Health

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Micro-organisms

Back 1

-get into the body by penetrating organisms interfaces with the environment-e.g skin-forms thick continuous layer so invasion occurs where the skin is broken
-easier entry at thin, moist, larger S.A, well supplied with blood vessels, parts of the skin
-gas exchange system (influenza and bronchitis)
-digestive system (cholera and typhoid)
.mucus, enzymes and stomach acid help defend against.

Front 2

Pathogens (Affect the Body)

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-damaging host tissues-sheer number of pathogens cause damage by preventing tissues working properly e,g, viruses inhibit synthesis of DNA and proteins by host cells
-producing toxins-cholera bacterium produces a toxin that leads to excess water loss from the S.I. lining

Front 3

Correlations and Causal Relationships

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.Correlation-when a change in one of two variables is reflected by a change in another variable. (no evidence)
.Causal relationship-when there is a definite factor that means one variable has control of influence over another.

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Risk

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-a measure of the probability that damage to health will occur as a result of a given hazard
. probability that a hazardous event will occur
.the consequences of that hazardous event
-measured by the likelihood of harm occurring in those exposed to hazards with those who are not
e.g. reducing cancer risk=giving up smoking, regular aerobic exercise/reducing salt intake/safe alcohol amounts

Front 5

Defences

Back 5

.Non-specific-mechanisms that respond to all pathogens in the same way, act immediately e.g. barrier to the entry of pathogens (skin) or by phagocytosis
.Specific-mechanisms that distinguish between different pathogens, less rapid responses but provide immunity, involve a lymphocyte (WBC) by cell mediated responses=T-lymphocytes and humoral responses: B-lymphocytes

Front 6

Time Lag

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-between exposure to pathogen and body's response.
-millions of lymphocytes exist-high chance that one L has a protein on its surface complementary to one of the proteins on the pathogen. when infection occurs-the type of L (small amount) is stimulated to build up its numbers to level effective in destroying it

Front 7

Fetus Infection

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-is rare-protected from outside world by placenta and mother
-lymphocytes collide with body's won material and some L's will have receptors that exactly fit those of the self cells-these L's die- remaining L's can fit foreign material

Front 8

Phagocytosis

Back 8

.bacteria too big to cross CSM-engulfed by cells in vesicles
1) antigens release chemical products, attracts phagocyte
2) phagocytes attach themselves to pathogen surface
3) they engulf pathogen to form a vesicle (phagosome)
4) lysosomes move towards vesicle/fuse and release lytic enzymes-break down pathogen (hydrolysis)
-soluble products-pathogen are absorbed in cytoplasm
-process causes inflammation at infection site-result of histamine-causes dilation of blood vessels-speeds up delivery of phagocytes to site of infection

Front 9

Antigens

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-part of an organism that is recognised as foreign by the immune system/stimulates immune response (antibody)

Front 10

Cell Mediated Immunity

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-lymphocytes formed from stem cells in bone marrow
-B-cells mature-bone marrow/ T-cells mature in thymus gland
.T-cells distinguish between invader cells and normal cells
-phagocytes that have engulfed/broken down pathogens present some of the pathogens antigens on their CSM.
-body cells invaded by virus present viral antigens on CSM-sign of distress. (cancer cells also)-antigen presenting cells.
.receptor on each T-cell respond to single antigen-many Ts

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Cell Mediated Immunity (Process)

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1) Pathogens invade body/taken in by phagocytes-places antigens from pathogen on CSM
2) Receptors on certian T-helper cells fit exactly onto antigen
3) Stimulates other T-cells to divide by mitosis=form clones
4) Cloned T-cells develop into memory cells that enable response to future infections from the same pathogen:
-stimulate phagocytes to engulf pathogens (phagocytosis)
-stimulate B-cells to divide
-kill infected cells (produce a protein-makes holes in the CSM, cell becomes freely permeable to all substances=dies
.affective against viruses-viruses need cells to reproduce)

