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Wendy AylmerJudith BrothertonMonika Khun

Anne Migheli

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Introduction v

Acknowledgments vi

CChhaapptteerr 11 Water for living 1

Mind map 21.1 Water is essential for living things 31.2 Water and the environment 141.3 Chemicals and natural water systems 251.4 Reducing water pollution 401.5 Local and global? 48

Chapter summary 58Exam-style questions 59

CChhaapptteerr 22 Plants 61

Mind map 622.1 Plant function 632.2 Seed germination and requirements 762.3 Factors affecting seedling growth 862.4 Water requirements of plants 912.5 Asexual reproduction in plants 1032.6 Biodiversity 109

Chapter summary 118Exam-style questions 119

CChhaapptteerr 33 Humans at work 121

Mind map 1223.1 The need for safety 1233.2 Breathing clean air 1323.3 Protecting eyes makes sense 1533.4 Protecting the ears 1673.5 Protecting the head 1753.6 Keeping mobile 187

Chapter summary 195Exam-style questions 196

CChhaapptteerr 44 Local environment 197

Mind map 2004.1 Factors affecting an environment 2014.2 Energy and matter in an ecosystem 2184.3 Local ecosystems: interactions and responses 2274.4 The impact of humans 242

Chapter summary 255Exam-style questions 256

A periodic table of the elements 258

Glossary 259

Index 263

ORGANISMS IN THEIR ENVIRONMENTS33CChhaapptteerr

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Playing a sport and performing other physical activities require good coordination.There are complex interactions between sense organs, nerves, muscles and bones.The bones and muscles of the body support the soft tissues. They give the body shapeand good posture as well as allowing movement.

The body is protected in many ways. Bones of the skull and the vertebral columnprotect the brain and spinal cord. Strong back and abdominal muscles also help sup-port and protect the back. Bones at a joint end with a cushion of softer cartilage andare bathed in a fluid which helps them move smoothly.

Reflexes are another protective mechanism. You blink when a foreign objectapproaches your eye. Your hand moves away quickly if you touch a hot iron. Thesereflex responses are much faster than your usual responses. They reduce the risk ofdamage to the body.

The immune system can also make a huge range of responses to defend the bodyagainst invading microorganisms.

In spite of all this natural protection, our modern way of life requires other ways toprotect the human body. Different demands are placed on the body in the workplaceand when playing sport. We should all be aware of safety risks because it is far easierto prevent damage to the human body than it is to repair it.

O u t c o m e sThis chapter contributes to the following Preliminary Course outcomes: P2 applies the processes that are used to test and validate models, theories and laws of

science, with particular emphasis on first-hand investigationsP3 assesses the impact of particular technological advances on scienceP4 identifies applications of science that affect society and the environmentP9 describes the structure of body organs and systemsP10 describes the effect of energy transfers and transformationsP11 identifies and implements improvements to investigate plansP12 discusses the validity and reliability of data gathered from first-hand investigations and

secondary sourcesP13 identifies appropriate terminology and reporting styles to communicate information and

understanding in scienceP14 draws valid conclusions from gathered data and informationP15 implements strategies to work effectively as an individual or as a member of a teamP16 demonstrates positive values about and attitudes towards both the living and non-living

components of the environment, ethical behaviour and a desire for a critical evaluationof the consequences of the applications of science.

122 Senior Science 1

duty of care

allergies

workplace

back injury

protection

protection

computers

industrial

concussion

helmets

meninges

skull

tears

PPE

sport

causes

natural

asthma

types ofhazards

respiratorydiseases

structure andfunction

structure andfunction

repetitive strain injury

shaken babysyndrome

structure andfunction

structure andfunction

properties ofsound waves

structure andfunction

cerebrospinalfluid

allergicreactions

risk analysis

eyecaresolutions

risks to youngworkers

hierarchy of control

personal protective equipment

occupationalhealth and safety

workplace

damage

eye

protection

natural

respiratory system protection

HUMANS AT WORK

skeleton

ear

causes of deafness

brain

natural

injuries workplace andsport

aging

Breathing clean air33..22

The human respiratory system

SSEECCTTIIOONN OOUUTTCCOOMMEESS When you have completed this section you shouldbe able to:• recall the role of the human respiratory system• relate the moist lining of lungs to the need to

dissolve oxygen so that it can then diffuse intothe blood

• perform a first-hand investigation to observediffusion

• outline how mucus, cilia and white blood cellsprotect the lungs

• describe how inflammation occurs and allergicresponses which may result

• outline the effect on lung tissue of chronicexposure to inhaled solids

• identify safety procedures in the school and workplace to reduce inhalation of harmful substances.

132 Senior Science 1

Respiration uses the reaction between oxygen and food to slowly con-vert stored energy into forms that can be used by the cell for activitiessuch as growth and repair.

The human respiratory system provides the body with a plentifulsupply of oxygen this process and excretes the waste product carbondioxide.

FIGURE 3.9

Recal lEvery living cell in the human body needs a supply of energy toperform its functions. This energy is provided by cellular respira-tion. The usual type of respiration is summarised by the followingequation:

Glucose + oxygen → carbon dioxide + water + energy

The human respiratory system(breathing system) providesoxygen and excretes carbondioxide. The oxygen is needed forcellular respiration.

Any particles which move about are capable of diffusion. If perfumeis spilt from a bottle, the fragrance can be detected very quicklyaround the room because of diffusion of the evaporated perfumemolecules. Gases diffuse very quickly because the particles in a gasmove very fast and there are only weak attractive forces betweenthem to slow them down. However, before oxygen from the air canenter a living cell, it must be dissolved in water so that it can diffusethrough the cell membrane. This also applies to carbon dioxide gas.

134 Senior Science 1

Gas exchange

Diffusion across a membraneInvestigation 3.1

All living cells are surrounded by a cell membrane,through which some substances may diffuse. Themembrane is described as semi-permeable (‘halfpenetrable’) because not all dissolved substancescan pass through it.

Aim

To observe evidence of diffusion through a semi-permeable membrane.

Materials

• 3 × 250 mL beakers• 3 × 20 cm lengths of dialysis tubing• 2 dropping pipettes• starch solution• dilute iodine solution• concentrated iodine solution• safety glassesWarning: Iodine stains skin and clothing. Take carenot to spill it. Wipe up any spills immediately. Wearsafety glasses.

