Mod 4 Chap 12: Communicable Diseases Flashcards Preview

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Flashcards in Mod 4 Chap 12: Communicable Diseases Deck (52)
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Define Health.

A state of complete mental, social and physical well being and not merely the absence of disease or infirmity.


Define disease.

Anything that impairs the body.
E.g. Mental health diseases / infectious diseases / genetic diseases / lifestyle diseases.


How are infectious diseases caused?

By pathogens and parasites
Pathogen: microorganism that causes disease
Parasite: organism that lives in or on a host and causes it harm


Name the four categories / types of pathogens.🌟



Describe bacteria as a pathogen.🌟

- are prokaryotes
- no membrane bound nucleus / organelles

Classified by either:
- their basic shapes: either rod shaped, spherical, comma shaped, spiralled, or corkscrew
- their cell walls: the two types of bacterial cell walls have diff structures + react differently to Gram Staining (gram +ve bacteria = purple-blue, gram -ve bacteria = red). = useful as type of cell wall affects how bacteria react to diff Antibiotics

- tuberculosis
- bacterial meningitis
- ring rot (in potatoes / tomatoes)


Describe viruses as a pathogen.🌟

- non living infectious antigens
- have some genetic material (DNA / RNA) surrounded by protein
- invade living cells, where they take over biochemistry of host cell to make more viruses
- successful pathogens as evolve by adapting to host
- viruses that attack bacteria = bacteriophages

- HIV / AIDS (in humans)
- tobacco mosaic virus (in plants)
- influenza (in animals)


Describe Protoctista as pathogens.🌟

- eukaryotic organisms
- small percentage of them act as pathogens
- those that cause disease = parasitic
- use ppl / animals as their host organism
- pathogenic protests may need vector to transfer them to hosts (e.g. Malaria), or may enter body directly through polluted water

- malaria
- potato / tomato late blight


Describe fungi as pathogens.🌟

- fungal diseases more problematic in plants
- eukaryotic organisms, often multicellular
- digest food extracellularly
- many are saprophytes (feed on dead decaying matter)
- some are parasitic (feed on living plants + animals)
- parasitic are ones that cause communicable diseases

- black Sigatoka (in bananas)
- ring worm (in cattle)
- athletes foot (in humans)


Describe how pathogens damage host tissues directly.🌟

- viruses take over cell metabolism
- some Protoctista take over cells + break them open as the new generation emerge
- fungi digest living cells + destroy them


Describe how pathogens produce toxins which damage host tissues.🌟

- most bacteria produce toxins to poison / damage host cells, causing disease
- some damage host cells by breaking down cell membranes
- some by inactivating enzymes
- some by interfering w/ host cells genetic material so it cannot divide
- these toxins are a by p-product of the normal functioning bacteria
- some produce toxins, affecting host cell + causing disease


Describe direct transmission of pathogens between animals. 🌟

Pathogen is transferred directly from one individual to another by:
- direct contact (for contagious diseases): e.g. exchange of bodily fluids, skin-to-skin contact, microorganisms from faeces transmitted on the hands
- inoculation: through a break in skin, from an animal bite, through a puncture wound or sharing needles
- ingestion: taking in contaminated food, or transferring pathogens from hands to mouth


Describe indirect transmission of pathogens between animals. 🌟

Pathogen travels from one individual to another indirectly by:
- fomites: inaminate objects e.g. bedding can transfer pathogens
- droplet infection: when healthy individuals breath in minute droplets expelled from mouth of saliva / mucus with pathogens in
- vectors: transmits communicable pathogens from one host to another, are often animals


Describe the factors affecting the transmission of communicable diseases in animals. 🌟

Probability of catch disease increased by:
- overcrowded living + working conditions
- poor nutrition
- poor disposal of waste
- climate change
- socioeconomic factors


Describe direct transmission of pathogens between plants.🌟

- involves direct contact of a healthy plant w/ any part of a diseased plant
E.g. Ring rot


Describe indirect transmission of pathogens between plants. 🌟

- soil contamination: pathogens in soil from infected plants can infect next crops
- vectors: wind, water, animals, humans


Describe the factors affecting the transmission of communicable diseases in plants.

Factors responsible:
- planting varieties of crops susceptible to disease
- overcrowding, increasing likelihood of contact
- poor mineral nutrition, reducing plant resistance
- climate change


Name plant the methods plants have for defence against pathogens. 🌟

Physical defences
Chemical defences
Also Active defences


Describe plants' physical defences against pathogens. 🌟

- High levels of the polysaccharide callose produced
- callose quickly synthesised + deposited between cell walls + cell membrane in cells next to infected cells
- callose papillae act as barriers to prevent pathogens entering plant cells around
- lignin added to make mechanical barrier to invasion thicker + stronger
- callose blocks sieve plates in phloem, sealing off infected part + preventing spread of pathogens
- callose seals off infected cells from healthy cells in plasmodesmata between them, to prevent pathogen spread


Describe plants' chemical defences against pathogens. 🌟

- Many produce chemicals to repeal insect vectors of disease / kill invading pathogens
- some so powerful we use / synthesise them to help control insects, fungi + bacteria
- insect repellents
- insecticides
- antibacterial compounds e.g. antibiotics, like phenols (antiseptics)
- antifungal compounds e.g. chitinases (enzymes that break down chitin in cell walls)
- general toxins e.g. cyanide


Describe plants' active defences against pathogens, when recognising an attack.

