Diseases/immune system *4

• name the four types of microorganisms which can cause communicable diseases in animals and plants ?

  bacteria, fungi , virus and protoctista
• two human diseases caused by bacteria ?

  tuberculosis and bacterial meningitus
• name two human diseases caused by viruses ?

  Influenza and HIV/AIDS.
• name one human disease caused by protoctist ?

  malaria
• what are two methods of direct transmission of pathogens between animals ?

  direct contact and droplet transmission.
• what are two methods of indirect transmission of pathogens between animals ?

  vectors and ingestion of contaminated food and water
• name three factors which can increase the chances of transmission of communicable disease between animals ?

  overcrowding, malnutrition and a weakened immune system
• what are the two methods of indirect transmission of pathogens within plants ?

  vectors and soil contamination
• name three factors which can increase the chances of transmission of communicable diseases between plants ?

  overcrowding, mineral deficiency and damp/warm conditions
• state five ways farmers and growers control the transmission of a communicable disease between plants ?

  crop rotation, thorough cleaning of equipment, controlling insect vectors, leaving more space between growing plants, removing plant material from soil after harvesting
• give four examples of passive physical barriers which help plant prevent the entry of pathogens ?

  bark, waxy cuticle, closing stomata,cellulose in cell walls
• how is a plant's response to attack by pathogens triggered ?

  by cell signalling involving the release of signalling molecules this is triggered by molecules associated with cell damage or pathogen entry attaching to receptors
• name two material actively produced by plants in response to infection ?

  callose and lignin
• where is callose deposited to help prevent the spread the spread of a pathogen in a plant ?

  in the cell walls, the phloem sieve plates and the plasmodesmata
• give five types of defence chemicals in plants ?

  insect repellents, insecticides, antibacterial compounds, antifungal compounds, toxins
• name two barrier defences which help prevent entry of pathogens in animals ?

  Skin and mucous membranes.
• name three defence mechanisms, other than barrier defences which help prevent entry of pathogens in animals ?

  blood clotting, wound repair, expulsive reflexes
• name two chemical secretions which help prevent entry of pathogens in animals ?

  lysozymes and stomach acid
• in the inflammatory response, which two chemicals are released by mast cells ?

  Histamine and cytokines.
• What are the effects of histamines on tissue ?

  dilation of blood vessels causing redness or warmth, and increased formation of tissue fluid causing swelling
• name two non-specific defence mechanisms which act in response to entry of pathogens in animals ?

  fever and phagocytosis
• what is a phagosome ?

  the vesicle which encloses a pathogen after it has been engulfed by a phagocyte
• what is a phagolysosome ?

  the structure formed when a lysosome and phagosome join
• which two types of white blood cells are involved in phagocytosis?

  neutrophils and macrophages
• which type of phagocytes is involved in both the non-specific and specific immune response ?

  Macrophages
• what is an antigen-presenting cell ?

  cells which present a foreign antigen on their cell surface membrane
• what is the term for immunity in which T lymphocytes respond to a foreign antigen ?

  Cell-mediated immunity
• what is the role of a T helper cell ?

  To produce cytokines called interleukins. These stimulates B cells to increase antibody production, phagocytes to ingest pathogens and the production of other T cell types
• which type of T cells live a long time after initial infection and allow a faster immune response if there is a subsequent infection ?

  Memory T cells
• what is the role of T regulatory cells ?

  to surpress the immune response to prevent an autoimmune response
• what term is used for the type of immune response in which B lymphocytes respond to a foreign antigen ?

  Humoral immune response
• which type of B cell produces antibodies in response to foreign antigen ?

  Plasma cells.
• what are the steps involved in the humoral immune response ?

  the response of B cells to a foreign antigen, clonal selection and the release of antibodies
• how does the secondary immune response differ from the primary immune response ?

  in the secondary immune response, plasma cells and antibodies are produced at higher speed and concentration due to the presence of memory cells produced during the primary immune response
• what is an antibody ?

  a protein produced by B lymphocytes in response to the presence of a specific antigen
• what is the name given to an antigen-binding site on an antibody ?

  the variable region
• what are four ways in which antibodies act to protect the body ?

  they act as opsonins, as agglutinins and as toxins. they also prevent pathogen entry into cells