Method

1 Moisten one end of each dialysis tubing under atap to help you separate the sides and form the flattubing into a cylinder.

2 Tie a firm knot at one end of each piece of tubing.3 Use a dropping pipette to partly fill one of the

tubes with concentrated iodine solution. Tie thetop of the tubing and rinse it with water to removeany traces of iodine solution from the outside.

4 Place this tubing in a beaker containing the diluteiodine solution as shown in Figure 3.12.

5 Rinse the dropping pipette and use it to add thedilute iodine solution to the second dialysis tubing.Tie the top of the tubing and rinse it with water toremove any traces of iodine from the outside.

6 Place this tubing in a beaker containing starchsolution as shown in Figure 3.12.

7 Use the second dropping pipette to partly fill thethird tubing with starch solution. Tie the top of thetubing and rinse it with water to remove any tracesof starch solution from the outside.

8 Place this tubing in a beaker containing diluteiodine solution as shown in Figure 3.12.

9 Note any colour changes and any changes in waterlevels that occur in the next 20 minutes.

concentratediodine solution

diluteiodinesolution

diluteiodinesolution

starchsolution

starchsolution

diluteiodinesolution

dialysis tubing withknot tied at both ends

beaker

FIGURE 3.12

Experimental set-up.

Diffusion is the movement of par-ticles from regions of high concen-tration to regions of lowerconcentration. The change in con-centration from high to low iscalled a concentration gradient.

Humans at work 135

The internal lining of the human lungs provides a large moist surfacearea which allows exchange of the gases oxygen and carbon dioxide.About 1 cm3 of human lung tissue has a surface area of 300 cm2 forgas exchange.

This large surface area is provided by tiny air sacs called alveoli. Eachalveolus is surrounded by tiny blood capillaries. Oxygen must diffusethrough cells in the alveoli walls and the walls of the capillary bloodvessel before it can come into contact with the blood. Dissolved inwater, it can diffuse along a concentration gradient through spacesbetween the cell membrane molecules to reach the blood. Here, it com-bines with the red pigment haemoglobin in red blood cells to be trans-ported around the body in the blood. As this oxygenated blood movesthrough capillaries in other body tissues, the concentration gradient isreversed. The oxygen is released from the haemoglobin and diffuses intosurrounding cells which have a lower concentration of oxygen.

Discussion

1 Draw a labelled diagram to summarise the resultsof the experiment.

2 Which substances were able to travel through thedialysis membrane? What evidence supports this?

3 Is this membrane semi-permeable (i.e. can someparticles travel through it but not others)?

4 Suggest a property of the iodine and starchmolecules which could account for any differencesin particle movement in the experiment.

Extension

Use library references to find out about the structureof the cell membrane and how this relates to the typeof substances which can travel through it.

permeablemembrane

semi-permeablemembrane

net movementof solute

no net movementof solute

solute

solvent

(a) (b) (c)

FIGURE 3.13

(a) Solute molecules diffuse through a solvent as they dissolve in it. (b) Solute molecules may diffuse through a permeable membrane until theconcentration of solute on both sides of the membrane is the same. (c) A semi-permeable membrane may not allow some solute particles todiffuse through it.

Exchange of gases in the lungs

Oxygen must dissolve in waterbefore it can diffuse into body cells.

a b c

First defencesSpecial mechanisms protect the warm moist surfaces in our airwaysfrom invasion by pathogens (microorganisms which cause disease).• Mucous membranes line the nasal passages, trachea, bronchi and

alveoli. The thick, sticky mucus that is secreted can trap dust andbacteria. It also contains lysozyme, an enzyme which is capable ofdestroying the cell walls of some bacteria. Another substance, an anti-body called IgA, may also be present in mucus. This reacts withinvading pathogens and destroys them.

• Cilia are tiny hairs that project from the cells lining the airways of therespiratory system. They sweep mucus along towards the openings ofthe nasal passage or the pharynx so that the dust and any bacteria itcontains may be removed from the respiratory system by coughing,sneezing or swallowing.

Protection from foreign infiltrationIf these first lines of defence are breached, and microorganisms enterthe blood, the immune system is mobilised. The primary organs andtissues of the immune system are the bone marrow and thymusgland, which is found just underneath the breastbone. The secondaryparts are the lymph nodes, spleen, tonsils, adenoids and appendix.

138 Senior Science 1

Protecting the airways

flow of mucusand trapped material

cilia

rows of cellslining trachea

mucus-producing cell

FIGURE 3.19

The epithelial (outer) layer of cells in therespiratory system contains some cellswhich produce mucus and other cells whichhave tiny hairs called cilia. The cilia beatback and forth to move the mucus to theback of the throat where it is swallowed orcoughed, or to the pharynx where it can beswallowed. This removes dust and invadingmicroorganisms.

adenoidslymphnodes

smallintestine

Peyer’spatches

bonemarrow

tonsils

spleen

largeintestine

appendix

lymphaticvessels

thymus

FIGURE 3.20

The primary and secondary organs of theimmune system are linked by blood vesselsand the lymphatic system.

Mucus and tiny cilia provide therespiratory system with protectionfrom invasion.

Humans at work 139

To understand some of the complex steps in the body’s response toinvasion by foreign material and microorganisms, it is important torealise that there are a variety of different white blood cells that can berecruited. These cells are made in the bone marrow and some of themare modified in the thymus gland before being released into lymphfluid.

leucocytes

monocytes which changeto macrophages

(large scavengers)

granulocytes(contain granules)

neutrophils(scavengers)

basophils

lymphocytes

B cells T cells

plasmacells

memorycells

killercells

helpercells

suppressorcells

memorycells

eosinophils

FIGURE 3.21

Types of white blood cells (leucocytes).

Front line troopsHuman body cells have proteins on their surface. These are calledmarkers as they help our immune system recognise them as its owncells. The ability to recognise ‘self’ and ‘non-self’ cells prevents theimmune system from attacking its own cells.

Foreign protein entering the body, such as on the surface ofpathogens (microorganisms such as bacteria and viruses) or the toxinsthey produce, are called antigens. They stimulate the formation of anti-bodies by B cells. It is the presence of foreign antigens and the absenceof ‘self’ markers that can stimulate a complex series of responses by theimmune system.

