Revision
Slides do conjunto (8)
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- • Anything that threatens or compromises the health of an individual
- • Living or non-living
- • Infectious or non-infectious
- • Causes of non-infectious diseases:
- - Malfunctioning of body structure
- - Environmental
- - Nutritional
- • Infectious diseases are caused by pathogens
- • A pathogen is an agent that causes a disease
- • A parasite is a pathogen that obtains nutrients from its host cell
- - Ectoparasite lives on outside
- - Endoparasite lives on inside
- • Primary host is when they grow and reproduce in the host organism
- • Secondary host is a temporary host for the pathogen
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- • 6 types: Bacteria, virus, prions, fungi, protist, and parasite
- Prions:
- • Abnormally shaped proteins which causes other proteins to become abnormally shaped.
- • Causes plaque to build up in the brain of the host organism, causing the brain to form a spongy structure resulting in large holes.
- Virus:
- • Non-living
- • Made of nucleic acid core and covered by protein shell
- • Enter host body, attach to cell, insert DNA/RNA into it
- • Host then makes new copies and cell breaks open infecting other cells.
- Bacteria:
- • Made of DNA encased by cell wall made of murein.
- • Identified by their shape.
- Protozoa:
- • Animal-like
- • Come in a variety of shapes/sizes
- Macroparasites:
- • Large parasites
- • Live in intestines, liver and bile ducts
- • Flatworms or roundworms
- Fungi
- • Small fibres called hyphae can enter a host and take root in a dark, warm environment
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- Virulence is the ability of a pathogen to cause disease
- Invasion factors are proteins that allows pathogens to enter cells
- Colonisation factors are proteins that allow the pathogen to live and multiply within the host’s environment.
- Endotoxins: are bound to the outer membrane of the pathogen and when the pathogen is damaged or destroyed, the toxin causes an inflammatory response in the host.
- Exotoxins: are toxins secreted by the pathogen. They are usually specifically named to address the system they impact: eg. Neurotoxins.
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- It can be measured by how many individuals affected, how quickly it spreads, and how many people die from contracting it
- Virulent factors are molecules that aid the survival of the pathogen
- Factors include:
- Adhesion, Colonisation factors, Invasion factors, toxins, Immune response blockers
- Pathogens need to stick to a host to infect it
- Many pathogens produce small surface glycoproteins called adhesins which attach to receptors on the membranes of the cells they wish to infect.
- Some pathogens have specific structures and some have generalised ones
- Some pathogens produce different proteins at different stages of their life cycle to help them colonise
- Many pathogens need to enter a cell to survive
- Viruses produce proteins which disrupt host cell membrane or stimulate endocytosis so that the cell actually welcomes the virus into it.
- Toxins are proteins that poison host cells and cause tissue damage. A large number of bacteria and fungi produce toxins. They do this to feed on the damaged tissue.
- Some bacteria and fungi have a capsule that blocks or switches off the host’s immune system.
- Others can create a layer of slime which protects them from being detected by the immune system. This enables large numbers of them to congregate in certain areas.
- Some bacteria and viruses produce super-antigens that bypass the host’s immune system but may cause an increase in the non-specific immune response- meaning the inflammatory response is likely to occur.
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- Innate Immune System:
- Present in all organisms
- Born with it
- Physical Barriers - skin, mucous membranes, tears)
- Also the presence of blood cells which identify and fight off foreign particles
- First Line of Defence:
- Physical and chemical barriers to stop pathogens entering the body
- Skin makes up most of the FLOD - sweat and oil makes it hard for pathogens to colonise
- Mucous membranes line the openings of the body - (throat, lungs... etc) - sticky to catch pathogens and cough them back up
- Skin, mucous membranes, Cilia, urinary and vaginal tracts, Alimentary canal, tears, urine.
- Second Line of Defence (SLOD):
- Inflammatory response and white blood cells (WBC)
- If the pathogen passes the first line of defence it meets the internal structures the body uses to fight off disease
- Include WBC and MHC proteins (major histocompatibility complexes)
- MHC - Type One
- Specialised proteins that every cell has
- Unique to every organism
- Determines which cells belong in the body
- If the cell does not have the correct MHC, it is marked by the immune system for destruction.
- This is how pathogens are detected
- The Complement System
- Made up 20 proteins, formed in the liver
- Activated by one of three pathways (Classical Pathway, MB Lectin pathways and Alternative pathway)
- Classical Pathway - recruitment of inflammatory cells
- MB-Lectin Pathway - Opsonisation of pathogens
- Alternative Pathway - Killing of pathogens
- Once activated they recruit inflammatory cells, signal phagocytes to consume pathogens, or break down a cell wall to connect it
