Chapter 10: Diseases and immunity Flashcards
Define ‘pathogen’
A microorganism that causes disease
Define ‘transmissible disease’
A disease in which the pathogen can be passed from one host to another
What are the 2 ways that a pathogen is transmitted?
Through direct contact, including through blood and other body fluids
Indirectly, including from contaminated surfaces, food, animals and air
Define ‘active immunity’
Defence against a pathogen by antibody production in the body
What are the body defences?
Skin, hairs in the nose, mucus, stomach acid and white blood cells
Define ‘antibody’
Proteins that bind to antigens on pathogens, which have specific shapes, leading to direct destruction of pathogens or marking of pathogens for destruction by phagocytes
How is active immunity gained?
After an infection by a pathogen or by vaccination
What is the process of vaccination?
Weakened pathogens or their antigens are put into the body, the antigens stimulate an immune response by lymphocytes, which produce antibodies, and memory cells are produced that give long-term immunity
What is the role of vaccination in controlling the spread of diseases?
Provides protection for the entire population because there are very few places for the pathogen to breed, known as herd immunity
What is the role of a clean water supply, hygienic food preparation, good personal hygiene, waste disposal, and sewage treatment in controlling the spread of diseases?
Water: can contain many different pathogens
Food hygiene: in the right conditions, bacteria can grow and reproduce on food
Personal hygiene: oil, dirt, and sweat left on the skin for too long can provide breeding grounds for bacteria
Waste disposal: if accumulated close to where people live, animals may forage for food and cause bacteria to breed in the waste, and dangerous chemicals can seep out and pollute the ground and waterways
Sewage treatment: untreated sewage, known as raw sewage, contains many bacteria and microorganisms such as pathogens, and if people come in contact with it, especially if it gets into their mouths, can get ill
Define ‘passive immunity’
A short-term defence against a pathogen by antibodies acquired from another individual, including across the placenta and in breast milk
What is the importance of breastfeeding for the development of passive immunity in infants?
A young baby’s immune system is not well developed, so the mother’s antibodies present in the breast milk can protect it against any diseases to which she is immune, for the first few months of its life
Are memory cells produced in passive immunity?
No
What is cholera?
A disease caused by a bacterium which is transmitted through contaminated water
How does cholera work?
Cholera bacteria live and breed in the small intestine, where they produce a toxin that stimulates the cells lining the intestine to secrete chloride ions into the small intestine. This lowers the water potential, causing water to move out of the blood into the lumen of the intestine by osmosis. This causes diarrhoea, dehydration, and loss of ions from the blood
