communicable disease Flashcards
what are the main disease causing pathogens in humans
bacteria and virus
what type of pathogen causes TB
bacteria
what pathogen causes TB
Mycobacterium tuberculosis
what does TB infects
phagocytes in the lungs
what does TB lead to
breathing problems, coughing, weight loss, fever and can result in death
what are examples of physical defences against pathogens in plants
cellulose cell walls
a lignin layer that thickens the cell wall
waxy cuticles
old vascular tissue is blocked to stop the pathogen spreading
what mechanisms are activated in plants when a pathogen is detected
closing of the stomata to prevent entry to the leaves
additional thickening of cell walls
callose deposits between cell wall and cell membrane near the site of infection to strengthen cell wall
necrosis which is when cells near the infection are killed by intracellular enzymes
what are the physical barriers against infection in animals
skin consisting of keratin
stomach acid that kills bacteria
gut and skin flora that compete with pathogens for food and space
explain inflammation
histamines released by mast cells in the injured tissue cause vasodilation which increases blood flow to the infected area and increases permeability of blood vessel.
antibodies, white blood cells and plasma leak out into the infected area and destroy the pathogen
explain lysozyme action
lysozymes are enzymes found in secretions such as tears and mucus that kills bacterial cells by damaging their cell walls
what is phagocytosis
a process in which white blood cells engulf pathogens, destroying them by fusing a pathogen enclosed in a phagocytic vacuole with a lysosome
explain blood clotting
reduces the blood loss by temporarily sealing the opening thus preventing the entry of pathogens
what are memory cells
cells that replicate themselves when exposed to an invading pathogen and remain in the lymph nodes searching for the same antigen thus resulting in a much faster immune response.
what are B effector cells
antibody producing cells
what are T helper cells
stimulate B cells and T killer cells to divide
what are T killer cells
destroy pathogen infected cells
explain the humoral response
a B cell is triggered when it encounters its matching antigen
the B cell engulfs the antigen and digest it
it then displays the antigen on its surface
a matching T cell is then attracted
the T cell secretes cytokines which help the B cell multiply and divide into plasma cells
then released into the blood and the antibodies lock onto matching antigens
explain the cell mediated response
macrophage ingests the antigens
processes them
presents them to a T helper cell
produces clones to produce a T helper cell, a T killer cell or a memory cell
what are antibodies
globular proteins produced by lymphocytes
explain antibody action
neutralisation- have a complementary shape to a specific antigen. they attach to the antigen and inhibit its action
agglutination- several antibodies clump the antigens together allowing easier digestion
describe the structure of antibodies
composed of four polypeptide chains which are linked by disulfide bridges
have a constant region and a variable region
contain hinge region responsible for flexibility
what is meant by active immunity
results from the production of antibodies by the immune system in response to the presence of an antigen
what is meant by passive immunity
the introduction of antibodies from another person or animal
direct transmission
direct contact (kissing, skin to skin contact) inoculation (break in skin, animal bite) ingestion (contaminated food or drink)
