C3.2 Defence against disease Flashcards
Three main types of cause for disease
Genetic, environmental (e.g. chemicals or radiation), infection with a pathogen
Pathogens
Cause infectious diseases, host of the pathogen develops disease
Main groups of pathogens
Viruses, bacteria (in humans eubacteria), fungi, protists
Primary defence against pathogens
Skin (hard physical layer) and mucous membranes (chemical barrier contains lysozyme which kills bacteria, e.g. in nose, trachea and urethra)
Process of blood clotting after skin is cut
Platelets are attracted to wounded tissues and release clotting factors –> initiate a chain of reactions and blood clots only when necessary –> in last reaction thrombin converts to long protein fibres (fibrin) which forms a mesh then clot to seal cut and prevent PATHOGENS from entering
Innate immune system
Non-specific, responds the same way to all pathogens and doesn’t change, PHAGOCYTES
Adaptive immune system
Specific, each pathogen encountered elicits a different response, immune responses develop, LYMPHOCYTES
Phagocytes
Endocytosis: phagocytes engulf all pathogens they encounter and digest them through the use of enzymes. Can happen in blood or they can move through walls of blood capillaries with tissues to site of infection
Lymphocytes in general
In lymph nodes and circulate in blood, produce antibodies (large proteins) to destroy pathogens
Lymphocytes structure
Two functional parts: a hypervariable region that binds into a specific molecule on pathogen, and a region that helps fight the pathogen
How do lymphocytes distinguish between self cells and non-self cells?
Differences in molecules: proteins, glycoproteins or polysaccharides on surface of pathogen called ANTIGENS
Process of producing antibodies with the helper T-cells and B-lymphocytes
- macrophage ingests pathogen and displays antigens, 2. Helper T is activated by macrophage, 3. T alerts antigen-specific Bs, 4. B divides to produce antibody-secreting plasma cells, 5. Antibodies produced by the clone of plasma cells specific to antigens help destroy the pathogen
Immunity
Ability to eliminate infectious disease from the body, due to antibodies and plasma b-lymphocytes (a few weeks or months) or memory B-lymphocytes (lifetime)
Memory B-lymphocytes
Do not actively secrete antibodies but persist a long time after infection, remain inactive until same pathogen enters and they respond rapidly
How is HIV transmitted
Through blood, semen, vaginal fluids, rectal secretions and breast milk
