immune system Flashcards
non specific defences in animals keeping pathogens out
skin- this acts as a physical barrier blocking pathogens fron entering the body. also acts as a chemical barrier by producing toxins that are antimicrobial and can lower pH inhibiting the growth of pathogens
mucous membranes- these protect body opening that are exposed to the environment such as th airways of the gas exchange. some membranes secrete mucus which is a sticky substance that traps pathogens and contains lysozymes which destroy bacterial and fungal cell walls. also contain phagocytes which remove remaining pathogens
blood clotting and wound repair
inflammation
expulsive reflexes
blood clotting and wound repair
blood clotting- a blood clot is a mesh of protein fibres (fibrin). blood clots plug wounds to prevent pathogen entry and blood loss. theyre formed by a series of chemical reactions that take place when platelets are exposed to damaged blood vessels
wound repair- the skin is able to repair itself in the event of an injury and re form a barrier against pathogen entry. the surface is repaired by the outer layer of skin cells dividing and migrating to the edges of the wound. tissue below the wound then contracts to bring the edges of the wound closer together. it is repaired using collagen fibres- too many collagen fibres can lead to a scar
inflammatory response
signs include swelling, pain, heat and redness
it is triggered by tissue damage. the damages tissues release histamines and cytokines. histamines increases the permeability of the blood vessels so they start to leak fluid into the surrounding areas. this causes swelling which helps to isolate any pathogens that may have entered the damaged tissues. histamines also cause vascodilation which increases blood flow to the affected areas. this makes it hot and cytokines attract white blood cells (pathogens) to the site which diposes of the pathogen by phagocytosis
expulsive reflexes
coughing and sneezing
a sneeze happens when the mucous membranes in the nostrils are irritated by things such as dust and dirt. a cough stems from irritation in the respiratory tract. both coughing and sneezing are an attempt to expel foreign objects including pathogens from the body. this happens automatically
steps for phagocytosis
pathogens produce chemicals that attract phagocytes
a phagocyte recognises the antigen on a pathogen
the cytoplasm of the phagocytes moves round the pathogen engulfing it
the pathogen is now contained in a phagosome- a type of vesicle- in the cytoplasm of the phagocyte
a lysosome fuses with the phagosome to form a phagolysosome. enzymes from the lysosome digest and destroy the pathogen
the phagocytes then presents the pathogens antigens. it sticks to the antigens on its surface to activate other immune system cells. when a phagocyte does this it is acting as an antigen- preseting cell (APC)
helpful chemicals
opsonins- molecules in the blood that attach to foreing antigens to aid phagocytosis
cytokines- cell signalling molecues informing other phagocytes that the body is under attack and stimulating them to move to the site of infection or inflammation
cell mediated immunity. phagocytes activate T lymphocytes
a T lymphocytes are another type of white blood cells
their surface is covered with receptors
the receptors bind to antigens present by APCs
each T lymphocytes has a different receptor on its surface
when a receptor on the surface of a T helper cells meets a complementary antigen it binds to it so each T helper cells binds to a different antigen
this actives T helper cells and produce interleukin ls which stimilates more T cells to divide rapidly by mitosis to produce clones of itself
the cloned T cells may
- develop into T memory cells which gives a rapid response if the pathogen invades the body again
- produce interleukins that stimulates B cells to divide
- produce interleukins that stimulates phagocytosis
- stimulates the development of a clone of T killer cells that are specific for the presented antigen and then destroy infected cell’s
different types of T lymphocytes
T helper cells- they have CD4 receptors on their cell surface membrane which binds to the surface antigens on APCs. they produce interleukins which are a type of cytokine. the interlukins stimulste the activity of B cells which increases antibody production of other types of T cells and attracts and stimulates macrophages to ingest pathogens with antigen- antibody complexes
T killer cells- these destroy the pathogen carrying the antigen. they produce a chemical called perforin which kills the pathogen by making holes in the cell membrane so its freely permeable
T memory cells- live for a long time and are part of the immunological memory. if they meet an antigen a second time they divide rapidly to form a huge number of clones of T killer cells that destroys the pathogen
T regulator cells- these cells suppress the immune system acting to control and regulate it. they stop the immune response once a pathogen has been eliminated and make sure the body recognises self antigens and does not set up an autoimmune response. interleukin are important in this control
hum oral response
activates T helper cells bind to B cells with the complementary antibody to the antigen. this is clinal selection
this B cell activates the repulse of interleukins from the T helper cell
The B cell rapidly divides by mitosis to make clones which differentiate into either memory B-cells or plasma cells this is clinal expansion
the plasma cells produce antibodies which attach to antigens on pathogens to help distort them by agglutination and marking them for phagocytosis
this is the primary immune response
B memory cells remain in blood after infection and can rapidly produce large amounts of antibodies if there is a reinfection of same pathogen
3 ways antibodies work
agglutination- clumping together of pathogens
marking pathogens - can act as opsonin when antibody antigen complex forms
anti-toxins- bind to them which prevents them entering cells and causing harm
what are antibiodies
globular quaternary proteins that have binding sites complemtary in shape to antigens
made of 4 polypeptide chains. 2 heavy 2 light
passive immunity
antibodies injected from another individual
active immunity
the immune system is stimulated to make its own antibodies
vaccinations
natural immunity
baby gets antibodies from mother in placenta
or when you produce own antibodies from infections
artificial immunity
giving immunity without any contact from pathogen
