Module 4.1.1- Communicable diseases, disease prevention and the immune system

Subdecks (1)

Cards (95)

  • Communicable disease
    a disease that is spread from one host to another caused by pathogens
  • Vectors
    An organism that transmits disease by conveying pathogens from one host to another
  • 2 ways bacteria can be identified
    by their basic shapes
    by their cell walls
  • What colour do gram-positive bacteria and gram-negative bacteria appear under staining respectively

    purple blue (+) and red (-)
  • Viruses
    smaller than bacteria and other pathogensinside the genetic material surrounded by a protein invade living cells in order to reproducewhen they invade, the cells are damaged or destroyed in the process of releasing new particles to infect other cells
  • Protoctista
    unicellular and multicellular eukaryotic organisms
    may be auto or heterotrophic
  • Fungi
    Kingdom composed of heterotrophs; many obtain energy and nutrients from dead organic matter (saprophytes)some are parasitic
  • Bacteriophage
    A virus that infects bacteria
  • How do viruses damage host tissues directly

    virus attaches to host cell
    insertion of viral nucleic acid
    replication of viral nucleic acid
    synthesis of viral protein
    assembly of viral particles
    lysis of host cell, spreading toxic particles to other cells
  • How can toxins damage host tissues

    break down cell membranes
    damage or inactivate enzymes
    interfere with host cell genetic material
  • Example of a plant and animal disease (bacteria)

    Ring rot and Tuberculosis or Bacterial meningitis
  • Example of a plant and animal disease (virus)

    Tobacco mosaic virus and HIV/AIDS or Influenza
  • Example of a plant and animal disease (fungus)

    Black sigatoka and Ring worm or Athletes foot
  • Example of a plant and animal disease (protoctist)

    Potato blight and Malaria
  • Direct methods of transmission

    direct contact - kissing, touching etc.
    inoculation - animal bite, break in skin etc.
    ingestion- contaminated food etc.
  • Indirect methods of transmission

    fomites- inanimate objects such as socks
    droplet infection- minute droplets of saliva etc.
    vectors
  • Factors affecting transmission of communicable diseases in animals
    overcrowded living and working conditions
    poor nutrition
    compromised immune system
    poor disposal of waste
    climate change
    culture and infrastructure
    socioeconomic factors
  • Types of vectors
    wind
    water
    animals
    humans
  • Factors affecting transmission of communicable diseases in plants
    planting crops susceptible to disease
    overcrowding
    poor mineral nutrition
    damp warm conditions
    climate change
  • How do plants recognise an attack
    plant cells recognise molecules produced by pathogens
    when pathogen(ie enzymes) break down the plant cell wall, the breakdown products are recognised
    signalling molecules alert nucleus to attack:
    • polysaccharides (callose and lignin) made to strengthen cell wall)
    • alarm other cells before they are attacked
    • attack pathogen directly
  • Function of callose
    deposited between cell walls and membranes to prevent pathogen entry
    block sieve plates in phloem sealing infected parts
    deposited in plasmodesmata to prevent spread
  • Chemical defences of plants

    • insect repellents
    • insecticides
    • antibacterial compound
    • antifungal compound
    • anti-oomycetes
    • general toxins
  • Non-specific defences animals- skin

    • covers the body preventing the entry of pathogens
    • has skin flora that outcompete pathogens for space on body surface
    • skin also produces sebum which inhibits pathogen growth
  • Non-specific defences animals- mucous membranes
    many of the body tracts are lined by this
    secrete sticky mucus trapping microorganisms and contains lysozymes and phagocytes
  • Non specific defences animals- lysozymes
    found in tears, urine and the acid in the stomach
    contains hydrolytic enzymes to break down pathogens
  • Blood clotting and wound repair

    cut detected by platelets thromboplastin is released
    serotonin is released clot dries and scabs form epidermal cells below the scab grows sealing wound damaged blood vessels regrowing collagen fibres deposited to give strength scab falls off
  • Thromboplastin (blood clotting)

    an enzyme that triggers a cascade of reactions resulting in the formation of a blood clot
  • Serotonin (blood clotting)

    makes the smooth muscle in the walls of the blood vessels contract, so they narrow and reduce the supply of blood to the area
  • Inflammatory response (non specific animal defence)

    localised response to pathogens resulting in inflammation at the site of a wound activating mast cells releasing histamines and cytokines
  • Mast cells
    Cells that release chemicals (such as histamine or cytokines) that promote inflammation.
  • Histamine role (in inflammation)

    make blood vessels dilate causing localised heat and redness
    temperature raised to prevent pathogens reproducing
    make blood vessel walls leaky so blood plasma is forced out as tissue fluid causing swelling and pain
  • Cytokines (in inflammation)

    attract white blood cells (phagocytes) to the site
    they dispose of pathogens by phagocytosis
  • Fever (non specific response)

    when pathogen invades body
    cytokines stimulate hypothalamus to increase temperature
    higher temperatures inhibit pathogen reproduction
    specific immune system works faster at higher temperatures
  • Why is increasing body temperature good for fighting off pathogens
    higher temperatures inhibit pathogen reproduction
    specific immune system works faster at higher temperatures
  • 2 types of phagocytes
    neutrophils and macrophages
  • Phagocytosis stages (neutrophil)


    • Pathogens produce chemical that attracts phagocytes and recognise it as non-self by then binding to it
    • Phagocyte engulfs pathogen to form phagosome
    • Phagosome binds with lysosome to form phagolysosome
    • Lysosome enzymes digest and destroy the pathogen
  • Phagocytosis stages (macrophage)

    After lysosome digests the pathogen, it combines antigens from the pathogen surface membrane with the major histocompatibility complex (MHC)
    The MHC complex moves pathogen antigens to the macrophage's surface membrane to become an antigen-presenting cell (APC)
  • Antigen-presenting cells (APCs)

    cells such as B cells, macrophages, and dendritic cells that can present exogenous antigens to naive or memory T cells, activating them
  • Cytokines
    act as cell-signalling molecules, informing other phagocytes that the body is under attack and stimulating them to move to the site of infection or inflammation
  • Opsonins
    chemicals that bind to pathogens and tag them so they are recognised more easily by phagocytes, e.g. antibodies.