The more you know…. Diseases Diseases can disrupt homeostasis (balance) Diseases can have many...
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Transcript of The more you know…. Diseases Diseases can disrupt homeostasis (balance) Diseases can have many...
The more you know…
Diseases
Diseases can disrupt homeostasis (balance) Diseases can have many causes:
Ex.: genetic, congenital (embryonic development), environmental, emotional/psychological, etc.
Infectious diseases are caused by pathogens and may be transmitted (contagious/communicable)
Pathogens = germs and other disease-causing agents: Ex.: Bacteria, viruses, parasites (protists, worms), prions
Germ Theory of Disease (1800s) States that some
microorganisms cause diseases
Important contributors: Louis Pasteur – first to grow
microbes from air in nutrient solution; vaccination (rabies, others); pasteurization (sterilization of milk, etc.)
Robert Koch – created the steps to prove that a microbe causes a disease (Koch’s postulates)
Koch’s Postulates – R. Koch demonstrated that anthrax bacteria cause disease in cattle and developed these rules:
Pathogens
How do pathogens cause disease?Disrupting the normal functioning of
the host’s cells:
Producing toxins (poisons) Destroying cells and tissues “Stealing” resources from body cells
How do contagious (communicable) diseases spread? indirect contact w/ infected person
- air, objects, substances direct contact w/ infected person
(touch) Water and food (contaminated) Animal bites – animal is the vector
*Many diseases spread through body fluids*
Disease Transmission
Vectors
Indirect contact through air
Indirect contact by objects
Direct contact
Disease Transmission Terms Epidemiology – study of how diseases spread in a population Outbreak – an unusual number of cases of a disease Endemic – a disease that always exists in a given area
Ex.: malaria in tropical Africa, common cold in U.S. Epidemic - a relatively large and increasing number of cases of a
diseaseEx.: Type II diabetes, obesity in the U.S., TB in Russia
Pandemic – an epidemic that has spread worldwideEx.: AIDS, influenza in 1918 (killed 50 million!)
Vector – animal, usually insect, that transmits an infectious diseaseEx.: mosquito that transmits malaria or yellow fever
Reservoir – animal, human, inanimate (water, soil) that serves as a source of pathogens
How small is a germ?Size Comparison:Pathogens & Human Cells
http://www.cellsalive.com/howbig.htm
http://www.unitedstreaming.com/index.cfm?media_file_id=1000667