Pathogens and Immunity

Question 1

Pathogen

Answer 1

a disease-causing organism

Question 2

Transmissible disease

Answer 2

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

Question 3

pathogen for a transmissible disease may be transmitted either through direct contact

Answer 3

Pathogens can spread through blood or other body fluids, or indirectly, e.g. from contaminated surfaces or food, from animals, or from the air

Question 4

Body defences

Answer 4

Mechanical barriers:
-Nostrils contain hair that trap dusts that might be carrying pathogens
-Skin has a thick outer layer, keratin (containing protein) it is very difficult to penetrate
-When skin is cut, blood clots seal wound, prevents blood loss and pathogens getting into the blood through the cut
Chemical barriers:
- Lining of the alimentary canal and the respiratory system produces sticky mucus, that trap pathogens. In the respiratory passages, cilia sweeps mucus back up the throat where it is swallowed.
-Stomach secrets strong HCL acid, kills many bacteria in food we eat as well mucus swallowed.
Cells:
-if pathogens get passed these barriers then the are destroyed by WBC, some of these digest the pathogens by phagocytosis, while others produce antibodies that incapacitate or directly kill pathogens.
Vaccination:
-Helps antibodies to be produced rapidly, if a person is infected by a pathogen that causes it.

Question 5

Antibodies and antigens

Answer 5

Pathogens can be detected by WBC and destroyed in an immune response. Each pathogen has its own antigens, which have specific shapes, so specific antibodies which fit the specific shapes of the antigens. Lymphocytes produce antibodies, which bind to antigens, specific antibodies which bind to its antigen to produce antibody-antigen complex. Each pathogen has a specific antigen, specific antibody complementary to the antigen. Antibodies lock on to antigens leading to direct destruction of pathogens, or marked for destruction by phagocytes

Question 6

Autoimmune disease

Answer 6

Some diseases are caused by immune response on healthy body cells, where they are targeted and destroyed by immune system. Ex: type 1 diabetes, where body targets pancreas, thus insulin can no longer be produced.

Question 7

Active immunity

Answer 7

Defence against a pathogen by antibody production in the body

Question 8

How active immunity is gained

Answer 8

It is gained after an infection by a pathogen, or by vaccination.

• Infection: After pathogen killed, some lymphocytes stay as memory cells. If same pathogen enters the body, lymphocytes recognize the antigens and produce antibodies more quickly. Memory cells stay in body for a long time, giving long term immunity
• Vaccination: Dead version of pathogen is given to patient. Antigen evoke an immune response, in which antibodies are produced. Memory cells produced in the Body give long term immunity

Question 9

Process of vaccination

Answer 9

– harmless pathogen given which has antigens
– antigens trigger an immune response by lymphocytes which produce antibodies
– memory cells are produced that give long-term immunity

Question 10

importance of hygienic food preparation

Answer 10

good personal hygiene, waste disposal and sewage treatment to control the spread of disease

Question 11

Role of vaccination in controlling the spread of diseases

Answer 11

By providing herd immunity can control the spread of diseases. Where large population is vaccinated thus population is immune to pathogens, thus diseases cannot spread.

Question 12

Passive immunity

Answer 12

short-term defence against a pathogen by antibodies acquired from another individual, e.g. mother to infant. Antibodies are passed to a baby through mothers milk, thus is important to reduce risk of diseases.
-Memory cells are not produced in passive immunity