipped with 3 “lines” ofdefence:

The 1st Line of Defence: Barriers to Invasion

There are a number of physical and chemicalbarriers which prevent most potentialpathogens from entering your body. The mostimportant ones are:

SkinMucous MembranesChemical Barriers & SecretionsFlushing Mechanisms & Reflexes

Secretionssuch as the tears from the

eyes, contain an anti-bacterialenzyme “Lysozyme”.

Chemical BarriersStomach is highly acidic.This kills most pathogensthat are swallowed with

food, or in mucus.

Urinary and reproductiveopenings are mildly

acidic... enough to inhibitthe growth of many

microbes.

MICROFLORALiving in, and on, the human body are many “friendly” microbes which share a symbiotic relationship with us.

Some live in the intestines and manufacture vitamins for us. Others live on skin and mucous membraneswhere they normally act as competitors to potential pathogens. They keep the population in check by out-

competing the pathogens, or by creating chemical conditions that pathogens cannot tolerate.MICROFLORA IMBALANCE CAN LEAD TO DISEASE

The female reproductive system is largely protected by its normal microflora. Taking medications,such as antibiotics, can upset the normal balance. The yeast Candida albicans, which is alwayspresent in low numbers, can take advantage and multiply rapidly. This results in a disease called

“Thrush”, with symptoms of itching, a white discharge and general discomfort.

Mucous MembranesThese membranes line thenatural body openings ofmouth and throat, and theurinary and reproductive

tracts. The mucous membranes

secrete mucus, a sticky fluidwhich traps pathogens.

In some places themembranes are lined with cilia.

These are microscopic hairswhich “beat” in a rhythmicway to move mucus (andtrapped pathogens) along

for disposal. For example, mucus in thebreathing tubes is movedupwards, until it can beswallowed into the acid

of the stomach.




11

Antigens and the Immune Response

Sooner or later, pathogens manage to get pastthe 1st line of defence and invade the body.Once the barriers are penetrated there are 2more lines of defence to combat the pathogens,but first the body has to recognise that foreigncells or toxins are present. It is the special cellsof your immune system which do this.

Each of your own body cells has on the outsideof its cell membrane, special proteins andglycoproteins (combinations of carbohydratewith protein) which act as identificationmarkers, proclaiming “SELF”. Your immunesystem constantly checks everywhere, butignores anything labelled as “self”.

Any foreign cell, cell fragment, or even just aprotein molecule or toxin will act as an “Antigen”.It will not be recognised as “self”, and thereforemust be foreign. This will set off a range ofdefence responses by the immune system.

Organ Transplants and “Tissue Rejection”

When a person receives an organ transplantsuch as a kidney transplant, the new organ is, ofcourse, from another person. The cells will havedifferent “marker” proteins on their cellmembranes.

Therefore, the cells of the new organ will act asantigens and set off the immune responses. Theimmune system reacts to the new organ as if itwere a foreign invader and attempts to kill it. Theresult is called “Tissue Rejection” and canquickly lead to the failure of the transplant.

To try to prevent this happening, the transplantdoctors:

• use only organs from donors who closelymatch the patient in their “tissue type”. Thismeans their cell markers will be similar and willnot act as antigens quite as strongly.

• treat the patient with “immuno-suppressant”drugs to reduce their immune response. Theirimmune system is partially shut-down and doesnot attack the transplant. However, this alsomakes the patient more vulnerable to pathogensand they must be protected from infection.

ANTIGENS are chemicalsrecognised as “NOT-SSELF”

(such as proteins on foreign cells)which trigger the immune response

BEFORE STUDYING THE IMMUNE SYSTEMYOU NEED TO KNOW MORE ABOUT BLOOD CELLS

BBLLOOOODD CCEELLLLSS

ERYTHROCYTESRed Blood CellsCarry oxygen

LEUCOCYTESWhite Blood CellsImmune System

BASOPHILSinvolved in

inflammation

B-CCELLS(2 types)produce

Antibodies

T-CCELLS(4 types)

Kill infected body cells

LYMPHOCYTES form the

3rd Line of Defence

EOSINOPHILS NEUTROPHILS

MACROPHAGES

These 3 types carry out“Phagocytosis”

All these types are part of the “2nd Line of Defence”

Notice thatthere are

many differentkinds of

“white cells”


12

When pathogens penetrate the 1st-Line barrierdefences their antigens will rapidly set offcounter-attack responses of the 2nd-Line ofDefence. This is “non-specific”, meaning thatthe exact identity of the foreign invader does notmatter... the response is the same.

PhagocytosisPhagocytosis means literally “to eat cells” andthat’s exactly what some of the white blood cellsare designed to do. The Eosinophils,Neutrophils and Macrophages are all“phagocytes” and able to eat and destroyforeign cells such as invading bacteria.

The phagocyte cells detect the antigens of aforeign cell, recognise it as “not-self” and attack it.

Phagocyte cells are “shape-changers” and notonly can they wrap around a pathogen to engulf it,they can also squeeze their way out of thebloodstream and move among the tissue cells.Whenever they encounter antigens that signal“NOT-SELF” they will carry out phagocytosis todestroy it.

When large numbers of phagocytes gather at asite of infection, they form “pus”. Pus is rathernasty stuff (it’s full of infectious pathogens) but isa healthy sign... it means your phagoctes are onthe job!

InflammationInflammation is the way the body reacts to anycell damage, such as a cut, abrasion, crushingor burn. When cells are damaged they releasechemicals which the immune systemrecognises as a “distress” signal.

In response, the white bood cells calledBasophils release the chemical histamine.

Effects of Histamine• dilation (widening) of the blood capillariesaround the injury site. This allows more blood toflow in, bringing more clotting factors and morephagocyte cells to destroy pathogens.

This also brings more body heat to the site. Heatcan inhibit some pathogens, and speeds up allchemical reactions for faster repairs.

• capillaries to become more permeable,allowing fluids to escape from blood into thetissues. This causes swelling. The extra fluid inthe tissues brings more phagocytes to fightinfections, and the extra pressure causesdrainage of fluid into the Lymph System. Thiswashes dead cell debris towards the lymphnodes for disposal, thus clearing the area forrepairs to begin.

Features of an inflammed wound• Hot and red, from extra blood & body heat• Swollen, from extra tissue fluid• Pus formation, from millions of phagocytes

Cell Death... ApoptosisSometimes at an infection site, the tissue cellsmay become so thoroughly infected by viruses,or infiltrated by so many bacteria, that the bestdefence is to seal off the area and sacrifice allthe body cells within.

