protection against infection (chapter 7)

• a.k.a ‘infectious’ or ‘transmissible’ diseases • characteristics: - caused by pathogens - contagious

• organism capable of causing disease • commonly: - bacteria - virus - parasite - fungi

• surrounded by plasma membrane, cell wall and slime • no nucleus/membrane bound cells • contains only DNA • cytoplasm containing ribosomes • comparatively larger (can be seen under light microscope)

• bacteria infected intestine; produce cholera toxin • causes severe diarrhoea which leads to dehydration

• bacteria produces a toxin that affects mucous membranes of mouth and nose • general flu symptoms: fever/chills/cough/core that)

• spores enter body through cuts and develop into bacteria; these spread to CNS and produce toxins (tetanusospasmin) • toxins prevent nerve signals to muscles - muscles spasms and stiffness

• bacteria usually attack lungs, symptoms depend on where bacteria grow • lungs: bad cough, pain in chest, cough up blood

• respiratory tract infection; cold-like symptoms, persistent dry cough • bacteria attach to cilia lining upper part of respiratory tract; cilia and airways swell

• enclosed with protein coat • no nucleus/membrane bound cells • contains RNA • no ribosomes • smaller (can only be seen under electron microscope)

• RNA • virus attacks CD4 helper (immune) lymphocytes • body is unable to fight off infections

• RNA • virus targets liver, immune and endothelial cells lining blood vessels • disrupts cell adhesion; leading to haemorrhaging and internal bleeding

• RNA • virus infects macrophages and dendritic cells, then B and T cells in lymph nodes • causes inflammation throughout entire body

• RNA • virus attacks epithelial cells of nose, throat and respiratory system; infects and kills NK immune cells

• contact (direct or indirect): chicken pox, genital warts • transfer body fluids (saliva, mucus, blood): HIV • infection by droplets: colds, influenza • ingestion (of contaminated food/water): salmonella • airborne transmission (can survive even once dried): tuberculosis • vectors: malaria (by mozzies), lyme disease (by ticks)

non-specific: - works against all pathogens (general) - body’s first line of defence - there are: - external defences - internal defences - protective reflexes specific: - directed at particular pathogens - immune system produces antibodies to target pathogens

• barrier; prevents entry of micro-organisms • large amount of bacteria live on the skin - occupying bacteria make it difficult for new (pathogenic) establishments • sebum; an oily secretion which kills some pathogenic bacteria • sweat; salts and fatty acids prevent growth of many micro-organisms

• found in digestive, urinary, respiratory and urogenital tracts • line body cavity (that open to exterior) • secrete mucus; inhibits entry of micro-organisms

• found in nose and ears • hair trap micro-organisms

• found in respiratory tract (line nasal cavity, trachea etc.) • tiny heir-like projections from cells • ‘beating’ motion moves mucus up towards throat (cough up/swallow)

• found in stomach and vagina and sweat • kills micro-organisms that are ingested with food or in mucus • reduces growth of micro-organism

• found in tears, saliva, sweat, nasal secretions and tissue fluid • enzymes kills bacteria

• found in outer ear • slightly acidic and contains lysozyme • prevents and traps pathogens from entering

• occurs in urine flowing through urethra, tears, sweat, saliva and vagina • cleansing action = prevents bacterial growth from travelling through ducts/tracts

• stimulus: irritation of walls of nasal cavity (noxious fumes/dust particles) • forceful expulsion of our from lungs, carries mucous/foreign particles/irritation gases out through nose and mouth