Macrophages are scavenger cells found near any site in the body thatmight be a target for invasion by pathogens. For example, they are foundin the airways, including the alveoli. They respond to the presence offoreign antigens by surrounding foreign cells with their cytoplasm andthen producing chemicals to destroy them. This process is known asphagocytosis. They also release chemicals which attract the other typeof scavenger, neutrophils, to the infection site. Neutrophils are the mostabundant of all the white blood cells but they are also very short lived.They mobilise in large numbers from the bloodstream to engulf theinvaders. As they die, they form pus at the infection site.

The two other types of granulocytes, eosinophils and basophils,release toxic chemicals from their granules to help destroy the invaders.Eosinophils produce chemicals which can destroy parasites in skin andlungs, but they are also involved in allergies. Basophils release histamineswhich help to bring about inflammation of the tissue being invaded.

FIGURE 3.22

Macrophages are ‘giant scavengers’. They arealso called phagocytes. This diagram shows a phagocyte engulfing a Streptococcusbacterium. The cytoplasm of the phagocytesurrounds the bacterium and digests it.Neutrophils are the other type of phagocyte.

A variety of white blood cells(leucocytes) protect therespiratory system from infection.

Streptococcus

antigen markermolecule

antibody

FIGURE 3.23

Antibodies are Y-shaped molecules pro-duced by white blood cells called lympho-cytes. Each antibody must be designed tofit the marker of a particular antigen as alock and key fit together.

Extra help for the immune system: complement proteinsA group of about 30 proteins, called complement proteins, is pro-duced by the liver and is present in blood plasma. It has a number ofdifferent roles to play in stopping an invasion. Complement proteinsinclude enzymes which may start to attack the outer proteins on thesurface of invading pathogens. The protective protein found on allthe body’s own cells prevents a similar attack. Others complementproteins attach to the outer cell wall of pathogens to help phagocytesin the blood identify them as intruders.

InflammationAny damage to tissues will activate tiny fragments of white bloodcells called platelets. Platelets have a role in blood clotting but theyalso release histamines which can begin the process of inflammation.Complement proteins are also involved in the inflammation process.

Inflammation can be identified by swelling and redness of the body’stissues There is increased blood flow to the damaged area, blood vesselsdilate and their walls become more permeable. Blood plasma and lymphfluid leak into the inflamed area. The heat of inflammation results fromthe extra blood supply, and the pain is caused by the increased volumeof fluids stretching the tissue. Phagocytes move from the blood into thedamaged tissue to engulf invading pathogens. Complement proteins alsojoin the attack. Damaged tissue, cell debris and any pathogens arewashed away by the increased volume of fluid at the site of the inflam-mation. They enter the lymph system where another immune responsemay be triggered.

Rearguard attackThe presence of antigens on the surface of invading organisms or theirtoxins triggers B cells to begin dividing. Some form plasma cellswhich produce large numbers of antibodies against the foreignantigen, and others form memory cells. The plasma cells are assistedby another type of lymphocyte, helper T cells. The antibodies areproteins which lock on to the antigen in a lock and key arrangement.

140 Senior Science 1

ww DDiidd yyoouu kknnooww??Platelets are not classified as cells.They have no nucleus but they aresurrounded by a membrane. They aremade in bone marrow by breaking offfrom one type of large white blood cellcalled a megakaryocyte.

The two types of lymphocytes, B cells and T cells,can take part in a variety of responses to the pres-ence of foreign antigens in the body, for example,a virus.

Some macrophages can absorb the foreign cellwith its antigen marker, but then present a fragmentof that antigen, held by one of its own marker pro-teins, on the outside. The macrophage then movesthrough the lymph system to lymph nodes. This is asignal for other cells to attack the antigen.

T cells are mobilised. One type of T cell, calleda helper cell, can recognise an antigen if it is dis-played by a macrophage. It forms an antibody-type

structure on its surface and binds to the macrophage(see Figure 3.24). Both cells then produce a numberof chemical messengers called lymphokines. Theselymphokines have a variety of roles:• stimulating the formation of more helper T cells

and another type of T cell called a killer cell• acting on one part of the brain, the hypothal-

amus, to induce a fever. This increases the rateof all chemical reactions in the body, includingthe rate at which the defence system can work

• triggering the formation of B cells, the othertype of lymphocyte. The B cells release anti-bodies to attach to the virus antigen

How lymphocytes work

Antigens and antibodies combinein a lock and key arrangement.

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The complement system of proteins is responsible for the initial rejectionof foreign organs in transplantoperations. The complement proteinsattack the outer proteins on themembrane of the foreign cell. Pig cells have been developed for use in human transplants by geneticallymodifying the outer cell membrane to produce the correct protectiveproteins that destroy complement.

Humans at work 141

• releasing a class of chemicals called interferons.These chemicals help healthy body cells resistattack by viruses. Some of the invading virus particles may manage

to penetrate the defence system, avoid furtherattack and then enter host body cells. Once insidethe host cell, the antigen in the protein coating ofthe virus is broken down and can no longer triggeran antibody response.

The virus overrides the genetic material of thehost cell and makes the host cell manufacture morevirus particles. In the process, the virus usually causessome change to the outer cell membrane so that thenormal protective MHC markers are altered. Killer Tcells are capable of detecting this change on the outersurface of human body cells. They lock onto theinfected cell and release chemicals which puncturethe cell membrane and destroy it.

B cells also join the attack. They move to lymphnodes and divide to form plasma cells. Plasma cellsproduce antibodies in response to the presence ofantigens. Each cell may produce antibodies directlywhen it encounters an antigen or it may process theantigen in a similar way to a macrophage to attracta helper T cell.

Once antibodies have attached to antigens,macrophages can engulf them or complement pro-teins can start to destroy them by attacking the cellmembranes.

1 What must happen to an antigen before a helper T cell will be able to recognise it as foreign?2 Once a helper T cell has attached to an antigen fragment, it produces chemicals called lymphokines.