Immune system cells can start the process ofApoptosis, in which cells are given a chemicalinstruction to “commit suicide”. The suicidalcell produces enzymes which chop the cell’sDNA to pieces, the energy-producingmitochondria swell and burst, and the cell self-destructs.

More importantly, special antigens appear onthe cell membrane which attract phagocytes todestroy the cell, and its load of pathogens.

In some cases, an infected site will be “walled-off” by a layer of cells forming a capsule or cyst,inside which all the cells have been ordered tosuicide. This isolates an infection and stops itspreading. Later, the dead debris inside the cystwill be destroyed by phagocytes, and the tissuerepaired.



PHAGOCYTOSISPPhhaaggooccyyttee

CCeellll

LLyyssoossoommeess((ccoonnttaaiinn ddiiggeessttiivvee

eennzzyymmeess))

BBaacctteerriiaallCCeellll

PPhhaaggooccyyttee eenngguullffssffoorreeiiggnn cceellll..

PPaatthhooggeenn wwrraappppeedd iinn aammeemmbbrraannee iinnssiiddee PPhhaaggooccyyttee..

LLyyssoossoommeess ffuussee wwiitthh tthheeppaacckkaaggee..

PPaatthhooggeenn ddeessttrrooyyeedd bbyyllyyssoossoommeess cchheemmiiccaallss

The 2nd Line of Defence: Non-Specific Immune Responses




13

The Lymphatic SystemAs the blood circulates through thetissues, some of the blood plasma alwaysseeps out of the capillaries and bathesthe cells in “tissue fluid”. The body is equipped with a system of “drains”to collect this fluid and return it tothe blood. This drainage system isthe Lymphatic System.

Lymph tubes form a one-waydrainage system from all bodyextremities, back to a point near the heartwhere tissue fluid is dumped back into avein to re-join the blood. Tissue fluid is squeezed through lymph vessels by the surroundingmuscles, and the tubes havevalves to prevent back-flow.

At various points along the lymph vessels there are special chambers called “lymph nodes”. These are important sites for the immune system to defend against disease.

If there is an infection in any body tissues, it is likely that pathogens will be carried along by the flow of lymph fluid.

The 3rd Line of Defence: Specific ImmunityThe 3rd line of defence said to be “specific” because the lymphocyte cells are able to identify

particular pathogens by their antigens and set up defences which will accurately target each one.The pathogen will be destroyed not only in the current infection, but in future infections as well...

you become immune to the disease.

The cells responsible are the white blood cells known as “T-lymphocytes” and “B-lymphocytes”. B-Lymphocytes produce protein molecules called “antibodies” which can “lock-on” to a foreignantigen rather like an enzyme fitting its substrate... i.e. it is a “key-in-lock” situation, with each

antigen needing a specific antibody to “fit” it.

T-LLYMPHOCYTESare produced in bone marrow, but mature and

multiply in the Thymus Gland (hence “T” cells).

“Cell-MMediated” Immune response.T-ccells attack body cells that are

infected by pathogens, or growing abnormally as cancers.

B-LLYMPHOCYTESare produced and mature in bone marrow

(hence “B” cells). Produce ANTIBODIES.

“Antibody-MMediated” Immune response.

Antibodies attack pathogens (and their toxins)which are NOT inside body cells,

but in the blood, lymph or tissue fluid.

The 3rd Line of DefenceTo help you remember which is which,think of “B for Bomber”... B-ccells are

like bomber aircraft which dropbombs (antibodies) on the enemy

without ever getting close to them.

This could spread pathogens throughout thebody, but the lymph nodes

generally prevent that.Lymph nodes contain manyphagocytes to “eat” foreign

cells, and also contain lymphocyte cells (below)

which are able to targetspecific pathogens and

destroy them.

When fighting a serious infectionthe lymph nodes become swollen

and painful. This is often a signof infection and an indication of

where it is. For example, swollenlymph nodes in one armpitindicate that an infection is

travelling up the arm, possiblyfrom an infection site in the

hand.

There are also several glands of the body which are

associated with the lymphaticsystem, and have a role in body

defences. These include theadenoids and tonsils, the thymus gland in the

upper chest, and the spleen. All act as“reservoirs” for immune sytem cells.

LYMPHATIC SYSTEMsshhoowwiinngg ssoommee ooff tthhee ddrraaiinnaaggee

LLyymmpphh NNooddeess nneecckk

aarrmmppiitt

ggrrooiinn

LLyymmpphh fflluuiiddrreettuurrnneedd ttoobbllooooddssttrreeaammnneeaarr hheeaarrtt

DDrraaiinnaaggee ppaatttteerrnnffrroomm aarrmmaanndd lleeggss

You also need to know about how T-cells and B-cells interact with each other, and how they destroy pathogens.

This is also described on the next page.

There are 2 categories of B-cells,and 4 categories of T-cell.

Some details about these areshown on the next page.




14

The 3rd Line of DefenceLYMPHOCYTES

B-CCells T-CCells

PlasmaCells

ProduceAntibodies

to fightthe currentinfection

Memory B-CCells

Remain in thesystem to

respond to futureinfections by thesame pathogen

Helper T-CCells

Interact withPhagocytesto set off

the specificimmune

responses

Cytotoxic(Killer)T-CCells

Attack bodycells whichare infected

bypathogens

SuppressorT-CCells

Suppressthe immune

response(turn it off)

after aninfection isdefeated

MemoryT-CCells

Remain inthe system to

respond tofuture

infections bythe samepathogen

HHooww WWhhiittee BBlloooodd CCeellllss IInntteerraacctt wwiitthh EEaacchh OOtthheerr

Step 1Phagocyte Displays an Antigen

A Phagocyte“eats” a pathogen.

Part of thepathogen (an antigen) is displayed on MHC molecule.

WWHHAATT IISS MMHHCC??MMHHCC ssttaannddss ffoorr ““MMaajjoorr HHiissttooccoommppaattiibbiilliittyy CCoommpplleexx””..

TThhiiss iiss aa ggllyyccoopprrootteeiinn mmoolleeccuullee wwhhiicchh aaccttss lliikkee aann eegggg-ccuupp ttoo hhoolldd aann aannttiiggeenn oouutt ffoorr

iinnssppeeccttiioonn bbyy aa llyymmpphhooccyyttee cceellll..

