infection and response

• pathogens are microorganisms that cause communicable diseases. pathogens are:

  • bacteria
  • viruses
  • protists
  • fungi
• communicable diseases are spread between organisms in different ways:

  • air - some pathogens can be found in droplets of coughs and sneezes e.g. ifluenza
  • water - some pathogens found in dirty water and picked up from drinking or bathing in it e.g. cholera
  • direct contact - pathogens can be picked up by touching contaminated surfaces or skin e.g. athelete's foot
  • vectors - pathogens can be transferred be vectors e.g. mosquitos
• to prevent diseases, you can :

  • keep good hygiene e.g. cathing sneezes and coughs in a tissue, washing hands regulary
  • isolate the individual with the disease
  • kill vectors and destroy their habitats to prevent them from breeding
  • get vaccines
• VIRAL DISEASES

  MEASLES

  • spread through the air
  • symptoms: red skin rash, fever, pneumonia
  • no proper treatment, but can get vaccinated at an early age

  HIV

  • spread through sexual contact, sharing needes, mother to baby
  • can be treated through antiretroviral drugs

  TMV (TOBACCO MOSAIC VIRUS)

  • plant virus which affects many different speces
  • distinct mosain pattern on leaves, discolouration limits photosynthesis and stunts growth
• BACTERIAL DISEASES

  SALMONELLA

  • bacteria that causes food poisoning by releasing toxins
  • symptoms: fever, cramps, vomiting, diarrhea
  • poulty are vaccinated

  GONORRHEA

  • spread by sexual contant
  • symptoms: thick yellow/green discharge, pain while urination
  • used to be treated with antibiotic penicillin, but strains of bacteria becomes resistant. now prevented using antibiotics and barrier methods
• FUNGAL DISEASES

  ROSE BLACK SPOTS

  • affects rose plants, spread in water and air
  • black/purple spots are visible, causing leaf to turn yellow and drop off leaf, limits photosynthsis and stunts growth
  • fungicids to treat plant

  PROTIST DISEASES

  MALARIA

  • transported between animals/humans by mosquitos
  • symptoms: repeating fever episode (can be fatal)
  • prevented by stopping mosquitos from breeding, mosquito nets, insecticides
• herd immunity

  • if enough of the population are vaccinated, the spread of disease can be reduced
• vaccines

  • dead or weak forms of the pathogen, including antigens
  • as pathogen is weakened, it will get easily destroyed
• antibiotics vs painkillers

  • painkillers (e.g. paracetemol) are used to treat symptoms like headaches and sore throats
  • antibiotics (e.g. penicillin) slow or stop the growth of harmful/infectious bacteria
  • they only work on bacteria and do not kill viruses
  • have been incredibly successful, but they have been overused to some strains have become resistant to the antibiotics
• DEVELOPING DRUGS

  Preclinical testing

  • before being given to patients, the drugs must be thoroughly tested to make sure its safe
  • then it will get peer reviwed to check the accuracy
  • to check for efficiency,drug is tested using computer models
  • for side effects, drug is given to animals
• DEVELPING DRUGS

  Clinical testing

  • after passing preclinical testing, drugs can be tested on humans
  • healthy people are tested with low dosages to ensure safety, and are gradually increased to determine the right dosage
  • to determine if it actually works, the double blind test is used (placebo test)
• double blind test

  • patients split into two groups
  • one is given the drug, and the other is given a placebo
  • the effects of the treatment are then observed
  • neither the patients or doctors know which group has the drug to avoid bias
• non-specific defences

  • they defend the body against all pathogens by preventing them to enter the body
• Skin

  • Acts as a physical barrier
  • If skin is broken (wounded), platelets gather at wound and a scab forms to maintain physical barrier
• Nose

  • acts as a physical barrier
  • Has hairs and mucus to trap any pathogens
  • They are removed when the person sneezes or blows nose
• Trachea and bronchi

  • Goblet cells produce mucus to trap pathogens
  • Lined with ciliated cells that have tiny hairs called cilia
  • Cilia wafts mucus and pathogens up to the throat, to be swallowed and sent to stomach
• Stomach

  • Contains hydrochloric acid (chemical barrier)
  • Pathogens enter in food or mucus and get killed by the acid
• Examples of non-specific defences

  • Skin
  • Nose
  • Trachea and bronchi
  • Stomach
• the immune syteme detects and kills pathogens that made it past the non-specific defences

  phahocytes and lymphocytes are types of white blood cells, responsible for immune response
• phagocytes

  • the non-specific process where phagocytes engulf and digest pathogens, sometimes aided by lymphocytes
  • lymphocytes produce antibodies that cause pathogens to clump together so they are easier to engulf

  A) phagocyte

  B) antibodies cause clumping of pathogens

  C) pathogens digested

  
• lymphocytes

  • memory cells are lymphocytes that remain in the blood after infection. if the person is infected with same pathogen in the future, memory cells quickly produce antibodies to destroy pathogen

  A) lymphocyte recognises pathogens by its antigens

  B) lymphocyte produces antibodies with specific shapes

  C) antibodies bind to pathogen and clumps