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41 Cards in this Set
- Front
- Back
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What is an infection? |
Interaction between the pathogen and the body's defense mechanisms |
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What is immunity? |
The ability for organisms to resist infection by protecting against harmful microorganisms/toxins |
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What are pathogenic bacteria? |
Bacteria which cause disease by entering the body through food/cuts/air passages |
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How do pathogenic bacteria cause symptoms? |
By damaging tissues by invading cells Releasing toxins (poisons) |
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What are the ways in which pathogens can be transmitted? |
-Vectors [organisms that pass pathogens from one host to another] (malaria/mosquitoes)
-Fomites (bedding) [object contaminated with pathogens] -Direct contact -Inoculation (HIV) -Inhalation (influenza) -Indigestion (Salmonella) |
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What are the two types of bacterial toxins? |
Endotoxins and exotoxins |
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What are endotoxins? |
Lipopolysaccharides/released when cell dies (lysis) and cell wall fragments are released/symptoms=fever/diarrhoea/vomiting e.g Salmonella and E.Coli |
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What are exotoxins? |
Soluble proteins/released by bacterial cells as they grow and reproduce/damage cell membranes=internal bleeding and cell breakdown/competitive inhibitors to neurotransmitters/directly poison cells |
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What to antigens allow the immune system to do? |
Identify pathogens/non-self material/toxins/abnormal cells (cancer cells) |
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What are the issues with immune response to non-self antigens? |
Organ and tissue transplants are recognised as non-self by the immune system and so a response is carried out to destroy the transplant |
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How is immune response to transplants minimised? |
doner tissues are matched closely to the patient (usually from relatives)/immunosuppressent drugs are given to reduce the immune response |
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What happens if lymphocytes respond to self-antigens? |
Programmed cell death called apoptosis |
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What are the body's first line of defence for infection? |
Saliva/tears: Contains antibacterial enzymes Skin: Physical barrier/skin flora to stop bacterial growth/pH 3-5 Stomach acid:low pH destroys pathogens/gut flora secretes lactic acid=defence against pathogens Mucus: lining traps dirt and microbes/contains lysosymes Vomiting: Effectively removes microbes from system |
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What is human flora? |
500-10,000 types of harmless/beneficial bacteria in the human body (includes skin and gut flora) |
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What are the non-specific responses to infection? |
Inflammation/fever/interferons/physical barrier/phagocytosis/lysosymes |
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How do lysosymes combat pathogens? |
Found in lysosomes/enzyme which breaks down pathogens |
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How do interferons combat pathogens? |
Proteins that inhibit viral replication within cells/produced by virally infected cells/diffuse into surrounding cells/bind to normal cell receptors/makes cells resistent to viral infection |
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How does a fever combat pathogens? |
The hypothalamus resets the body's temperature to above 37 C /stop the rapid growth of pathogen (37 C or below)/allow for better specific immune response |
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How does a fever differ between a bacterial infection and a viral infection? |
Bacterial infection: constant high temperature Viral infection: Fever tends to spike |
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What is inflammation? |
A localized response to injury resulting in swelling/redness/heat/pain to reduce the number of pathogens which enter the body |
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Describe the process of inflammation. |
Tissue(skin) is damaged/pathogens may enter the body/pathogens then damage cells/damaged cells release chemical substances (histamines)=inflammatory mediators/blood cells dilate/increased blood flow to location of injury/area flooded with fluid/blood-clotting elements=swelling/redness/damaged tissues also trigger phagocytosis/ anti-flammatory factors |
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Describe the process of phagocytosis? |
Pathogens release chemokines that attract phagocytes/phagocyte engulfs pathogen and forms phagosome/lysosomes fuse to phagosome=phagolysome/release lysosymes into phagosome/enzymes digest pathogen/useful material absorbed/rest expelled |
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What are the types of specific immune response? |
Cell-mediated immunity and humoral immunity |
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What is an antigen? |
Part of an organism or substance that is recognised as foreign by the immune system, stimulating an immune response. Usually (glyco)proteins. |
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Where are antigens usually found? |
On the cell-surface membrane of: - invading microorganisms - virus infected cells - cancer cells - transplanted cells - allergens (pollen) |
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What is an antibody? |
Molecules secreted by B lymphocytes in response to stimulation by the appropriate antigen (how they work depends on the structure) |
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What is a cell-mediated response? |
Highly specialised cells that target pathogens inside cells |
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What is a humoral response? |
Targets pathogens in body fluids with antibodies |
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What are lymphocytes? |
White blood cells found in blood/lymph nodes/recognise antigens and carry out immune response |
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What are the two types of lymphocytes? |
T lymphocytes and B lymphocytes |
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What are B lymphocytes? |
Made and mature in bone marrow/found in lymph glands/free in body/make antibodies/associated with humoral immunity (producing antibodies in response to pathogen) |
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What are T lymphocytes? |
Made in bone marrow/mature in thymus/found in thymus gland/associated with cell-mediated immunity (cells directly interacting with pathogen) |
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What are the two types of T lymphocytes? |
T helper cells and T killer cells |
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What are T helper cells? |
Detect pathogen and produce chemical signals/trigger rapid division of T killer cells and effector B cells |
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What are T killer cells? |
Produce chemicals to destroy pathogens. |
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Describe the process of a cell-mediated response. |
phagocyte destroys pathogen (phagocytosis)/becomes antigen presenting cell (APC)/T helper cell triggers APC to release interleukin-1 (cytokine)/stimulates T helper cell to release interleukin-2/stimulates T cell division to produce cytotoxic T cells and memory T cells/cytotoxic cells detect APC and produce perforin/destroys APC/memory T cells produced=future response |
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What are the two types of T killer cells? |
Cytotoxic T cells: destroy pathogen directly (attaching/releasing perforin) Memory T cells: Future response to same pathogen |
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What are suppressor cells? |
Slow down cyotoxic T cells and T helper cells |
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Describe the process of humoral immune response. |
Antigen enters the B cell (endocytosis)/becomes APC/ T helper cells trigger APC to release interleukin-1/T helper cell releases interleukin-2/APC divides (mitosis)/produces plasma cells/produce large amounts of antibodies/attach to pathogen and destroy it/memory B cells produced=future response |
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What are plasma cells? |
Secrete antibodies into blood plasma/survive for a few days/produce large amounts of antibodies/primary immune response |
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What are memory B cells? |
Secondary immune response/live longer/circulate blood and tissue fluid/encounter pathogen again=divide rapidly and produce plasma/memory cells/response before pathogens can cause harm |