PPhhaaggooccyyttee CCeellll MMHHCCmmoolleeccuullee

AAnnttiiggeennbbeeiinngg

ddiissppllaayyeeddPPaatthhooggeenn hhaassbbeeeenn ddeessttrrooyyeedd

Step 2Antigen is “Inspected” by a Helper T-Cell

Helper T-Cells will “dock” with a phagocyte and “inspect” the antigen. The T-Cellthen releaseschemical messageswhich stimulate theproduction of hugenumbers of specificPlasma (B) Cellsand Cytotoxic (T) Cells, each “keyed” to that specific antigen shape.

PPhhaaggooccyyttee CCeellllHHeellppeerrTT-CCeellll

AAnnttiiggeenn

MMHHCC TT-CCeellllrreecceeppttoorr

Step 3

Killer T-CCells

AAnnttiiggeennrreecceeppttoorr

IInnffeecctteedd bbooddyy cceellllss..AAnnttiiggeennss aappppeeaarr oonn

cceellll mmeemmbbrraanneess

TT-CCeellllss ““ddoocckk”” wwiitthhaannttiiggeennss oonn iinnffeecctteedd

bbooddyy cceellllss..CCeellllss aarree kkiilllleedd bbyy bbeeiinnggbbuurrsstt ooppeenn bbyy eennzzyymmeess

ffrroomm TT-CCeellll

Chemical Signals stimulateproduction of millions of

specific Lymphocytes

Produce Antibodies

Antibodies lock ontopathogens so they are

neutralized and immobilized. Phagocytes then destroy them.

Antibodies areproteins with a

shape to fitantigens on

each pathogenexactly

Plasma B-CCells

KKiilllleerr TT-CCeellllss


15

ImmunityOnce a person has been infected by a particularpathogen and then recovers from the disease,the immune system stops producing T-Cells andB-Cells for that pathogen. (This is done by“Suppressor T-Cells”)

However, “Memory T-Cells” and “Memory B-Cells” remain in the system for yearsafterwards, possibly for life. If that samepathogen invades the body again, the 3rd Line ofDefence is already primed and ready. It reactsrapidly with a flood of T-Cells and antibodies sothat the pathogen is usually destroyed beforeany disease symptoms are produced. The personcannot be affected by that pathogen ever again...he or she is immune to that disease.

This is why many diseases, such as childhoodmeasles, are only ever caught once. At the firstinfection it takes time for the immune system tobegin producing specific lymphocytes, so thedisease takes hold and symptoms appear. Laterin life many re-infections with measle virus mayoccur, but the primed immune system destroysthe pathogen so symptoms do not occur again.

The Success of VaccinationIt was mentioned in a previous section how the useof antibiotics was a tremendous step forward in ourability to cure certain infectious diseases. Evenmore important has been the prevention (alwaysbetter than cure) of disease by programs of massimmunization by vaccination.

Smallpox is a viral disease which, if untreated,has a high death rate and survivors are leftdisfigured and scarred for life. In the 1950’ssmallpox was targetted by the World HealthOrganization as “public enemy No.1”. A world-wideeffort of vaccination resulted in the disease beingtotally eliminated by 1977... the most outstandingsuccess against any disease in history.

Poliomyelitis (“Polio”) is a viral diseasewhich results in paralysis of limbs, causing thevictim to be disabled for life. It used to kill or cripplehundreds of Australian children every year.

Since the 1950’s, the use of polio vaccines(originally injected, now taken orally) haseliminated the disease from Australia, and almostfrom the world. The disease still occurs in a fewAfrican nations only.

Diphtheria is a disease caused by a highlycontagious bacterium. It can lead to permanentnerve and heart problems, even when patients arecured of the infection. Therefore, prevention isdefinitely far better than cure.

In the 1920’s, several thousand Australian childrendied from Diphtheria, or were permanentlyweakened by it. Vaccination programs had virtuallyeliminated it by the 1970’s.

It is now compulsory in Australia for all children tobe vaccinated against Diphtheria, Tetanus, Polio,and another one-time child-killer, “WhoopingCough”. Other diseases for which successfulvaccination programs exist include Rubella,Hepatitis, Measles and Influenza.



However, some pathogens keep altering the“antigens” on their cell membranes or viral capsules.This means the memory lymphocytes from theprevious infection are useless, and the immunesystem must “re-llearn” to recognise the pathogen.

This is why diseases such as the common cold canbe caught over and over again.

“Vaccination” comes from the Latin word“vacca” which means “cow”.

Edward Jenner(English, 18th century)had noticed that milkmaids always caught a mild disease “cowpox” from the cows, but never suffered the deadly smallpox.

Jenner used pus from a cowpox sore to deliberatelyinfect people with cowpox. This caused later immunityto smallpox. (We now know that the viruses are sosimilar that antibodies for one, work against the other).So, “vaccination” literally means “cow-aation”.

VaccinationThe problem with becoming immune to a diseasethe natural way is that a person has to actuallysuffer the disease in order to gain immunity.

Vaccination is the process of deliberately puttingantigens into a person’s body so that the immunesystem reacts, and the person becomes immune,but without danger from the actual disease.

The “vaccine” might be injected, or taken orally, tointroduce one of the following into the body:-

Live pathogens that are “attenuated”... harmlessstrains of the pathogen which have been bred.

Pathogens that have been killed by heat orchemicals.

Fragments of pathogens, such as part of the cellwall of a bacterium, or the capsule of a virus.

A “toxoid”, which is a toxin molecule from thepathogen, but rendered harmless by sometreatment.

The antigens in the vaccine set off the immune response,eventually giving the person immunity to that disease.

“Antigens” are chemicals which triggerthe o)............................ ..............................Antigens are proteins which the bodyrecognizes as p)......................... After anorgan transplant, the patient’s immunesystem must be q)....................................by drugs, otherwise their immunesystem will r)..................................... thetransplanted organ. The immune systemis made up of a variety of types of whiteblood cells, or s).................................

The 2nd Line of Defence ist)...................... (specific or non-specific).Three types of leucocyte (calledu).............................., .......................... and.........................) carry out phagocytosis.This is when the “phagocyte” cellenvelopes a foreign cell and digests itwith enzymes from the v).........................(organelle)

Another type of leucocyte calledw)........................ set off thex)............................ response wheneverthe body has suffered damage.Basophils release the chemicaly)...................... which z)..........................blood capillaries, resulting in swelling,hotness and redness around the injuredsite.

Sometimes body cells can be giveninstructions to “commit suicide”. Thisprocess is called aa)...........................

The Lymphatic System is a system ofab).......................... which return tissuefluid to the blood. If an infection ispresent, pathogens could rapidly spreadvia the lymph tubes. To prevent thisthere are “Lymph ac)..............................”at various points such as the neck,ad).......................and ............................Each lymph node has many phagocytesand lymphocytes to destroy anypathogens.

