Diseases and immunity

Pathogen

A disease causing organism. Causes damage to cells and disrupt functioning of tissue causing symptons and triggering an immune response in the host. E.g virusses, bacteria, fungi and parasite worms

Disease

A disorder of a structure or a function with a specific group of symptoms

Transmissible disease

A disease in which the pathogen can be passed from one host to another

Direct contact

Transfer of pathogen through blood or other bodily fluids. E.g sharing needles or STIs

Indirect contact

Transfer of pathogen via contaminated surfaces, food, animals or air, E.g cutting boardsm coughing, mic flies

Body defences

Skin, nose hair, mucus, stomach acid, white blood cells

Skin

Epidermis acts as a physical barrier, prevents pathogens from entering the body

Nose hair

Filters out bacteria and foreign

Mucus

Traps pathogens in trachea and bronchi, cilliated cells move mucus away from the lungs to the stomach where it is digested

Stomach acid

Hydrochloric acid kills ingested pathogens

White blood cells

Phagocytes engult pathogens, Lymphocytes produce antibodies

Controlling the spread of disease

Clean water supply, hygenic food preparations, good personal hygiene, waste disposal, sewage treatment

Clean water supply

Water contaminated with sewage or animal waste contains harmful bacteria and could infect vast numbers of people if used

Water treatment involves…

Filtration, chlorination or boiling water

Hygenic food preprations

Meat should be throughly cooked, raw meat should be prepared seperately (as contains bacteria). Precooked food should be eaten cold or throughly heated. Washing hands e.t.c

Good personal hygiene

Hands should be washed after using the toliet and before touching food

Waste disposal

Flies and vermin are a vechile for pathogens, waste should be properly stored and disposed of

Sewage treatment

Raw sewage may contaminate drinking water, sewage shoudl be treated before being discharged

Active immunity

Defence against a pathogen by anitbody production in the body, gained after an infection by a pathogen or a vaccination

Antibodies

Proteins that bind to antigens leading to direct destruction of pathogens or marking it for destruction by phagoctyes. Produced by lymphocytes

Anitgens

Each pathogen has its own anitgens, which have specific shapes. Specific antibodies have complementary shapes which fit specific antigens, They line the surface membrane of pathogens

Memory cells

Following an infection, some lymphocytes that produced specific antibodies become memory cells, If the same antigen/pathogen is detected by the body a second time, the memory cells quickly divide and make more anitbodies to neutralise the threat.

Vaccination

Active immunity can be gained through vaccination : Weakend pathogens or their antigens are pput into the body, the antigens stimulate and immune response by lymphocytes which produce anitbodies, memory cells are produced that give long term immunity

Passive immunity

Short term defence againsta pathogen by anitibodies acquired from another individual across the placenta and in breat milk. Memory cells are not produced in passive immunity.

Breast feeding is important for the development of passive immunity in infants because…

Newborn babies haven’t had time to build up active immunity so recieve antibodies from the mother instead. Protects them from contracting diseases while their own immune system is still developing.

Chlorea

Disease caused by a bacterium which is transmitted in contaminated water

Chlorea function

Cholera bacterium produces a toxin which secretes chloride ions into the small intesting, water moves into the gut by osmosis.

Chlorea causes

Diarrhoea, dehydration, loss of ions from blood or even kidney failure

Chlorea treatment

Intravenous rehydration, replacement of salts and use of anitbodies to kill bacteria.