Disease and Immunity

• A pathogen is a microorganism that can cause disease
• Bacteria release toxins into the body, making people ill
• Viruses enter your cells and reproduce inside them, hundreds and thousands at a time, eventually causing the cell host to explode.

  The virus can then pass through the airways / bloodstream, and can spread to the rest of the population.
• • Bacteria
  • Viruses
  • Fungi
  • Protists
• Protists ─ single celled organisms.

  They live in, or on, other organisms, causing harm.

  (i.e.─ malaria)
• Pathogens can be spread by

  • direct contact
  • water
  • air
  • bodily fluids
  • other organisms (i.e.: mosquitos)
• Preventing disease:

  • hygiene
  • sanitation
  • vaccinations
  • isolation / quarantine
• viruses are not living
• measles (virus) causes:

  • red rash
  • fever
  • spread by sneezing/coughing
  • can be fatal
  • vaccination
• HIV (virus)

  • spread by sexual contact ─ exchanging bodily fluids
  • human immunodeficiency virus
  • flu-like symptoms for the first few weeks
  • fever
  • tiredness
  • aches
  • (then feel better, but the immune system is actually extremely weak)
  • can get unusual infections or cancer
  • results in AIDS
  • antiretroviral drugs
• TMV (tabacco mosaic virus)

  • affects plants
  • discolors patches on leaves
  • photosynthesis cannot take place in these patches
• bacteria :

  • single-celled organisms
  • can reproduce by themselves, but often reproduce rapidly within our own bodies due to good food supply
  • produce toxins - making us feel ill by damaging our cells / tissues
• salmonella (bacteria - food poisoning):

  • chicken
  • fever
  • stomach cramps
  • vomiting
  • diarrhea
  • affects intestines
  • passes by itself in a week
• gonorrhea (bacteria - STD)

  • sexual contact : unprotected sex
  • pain when urinating
  • thick yellow / green discharge from an infected persons genitals

  (ew☹)
• Fungi - eukaryotic organisms (can be unicellular or multicellular)
• multicellular fungi have hyphae
• Hyphae can :

  • penetrate human skin
  • produce spores
• Rose Black Spot (fungal disease)

  • reduces plants ability to photosynthesis
  • leaves drop off
  • don't grow so well
  • transported by water, or wind
  • treatment : chop off all infected leaves
  • treatment : spray with fungicide
• Protists are Eukaryotes (most are unicellular)
• Most Protists are Parasites
• Protists are transported by Vectors (other organisms)
• Malaria

  • fever
  • headaches
  • recurring symptoms
  • can be fatal
• Physical and Chemical Barriers :

  • secretes oils and antimicrobial substances : kills pathogens
  • our noses have hairs and mucus to trap pathogens
  • trachea, bronchi and bronchioles are covered in a layer of mucus and cilia
• Hydrochloric acid in stomach kills pathogens
• Immune system:

  • white blood cells: phagocytosis, anti-toxins and antibodies
  • by phagocytosis, certain white blood cells track the pathogens down, bind to them, engulf them and destroy them.
  • anti-toxins : small molecules that bind and counteract toxins
  • antibodies : small proteins that are made by the white blood cells that can lock onto the antigens, send signals to white blood cells so they can come and destroy them.
• antibodies :

  • lock onto antigens, creating a signal to white blood cells so they can come and destroy them
  • antibodies are specific to different antigens
• white blood cells produce antibodies and antitoxins
• phagocytosis :

  • white blood cells can ingest and destroy pathogens
  • the white blood cell detects chemicals released from a pathogen and moves towards it
  • the white blood cell ingests the pathogens
  • white blood cell uses enzymes to destroy the pathogens
• antibodies:

  • protein molecules produced by white blood cells
  • antibodies stick to pathogens
  • antibodies are specific to certain antigens. it does not protect the body against other pathogens
• Pros of Vaccines :

  • protection from diseases
  • control common diseases
  • prevent outbreaks of disease
  • herd immunity
• Cons of Vaccines :

  • don't always work
  • bad reactions - fevers, seizures, swelling
• Inside a vaccine are the pathogens we want to be immune to. They have been weakened - are not strong enough to cause us any disease.

  Body produces antibodies for these antigens : developing immunity
• Vaccines can work against bacteria and viruses
• Drugs that relieve symptoms :

  • aspirin
  • paracetamol
  • cough medicine
• Drugs that treat the disease:

  • antibiotics : directly kill the pathogens causing harm or prevent the growth of any new bacteria
• Antibiotics cannot treat viruses
• Antibiotics don't work on viruses because :

  • antibiotics are made specifically to treat bacteria, and as viruses are so different, antibiotics cannot do anything to them.
  • antibiotics would not be able to find viruses even IF they COULD kill them, as they hide within the body's own cells, which makes it near impossible to destroy them without destroying our own cells as well.
• each antibiotic can only kill certain types of bacteria