16



Worksheet 4 Non-Specific Body DefencesFill in the blank spaces Name....................................

The 1st Line of Defence are thea)...................... to infection. The skin ismade of layers of b).............................cells which are very difficult for apathogen to c)...............................

d)............................... membranes linethe body openings. They secetee).................. which traps pathogens.Some mucous membranes are linedwith f).......................... which beatrhythmically to remove mucus andtrapped pathogens.

The g)............ conditions of the stomachare a h)........................... barrier whichkills microbes that are swallowed.

Emptying the i)................................ andblinking the eyelids both serve to“flush” microbes away. Tears alsocontain an enzyme calledj).................................. which can killbacterial cells.

Reflex actions, such as k).......................or vomiting helps to remove microbesthat have been breathed in orswallowed.

It is normal for the body to have many“friendly” microbes living in and on it.These are called the body’sl).................................... Theseorganisms help control potentialpathogens by competing with them. Ifthere is an imbalance of microflora, am).......................................... may result.An example is the fungal disease calledn)............................................

WHEN COMPLETED, WORKSHEETS BECOME SECTION SUMMARIES

WORKSHEET 6 COVERS THE IMMUNE SYSTEM & VACCINATION

Multiple Choice1. An example of a “chemical barrier” toinfection is:A. mucus in your breathing tubesB. acid in your stomachC. dead, dry skin cellsD. cilia in a mucous membrane

2. An “antigen” is:A. a protein that can “lock-on” to a pathogen

and neutralise it.B. a chemical which can kill pathogen cells.C. a foreign protein which sets off an immune

response.D. a blood cell which releases antibodies.

3. The white blood cells Eosinophils, Neutrophilsand Macrophages are all:A. phagocytesB. lymphocytesC. antibody producersD. part of the “1st line of defence”

4. “Apoptosis” is the process of:A. programed cell “suicide”.B. enveloping and “eating” a foreign cell.C. pus formation at a site of infection.D. red swelling of infected tissue.

5. The diagram shows part of the A. Circulatory system.B. Immune systemC. Nervous systemD. Lymphatic system

6. Antibodies are produced by:A. killer T-cellsB. basophilsC. plasma cellsD. phagocytes

7. Before the “specific” immune response can bemounted by lymphocytes for the first time:A. killer T-cells need to “lock-on” to

infected body cells.B. helper T-cells need to “inspect” an antigen

presented by phagocytes.C. memory B-cells need to activate

antibody production.D. antibodies need to combine with an antigen.

8. Which of the following would NOT be suitable touse as a vaccine?A. live, attenuated pathogensB. fragments of pathogen cellsC. active toxin from a pathogenD. killed pathogen cells

Longer Response QuestionsAnswer on reverse if insufficient space.

9. (3 marks) Describe the location and features of the body’smucous membranes in helping to protectagainst disease.

10. (4 marks)Explain how the natural “microflora” of the bodyhelp protect against disease and, using a namedexample, how an imbalance in the microfloracan result in disease.

11. (4 marks)One of the responses to infection or tissuedamage is “inflammation”. a) Name the type of leucocyte responsible forinitiating inflammation.

b) Explain how the typical features ofinflammation (namely hot, red and swollentissue) are brought about.

12. (4 marks)Compare and constrast “B-cells” and “T-cells”and their methods of attack against invadingpathogens.

13. (4 marks)There are 4 varieties of “T-lymphocytes”...“helper”, “killer”, “suppressor” and “memory”cells.Briefly outline the function of each.

14. (5 marks)a) Explain how vaccination can make a personimmune to a disease, possibly for life, withoutthem ever getting sick from that disease.

b) Name a previously serious disease which hasbeen brought under control by vaccination.

17



Worksheet 5 Test Questions section 2 Name....................................


18

EpidemiologyEpidemiology is the study of the occurrence ofdiseases. It is very much about collecting data andanalysing it statistically to look for patterns andcorrelations between the incidence of disease andthe many factors that may be involved in thecause(s) and the spread of disease.

The data collected by epidemiologists includesinformation from:

The results of an epidemiological study mightinclude:

Such findings allow health authorities andgovernments to plan and allocate resources tobetter meet the health needs of a community.For example, epidemiology results might pointout the need for a new hospital to be built in acertain place, or for a law to be made to ban theadvertising of products that endanger health,such as tobacco products.

A classic example which shows the value ofepidemiology is the case of the drug thalidomide.In the 1960’s this drug was commonly prescribedto pregnant women to prevent “morningsickness”. Throughout history there have alwaysbeen some children born with deformities, andno-one noticed that there had been a slightincrease in these cases. However, anepidemiology study revealed a correlationbetween the use of thalidomide and an increasedrisk of babies being born without arms or legs.The drug was quickly banned, saving many morepeople from its terrible effects.

Case Study Epidemiology of Lung CancerNow that many infectious diseases are more orless under control, the major causes of death inour society are heart disease and cancer. In theUSA in 1996, of all the many deaths by cancer,those due to lung cancer amounted to 25% in menand 14% in women. Epidemiology has nowestablished beyond doubt that there is a verystrong link between lung cancer and smoking.

The correlation between smoking and a number ofhealth problems, including lung cancer, wassuggested by epidemiology data as early as the1950’s. The powerful and influencial tobaccocompanies were able to argue that...

Throughout the 1970’s and 1980’s theepidemiology studies kept collecting data andcompiling evidence showing that smoking waslinked to lung cancer. Experiments to try to provethe causation were done too. For example,thousands of laboratory rats were forced tobreathe tobacco smoke for long periods of timeand the incidence of lung cancer compared with“non-smoking” rats. Eventually the evidencebecame overwhelming:

• Annual deaths from lung cancer are about 5 timeshigheramong smokers than non-smokers.

• Quitting smoking immediately begins reducingthe chance of developing lung cancer

• Since the banning of tobacco advertising andpublic awareness programs, the percentage ofsmokers in the population has declined. Theincidence of lung cancer (and other smoking-related problems) has declined exactly in parallel.



3. NON-INFECTIOUS DISEASES

Hospitals and health-ccareworkers whoreport on theirpatients and thetreatments given.

Government studies such asthe national census, whichmeasures the size and age

distribution of thepopulation, where people

live, what they do for a livingand so on.

Case studies of particular diseases, inwhich detailed information is gathered

about those people suffering thedisease, and compared to a “control

group” of similar people without the disease.

IIddeennttiiffyyiinngg tthhaatt aanneeww ddiisseeaassee hhaass

aappppeeaarreedd..