What changes are caused by lymphokines?3 Helper T cells and B plasma cells benefit from each other. Explain how.4 What triggers a killer T cell to attack a body cell which contains viruses?5 What role do the complement proteins play in working with B cells and helper T cells to fight an infection?

virus with antigen

virus with antigen

protective proteinmarker onmacrophage cell

macrophageengulfsantigen

macrophage breaks upantigen but displays part ofthe antigen on its markerprotein

a helper T cell canrecognise the antigennow it is displayed on themarker molecule by themacrophage

macrophagereleases chemicals(lymphokines) to help mature the T cell

FIGURE 3.24

A T cell cannot recognise an antigen unless it has first been brokendown and then displayed on a protein marker molecule by anotherwhite blood cell, for example, a macrophage.

antigen

B cell

marker molecule

An antigen-specific receptoron a B cell recognises andattaches to an antigen.

The B cell takes in the antigen and digests it.

The antigen fragments are displayedon its own distinctive marker molecule.

The combination of antigenfragment and marker moleculeattracts the help of a mature,matching T cell.

Lymphokines secreted by the T cellallow the B cell to multiplyand mature into antibody-producingplasma cells.

Released into the bloodstream, antibodieslock onto matching antigens. Theseantigen–antibody complexes are sooneliminated, either by the complement cascadeor by the liver and the spleen.

antibodies

FIGURE 3.26

B plasma cell absorbs the foreign cell and displays part of theantigen fragment, attached to a marker molecule, on its surface.This combination then attracts a helper T cell which will start toproduce lymphokines to stimulate the production of more Bplasma cells and more antibodies.

chemicals releasedby killer T cell to

destroy cell membrane killer T cell attaches tochanged marker proteins

virusmarker protein ischanged by virus

infecting a human cell

FIGURE 3.25

Killer T cells are stimulated into action by the chemicals (lymphokines)produced by helper T cells which have detected an antigen. Theyattack human body cells infected with virus particles. The killercells have detected a change in the outer protein markers of thecell. They produce chemicals which attack the cell’s outer mem-brane. Killer T cells also attack cancer cells, fungi and transplantedtissue.

AntibodiesThere are five main groups of antibodies. They are all calledimmunoglobulins (symbol Ig).• IgA concentrates in body secretions, for example, tears, saliva, respi-

ratory system, intestine.• IgD is found on the membranes of B cells. It helps in activating B

cells.• IgE is probably intended as a defence against parasites, but is the anti-

body responsible for the symptoms of allergies like hay fever.• IgG is the major immunoglobulin. It works by making a coating

around bacteria and viruses so that they may be taken up anddestroyed by phagocytes.

• IgM is found in the bloodstream where it kills bacteria directly.Antibodies work in different ways depending on the antigen. Some

lock onto toxins and deactivate them. Others form an antigen–antibodypair which is destroyed by complement proteins. Some block virusesfrom entering cells. Some cover bacteria with a coating which attractsphagocytes. Some form a coating which attracts other white blood cells.

After the battle has been won, suppressor T cells stop the formationof more B plasma cells and helper T cells. Some of the B cells and T cellsbecome memory cells, ready to respond quickly if there is a secondattack by the same antigen.

142 Senior Science 1

ww DDiidd yyoouu kknnooww??HIV (human immunodeficiency virus)invades T cells. Because the virusblocks the normal functioning of thesecells in fighting infection, peoplesuffering from HIV may develop awhole range of unusual infectionswhich are associated with AIDS(acquired immune deficiencysyndrome).

ww DDiidd yyoouu kknnooww??Some toxins can stimulate theformation of such a large number of Tcells, that toxic shock syndrome canoccur. The immune response is somassive, the chemicals produced cancause death.

level ofantibodyin blood

primaryimmuneresponse

primaryinfection

10 3020 10 30 days20

laterinfection

secondaryimmuneresponse

fasterlargerlonger

FIGURE 3.28

The second time an antigen enters the body,memory T cells and B cells have the antibodycode ready. They divide quickly to mount aquicker response to the infection.

FIGURE 3.27

Sir Frank Macfarlane Burnet (1899–1985)was an Australian scientist who, in 1960,was awarded the Nobel Prize for Medicineand Physiology with an English scientist,Peter Medawar, for his work in immunology.He studied how the immune system recog-nises the difference between its own cellsand foreign cells (‘self and non-self’). Where these battles happen

Inflammation occurs at the site of an invasion. Neutrophils convergeon the site to engulf the invaders. As they die, they form pus.Macrophages also engulf the invaders and present the antigens ontheir surface to stimulate T cells and B cells into action. B cells aremanufactured by bone marrow and mature quickly to form plasmacells in response to an infection. T cells are made in bone marrow butmigrate to the thymus gland where they mature.

Humans at work 143

B cells and T cells move through the blood and lymph system butthey are concentrated at lymph nodes, the spleen and the thymus gland.Macrophages move from the infection site to lymph nodes to get aquicker response.

complement

macrophage

virus

killer cell

B cell

antibodies

T cell

lymphokines

FIGURE 3.29

An arsenal of immune responses is awaiting a virus which enters the nasal passage to invadethe respiratory system.

The symptoms of allergy include wheezing, sneezing, runny nose,itching, nausea, vomiting and diarrhoea. These symptoms are trig-gered in sensitive individuals by materials such as pollen or housedust mite.

People who suffer from allergies have inherited the tendency. Theirimmune system identifies as an antigen a substance which is normallyconsidered harmless. Such antigens are called allergens. B cells respondto the allergen by producing large quantities of IgE antibodies. Theseantibodies then attach themselves to one type of white blood cell, abasophil, and a related cell called a mast cell. Mast cells are present inthe lining of the respiratory system and the digestive system. They aredesigned to be part of the immune response system. Once the IgE anti-bodies have attached to basophils and mast cells, they release large quan-tities of histamines the next time the antigen is encountered. Otherchemicals are also released which attract other white blood cells, theeosinophils and neutrophils, and cause the symptoms of allergy. Bloodvessels dilate, causing blood pressure to drop. The spaces between cellsfill with fluid.

Allergies

In an allergy sufferer, substancesthat are normally harmless areidentified as antigens (allergens)by the immune system.