- plants respond rapidly to attach (so not passive)
- cell receptors respond to molecules from pathogens produced when plant is attacked
- stimulates release of signalling molecules to switch on genes in nucleus
- then triggers cellular responses e.g. producing defensive chemicals sending alarm signals to unaffected cells to trigger their defences, + physically strengthening cell walls


Describe the non specific barrier defences against pathogens in animals. 🌟

- the skin: covers body + prevents entry of pathogens, has a skin flora of healthy microorganisms that outcompete pathogens for space on body surface, produces sebum (oily substance to inhibit pathogen growth)
- many of the body tracts = lined by mucous membranes = secrete sticky mucus = traps microorganisms + contains lysosomes (to destroy bacterial + fungal cell walls) + phagocytes (to remove remaining pathogens)
- lysosomes in tears + urine, + acid in stomach, prevent entry of pathogens


Describe the non specific expulsive reflex defences against pathogens in animals. 🌟

- coughs + sneezes eject pathogen-laden mucus from gas exchange system
- vomiting + diarrhoea expel contents of gut w/ any infective pathogens


Describe blood clotting and wound repair as a non specific defence against pathogens in animals. 🌟

When platelets come into contact w/ collagen in skin or the wall of the damaged blood vessel, they secrete substances e.g:

- thromboplastin: enzyme triggering cascade of reactions to form a blood clot
- serotonin: makes smooth muscle in walls of blood vessel contract, so narrow, reducing supply of blood to area


Describe the cascade of reactions that form a blood clot.🌟

Damaged tissue
= platelets activated
= platelets release thromboplastin
= thromboplastin catalyses reaction of / combines w/ prothrombin + Calcium
= makes thrombin
= thrombin catalyses / reacts w/ fibrinogen to produce fibrin
= fibrin forms blood clot


Describe the inflammatory response as a non specific defence against pathogens in animals. 🌟

- is a localised response to pathogens resulting in inflammation at site of a wound
- main symptoms of inflammation: pain, heat, redness, + swelling
- mast cells activated in damage tissue + release histamine + cytosine chemicals

- make blood vessels dilate, causing localised heat + redness, raised temp helps prevent pathogens reproducing
- make blood vessels walls more leaky so blood plasma forced out, to become tissue fluid, which causes swelling (oedema) + pain

- attract white blood cells (phagocytes) to site, dispose of pathogens by phagocytosis


Describe the structure and mode of action of phagocytes (eventually for phagocytosis) as a non specific defence against pathogens in animals.🌟

- phagocytes = specialised white cells that engulf + destroy pathogens
- two main types: neutrophils + macrophages
- they build up at site of infection + attack pathogens


Describe the process of phagocytosis FOR NEUTROPHILS as a non specific defence against pathogens in animals. 🌟

- pathogens produce chemicals that attract phagocytes
- phagocytes recognise non human proteins on pathogen (a response to a cell or organism that is non self)
- phagocyte engulfs pathogen + encloses it in a vacuole called a phagosome
- phagosome combines w/ a lysosome to form phagolysosome
- enzymes from lysosome digest + destroy pathogen
- digested pathogen absorbed by phagocyte-antigens combine w/ MHC in cytoplasm
- MHC / antigen complex = displayed on phagocyte membrane, making an antigen presenting cell


Describe the MHC and its role in the more complex process of phagocytosis FOR MACROPHAGES. 🌟

= Major Histocompatibility Complex (MHC)
- when a macrophage digests a pathogen, it combines antigens from pathogen surface membrane w/ special glycoproteins in cytoplasm called MHC
- MHC moves pathogen antigens to macrophage's own surface membrane, becoming an antigen presenting cell


Describe the helpful chemicals of cytokines and opsonins that phagocytes produce. 🌟

Cytokines: act as cell signalling molecules, informing other phagocytes that body is under attack, to stimulate them to move to site of infection. Can also increase body temp + stimulate specific immune system.

Opsonins: chemicals that bind to pathogens + 'tag' them so more readily recognisable by phagocytes.


Describe antibodies in the specific immune response system.🌟

- Y shaped glycoproteins called immunoglobulins
- specific to a particular antigen
- made of two pairs of polypeptide chains (2 long and heavy, H chains (1 pair), + 2 short and light, L chains (second pair))
- held together by disulphides bridges
- know diagram of it containing: variable region, hinge region + constant region
- when an Antigen binds to an antibody, it forms an antigen-antibody complex