Diseases and immunity flashcards

10.1 Diseases and immunity

Pathogen and transmissible disease

Pathogen: a disease-causing organism. Transmissible disease: one in which the pathogen can be passed from one host to another.

Direct vs indirect transmission

Direct: contact with blood or other body fluids. Indirect: contaminated surfaces, food, animals or air.

Mucus (body defence)

Traps pathogens in the airways.

Stomach acid (body defence)

Kills pathogens in food and drink.

Five ways to control the spread of disease

Clean water supply, hygienic food preparation, good personal hygiene, waste disposal, sewage treatment.

Antigen and antibodyExtended

Antigen: a molecule on a pathogen with a specific shape. Antibody: a protein made by lymphocytes with a shape complementary to a specific antigen; it binds to it.

Active immunity: definition and how it is gainedExtended

Defence against a pathogen by antibody production in the body. Gained after infection by the pathogen or by vaccination. Memory cells give long-term immunity.

How vaccination worksExtended

Weakened pathogens or their antigens are put into the body. The antigens stimulate lymphocytes to produce antibodies, and memory cells are made, giving long-term immunity. (Vaccines do not contain antibodies.)

Passive immunityExtended

Short-term defence by antibodies acquired from another individual, e.g. across the placenta or in breast milk. No memory cells are made, so it does not last.

How cholera causes dehydrationExtended

The bacterium produces a toxin that causes chloride ions to be secreted into the small intestine. Water moves into the gut by osmosis, causing diarrhoea, dehydration and loss of ions from the blood.