DDiissccoovveerriinngg tthhaatt aanneexxiissttiinngg ddiisseeaassee hhaass

cchhaannggeedd iinn iittssooccccuurrrreennccee..

IIddeennttiiffyyiinngg tthheeppoossssiibbllee

ccaauusseess oorr rriisskkffaaccttoorrss ooff aa

ddiisseeaassee..

AAsssseessssmmeenntt ooff tthheeeeffffeeccttiivveenneessss ooff ppuubblliicc

hheeaalltthh ssyysstteemmss aannddvvaacccciinnaattiioonn pprrooggrraammss..

...“correlation doesn’t prove causation”

This is quite true. Just because 2 thingsoccur together doesn’t prove that one

causes the other. As the ancient Romansknew, malaria is more common around

swamps. They thought it was the “bad air”.Now we know it’s because of the mosquito

vector breeding in the swamps.




19

An Inherited DiseaseHaemophilia

OccurrenceHaemophilia occurs in males only, at a rate of 1in every 5,000 male births.

SymptomsThe person’s blood lacks certain blood“factors” involved in blood clotting, so theirbody is unable to stop the bleeding from minorinjuries. Even gentle activity can cause minorbleeds at joints and in muscles.

With haemophilia, there is continued internalbleeding, extreme pain in joints, and this leadsto joint damage and disability. Untreated, it isusually fatal during childhood.

CauseHaemophilia is caused by a recessive, sex-linked gene. The recessive gene is carried onthe “X” chromosome and so is inherited morecommonly in males than females.

In fact, it is virtually unknown in femalesbecause to have haemophilia a female must bethe daughter of a haemophiliac father. Untilrecently no haemophiliac males survived longenough to father children.

Treatment/ManagementModern treatment allows haemophilia sufferersto lead a fairly normal life. Treatment involves 2-3 injections per week of blood clotting factorsextracted from donated blood.

A Nutritional Deficiency DiseaseScurvy

OccurrenceIn modern Australian society, scurvy is

virtually non-existant because of thegenerally high quality diet available. (We eat

too much... but that’s another story.)

In history, scurvy was a significant disease,especially on long sea voyages. A British

report in 1600 indicated that 10,000 sailorshad died of scurvy in the previous 20 years.

SymptomsThe main protein of skin, bone and hair is“collagen”. In scurvy, the collagen cannot bemade properly by the body, so • hair falls out• skin erupts, flakes and discolours• teeth loosen and fall out• blood capillaries leak blood, so bruising

spots appear all over the body

CauseLack of Vitamin C in the diet.

Vitamin C is found in citrus fruits such as oranges, and in some vegetables such as tomatoes.

The enzyme responsible for a critical step inmaking collagen requires ascorbic acid(vitamin C) for its correct functioning.

Treatment/ManagementA balanced diet including fresh fruits and

vegetables, will prevent scurvy.

OccurrenceMelanoma is the 3rd or 4th most common cancerin Australia, and approximately 2,000 Australiansdie from it each year. Between 1950 and 1990 itsoccurrence tripled, and Australia has the highestincidence of melanoma in the world, per capita.

SymptomsDark, irregular-shaped moles appear on the skin.These may become raised, and later bleed andbecome ulcerated.

This “primary” tumour may shed cells which canspread in the blood and establish “secondary”tumours in vital organs such as lungs, kidneys,liver or brain.

CauseMelanoma is classed as an “environmentaldisease” because its major cause is a factor ofthe Australian environment... ultra violet (UV)rays from the Sun.

Cause (cont)Exposure to UV damages skin cells, causesmutations in the DNA and greatly increases therisk of a melanoma developing.

It can also be considered a “lifestyle disease”since its occurrence is related to outdoorlifestyles, and activities such as sunbaking.People with fair skin are more at risk.

Treatment/ManagementThe primary tumour can be removed by surgery.Secondary tumours are treated by surgery,radiation therapy and anti-cancer drugs. Earlydetection greatly increases the chances ofsurvival.

Prevention (always the preferred strategy)includes avoiding skin exposure to the Sun bythe use of protective clothing, and sunscreenlotions, and changing lifestyle by avoidingdeliberate sunbaking.

Case Studies of Non-Infectious Diseases

An Environmental Disease: Melanoma




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Plant and Animal DiseasesPlants and animals suffer from diseases causedby the same range of pathogens as do humans.In addition, plants suffer a lot of damage fromherbivorous animals feeding on them,especially from insects.

In your practical work you may have examinedplant shoots and leaves and gathered evidenceof pathogens and insect damage.

Leaf GallsA common sign of disease in many plants is thegrowth of a “gall” in the plant tissue. A gall isthe plant’s response to an infection or irritationcaused by a microscopic pathogen or macro-parasite.

The plant grows layers of tough, woody tissuearound the infection site in an attempt to “wall-off” the pathogen and prevent the infectionspreading.

Disease and Pest ControlAustralia’s agricultural industry not onlysupplies us with most of our food, but is a majorpart of the nation’s economy.

Disease, or insect pests in crops, could have adevastating effect on this industry. Therefore,our governments and industry organizationsuse a variety of strategies to control diseaseand agricultural pests.

QuarantineEven in ancient times, people understood theprinciple of quarantine... for example, peoplesuffering the disease leprosy, were isolated in“leper colonies” to prevent the diseasespreading through a community.

In modern Australia, quarantine is a majorstrategy used to prevent the entry and spread ofa variety of plant and animal diseases and pestswhich could have devastating effects on ouragricultural and pastoral industries.

The government agency responsible is theAustralian Quarantine Inspection Service(AQIS). Every airport and other point of entry forpeople and goods into Australia is under AQISscrutiny. Tourists may not bring plant seeds,fresh foods, animal skins or soil (even muddyboots) in from another country.

People who wish to bring in live animals, suchas pets or racehorses, must go through lengthyand expensive procedures to ensure the animalis not carrying a disease. The animal will bequarantined... placed in isolation for possiblyseveral weeks, and regularly examined by aveterinarian for any signs of disease.

People entering from certain “risky” parts of theworld must show proof of vaccination againstsome diseases, or else they too will bequarantined until it is proven they are notcarrying an excluded pathogen.

The Success of QuarantineThe fact that Australia has remained totally freeof certain human, plant and animal diseases isevidence of the effectiveness of our quarantinesystem. Australia is free of:

• Foot-and-Mouth disease which could devastate sheep & cattle herds.

• Malaria and Rabies. (serious human diseases)• Sorghum Downy Mildew, a fungal pathogenwith potential to destroy many cereal crops and native grasses... and many others.

