B2 - Keeping Healthy

microorganisms & disease
1. Symptoms - effect an infection has on the body. Different micro-organisms cause different symptoms, but all damage bodies cells.
2. some micro-organisms damage cells directly (malaria)
3. infectious microorganism produce toxins that damage cells
  1. some bacteria produce proteins that damage material holding cells together - helps bacteria invade deeper
  2. others produce toxins that poison cells - causing fever/inflmmation
4. microorganisms reproduce quickly
  1. bacteria reproduce by making copies of themselves - need source of nutrients for energy & warm/moist conditions for chemical reactions
    1. conditions found in human body - easy to reproduce
  2. viruses need other cells to reproduce - use parts of other cells to make copies
    1. certain viruses - reproduce easily in human body (lots of right cells)
  3. calculate growth of microorganism population
The Immune system
1. role - deal with infection micro-organisms that enter the body.
2. immune response always involves white blood cells
  1. white blood cells detect things that are 'foreign' to body
    1. they then engulf the microbes & digest them
      1. these white blood cells are non-specific
3. antibodies recognise foreign microorganisms
  1. these white blood cells have receptors that recognise antigens
    1. antigens - substances that trigger immune responses
      1. usually protein molecules on surface of micro-organism cell
  2. antibodies are proteins specific to a particular antigen - different microorganisms have different antigens
  3. antibodies latch onto invading organisms and do 1 of 3 things
    1. 1. mark microorganism so other white blood cells engulf & digest it
    2. 2. bind to an neutralise viruses or toxins
    3. 3. some attach to bacteria & kill them directly
  4. once white blood cell recognises antigens on micro-organism - it divides to make more identical cells (makes more of right antibody)
    1. white blood cells stay in blood after original infection = memory cells
      1. can reproduce quickly if same antigens enter body again
        then produces antibodies & kill of microorganism before you become ill = immunity
vaccination
1. 1.immunisation involves injecting dead/inactive micro-organisms
  1. 2. carry same antigens, so body produces antibodies - even thought micro-organism is harmless
    1. 3.body produces memory cells - recognise antigens & stays in the blood
      1. 4.if live microorganisms of same type appear again, memory cells rapidly mass produce antibodies to kill them off
        5.means you can get rid of disease-causing microorganism before getting sick
2. epidemics prevented - by vaccinating large percentage of population
  1. if significant number not vaccinated, disease can spread quickly
  2. fewer people to pass on to if vaccinated
3. can never be completely safe for everyone - can have side effects
  1. genetic differences also mean people react differently to drugs/vaccines
Antimicrobials
1. chemicals that inhibit growth of microorganisms/kill them without damaging own body cells
2. useful for clearing up infection that immune system can't
3. antibiotics are a type of antimicrobial that kill bacteria
  1. don't kill viruses
4. microorganisms can evolve & become resistant to antimicrobials
  1. develop random mutations in DNA
    1. can lead to changes in microorganisms characteristics - less affected by antimicrobial
      1. gives microorganism advantage - better able to survive & reproduce
        leads to gene for resistance being passed on to offspring (natural selection) - becomes more common
  2. the more often antibiotics are used, the bigger the problem of antibiotic resistance becomes
    1. antibiotics create situation where resistant bacteria have an advantage and so increase in numbers
    2. important to finish antibiotic course - stopping taking them can increase risk of antibiotic resistant bacteria emerging

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B2 - Keeping Healthy

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	Created by Meg Galligan about 11 years ago