Disease+Immunity Flashcards
What is disease
A condition that impairs the normal functioning of an organism
What is a pathogen
An organism that causes disease
What is a communicable disease
A disease that can spread between organisms
What does Tuberculosis affect and what pathogen is responsible for it
Animals, typically humans and cattle and is a bacterium
What does bacterial meningitis affect and what pathogen is responsible for it
Humans and bacterium
What does ring rot affect and what pathogen is responsible for it
Potatoes, tomatoes and is bacterium
What does HIV/AIDS affect and what pathogen is responsible for it
Humans and a virus
What does influenza affect and what pathogen is responsible for it
Animals including humans and is a virus
What does tobacco mosaic virus affect and what pathogen is responsible for it
Plants and virus
What does black sigatoka affect and what pathogen is responsible for it
Banana plants and a fungus
What does ringworm affect and what pathogen is responsible for it
Cattle and a fungus
What does athlete’s foot affect and what pathogen is responsible for it
Humans and a fungus
What does late blight affect and what pathogen is responsible for it
Potatoes/tomatoes and is a protoctist
What does malaria affect and what pathogen is responsible for it
Animals, including humans and a protoctist
What is direct transmission
When a disease is transmitted directly from one organism to another
What is indirect transmission
When a disease is transmitted from one organism to another via an intermediate such as air, water or food.
Examples of direct transmission
HIV through sexual intercourse or athlete’s foot via touch
Examples of indirect transmission
Late blight is spread when spores are carried between plants and malaria is spread between humans via mosquitoes as they act as vectors and spread it.
Three factors affecting disease transmission
Overcrowding, climate, social
Example of how overcrowding affects disease transmission
TB is increased risk with lots of people together in a small space as is spread by droplet infection which can remain in the air for long periods of time
Example of how climate affects disease transmission
- Late blight is common during wet summers as spores need water to spread
- Malaria is common in tropical countries as they are ideal conditions for mosquitoes
Example of how social factors affects disease transmission
- Good healthcare as people are less likely to be diagnosed and treated for HIV and drugs are less likely to be available and the disease more likely to be spread
- Good health education as helps to inform people how HIV is transmitted and how to avoid it
What are the primary non specific defense’s against pathogens in animals
Skin, mucous membranes, blood clotting, inflammation, wound repair, expulsive reflexes
How does skin act as a barrier to infection
Blocking pathogens from entering the body. Acts as a chemical barrier producing chemicals that are antimicrobial, can lower pH, inhibit the growth of pathogens
How does mucous membranes act as a barrier to infection
Protect body openings that are exposed to the environment, some secrete mucus a sticky substance trapping pathogens and contain antimicrobial enzymes
How does blood clotting act as a barrier to infection
It is a mesh of protein fibres that plug wounds to prevent pathogen entry and blood loss. They are formed by chemical reactions that take place when platelets are exposed to damaged blood vessels
How does inflammation act as a barrier to infection
It is triggered by tissue damage that releases molecules increasing the permeability of the blood vessels so they start to leak fluid into the surrounding area. This causes swelling and helps to isolate any pathogens that may have may have entered the damaged tissue. The molecule also causes vasodilation increasing blood flow to the affected area making it hot and brings WBC to infected area.
How does wound repair act as a barrier to infection
The skin is able to repair itself after injury preventing entry of the pathogen. The surface is repaired by the outer layer of skin cells dividing and migrating to the edges of the wound. The tissue below the wound then contracts to bring the edges closer using collagen fibres. Too many collagen fibres=scar.
How does expulsive reflexes act as a barrier to infection
Coughing and sneezing to expel foreign objects including pathogens using irritation.
What are the physical defenses against pathogens in plants
Waxy cuticle, cell walls and production of callose
How is the waxy cuticle used as a plant physical defenses
Produces a physical barrier against pathogen entry and also stops water collecting on the leaf reducing risk of infection
How is the cell walls used as a plant physical defenses
Form a physical barrier that are made past the waxy cuticle
How is the production of callose used as a plant physical defenses
It is a polysaccharide that gets deposited between plant cell walls and plasma membranes during times of stress (pathogen invasion). Callose deposition may make it harder for pathogens to enter cells and at the plasmodesmata limits the spread of viruses between cells.
What are the physical defenses against pathogens in animals
Produce antimicrobial chemicals and secrete toxic chemicals
How does the production of antimicrobial chemicals act as a chemical plant defence
They kill pathogens or inhibit their growth:
- Some plants produce saponins that destroy the cell membranes of fungi and other pathogens
- Some produce phytoalexins which inhibit the growth of fungi and other pathogens
How does the production of toxins act as a chemical plant defence
Reduces the amount of insect-feeding on plants and therefore reduces risk of infection by plant viruses carried by insects.
What are antigens
Molecules found on the surface of the cells that activates cells in the immune system as identifies the foreign body
What does the immune response involve
It involves specific (T and B lymphocytes) and non-specific stages
How does phagocytosis occur
1) A phagocyte recognizes the antigens on a pathogen
2) The cytoplasm of the phagocyte move round the pathogen, engulfing it. This may be made easier by the presence of opsonins
3) The pathogen in now contained in a phagosome
4) A lysosome fuses with the phagosome and the enzymes break down the pathogen
5) The phagocyte then presents the pathogen’s antigens. It sticks the antigens on its surface to activate other immune system cells. When a phagocyte does this is it acting as an antigen-presenting cell (APC)
What are opsonins
Molecules in the blood that attach to foreign antigens to aid phagocytosis. Some hide the negative charges on the membrane of the pathogen, making it easier for the negatively-charged phagocyte to get closer to the pathogen
What is a phagosome
A type of vesicle membrane that engulfs a pathogen
What are neutrophils
A type of phagocyte and the first WBC to respond to a pathogen as they move towards a wound in response to signals from cytokines.