Infection And Response
Overzicht
A single bacterium settling into a warm cut can, in good conditions, split in two every twenty minutes. Thirty divisions later, before a working day is out, one cell has become more than a thousand million. Nothing about your body has changed in those hours except the number of uninvited organisms living inside it, and yet you may go from perfectly well to seriously ill. That is the arithmetic every immune system is built to beat.
This lesson follows that race from both ends. You will see how bacteria and viruses actually make an organism ill, meet the three jobs white blood cells do about it, and find out why recovering from a disease once often protects you for life. Then you will look at the two things people have added to those natural defences, vaccination and antibiotics, and at the sharp limit on what the second of them can reach.
Doelstellingen
- Microorganisms that cause infectious disease are called pathogens.
- Bacteria and viruses may reproduce rapidly inside the body. Bacteria may produce poisons (toxins) that make us feel ill. Viruses live and reproduce inside cells, causing damage. Knowledge of the structure of viruses is not required.
- White blood cells help to defend against pathogens by: ingesting pathogens (phagocytosis); producing antibodies, which destroy particular bacteria or viruses; producing antitoxins, which counteract the toxins released by the pathogens.
- The immune system of the body produces specific antibodies to kill a particular pathogen. This leads to immunity from that pathogen. In some cases, dead or inactivated pathogens stimulate antibody production. If a large proportion of the population is immune to a pathogen, the spread of the pathogen is very much reduced.
- People can be immunised against a disease by introducing small quantities of dead or inactive forms of the pathogen into the body (vaccination). Vaccines stimulate the white blood cells to produce antibodies that destroy the pathogen. This makes the person immune to future infections by the microorganism, because the body can respond by rapidly making the correct antibody, in the same way as if the person had previously had the disease. The MMR vaccine is used to protect children against measles, mumps and rubella. Details of vaccination schedules and side effects associated with specific vaccines are not required. Students should be able to evaluate the advantages and disadvantages of being vaccinated against a particular disease.
- Antibiotics, such as penicillin, are medicines that help to cure bacterial disease by killing infective bacteria inside the body. It is important that specific bacteria should be treated by specific antibiotics. The use of antibiotics has greatly reduced deaths from infectious bacterial diseases.
- Antibiotics cannot kill viral pathogens. Students should be aware that it is difficult to develop drugs that kill viruses without also damaging the body’s tissues.
Mindmap
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Lesevaluatie
Gefeliciteerd met het voltooien van de les op Infection And Response. Nu je de sleutelconcepten en ideeën, het is tijd om uw kennis op de proef te stellen. Deze sectie biedt een verscheidenheid aan oefeningen vragen die bedoeld zijn om uw begrip te vergroten en u te helpen uw begrip van de stof te peilen.
Je zult een mix van vraagtypen tegenkomen, waaronder meerkeuzevragen, korte antwoordvragen en essayvragen. Elke vraag is zorgvuldig samengesteld om verschillende aspecten van je kennis en kritisch denkvermogen te beoordelen.
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- Which statement best describes a pathogen? A. Any microorganism found inside the human body B. A microorganism that causes an infectious disease C. A white blood cell that ingests bacteria D. A poison released by a bacterium Answer: B
- Which of these is NOT a way in which white blood cells defend the body? A. Ingesting pathogens by phagocytosis B. Producing antibodies C. Producing antitoxins D. Producing toxins that destroy body tissue Answer: D
- A patient has influenza, which is caused by a virus. Why would an antibiotic not help? A. Antibiotics only work on toxins B. Antibiotics kill bacteria and have no effect on viruses C. Antibiotics only work if the patient is already immune D. Antibiotics destroy antibodies Answer: B
- A bacterium divides once every 30 minutes. Starting with 4 bacteria, how many are present after 3 hours if none die? A. 24 B. 64 C. 256 D. 512 Answer: C
- Why does a vaccine contain a dead or inactive form of a pathogen? A. So that the pathogen reproduces only slowly inside the body B. So that antibody production is stimulated without the pathogen causing the disease C. So that white blood cells produce antitoxins instead of antibodies D. So that the antibodies produced will work against every pathogen Answer: B
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