Unit 4 Immunology & Public Health – Non Specific Defences: – 2013 Section C2B: Describe non-specific defences that the body uses to protect itself from pathogens. (10) Describe non-specific defences that the body uses to protect itself from pathogens 1 The skin prevents the entry of pathogens / is a physical barrier. 2 Epithelial cells (in cavity linings) produce (protective chemical) secretions 3 Description of one non-specific defence e.g. mucus in windpipe / acid in stomach / lysozyme or anti-bacterial substances in tears / coughing or sneezing / blood clotting 4 The inflammatory response is caused by the release of histamine from mast cells 5 Vasodilation / increased capillary permeability / increased blood flow (occurs) 6 Increased blood flow / secretion of cytokines results in the accumulation of phagocytes 7 It also results in the delivery of antimicrobial proteins / clotting elements to the site 8 Phagocytes recognise surface antigens/ protein markers on pathogens 9 They then destroy the pathogen by engulfing it / by phagocytosis 10 Natural killer (NK) cells induce the pathogen to destroy itself / apoptosis 11 (The NK cells cause) the pathogen to produce digestive / self-destructive enzymes 12 Phagocytes / NK cells release cytokines that stimulates the (specific) immune response 8 marks The coherence and relevance marks are only awarded when at least five marks have been scored from points 1 to 12 and the following criteria are met. Relevance A single short reference to an irrelevant point is not penalised but – development of the point is penalised. However, two irrelevant points without development are penalised.
Unit 4 – Immunology & Public Health Non – Specific Defences: 2013 Section C2B: Describe non-specific defences that the body uses to protect itself from pathogens. (10) Describe non-specific defences that the body uses to protect itself from pathogens 1 The skin prevents the entry of pathogens / is a physical barrier. 2 Epithelial cells (in cavity linings) produce (protective chemical) secretions 3 Description of one non-specific defence e.g. mucus in windpipe / acid in stomach / lysozyme or anti-bacterial substances in tears / coughing or sneezing / blood clotting 4 The inflammatory response is caused by the release of histamine from mast cells 5 Vasodilation / increased capillary permeability / increased blood flow (occurs) 6 Increased blood flow / secretion of cytokines results in the accumulation of phagocytes 7 It also results in the delivery of antimicrobial proteins / clotting elements to the site 8 Phagocytes recognise surface antigens/ protein markers on pathogens 9 They then destroy the pathogen by engulfing it / by phagocytosis 10 Natural killer (NK) cells induce the pathogen to destroy itself / apoptosis 11 (The NK cells cause) the pathogen to produce digestive / self-destructive enzymes 12 Phagocytes / NK cells release cytokines that stimulates the (specific) immune response 8 marks The coherence and relevance marks are only awarded when at least five marks have been scored from points 1 to 12 and the following criteria are met. Relevance – A single short reference to an irrelevant point is not penalised but development of the point is penalised. However, two irrelevant points without development are penalised.
Revision-Booklet-for-all-4-Units-Marking-Scheme.docx