Chapter 12 ~ Communicable Diseases Flashcards
what is a pathogen
an organisim which can cause infectious diseases
what are the types of pathogens
bacteria, viruses, protoctista, fungi
what are communicable diseases
diseases which can be spread directly/ indirectly from person to person by social factors/living conditions or due to climate.
what are the pathogen modes of action
1) damaging the host cell directly
2) Producing toxin which damages the host tissue
what is the plants physical defence system
waxy cuticle
cell wall
CALLOSE between cell wall and plasma membrane.
How does callose defend plants
Callose is synthesised and depositied between cell wall and cell membrane, it acts as a barrier preventing pathogens entering.
Lignin, mechanical support
Callose blocks sieve plates in the phloem preventing spread of pathogen
what are the chemical defences of a plant
insect repellent
insecticides
antibiotics (phenols)
antifungals (chintinases, these are enzymes which break d0wn chintin in fungal cell walls)
general toxins (chemicals which break down to form cyanide which is toxic)
what are the non specific animal defences against pathogens?
Skin, covers most of thr body sebum which inhibits growth of pathogen
Many body tracts are lined with mucous membranes this contains mucus which traps microorganisims and contains lysosomes
lysoszymes in tears and urine
acid in stomach
Blood Clotting and Wound repair
platelets come into contact with collagen in skin or wall of damaged blood vessels and secrete substance such as thromboplastin this triggers cascade of reactions resulting in formation of a blood clot and sterotonin which makes the smooth muscle in cell walls of blood vessels contract so they narrow and reduce blood supply
clot dries and forms a scab
what is the inflammatory response
HISTAMINES AND CYTOKINES
what do histamines do
they make the blood vessels dilate causing heat to increase preventing pathogens reproducing
what do cytokines do
they attract wbc and dispose of pathogens via phagocytosis
what is the function of phagocytes
to engulf and destroy patogens
what are the two types of phagocytes
macrophages and neutrophils
what is the stages of phagocytosis
1) pathogens produce chemicals which attract pathogens
2)phagocytes recognise non human protein on pathogen which is a response to foreign pathogen
3) phagocyte engulfs pathogen and encloses in a vacuole known as the phagosome
4)phagosome and lysosome combine to form phagolysosome
5) enzymes from the lysosome digest and destroy pathogen
what takes longer macrophage or neutrophil
macrophage
what occurs when a macrophage digests a pathogen
it combines antigens from pathogen surface membrane with glycoproteins in the MHC
MHC complex moves the pathogen antigens to the macrophages own surface membrane becoming an APC
APC antigens stimulate other cells
what do cytokines do
cell signalling molecules
increase body temp
stimulate specific immune system
what do opsonins do
chemicals which bind to pathogens and tag them so that they can be more easily recognised by pathogens
what is the specific immune response system based on
T lymphocytes and B lymphocytes
where do T lymphocytes mature
Thymus Gland
where do B Lymphocytes mature
Bone Marrow
what are the 4 main T lympohocytes
1) T killer
1) T memory
3) T regulatory
4) T helper
what do T helper cells do
they produce interleukins which stimulates activity of B cells this increases antibody production and stimulates production of other T cells
what do T killer cells do
they produce perforin which kills pathogen by making holes in cell membrane so it is freely permeable
what do T regulatory cells do
supress the immune system
make sure that the body recognises self antigens and does not set up an autoimmune response
what does T memory cells do
they are apport of the immunological memory, if they meet an antigen again they divide rapidly forming a huge number of clones of the T killer cells and destroy the pathogen
when are B cells activated
when cytokines are released from T helper cells
when antibody molecules on their cell surface binds to a complementary antigen
what are the main types of B lymphocytes
plasma cells, B effector cells, B memory cells
what are plasma cells
produce antibodies which complementary shape to antigen
What are b effector cells
divide to form plasma cell clones
what are B memory cells
immunological memory
cell mediated immunity
Humoural immunity
what is an auto immunine disease
it is a disease which occurs when a persons immune system fails to distinguish self antigens from forein antigens and begins to attack normal body cells eg type 1 diabetes, lupus
what is the structure of antibodies
it is a glycoprotein which can bind to a specific antigen on patjpgrn or toxin which has triggered the immune response
it is made up of 2 poly peptide chains which are joined by disulfidr briges.
how do antibodies defend the body
1) antigen-antibody complex acts as opsonin so the complex is engulfed and digested
2) pathogens cant invade any host cells
3) antiobodies act as agglutinins causing pathogens carrying antigen-antibody complexes to clumo oreventing spread easier for phagocytres to engulf