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Humoral Immunity (Process)

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1) Surface antigens on pathogen taken up by B-cells
2) B-cells process antigens and present them on surface
3) T-helper cells attach the processed antigens on the b-cells=activating them
4) B-cells activated to (mitosis)-to give clones of plasma cells
5) Clones plasma cells produce antibodies-exactly fit the antigens on the pathogens surface
6) Antibodies attach to antigens on pathogen and destroy them (primary response)
7) Some b-cells develop into memory cells-respond to future infections by same pathogen-divide rapidly and develop into plasma cells that produce antibodies (SEC)

Front 13

Plasma and Memory Cells

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PC-survive for few days-immediate defence against infection
MC-live decades-divide into new memory cells when encountered with same pathogen, circulate in readiness for any future infection=provide long term immunity.
-ensures new infection is repulsed before it can cause harm.

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Antigenic Variability

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.MC function explains why-infected once by chicken pox.
-influenza-100 different strains-antigens are constantly changing (AV)-antigens will not correspond to the antibodies or memory cells formed during previous infections
-so only way overcoming infection-primary response.(body reacts as if each infection is new-immune response=slower

Front 15

Antibodies (Structure)

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-huge variety in antibodies-made of proteins-molecules that occur in almost infinite number of forms.
-variable region=top halves (different on different antibodies)
-constant region=bottom halves (same on all antibodies)
-4 polypeptide chains-they change shape to help antibody fit around the antigens (antigen-antibody complex)

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Monoclonal Antibodies (Uses)

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.a single antibody which can be isolated and cloned. uses:
-separation of a chemical from a mixture
-immunoassy-calculating amount of substance in a mixture-pregnancy tests, urine drug samples, AIDs test
-cancer treatment-MA's can be made to attach to only cancer cells, activate a cytotoxic drug=causes cancer cell= destroy
-transplant surgery-transplanted organ may be rejected by t-cells-MA's knock-out these specific t-cells.

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Monoclonal Antibodies (Production Ethical Issues)

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-production involves use of mice to produce antibodies and tumour cells= (deliberately inducing cancer in mice)
-there has been some deaths associated with their use in the treatment of multiple sclerosis.

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Immunity

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-the ability of an organism to resist infection
.passive immunity-produced by the introduction of antibodies into individuals from an outside source-not produced by individuals themselves so not replaced when broken down
.active immunity-produced by stimulating the production of antibodies by the individuals own immune system-long lasting
-vaccination=introduction of a substance to body with intention of stimulating active immunity against a disease.

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Successful Vaccination Programmes

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-must be economically available in sufficient quantities to immune all of the vulnerable population
-few side effects (may discourage vulnerable population
-means of producing, storing and transporting available
-possible to vaccinate vast majority of vul. pop. (but when non of pop. have disease/transmission of the pathogen is interrupted (herd immunity)
.Ethics-production of vaccines=use of animals
-side effects-some are long term

Front 20

Vaccination (Doesn't Eliminate Disease)

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-fails to induce immunity to certain people-defective I-systems
-people may develop the disease immediately after vaccination before immunity levels are high enough to prevent it-people may harbour pathogen and reinfect others.
-AV-influenza changes antigens freq,=immunity is short lived and people succumb to repeated bouts of flu.
-may be varieties of a particular pathogen-difficult to develop a vaccine effective against them all

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Problems Controlling Cholera by Vaccination

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-internal disease-not easily reached by immune system-oral treatment no time to be effective-flushed out (diarrhoea)
-AV on cholera pathogen-difficult to develop effective/lasting vaccine
-mobile pop. (refugees, tourism)=spread cholera-makes it difficult to ensure individuals are vaccinated

Front 22

Problems Controlling TB by Vaccination

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-increase if HIV-more people with impaired I-systems-more likely to contract TB
-poverty,walls=refugees=live in overcrowded accommodation
-elderly pop. increasing-less effective i-systems=vaccination less effective at stimulating immunity