Communicable Diseases Flashcards
what’s a communicable disease?
caused by infective organisms known as pathogens - bacteria , viruses, fungi, proctista.
how are communicable diseases passed on?
vectors- carry pathogens from one organism to another
types of pathogen?bacteria?
prokaryotes - don’t have a membrane bound nucleus or organelles.
rod shaped , or spherical, comma etc.
two types of cell walls which react differently through gram staining
viruses?
non living infectious agents. 0.2 nanometres.
DNA or RNA surrounded by protein.
viruses invade living cells, take over the host to generate more viruses.
proctista?
eukaryotic organisms with a variety of feeding methods.
include both single celled and cells grouped into colonies.
proctista that cause disease are parasites.
need a vectorm
fungi?
cause devastation in plants.
eukaryotic organisms - often multicellular although yeast is single celled and affects humans.
can’t photosynthesise and digest food extra cellularly .
many are saphropytes, feed in dead and decaying matter.
some are parasitic.
pathogens - modes of action?
viruses take over cell metabolism. gets Into host cell and uses it to make more viruses, then burst and continue.
proctista - take over cells and break them open as the new generation emerge, they digest and use cell contents as they reproduce.
fungi digest living cells and destroy them
direct transmission?
direct contact
inoculation - break in the skin
ingestion
indirect transmission?
- fomites - inanimate objects such as socks.
- droplet infection - as you talk or sneeze , droplets are breathed in by another and infect.
- vectors, one host to another
factors affecting disease in animals?
increase if : overcrowded living/ working condition poor nutrition poor immune system - HIV climate change
How plants spread disease?
indirect transmission:
soil contamination - reproductive spores from protoctisa and fungi.
vectors - wind, spores carried by the wind
water
animals
humans
factors affecting disease in plants?
overcrowding
poor mineral nutrition reduces resistance of plants.
damp, warm conditions increase the survival and spread of pathogens and spores
defense against pathogens?plants?
plants aren’t passive.
receptors respond to molecules from the pathogen.
stimulates release of signalling molecules that switch on genes in the nucleus. triggers a response such as defensive chemicals or strengthening the cell wall
physical plant defenses?
produce a high level of callose(polysaccharides)
- immediately callose is synthesised and deposited between the Cell wall and cell membrane next to infected cells acting as barriers
chemical plant defenses?
powerful chemicals that repel the insect vectors of a disease or kill invading pathogens.
insect repellent
insecticides
general toxins - break down to form cyanide
non specific animal defences?
skin,
mucus
lysosomes in tears and urine, stomach acid
how does blood clotting occur?
thromboplastin - an enzyme that triggers a cascade of reaction resulting in the formation of a blood clot.
serotonin , makes smooth muscle in the walls of the blood vessels contract so they narrow and reduce the supply of blood to the area.
-seals wound, forms a hard scab , keeps pathogens out
inflammatory response?
localised response.
-mast cells are activated in damaged tissue, release chemicals called histamines and cytokines.
histamines dilate blood vessels.raising temp , preventing pathogen reproducing.
cytokines attract white blood cells(phagocytes) to this site
getting rid of pathogens? phagocytosis?
- pathogens produce chemicals to attract phagocytes.
- phagocytes recognise non human proteins on the pathogens.
- phagocyte engulfs the pathogen and enclosed it in a vacuole called a phagosomes.
- phagolysosome formed of phagosome and lysosome.
- enzyme from lysosome digest and destroy the pathogen
bacterial disease in plants?
ring rot
fungi in plants?
black sigatoka
proctista in plants?
potato blight
bacteria in animals
tuberculosis
virus in humans?
HIV