If the response of the immune system is severe enough, the personmay go into anaphylactic shock, a life-threatening reaction where theallergic response occurs throughout the body, causing a sudden large fallin blood pressure and swelling of body tissues. This swelling may besevere enough to block airways and cause death. The only effectivetreatment for anaphylaxis is the immediate injection of adrenaline (alsocalled epinephrine). This hormone constricts blood vessels and opensairways.

Another role of complementComplement takes part in the allergic response. Complement pro-teins begin binding to the allergen–antibody site of the basophil andmast cell. They set off a chain of reactions which results in proteinchannels being set up in the cell membranes. These channels allowthe histamines to leak from the mast cells and basophils. These cellsdie. Protein fragments released by the complement also trigger theformation of other chemicals and stimulation of other white bloodcells.

144 Senior Science 1

grass pollen

B cell

antigenreceptor

IgE

plasma cell

mast cell

histamines

symptoms

The first time the allergy-proneperson comes into contact withan allergen such as grass pollen

The second time that person hascontact with the same grass pollen

the IgE-primed mast cell willrelease its powerful chemicalscalled histamines

and the person will suffer thewheezing and/or sneezing,runny nose, watery eyes, anditching of allergy.

he or she makes large amountsof grass pollen IgE antibody.

These IgE molecules attachthemselves to mast cells whichline the respiratory system.

FIGURE 3.30

B plasma cells make antibodies in response to the presence of an allergen. These antibodies attach to mast cells in the respiratory tract. Asecond contact with the allergen causes the mast cells to release histamines.

Complement proteins play a rolein causing the symptoms ofallergies such as asthma.

Humans at work 145

Over 2 million Australians suffer from asthma. The incidence ofasthma is growing in Australia, with one in four children, one inseven adolescents and one in ten adults suffering from it. Fortunatelythe death rate is decreasing, thanks to better diagnosis and treatment.A National Asthma campaign has estimated that asthma costs theAustralian community up to $720 million each year. It also claimsthat asthma is the main cause of hospitalisation of children and themost common reason for school absenteeism.

CausesAsthma can be caused by an allergic reaction. The main triggers forthe allergy are dust mites, pollen, fur from household pets andmoulds. Smoking or passive smoking (inhaling smoke from otherpeople’s cigarettes) may also trigger asthma or make a person morelikely to suffer asthma if they are allergic to any of the triggers alreadymentioned. Asthma may also be triggered in susceptible people whoare suffering from a respiratory tract infection such as a cold, bron-chitis or influenza.

Effect on respiratory systemAsthma causes the muscles surrounding the air passages to contractand constrict the airway. At the same time, the mucous membraneslining the airway may swell and secrete more mucus.

SymptomsBecause the passage of air is restricted, people with asthma have dif-ficulties breathing. It is harder to exhale than it is to inhale. Theremay be wheezing, coughing and shortness of breath. Oxygen supplyto body cells is therefore restricted and the person suffering fromasthma lacks energy. If untreated, a severe attack of asthma can resultin death.

PreventionSometimes it is possible to restrict access to the materials that triggeran allergic reaction. For example, the dust mite is the major cause ofasthma and other allergic reactions of the respiratory tract. It lives inbeds and carpets. It eats discarded human skin cells and producesdroppings which are responsible for the allergic response. Dust mitesare harboured in thick woollen underlays, mattresses and doonas.They also live in carpet. Removing wall-to-wall carpets from a houseand replacing them with polished floorboards or tiles is one solution.Covering pillows, mattresses and doonas with mite-proof covers and washing bed linen with very hot water to kill dust mites may also help.

Asthma

muscle

lining

airway

muscle spasmcontracts aroundairway

lining of airwaythickens due toinflammation

mucus issecretedby lining

FIGURE 3.31

In asthma, a combination of muscle spasm,inflammation and mucus production nar-rows airways. It is harder to breathe outthan in.

The incidence of asthma isincreasing in Australia. Severecases may result in death if nottreated.

Avoiding cigarette smoke and having vaccinations against respiratorydiseases such as influenza also help prevent this disease.

Chronic sufferers of asthma can also take special medications such ascorticosteroids which suppress the immune system and stop an allergicresponse.

TreatmentBronchodilators such as Ventolin cause the muscles surrounding theairways to relax and thus help airflow once an asthma attack has beentriggered. Artificial ventilation may also be necessary for severeasthma attacks.

Current areas of researchThe incidence of asthma is increasing worldwide. Current researchaims to find out why this is happening as well as better means oftreatment. Occupational asthma is one area that needs continuingstudy. There is a growing list of dusts, vapours and other chemicalswhich have been identified as triggering asthma in the workplace forsome susceptible individuals.

146 Senior Science 1

1 Perform a survey at your school to estimate theprevalence of asthma among school children.Find out how your estimates compare with figuresprovided by the National Asthma Foundation. Isthere any relationship between climate and theincidence of asthma?

2 Construct a mind map to summarise what youhave learned about asthma.

3 Use the library, WorkCover pamphlets or Internetsites to gather, process and analyse information

about one of the following respiratory diseases:silicosis, hypersensitivity pneumonitis,legionnaire’s disease, black lung disease (coalworkers’ pneumoconiosis), brown lung disease(byssinosis). Present your findings as adescriptive report under the following headings:cause, effect on the respiratory system,symptoms, prevention, treatment, history andcurrent research.

Finding out more about respiratory diseases

The workplace and respiratory disease

Lung disease is often very slow to develop and may be triggered bylow concentrations of irritants over a long period of time in the work-place. Once it has developed, it is difficult to treat.

Large dust particles may be removed by cilia and mucus that line therespiratory tract but some very fine particles may move down andbecome lodged in the alveoli. The body’s defence mechanisms will beactivated and inflammation will occur. If these particles are too large to be

FIGURE 3.32

The human dust mite uses discardedhuman skin cells as food. Its droppings cancause allergies like asthma.

Activity 3.4

Humans at work 147

engulfed by phagocytes, they may be surrounded and isolated. Layers ofmacrophages and lymphocytes surround the foreign body. They in turnbecome surrounded by a protein called fibrin which forms a tough pro-tective wall. The whole structure is called a granuloma. Some infectionssuch as tuberculosis also cause the formation of granulomas in the lungs.

FIGURE 3.33

In this chest X-ray, the dark areas represent granulomas caused by a tuberculosis infection.The tuberculosis bacteria are isolated by dead white blood cells and a wall of fibrin proteinto make the granuloma.

