diseases and immunity

Question 1

Explain how vaccination can control the spread of diseases

Answer 1

1. Weakened pathogens are put into body by vaccination.
2. This stimulates an immunse response by lymphocytes which produce antibodies.
3. Memory cells would be produced, giving long-term immunity.
4. Memory cells will recognize the pathogen, and have a complementary shape to the pathogen’s antigen - then bind with the antigen, resulting in either direct destruction, or marking of destruction by phagocytes.

Question 2

Define pathogen

Answer 2

Disease causing organism

Question 3

define host

Answer 3

An organism in which a pathogen lives & reproduces.

Question 4

Define transmissible disease

Answer 4

Disease in which the pathogen can be passed from one host to another.

Question 5

What are the 5 body defenses?

Answer 5

Skin
Act as a barrier to pathogens. If damaged, blood clots quickly to seal cuts & keep microorganisms out.
Hairs in the nose
Trap particles from the air that could contain pathogens.
Mucus
Cells in trachea & bronchi produce mucus, which trap pathogens. Swept up to the back of the throat & swallowed.
Stomach acid
Stomach contains hydrochloric acids which kills most pathogens that are swallowed.
WBC
- Phagocytes
Engulf pathogens by phagocytosis

Question 6

Important factors in controlling diseases

Answer 6

Clean water supply
* Contaminated water can contain pathogens or toxins e.g cholera
* Chlorine is used to kill microorganisms in it.

Hygienic food preparation
* Contaminated food can contain pathogens or toxins that can cause food poisoning e.g salmonella.
* Keep animals away from food (houseflies)
* Don’t keep foods at room temp for long periods.
* Keep raw meat away from other foods.

Good personal hygiene
* Reduces chances of contacting or transmitting disease. Simple hygiene measures.

Waste disposal
* Waste & rubbish is a source of infection.

Sewage treatment
* Reduce risk from contaminated human waste.

Question 7

Define Active immunity

Answer 7

Defence against a pathogen by antibody production in the body

Question 8

How is active immunity gained?

Answer 8

• after an infection by a pathogen
• or by vaccination.

Question 9

Role of vaccination in controlling the spread of diseases

Answer 9

• Mass vaccination can prevent spread of pathogen into wider population
• When a significant number of people have been vaccinated, it gives protection to those who do not have immunity (herd immunity.)

Question 10

define Passive immunity

Answer 10

• short-term defence against a pathogen by antibodies
• acquired from another individual,
• including across the placenta & in breast milk

Question 11

Importance of breast-feeding for the development of passive immunity in infants

Answer 11

• Breast milk contains antibodies from mother passed onto her baby.
• Infants immune system is not well developed → mother’s antibodies can protect it against any diseases which she is immune to, for the first few months of its life.

Question 12

Are memory cells produced in passive immunity

Answer 12

no

Question 13

how else can passive immunity be gained

Answer 13

• Passive immunity can also be gained by being injected with antibodies made by another organism.

Question 14

Define cholera

Answer 14

• a disease caused by a bacterium
• which is transmitted in contaminated water

Question 15

What does the cholera bacterium produce?

Answer 15

• a toxin that causes secretion of chloride ions into
  the small intestine,
• causing osmotic movement of water into the gut,
• causing diarrhoea, dehydration and loss of ions from the blood

Question 16

How is cholera spread?

Answer 16

through water & food that’s been contaminated with faeces from an infected person.

Question 17

The cholera bacteria release toxins.
The toxin releases what?

Answer 17

CI- ions