Human Defence Systems

Question 1

What are the main defence systems against pathogens?

Answer 1

Skin - first barrier
Trachea and lungs to trap microorganisms
Blood clots seal wounds
Stomach secretes hydrochloric acid killing microorganisms
Ear wax, Tears, eye lashes and nostril hairs all keep out microorganisms

Question 2

What are the internal defences?

Answer 2

White blood cells ingest pathogens making anti bodies and anti toxins that destroy bacteria or viruses and counter pathogen toxin

Question 3

How does vaccination work?

Answer 3

1. immunise large proportion of population
2. Small quantities of dead or inactive forms of pathogen into body or stimulate white blood cells so they produce antibodies
3. The white blood cells then respond quickly if same pathogen enters

Question 4

How do antibiotics work?

Answer 4

These treat disease
Antibiotics eg penicillin help to cure bacterial disease killing infected bacteria in the body
The right antibiotic is needed for each specific disease
However some bacteria now resist antibiotics
Only prescribe antibiotics when necessary - not for viruses
Take the whole course otherwise may leave some bacteria in your body

Question 5

How do painkillers work?

Answer 5

Treat the symptoms of disease but do not kill pathogens

Question 6

What is the problem with antibiotic resistant bacteria?

Answer 6

MRSA
Developed from natural selection as mutation of pathogens produce new strains as individual resistant pathogens reproduce
If antibiotic and vaccination not effective they cannot be treated so strain will spread rapidly
New antibiotics needed

Question 7

Discovery and development of new drugs

Drugs extracted from plants and microorganisms

Answer 7

Heart drug digitalis from foxgloves
Painkiller aspirin from willow
Penicillin from penicillium mould - discovered by Fleming

Question 8

New drugs synthesised in pharmaceutical industry

Answer 8

Starting point may still be chemical extract from plant
Drugs trialled before use
Tested for toxicity, efficacy, dose
Preclinical lab tests on cells, tissues, live animals
Clinical trials on healthy volunteers and patients - low doses
Further clinical trials then work out optimum dose
Blind trial with placebos