4. STRATEGIES TO PREVENT DISEASE IN PLANTS & ANIMALS

Leaf damagefrom a “leafminer” insect

Fungaldisease

QUARANTINED


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Use of PesticidesA “pest” species is any plant or animal that wefind troublesome or destructive to ouragriculture and animal husbandry.

In the 20th century many “pesticides” weredeveloped in an attempt to control pest species. Ingeneral terms, a “pesticide” is a chemical whichcan kill a pest species without serious harm to theplant crop or animals we wish to protect.

Genetic Engineering for Disease & Pest Resistance

Genetic Engineering (GE) is the process ofaltering the genetic make-up of a species. Manyof the modern developments in GE are aimed atmodifying our crops and animal herds to makethem resistant to various diseases or pests sothat usage of pesticide chemicals can bereduced or eliminated.



Insecticideskill insects.

The originalwas DDT

Dips & Drenchesare given or applied

to animals to killmacro-pparasitessuch as worms &

ticks

Fungicideskill fungalpathogens

Herbicideskill plant “weeds”

The best known is“Roundup”

Originally, the pesticides were thought to be“magic bullets” which would keep pest speciesunder control. This attitude has changed, asmany pesticides either lose their effectiveness,or create environmental problems.

It is now realised that, although many pesticideshave been effective, it is better in many cases tolook for alternative ways to deal with pests...once again the principle is all about preventionand avoidance, rather than cure. Two importantstrategies are:

• Biological Controls... using natural predatorsand pathogens to control a pest, and• Genetic Engineering...

Pests Develop Resistance

In almost every case of apesticide, the pest speciesshow a tendency todevelop resistance. This isNatural Selection inaction, resulting inthe evolution ofresistant pests.

Pesticides are Indiscriminant

Insecticides, for example, killany insects, not just the“target” pest species. Thiscreates even worse pestproblems because the

natural competitors andpredators of the pest are

killed too.

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ttoo ccoonnssuummeerrss

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ffoooodd cchhaaiinnss.. FFiisshh aarreekkiilllleedd bbyy iinnsseeccttiiddeess.. DDDDTT

hhaadd sseevveerree iimmppaaccttss oonn tthheerreepprroodduuccttiioonn iinn mmaannyy bbiirrdd

ssppeecciieess..

Case Study:Cotton Bollworm (Heliothis caterpillar)

This insect pest chews holes in cotton, maize,tomatoes and peanut crops. As well as thisdamage itself, the crop becomes more prone tofungal disease.

Insecticides are not the answer, becauseHeliothis has evolved resistance, and manynatural enemiesand predatorsof Heliothis arekilled by sprays.

In the field of human disease control, theemphasis has shifted from treatment and cure,towards prevention. While antibiotics still havetheir value as treatment drugs, the greatsuccess story of human health has been massvaccination to prevent millions of people evergetting certain diseases.

The same trend, from treatment towardsprevention, is occurring with plant and animaldiseases, and pest control.

Pesticides

GE Strategy No.1

Scientists havetransferred agene from abacterium intocotton plants. Thegene is for theproduction of atoxin, which islethal to thecaterpillar if eaten.

Since cotton is nota human food,and the toxin isonly produced bythe leaf cells inthe plant, thepresence of thebacterial toxin isnot a problem forhumans.

GE Strategy No.2

Research is being done with avirus which specifically infectsHeliothis caterpillars only, andwill not infect other species.

The virus already causes adisease in the caterpillar, butscientists are developing waysto genetically alter the virus toinclude a gene for a lethal toxin.

The idea is to produce billionsof GE viruses and then deliverthem in a spray to crops thathave a Heliothis infestation. Noother species would beaffected.

The 3rd Line of Defence is a)...............................(specific/non-specific) immunity, meaning thatthis system “targets” each antigen specifically.The white blood cells involved are calledb).................................. and are of 2 main typescalled c)..........-cells and .........-cells.

T-cells have 4 sub-categories as follows:Helper T-cells interact with phagocytes to“learn” about a new d)................................... andthen send chemical signals to cause theproduction of millions of “specifically targetted”lymphocytes.

e)......................... (killer) T-cells can recognisebody cells which are infected with a pathogenand kill the cell by bursting its cellf)............................ with enzymes.

Suppressor T-cells g).................................... theimmune response after an infection has beendefeated.

h)........................ T-cells remain in the system torespond to future attacks by the same pathogen.

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Worksheet 6 Immune System & VaccinationFill in the blank spaces Name....................................

Worksheet 7 Non-Infectious DiseasesFill in the blank spaces Name....................................

There are 2 sub-categories of B-cell:i)............................ cells produce proteins calledj)....................................... These are able to bindto a specific antigen (rather like the lock-and-key system with enzymes and substrates).

By surrounding the antigen, antibodiesneutralize it and attract k)....................................which “eat” and destroy it. l)...............................B-cells remain in the system to respond tofuture attacks by the same pathogen.

Once a disease pathogen has been defeated,the m).............................. lymphocytes remain onguard, ready to respond to future infection bythe same pathogen. This means the person isn)....................... to that disease, because thepathogen will be destroyed before anysymptoms occur.

o)............................ is an artificial method ofmaking people immune to a disease. The“vaccine” contains p)........................... to set offthe immune response, without causing thedisease. Programs of mass vaccination havebeen very successful against some diseases.For example, q)........................... has been totallyeradicated, diseases such as r)..........................and ............................. are virtually non-existant.

It is caused by a recessive gene carried on thep).............. chromosome, so it is said to beq)...............-linked. The disease was invariablyfatal in the past, but modern treatments involvethe injection of r)..............................................from donated blood.

Scurvy is an example of a s)..................................deficiency disease. It is due to a lack oft)............................ in the diet and used to be asignificant risk during u)............................................. with no supplies of fresh fruitavailable. Symptoms include hair and teethv)............................, and skin eruptions andbruising due to leaking of blood fromw)..........................................

Melanoma is a very dangerous form ofx)................... cancer. It can be classed as an“Environmental Disease” since a majorcausative factor is exposure to y).........................rays from the Sun. Approximatelyz)...................... (number) of Australians die frommelanoma each year. This is theaa)............................. rate in the world, on a percapita basis.

Epidemiology is the study of thea)........................ of diseases. By collecting andb)......................... data, the patterns andc)........................... between various factors canbe used to identify disease risks and assess theeffectiveness of d)................................ programs.These findings help health authorities andgovernments make decisions and laws aboutcommunity health, such as banning advertisingfor e)......................................

