diseases and immunity Flashcards
what is a pathogen
a disease-causing organism.
what is a transmissible disease
a disease in which the pathogen can be passed from one host to another.
how are pathogens for transmissible diseases transmitted
Direct contact e.g. through blood, body fluids
Indirectly e.g. from contaminated surfaces/food, from animals, from air
what are the mechanical barriers against pathogens
Nostrils contain hairs that help trap dust
Skin has a thick outer layer of dead cells
what are the chemical barriers against pathogens
Sticky mucus which can trap pathogens
In the stomach, hydrochloric acid is secreted which kills many of the bacteria in food
how do white blood cells stop pathogens
Phagocytes: these cells take in and digest the pathogens by phagocytosis
Lymphocytes: produce antibodies that incapacitate or kill the pathogen
purpose of vaccination
Vaccines immunise children against diseases caused by pathogens. Vaccination against disease helps antibodies to produce very quickly
how do antibodies work
An antibody is a protein molecule which fits into another molecule
Pathogen molecules are called antigens.
To destroy a pathogen, antibody molecules must be made which are exactly the right shape to fit into molecules (antigens) on the outside of the pathogen.
Antibodies lock onto antigens leading to destruction of pathogen / marking of pathogens for destruction by phagocytes
If a pathogen enters the body, it meets a large number of lymphocytes. One of these will recognize the pathogen and divide rapidly by mitosis
These lymphocytes then secrete antibody, destroying the pathogens
what is active immunity
defence against a pathogen by antibody production in the body.
how is active immunity gained
Active immunity is gained after an infection by a pathogen or by vaccination.
process of vaccination
Harmless pathogen given which has antigens
Antigens trigger an immune response by lymphocytes which produce antibodies
Memory cells are produced that give long-term immunity
ways to control spread of disease
In controlling the spread of disease, it is important to consider hygienic food preparation, good personal hygiene, waste disposal and sewage treatment
what is passive immunity
short-term defence against a pathogen by antibodies acquired from another individual, e.g. mother to infant
Memory cells are not produced in passive immunity
passive immunity in infants
Babies get passive immunity by breast feeding.
Breast milk contains antibodies from the mother which are passed on to her baby.
Useful because a young baby’s immune system is not well developed and so the mother’s antibodies can protect it against any diseases to which she is immune for the first few months of its life
which diseases target the immune system
Some diseases are caused by the immune system targeting and destroying body cells (Type 1 diabetes)