Diseases related to asbestosAsbestos is the general name given to a number of related mineralswhich have been used in the building industry. It was not until 1968that it was identified as the cause of a number of potentially fatal lungdiseases. There is usually a lapse of between 20 and 40 years fromwhen asbestos dust is first inhaled to the time that the first symptomsof disease appear. WorkCover estimates that over 1000 workers havedied in Australia since 1968 because of exposure to asbestos fibres.

Asbestos may cause any of the following diseases.• Asbestosis—scarring of lung tissue. This reduces the elasticity of the

lungs and lung volume. It is a progressive disease, so the supply ofoxygen to body tissues is slowly reduced.

• Pleural disease—the pleura are membranes which surround the lungsand anchor them to the chest wall. If these membranes becomeinflamed, fluid may build up between the chest wall and the lungs.Sufferers are short of breath and experience pain on breathing. Insevere cases, fluid build-up in the alveoli severely restricts the volumeof oxygen available to the body.

• Mesothelioma—cancer of the outer lung lining (pleura) or the liningof the abdominal cavity (peritoneum). All identified cases ofmesothelioma so far have been associated with exposure to airborneasbestos particles.

• Carcinoma (cancer)—starts as abnormal growth of cells in outer layers ofthe bronchi. The tumour invades surrounding tissue and blocks airways.As the health risks of asbestos became apparent, its use in the

building industry was reduced. Before 1976, white asbestos was sprayedon surfaces needing fire protection or insulation from heat or sound. It

ww DDiidd yyoouu kknnooww??The most common types of asbestosare white asbestos (chrysotile), blueasbestos (crocidolite) and brownasbestos (amosite). White asbestoswas the type most often used inindustry. It is less dangerous than theothers.

Exposure to asbestos isassociated with a variety of veryserious diseases.

was used in brake and clutch linings, in adhesives and cements, in fibrosheeting, asbestos cement pipes and in filter papers and gasket materials.It was also found in the insulating heat mats used to protect bencheswhen using Bunsen burners in school science laboratories.

Today, new fibrous cement products no longer contain asbestos.Asbestos has been removed from a number of building sites, with theworkers involved wearing special protective clothing and protectivemasks. However, old fibro sheeting containing asbestos is still in somebuildings and old asbestos cement pipes are still used to carry water, fordrainage and as flue pipes. WorkCover states that these materials aresafe if they are maintained in good order. They are a risk to health onlyif they are disturbed in renovations or demolitions, with asbestos dustthen being released.

148 Senior Science 1

Power stations in the Latrobe Valley

The Latrobe Valley is about 160 km east ofMelbourne. From the 1920s, it was developed as asite for power stations, using coal from local open-cut mines. The State Electricity Commission ofVictoria (SECV) built Yallourn A power station in1924. This was the first in a complex of power sta-tions (Yallourn A, B, C and D) which was a majorsupplier of electricity for the city of Melbournefor many decades. The town of Yallourn was laterbuilt especially to cater for the needs of thousandsof electricity workers and their families. Asbestosmaterials were used extensively in all these powerstations to insulate against the large amounts ofheat generated. For example, it was used for laggingpipes and for walls, ceilings and roofs.

In February 2001, an ABC Four Corners programstated that some reports had been published in the1930s suggesting that asbestos might cause disease.In 1944, a doctor working for the Victorian HealthDepartment noted that asbestos formed a veryharmful dust and suggested that the Yallourn elec-tricity workers should be given health checks. TheABC program claimed that at that time theElectricity Commission stated that the need formedical checks was a private matter for each indi-vidual to decide. By the 1960s a number of workerswere developing symptoms such as coughing andshortness of breath. At that time, the symptomswere not associated with any workplace hazards.

By the early 1970s, it was becoming apparentthat asbestos dust might be a great health risk to theworkers in the power stations, but the full effect ofexposure to asbestos only became apparent decadeslater. Today, a large number of power stationworkers have been diagnosed with mesotheliomaand the State Electricity Commission of Victoria haspaid ‘pain and suffering’ workers compensation tothousands of ex-employees.

The town of Yallourn was disbanded by the1980s so that the rich coal seam underneath it couldbe mined. The massive Yallourn power complexstopped operations in 1989. Asbestos inside thesepower stations was removed before they weredemolished in 1998. Explosives were used to helpdemolish them. Huge clouds of dust were releasedinto the atmosphere as the power stacks collapsed.Onlookers were hopeful that all the asbestos hadbeen removed effectively before this demolition.

The SECV no longer exists because the powerindustry has been privatised. However, workers’compensation claims from Yallourn power workersare still continuing.

FIGURE 3.34

Cooling towers of the Loy Yang power station, Victoria’s LatrobeValley.

Case Study 3.1

Humans at work 149

Preventing lung diseaseLung disease is a common workplace problem. It is very difficult totreat successfully. A much better solution is to prevent the disease bycontrolling exposure to the irritants and triggers that cause it.According to occupational health and safety legislation, it is part ofan employer’s duty of care to protect workers from exposure to dustand chemicals which cause irritation and lung disease. This is partic-ularly important in industries such as spray painting, carpentry,mining and sand blasting.

A number of different procedures can be followed.• Any potential source of dust should be kept moist to reduce the

chance of it becoming airborne.• Dust extractors should be provided to extract gases and dust from

the workplace area.• Masks may also be provided. For very hazardous sites, these masks

should include respirators to completely isolate the worker fromthe factory air.

• Protective clothing and boots must be worn and removed beforeleaving the worksite. In some very hazardous conditions, workersmay need to shower at the worksite.

• The worksite should have adequate ventilation.

1 Why was the town of Yallourn built? Why was it later levelled?2 Where was asbestos used in the Yallourn power station complexes? What was its function?3 What were the first symptoms of respiratory disease reported by Yallourn electricity workers? Why do you

think there were no grave concerns for the workers at that time?4 If given the opportunity, would you have chosen to be an onlooker when the Yallourn power stations were

demolished? Give a reason for your answer.5 What disease has been identified in Yallourn electricity workers?6 Use Internet sites or recent medical journals to research current treatments for this form of asbestos-

related cancer.