Epidemiology has established the link betweenf)............................. and smoking. The death ratefrom lung cancer among smokers is g).................(number) times higher than among non-smokers. Since the ban on tobacco advertising,and h)........................... programs, the percentageof smokers has i)........................ and so has thej)......................... of lung cancer.

Haemophilia is an example of ank)............................ disease. Its occurrence is inl)....................... only, at a rate of 1 case everym)............. (number) male births. The diseasecauses internal n)......................... due to the lackof o)................................... factors in the blood.

Fungicides for n)............................., and Dips andDrenches to kill o)............................... in animals.

It is now realised that pesticides are not aswonderful as once thought, because:• pests develop p)..........................................• pesticides are a toxic risk to q)............................• insecticides are indiscriminate, killing not onlypests, but r)........................................ as well.• pesticides can pollute the s)...............................and affect other life forms such as fish or birds.

One alternative to pesticides ist)........................................... For example, thepest caterpillar u)............................... attackscotton, maize, tomato and peanut crops and isone of Australia’s worst agricultural pests. Twodifferent G.E. strategies are being researchedand tested to control this pest. One involvesinserting genes from a v)............................... intocotton plants so they produce aw)............................... which kills any insect thateats it. Another strategy involves geneticallymodifying a x)......................... which attacks onlythe caterpillar. The virus will be geneticallymodified to produce a fast-actingy)............................. to kill the caterpillars rapidly.

As for human disease control, the emphasis hasshifted from z).................................diseases/pests towards aa).............................them occurring.

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Worksheet 8 Strategies for Plant & Animal DiseasesFill in the blank spaces Name....................................

Worksheet 9 Test Questions sections 3 & 4 Name....................................

Inspection of plant foliage often revealsa)........................... due to pathogens and insects.A “gall” is a plant’s response to b).........................or irritation. A gall is a capsule of woody tissuethat grows around an infection site in an attemptto c).....................................................................

The importance and economic value of ouragriculture demands strategies to combatdisease and pest species.

A major stategy is d)................................. whichmeans to isolate potential sources of infection,to prevent their entry and spread. Thegovernment agency responsible is callede).................... (abbreviation) and it checks allpeople and goods entering Australia. Prohibitedgoods include f)..................................,................................ and .........................................Animals, such as pets or livestock, must beplaced in g)......................................... for severalweeks and examined and tested to ensure theyare not harbouring h)..................................

Our quarantine system has been successful atkeeping Australia free from animal disease suchas i)............................., human diseases likej)................................. and .............................. andplant diseases such as k).......................................

“Pesticides” include l)............................ to killinsects, m)....................... to kill weeds,

Multiple Choice1. The results from an Epidemiology study wouldprobably NOT be useful for:A. experiments to extract an antibiotic from a fungus.B. assessing a vaccination program.C. identifying risks of an environmental disease.D. discovering the appearance of a new disease.

2. The disease which has risk factors of anenvironmental and lifestyle nature is:A. malaria . B. melanomaC. scurvy D. haemophilia

3. The effectiveness of Australia’s quarantine systemcan be seen by the:A. amount of prohibited articles seized at airports.B. difficulty of bringing a pet animal into Australia.C. small number of tourists with diseases.D. absence of certain diseases and pests in Australia.

4.Using pesticides against agricultural pests is similarin principle to the use (in human medicine) of:A. vaccinationB. quarantineC. epidemiologyD. antibiotics

Longer Response Questions

5. (3 marks)Outline some of the epidemiologicalcorrelations that point to the link betweensmoking and lung cancer.

6. (4 marks)You have studied an hereditary disease.Name the disease you studied and describe:a) the occurrencea) the symptomsb) the causec) the treatment or management

... of the disease.

7. (5 marks)a) Briefly discuss reasons why the widespreaduse of pesticides against agricultural pestspecies and diseases is no longer considered asthe best strategy for control.

b) Using a named example of a pest species,outline an alternative strategy involving GeneticEngineering.




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CONCEPT DIAGRAM (“Mind Map”) OF TOPICSome students find that memorizing the OUTLINE of a topic

helps them learn and remember the concepts and important facts. Practise on this blank version.

THE SEARCHFOR BETTER

HEALTH


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Answer SectionWorksheet 1a) complete physical, mental and social well-being.b) which disturbs the normal functioning of the body.c) pathogen d) contagiouse) vector f) specialisedg) identical h) genesi) correct hygienic j) foodk) hygiene/cleanliness l) filteredm) chlorinated n) pathogeno) disease p) Louis Pasteurq) microbes r) contact with airs) Robert Koch t) anthraxu) the pathogen of a disease to be identifiedv) protozoan w) (Anopheles) mosquitox) Plasmodium y) Ronald Rossz) chloroquine aa) resistanceab) vaccine ac) 2-3 million

Worksheet 2a) macroscopic b) leeches/ticks/licec) vectors d) insidee) Taeniasis f) Taenia saginatag) Tinea h) Tinea pedisi) Protozoa j) Plasmodiumk) procaryotic l) smallm) Tetanus n) Clostridium tetanio) proteinp) nucleic acid (DNA or RNA)q) make new viruses r) AIDS, ‘flu, measles, etcs) Prions t) nervousu) CJD (Creutzfeldt-Jakob disease)

v) Clostridium tetani w) is notx) a deep wound y) anaerobicz) dead tissue aa) toxinab) nerveac) seal off/ inhibit pathogensad) phagocytes ae) antibodiesaf) muscular seizures ag) breathingah) antibodies ai) vaccinationaj) tetanus toxin, made harmless by chemicaltreatmentak) 10 al) bacteriaam) viruses an) antibiotic resistance

Worksheet 31. B 2. D 3. C 4. C 5. A 6. D

7.a) Disease caused by a pathogen.b) Disease that does not involve a pathogen.c) An organism which invades the body anddisturbs the normal functioning of it.d) A disease which can be “caught” bytransmission from an infected person.e) An organism (usually animal) which carries apathogen from one host to another.



8.• Water typically sits in reservoir which allows alot of suspended matter, and pathogens, tosettle out.• It is often filtered to remove remainingsuspended solids.• It is chlorinated to kill any pathogens.

9.• Anti-malarial drugs (such as Chloroquine) weresuccessful treatments, but the parasite has nowdeveloped resistance.• Attempts to eradicate the mosquito vectorusing insecticides lowered the incidence ofmalaria at times, but overall this strategy failed.• All attempts so far, to develop a vaccine havefailed.

