Human defences against disease

Question 1

What are non-specific defences?

Answer 1

• Defences that work against all pathogens to try and stop them entering the body

Question 2

What are the body’s defences?

Answer 2

• Enzymes in the TEARS destroy microorganisms
• The NOSE traps particles that may contain pathogens
• SKIN is a physical barrier to the entry of pathogens
• GLANDS in the STOMACH wall - produce hydrochloric acid, which kills bacteria in food.

Question 3

What does the immune system do?

Answer 3

• If a pathogen enters the body, the immune system tries to destroy it
• WHITE BLOOD CELLS help to defend against pathogens through PHAGOCYTOSIS

Question 4

What is Phagocytosis?
(Steps:)

Answer 4

• Where the white blood cell surrounds the pathogen, then engulfs and digests it.

1. Microorganisms invade the body
2. The white blood cell finds the microorganism and engulfs them
3. The white blood cell ingests the microorganisms
4. The microorganisms have been digested and destroyed

Question 5

What are antibodies?

Answer 5

• Special protein molecules which attach to antigen molecules on the pathogen.

Question 6

Antibody production:

Answer 6

1. Antigens are markers on the surface of the microorganism.
2. The white blood cells become sensitised to the antigens and produce antibodies.
3. The antibodies then lock onto the antigens
4. This causes the microorganisms to clump together, so that other white blood cells can digest them

Question 7

What are antitoxins?

Answer 7

• Chemicals that neutralise the poisonous effects of toxins

Question 8

What is immunity?

Answer 8

• If the same pathogen re-enters the body, the white blood cells respond more quickly to produce the correct antibodies.
• This quick response prevents the person from getting ill and is called IMMUNITY

Question 9

What do vaccinations do?

Answer 9

• When a person has a vaccination, small quantities of dead or inactive forms of a pathogen are injected into the body.
• Vaccination stimulates the white blood cells to produce antibodies and develop immunity

Question 10

Steps of vaccination:

Answer 10

1. A weakened/dead strain of the microorganism is injected.
2. Antigens on the modified microorganism’s surface cause the white blood cells to produce specific antibodies
3. The white blood cells that are capable of quickly producing the specific antibody remain in the bloodstream

Question 11

What does immunisation rely on?

Answer 11

• Immunisation relies on the majority of the population being vaccinated.
• It protects those who cannot get a vaccine e.g. if they’re immunocompromised
• Immunisation stops pathogens from spreading