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A group of Australian scientistsannounced early in 2001 that they hadshown that malignant tumours areable to create lymph vessels. Theselymph vessels feed into the body’slymph system and allow the cancer tospread (metastasis). The scientistsidentified a protein on the outside ofthe cancer cell that caused the vesselsto form. It is called VEGF (vascularendothelial growth factor). They alsoshowed that VEGF could be blocked byan antibody.

FIGURE 3.35

It is far easier to prevent lung disease than to cure it. Employers are required to provide protective face masks if there is any danger of expo-sure to dust or fumes in the workplace. (a) Disposable dust mask (for low to medium dust levels). (b) Cartridge respirator (for low to mediumdust levels). (c) Battery-powered respirator, filters the air (for medium dust levels). (d) Air-line hood respirator, supplies clean air (for very highdust levels).

b c da

Cigarettes were first manufactured on a large scale towards the endof the 19th century. In World War 1, they were supplied to soldiersas part of their rations, and after that war, cigarette smoking becamemore popular. In the early 20th century, lung cancer was a rare dis-ease, but by the 1930s, doctors were reporting an alarming number oflung cancers in their patients. By the 1970s, lung cancer was esti-mated to be the major cause of death by cancer in the western world.

The Cancer Council New South Wales supplies statistics on cancer-related deaths in Australia. In 1997, 22 per cent of all cancer deaths inmales were due to lung cancer, the highest figures for any form ofcancer. In the same year, more women died of breast cancer than lungcancer (18 per cent compared with 15 per cent) but the incidence oflung cancer in women has doubled over a 10-year period. Statisticiansestimate that 90 per cent of all lung cancers are preventable and the wayto prevent them is to avoid exposure to cigarette smoke.

Cigarette smokeCigarette smoke contains more than 3800 chemicals. These include:• 30 identified poisons, including a range of benzene compounds• 43 known carcinogens (chemicals which cause cancer). These

include naphthylamine and nitrosamines which produce lungcancer. These compounds may also be absorbed through the lungsand cause cancer in the kidneys, bladder and pancreas

• chemicals which damage the cilia lining the respiratory system.These include hydrogen cyanide, ammonia, nitrogen dioxide andformaldehyde. The cilia become paralysed and cannot sweepmucus and the dust it contains out of the lungs

• carbon monoxide, which combines with haemoglobin in red bloodcells, preventing the uptake of oxygen. Chronic smokers are not asfit as they should be because less oxygen is getting to their bodytissues, including muscles

• tar, a mixture of gases which cools to form a sticky brown sub-stance which can build up in the alveoli. This blocks oxygenuptake and triggers allergic responses like inflammation

• nicotine, which is addictive and poisonous in very high concentra-tions. It is used in some pesticides.

150 Senior Science 1

1 Prepare a survey of your school to find out if thereare any areas where harmful dusts and vapoursmay be inhaled. List the safety procedures andPPE which are supplied to reduce any risks thatthese substances may pose.

2 Research a particular worksite where dust orhazardous fumes pose a risk. Find out what PPE

is used. As part of your research, you may be ableto visit the worksite or interview someone whoworks there. Prepare a safety poster which couldbe displayed at the worksite, describing the typesof hazards, the risks they pose and theprecautions which must be taken to ensure thesafety of everyone there.

Investigating a worksite

Smoking

Exposure to cigarette smokeincreases the risk of developinglung cancer and other seriousdiseases.

Activity 3.5

Humans at work 151

Passive smokingPeople who are near smokers are exposed to the hazards of cigarettesmoke. Sidestream smoke is the smoke emitted from the end of alighted cigarette. It has been shown to contain greater concentrationsof harmful substances than the mainstream smoke inhaled and thenexhaled by the smoker. Sidestream smoke also contains smaller parti-cles which can penetrate more deeply into lung tissue.

Passive smokers may therefore be more prone to respiratory diseases(asthma, bronchitis), heart problems and increased risk of lung cancer.The Occupational Health and Safety Act 1983 makes no direct mentionof exposure to cigarette smoke in the workplace but employers have aduty of care to ensure the health and wellbeing of their employees.

Since the effects of passive smoking have been published by a widerange of scientific studies, employers risk fines and large workers com-pensation payouts if they do not ensure clean air in the workplace.

ww DDiidd yyoouu kknnooww??Smokers are 11 times more likely tosuffer from lung cancer than non-smokers. If smokers are also exposedto asbestos dust, they are 92 timesmore likely to contract lung cancer.Cigarette smoking and passivesmoking increase the risk of a widerange of cancers.

EEssttiimmaattiinngg ttaarr ccoonntteenntt iinn aa cciiggaarreetttteeInvestigation 3.2

Aim

To measure the tar content of different brands ofcigarette.

Materials

• 2 different brands of cigarette• plastic syringe• filter paper• extraction equipment (see Figure 3.36)

Method

Warning: This experiment should be done in a fumecupboard.

If you either have a cigarette tar extractor or canimprovise equipment to make one (see Figure 3.36),perform an experiment to determine the tar content of two different brands of cigarette supplied by your teacher.

Discussion

What factors need to be controlled to make it a fairtest? Write up your findings as an experimental report.

cigarette

tar extractor equipment

filter paper

syringe to draw airfrom tar extractor

plunger

FIGURE 3.36

Equipment used to collect tar from a lighted cigarette.

Find out what types of information and help isavailable to help people stop smoking. Design your

own pamphlet to be used as part of a QUITcampaign.

An anti-smoking campaign Activity 3.6

1 Describe the process by which oxygen in the alveoli of the lungs reaches haemoglobin in redblood cells.

2 Name three different types of white blood cells anddescribe their role in providing immunity.

3 Describe how inflammation of tissues occurs.

4 Describe the steps which trigger an allergicresponse.

5 Name four respiratory diseases which are caused byexposure to dust or harmful chemicals.

Questions

152 Senior Science 1

Further questionst

1 Choose a respiratory disease you have studied andwrite a descriptive report with the followingparagraphs: symptoms, causes, prevention andtreatment.

2 What type of allergens can trigger asthma? Whatsteps can be taken in a home to minimise exposureto these allergens?

3 Explain why passive smoking may be more harmfulthan smoking cigarettes directly.

4 In Figure 3.37 which stages in the hierarchy ofcontrol do each of the diagrams address? Name twoworksites where each of these practices would beused to ensure the safety of workers.