10.Macro-parasites eg Taeniasis (Tapeworm disease)Fungi eg TineaProtozoa eg MalariaBacteria eg TetanusViruses eg AIDSPrions eg CJD (Creutzfeldt-Jacob disease)

11. Disease: Tetanusa) Clostridium tetani (bacterium)b) Violent, painful muscle spasms, which caninterrupt breathing.c) Pathogen enters a deep wound, such asstepping on a nail. Disease is NOT contagious.d) Normal responses: inflammation aroundwound, immune system begins to respond totetanus toxin, but progress of the untreateddisease is too fast for immune system to cope.e) Muscle-relaxant drugs to treat spasms.Antibiotics to kill bacteria. Clean woundsurgically.Administer Tetanus antitoxin, which isantibodies from an immune person or animal.f) Vaccination with tetanus “toxoid” givesimmunity and is 100% effective at preventingdisease.

Worksheet 4a) barriers b) dead, dryc) penetrate. d) Mucouse) mucus f) ciliag) acid h) chemicali) bladder j) lysozymek) coughing l) microfloram) disease n) Thrusho) immune response p) foreignq) suppressed r) reject / attacks) leucocytes t) non-specificu) eosinophils, neutrophils & macrophagesv) lysosome w) basophilsx) inflammation y) histaminez)dilates aa) apoptosisab) tubes/vessels/“drains”ac)nodes ad) armpits & groin


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Workskeet 51. B 2. C 3. A 4. A5. D 6. C 7. B 8. C

9. Mucous membranes line all the body openingsat mouth, nose, throat and reproductive anddigestive openings.Membranes produce mucus, a thick fluid wichtraps dust and microbes. In some places (egtrachea) there are microscopic hairs (“cilia”)which beat rhythmically to move mucus alongfor removal.

10.The skin, mouth, digestive and reproductivetracts all have a natural population of microbesliving there, many in a mutualistic relationship.They control potential pathogens by out-competing them, or by creating conditions thatthe pathogens cannot tolerate.

If this natural “microflora” population becomesunbalanced or damaged, an opportunisticpathogen may multiply and cause disease. Anexample is the yeast Candida albicans which isusually present in the female reproductive tract,but kept under control by the microflora. Anoutbreak of Candida results in the disease“Thrush”.

11.a) Basophilsb) Basophils release Histamine which causes:• dilation of blood capillaries; more blood andbody heat flows to area... hence hot and red• capillaries become more porous, so moreplasma leaks out causing swelling.

12. Comparison (similarities): T-cells and B-cellsare both lymphocytes which can defend againstspecific pathogens.

Contrast (differences): B-cells produceantibodies; proteins which “lock-on” toantigens and neutralize pathogens/toxins whichare free in bloodstream or tissues. Neutralizedpathogens are then destroyed by phagocytes.

T-cells are able to recognise body cells that areinfected by a pathogen (eg has a virusmultiplying inside it) and kill the cell bybursting its membrane with enzymes.

13. “Helper” T-cells interact with phagocytes which“present” a new antigen to them. Helper cellsthen send chemical signals which cause thecloning and rapid production of millions oflymphocytes able to “target” that specificantigen.

13. (cont)“Killer T-cells” are able to identify and “lock-on”to body cells which are infected with a specificpathogen, such as a virus. They destroy the cellby bursting its membrane with enzymes.

“Suppressor” T- cells turn off the response aftera pathogen has been defeated.

“Memory” cells remain in circulation, possiblyfor life, ready to quickly re-activate the immunesystem against future invasions by that specificpathogen.

14.a) Vaccination is the process of introducing intoa person’s body an antigen which will set off theimmune response without making the person ill.

For example, a vaccine might contain harmless,killed bacteria. This will set off the immuneresponse so that future infection by the livingbacterial pathogen will be destroyed beforesymptoms appear. The person is “immune” tothat pathogen.

Worksheet 6a) specific b) lymphocytesc) B-cells & T-cells d) antigense) cytotoxic f) membraneg) suppress h) Memoryi) Plasma j) antibodiesk) phagocytes l) Memorym) memory n)immuneo) Vaccination p) antigensq) Smallpox r) Polio & Diphtheria

Worksheet 7a) occurrence b) analysingc) correlations d) public healthe) tobacco products (or other dangerous products)f) lung cancer g) 5h) public awareness i) declinedj) incidence k) inheritedl) males m) 5,000n) bleeding o) clottingp) X q) sexr) clotting factors s) nutritionalt) vitamin C u) long sea voyagesv) loss w) capillariesx) skin y) ultra-violetz) 2,000 aa) highest




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Worksheet 8a) damage b) infection/ a pathogenc) prevent the infection spreadingd) quarantine e) AQISf) plants, fresh food, soilg) quarantineh) pathogens i) Foot-and-Mouthj) Malaria & Rabiesk) Sorghum Downy Mildewl) insecticides m) herbicidesn) fungi o) macro-parasitesp) resistance q) humansr) their predators t) Genetic Engineeringu) Heliothis v) bacteriumw) a toxin x) virusy) toxin z) treating/killingaa) preventing

Worksheet 91. A 2. B 3. D 4. D

5.The data shows that the chances of contractinglung cancer are about 5 times higher amongsmokers than among non-smokers.

The incidence of lung cancer among ex-smokers shows a steady decline against thetime since they quit.

The incidence of lung cancer in society hasshown a decline exactly in parallel with thedecline in the number of smokers, broughtabout by the ban on tobacco advertising, andpublic awareness programs.

6. Haemophiliaa) Occurs in males only, at the rate of 1 per 5,000male births.b) The blood fails to clot properly, so any activitycan result in internal bleeding into joints,bruising etc. This leads to painful joint damageand disability. If untreated, it is usually fatal inchildhood.c) Inheritance of a recessive gene, carried on theX-chromosome. This means it is “sex-linked”and appears in males much more commonlythan females.d) Clotting factors extracted from donated bloodare injected 2-3 times per week. This allows thepatient to lead a relatively normal life, but gentleexercise and injury avoidance are important.

7.a) • many pests have developed resistance tothe pesticide.• pesticides pose a toxic threat to humans whouse them, and to consumers.• Some pesticides cause environmentalproblems, such as the widespread effects ofinsecticide DDT on bird reproduction up untilthe 1970’s.

b) The Heliothis caterpillar is a major pest incotton crops, but is now resistant toinsecticides.

Scientists have genetically engineered cottonplants by inserting into their chromosomes abacterial gene which causes the production of atoxin. The cotton plant produces toxin whichkills any insects which eat the crop, eliminatingthe need to spray pesticides.



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