12.5 Non-Specific Animal Defences Against Pathogens Flashcards
(26 cards)
What are the key barriers for pathogens in humans?
-Skin
-Tears
-Stomach acid
-Saliva
-Mucus membranes
-Body responses
What are body responses in relation to barriers to pathogens?
Sneezing, coughing, vomiting, diarrhoea
How does blood clot? (Simple answer, no chemical processes)
When platelets come into contact with collagen in skin or walls of damaged blood vessels, they adhere and begin secreting serotonin and thromboplastin that cause clotting.
What are the two chemicals that platelets produce to cause clotting?
Serotonin and thromboplastin
What cell causes blood clotting?
Platelets
What does serotonin do?
Makes smooth muscle in the walls of the blood vessel contract, narrowing and reducing supply of blood to the area.
What does thromboplastin do? (No chemical processes)
Triggers a cascade of reactions, resulting in the formation of a blood clot.
State the chemical process starting with thromboplastin that causes clotting.
-Thromboplastin released by platelet
-Thromboplastin catalyses the conversion of prothrombin to thrombin (with the presence of Ca2+ ions)
-Thrombin catalyses the conversion of fibrinogen to fibrin
What does fibrin do?
Adhere to the platelets to form an insoluble clot.
What is an inflammatory response?
A localised response to pathogens/damage/irritants, resulting in inflammation at the site of a wound.
How is an inflammatory response started?
Mast cells are activated in damaged tissue, and release chemicals called histamines and cytokines
What do cytokines do?
Attract white blood cells to the site, disposing of pathogens by phagocytosis.
What do histamines do?
-Make blood vessels dilate, causing localised heat and redness (preventing pathogens from reproducing)
-Make blood vessel walls more leaky, so blood plasma is forced out into tissue fluid, causing swelling
What is the purpose of causing localised heat around damage?
To prevent pathogens from reproducing.
Why might a lymph node be swollen?
Because it is active, producing and releasing lymphocytes (white blood cells)
What is the normal body temperature in degrees celsius?
37
How do cytokines increase your temperature?
They stimulate your hypothalamus to reset your thermostat, and your temperature increases
Why is it important to raise your temperature to protect against pathogens?
-Higher temperatures inhibit pathogen reproduction
-The specific immune system works faster at higher temperatures
What cells perform phagocytosis?
Neutrophils and macrophages
What is pus?
Dead neutrophils and pathogens
State the process of phagocytosis that both neutrophils and macrophages can perform.
1- Pathogens produce chemicals that attract phagocytes
2- Phagocytes recognise non-human proteins on the pathogen
3- Phagocyte engulfs the pathogen and encloses it in a phagosome
4- Phagosome combines with a lysosome to form a phagolysosome, and digests the protein
State the process of phagocytosis that only macrophages can perform.
5- Macrophage combines antigens from the pathogen surface membrane with the MHC Complex (MAJOR HISTOCOMPATIBILITY COMPELX)
6- MHC Complex moves tee antigens to the macrophage’s cell surface membrane, becoming an antigen-presenting cell.
What does MHC stand for?
Major histocompatibility complex
What does APC stand for?
Antigen-presenting cell