FIGURE 3.37

(a) Extraction ventilation in a mine; (b) water coil attachment fittedto a jackpick; (c) cab fitted with air filtration unit (not an ordinaryair-conditioner which does not trap fine dust); (d) wetting downwork areas.

a b

c d

■ The Occupational Health and Safety Act 1983 states that employers have a ‘Dutyof Care’ to ensure the health, safety and welfare of all their employees.Employees also have an obligation to follow all safety procedures and behaveresponsibly.

■ Potential sources of risk should be assessed at a worksite. Once a riskassessment is done, a series of steps called the Hierarchy of Hazard Controlshould be followed to eliminate or minimise the identified risk.

■ The human respiratory system provides a large surface area where dissolvedoxygen diffuses from the lungs to bind with haemoglobin in red blood cells. Fromthere it can diffuse through interstitial fluid into body cells to be used in cellularrespiration.

■ Mucus and fine cilia lining the respiratory tract help protect the respiratory systemfrom dust and microorganisms. A variety of white blood cells can respond to thepresence of microorganisms by destroying them and providing natural immunity.

■ Exposure to fine dust at a worksite can increase the risk of respiratory diseaseslike lung cancers, asbestosis, silicosis, mesothelioma and pleural disease.Personal protective equipment like face masks and respirators can reduce the riskof these diseases.

■ Good vision is very important. The retina in the human eye has receptors calledrods to detect light and three types of cones to detect the three primary colours of light.

■ The eye has natural protection. Although the bones of the skull, the eyelid andtears all provide some form of protection, the eye can be very easily damagedwhen playing sport or at some worksites. Most eye injuries can be prevented bywearing protective eyewear.

■ The middle and inner parts of the ear are protected by the skull, but wave energyfrom loud noises can enter the auditory canal and cause hearing damage. Loudnoises at worksites can be reduced by the use of ear plugs and ear muffs.

■ The brain controls the coordination of the body. It regulates activities needed forsurvival such as heartbeat and breathing rate. It is the site of all our thinking, ourmemories and all our learning.

■ Natural protection for the brain is the skull, the meninges and the cerebrospinalfluid but the workplace and sporting activities can pose hazards to the brain.

■ Brain damage is most often associated with movement—either a person stoppingsuddenly or a moving object impacting on the brain. Protective headgear isdesigned to absorb the energy over a longer period of time and for a longerstopping distance if a person is stopping suddenly (e.g. bicycle helmets). Forimpact with a moving object, protective headgear is designed to deflect theenergy of impact.

■ The human skeleton protects and supports the body. It also allows movement.■ Back injury is a very common workplace injury which can be prevented or

minimised if appropriate work practices are followed. Other workplace injuriesinclude repetitive strain injuries. These injuries can also be minimised byworkplace procedures.

■ The majority of workplace injuries and sporting injuries can be prevented. Manyworkplace injuries cause permanent damage to the body. It is much easier toprevent an injury than to treat it.

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Exam-style questions

1 The activity which could provide a biological source ofrisk at a worksite isA wearing a hard hat when working in a coal mineB wearing protective gloves all day at a worksite

where food is preparedC working in a spray booth at a car manufacturing

siteD welding metal while wearing a safety helmet and

face shield

2 The last step in the Hierarchy of Hazard Control isA eliminate the hazardB isolate the worker from the hazardC provide personal protective equipment D substitute a less hazardous substance

3 In New South Wales Workcover has identified theindustry with the most workplace injuries asA constructionB hospitalityC transportD mining

4 Of the following statements the incorrect one isA lymph vessels contain valves which allow lymph

to move in one direction onlyB the thymus gland is an important part of the

lymphatic systemC lymph nodes may swell at the time of an infectionD the lymphatic system is a closed system of vessels

5 The white blood cell which acts as a scavenger toengulf invading microorganisms in very largenumbers and which makes pus is theA neutrophilB macrophageC T helper cellD B plasma cell

6 The smoke from cigarettes A contains large amounts of carbon dioxide which

blocks uptake of oxygen by haemoglobinB contains no identified carcinogensC is removed from the lungs by the cilia which line

the respiratory tractD is more hazardous as sidestream smoke which is

inhaled by passive smokers

7 In the human eyeA the main structure for focusing light is the lensB cones are responsible for colour visionC rods are receptors found mostly in the foveaD the iris is responsible for accommodation

8 In the human earA the semicircular canals detect different

frequencies of sound

B most noise damage is caused by loud sounds witha very low frequency

C loud sounds increase the amplitude of vibrationsof the eardrum

D nerve messages are carried from the inner ear tothe brain by the optic nerve

9 In the human brainA cerebrospinal fluid is part of the lymphatic system,

helping the body fight infections in the brainB damage can occur by a blow to the head causing

the brain to hit the skullC concussion occurs only if the patient has been

unconscious for over five minutesD damage to the left hemisphere can be detected by

dilation of the left pupil in the eye

10 In the human skeletonA all cartilage has formed bone by adulthoodB ligaments apply forces to bones which allow joints

to bendC the elbow and knee are examples of a hinge jointD there are no fixed joints

11 Emphysema is a respiratory disease that begins withnarrowing of the bronchioles. Lung tissue also losesits elasticity.a Name two symptoms you would expect if a person

were suffering from emphysema. b What effect would emphysema have on the heart?c Name another respiratory disease you have

studied. What causes this disease? What are thesymptoms?

12 Tears contain secretions from goblet cells, lachrymalglands and from Meibomian glands. Describe howeach of these secretions contributes to the protectivefunction of tears.

13 a What natural protection does the eye have from UV light?

b Give two examples of eye damage by UV light.c Explain why UV light from a laser causes more

damage than UV light from the Sun.d What type of protective lens must be used to

prevent damage from laser light?

14 Outline a first-hand investigation that you haveperformed to find the effect of loud noise on hearingand learning. Discuss your findings.

15 a Describe how a baby’s brain can be damaged byviolent shaking.

b Explain how a bicycle helmet is designed toreduce brain injury.

c What are the limits to the effectiveness of a bicyclehelmet?

196 Senior Science 1