Infection and response Flashcards
What is a pathogen?
Pathogens are microorganisms that cause infectious diseases.
How can pathogens be spread?
They can be spread by:
-direct contact
-water or air
- Vectors (organisms that carry and pass on the pathogen without getting the disease.)
How you can prevent the spread of infectious diseases?
-washing hands
-destroying vectors
- isolating infected individuals so they cannot pass on the pathogen
-Taking a vaccination.
Measles.
-Disease caused by a virus
- Symptoms are fever and red skin rash.
-Spread by breathing in droplets from sneezes/coughs.
-Vaccinations are available.
HIV (human immunodeficiency virus)
-Spread by sexual contact or exchange of bodily fluids eg needles.
-Can cause a flu-like illness.
-If untreated the virus enters the lymph nodes and attacks the body’s immune cells.
-Taking antiviral drugs can delay this happening.
-Late stage HIV or AIDS is when the body’s immune system is damaged and cannot fight off infections or cancers.
What do viruses do?
They reproduce rapidly in body cells, causing damage to the cells.
What do bacteria do?
They may damage cells directly or produce toxins (poisons) that damage tissues.
Salmonella.
Type of food poisoning caused by bacteria:
-Might have not been cooked properly or in hygienic conditions.
-Bacteria secrete toxins that can cause fever, abdominal cramps etc.
- Chickens are vaccinated to control the spread.
Gonorrhoea.
- Cause by bacteria.
-Spread by sexual contact. - Symptoms are a thick, yellow or green discharge from the vagina or penis and pain when urinating.
- Easily treated with penicillin but many resistant strains have now appeared.
-Use of a barrier method of contraception can stop the bacteria from being passed on.
What are protists?
They are single-celled organisms and are eukaryotic.
Malaria.
Caused by a protist.
- The protists use a particular type of mosquito as a vector.
- Passed on to a person when they are bitten.
- Causes severe fever.
-Prevention= Killing the mosquitoes or mosquito nets.
Rose black spot.
Fungal disease.
-spread when spores are carried from plant to plant by water or wind.
- Purple or black spots develop on leaves which often turn yellow and drop off.
- Loss of leaves stunt growth of the plant because photosynthesis is reduced.
-Can be treated by fungicides and removing the affected leaves.
What are the body’s defences?
Tears- enzymes in tears destroy microorganisms.
Nose- Traps particles that may contain pathogens.
Goblet cell- mucus traps particles and bacteria. Cilia create a wave motion that sweeps mucus along.
Glands in the stomach wall produce HCL which kills bacteria in food.
What is phagocytosis?
It is when the pathogen is surrounded and then engulfed and digested by a white blood cell.
What are the steps of phagocytosis?
1) Microorganisms invade the body.
2) The wbc finds the microorganisms and engulfs them.
3) The wbc ingests the microorganisms.
4) The microorganisms have been digested and destroyed.
What are the steps of making antibodies?
1) Antigens are markers on the surface of the microorganism.
2) The wbcs 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 wbcs can digest them.
What is immunity?
If the same pathogen comes again the wbcs response will be quicker to produce antibodies. This quick response prevents the person from getting ill and is called immunity.
