10. Diseases and immunity

Question 1

Pathogen

Answer 1

A disease-causing agent such as a virus, bacteria, fungi or protoctist

Question 2

Virus

Answer 2

Microscopic particle consisting of genetic material surrounded by a protein coat.

Not living organsims but still act as pathogens.

Question 3

Transmissable disease

Answer 3

A disease in which a pathogen can be passed from one host to another.

Can be through direct contact (through body fluids)

Or indirect contact (such as from air or contaminated surfaces)

Question 4

Direct contact causing transmission of disease, examples.

Answer 4

• Into blood, for example from a scratch.
• Body fluids during sexual intercourse
• Skin to skin contact

Question 5

Indirect contact causin disease transmission, examples.

Answer 5

• In air
• In food and drink
• Injected into blood by animal vector
• Touching contaminated substances, surfaces or food

Question 6

Defence against pathogens - Mechanical barriers

Answer 6

Barriers that prevent the entry of pathogens into the body.

• Hair of the nose trap dust particles and pathogens
• Skin acts as barrier
• Eyelashes
• Ciliated epithelial cells moves mucus + trapped particles away from the lungs

Question 7

Defence against pathogens - Chemical barriers

Answer 7

Barriers in the body that trap and kill pathogens.

• Mucus present in the trachea traps dust and pathogens
  (Inner lining of gut and lungs also produce mucus)
• Acid secreted in the stomach kills microorganisms in food and water

Question 8

Lymphocytes

Answer 8

• Every pathogen has specific antigens
• The lymphocytes (a type of white blood cell) build the correct antibody (a type of protein) , specific to the antigen.
• The antibodies then bind to the antigens –> causes the pathogens to clump together.
• Afterwards the phagocytes consume the pathogens.
• Some anitbodies remain in the blood as memory cells.

Question 9

Phagocytes

Answer 9

• After lymphocytes have created anitbodies and caused the pathogens to clump together pahgocytes do their work.
• Engulf pathogens into the phagocyte + digest them
• When pathogen is inside the phagocytes it gets engulfed by structure called lysosome.
• Inside the lysosome, the pathogen gets digested by digestive enzymes.

Question 10

How to control the spread of diseases.

Answer 10

Clean water supply

• Stops water-borne disease bc people don’t rely on polluted water sources.

Good personal hygiene

• Washing hands with soap after toilet –> removes pathogens from faeces.
• Covering mouth + nose when coughing and sneezing –> stops pathaogens from passing into the air –< disposing used tissues + washing hadns after this.

Hygienic food preparation

• Food covered to stop flies from landing on it (flies could be vectors)
• Meat, fish + dairy –> kept in fridge + eaten fast bc good growing environment for pathogens
• Cooked food + uncooked food, prepared seperately –> eg. prevents salmonella

Proper waste disposal + Sewage treatment

• Disposing of waste away from human habitation –> in landfill tips by burning or by conmposting it.
• Collecting human waste in sewage systems + keeping it separate from drinking water supplies unitl treated –> treatment kills pathogens so it can be later released into the environment.

Question 11

Vector

Answer 11

An organism that does not cause disease itself but that can spread infection by transferring pathogens from host to host.

Question 12

Cholera

Answer 12

Bacterial infection caused by water / food contamination. Cause watery diahorrea + people die bc of dehydration.

1) Vibrio Cholerae secrete cholera toxin in intestinal lumen.
2) Cholera toxin enters interstinal cells (microvilli/ epithelial).
3) Causes chloride ions to be secreted into lumen.
4) Osmosis causes water to move out into intestine to balance ions vs water concentration.

Treatment - Oral rehydration / antibiotics

Prevention - Washing hands / cooking + covering of food/ boiling water / building latrines/ chlorination of water to kill bacteria

Question 13

Active immunity

Answer 13

Immunity that develops in response to a pathogen and involves the activation of memory cells. (long-term immunity eg. years/ lifetime)

Question 14

Antigens

Answer 14

Substances that trigger the immune response and cause the production of antibodies.

They are often proteins, but can be fats or carbohydrates.

Each pathogen has specific shape of antigen.

(found on the surface of pathogens)

Question 15

Antibodies

Answer 15

Proteins produced by lymphocytes (a type of white blood cell)

Antibody for specific antigen is complementary to the shape of the antigen

Question 16

Active immunity

Answer 16

Immunity that develops in response to a pathogen and involves the activation of memory cells.

(gained after infection by the pathogen)

When the immune systenm responds to a particular pahtogen for the first time it is called a primary response.

Second time it gets infeced (secondary response) -> the body reacts much quicker.

Question 17

Primary response - antibodies

Answer 17

The immune response mounted when someone is infected by a pathogen for the first time, or vaccinated against it.

Question 18

Secondary response (immune system)

Answer 18

Immune response mounted after re-infection by a pathogen.

Question 19

Memory cell

Answer 19

• Cell that forms from a lymphocytes as the immune systems response to an infection.
• Remains in the bloodstream and recognises if the same pathogen infects the body a second time.
• Then differentiates to form antibody-producing lymphocytes that mount a secondary response.

Question 20

Active imunity - Types

Answer 20

Natural active immuntiy = Antibodies + memory cells after 1st infection

Artificial active immunity - Vaccination

Question 21

Vaccination

Answer 21

Artificial active immunity

• Vaccines contain small amounts of material from teh pathogen/ dead/ weakened pathogens (can’t cause disease)
• Vaccine introduced to boyd thorugh injection (sometimes mouth (polio))
• Triggers immune response –> lymphocytes mount a primary response to the antigens formt eh pathogen + antibodies + memory cells produced
• Somememory cells last for life, other for years

Question 22

Immunisation programs

Answer 22

Vaccines offered to everyone at certain age

Creates herd immunity

eg. Smallpox (creates blisters) eradicted in 1980 after worldwide vaccination

Question 23

Herd immunity

Answer 23

Protection against infection occurring when enough people in a population possess antibodies to a pathogen through vaccination, reducing the risk of contact with the pathogen and the spread of disease.

Question 24

Passive immunity - Def + how it works (not types)

Answer 24

Short term immunity caused by transferred antibodies

• No memory cells are produce so protection only lasts a couple of weeks/months but protection happens immediately bc antibodies recognise pathogen immediately
• Antibodies can be taken from blood of immune people or from animals (eg. rabbits) that are immunised against pathogen

Question 25

Passive immunity - Types

Answer 25

Artificial passive immunity - Antibiotics

Natural passive immunity - breasfeeding

• Antibodies travel from mothers blood to fetus in placenta.
• After brith initial milk produce by mother (colustrum) high in antibodies.
• Breast milk less rish but also contains antibodies.
• During this time the baby builds up its own supply of antibodies