Defence Against Disease Flashcards
All 14 cards in this deck
How does the skin defend the body against pathogens?
It acts as a physical barrier that stops pathogens entering the body.
If it is cut, a blood clot/scab seals the wound to prevent bacteria entering.What is the role of mucus in defending the airways against pathogens?
It is a sticky physical barrier that traps pathogens and dust before they reach the lungs.
What do cilia in the airways do as a defence against pathogens?
They beat to sweep mucus containing trapped pathogens up to the throat, where it is swallowed.
What is the role of lysozymes in tears?
They are enzymes that destroy bacteria by breaking down their cell walls.
How does hydrochloric acid in the stomach act as a chemical defence?
Its low pH kills pathogens in swallowed food and mucus.
True or false? Mucus and cilia are chemical defences against pathogens.
False. They are physical barriers; lysozymes and hydrochloric acid are the chemical defences.
What is an antigen?
A molecule on the surface of a pathogen that the immune system recognises as foreign.
What are the steps of the specific immune response?
e.g. a bacterium enters the body for the first time- Antigens on the pathogen are recognised as foreign.
- Lymphocytes produce antibodies specific to that antigen, leading to destruction of the bacterium.
- Memory lymphocytes are also produced.
True or false? One type of antibody can bind to any type of antigen.
False. Each antibody is specific — its shape is complementary to only one type of antigen.
How does the secondary response differ from the primary response when the same pathogen infects again?
Antibodies are produced faster and in much greater amounts, because memory lymphocytes are already present.
The pathogen is destroyed before symptoms appear.What does a vaccine contain?
An inactive (dead) or weakened form of the pathogen, which still carries its antigens.
How does immunisation make a person immune?
e.g. the tetanus vaccine- Antigens in the vaccine trigger an immune response.
- Lymphocytes produce antibodies and memory lymphocytes.
- If the live pathogen later enters, a secondary response destroys it quickly, so the person does not get tetanus.
True or false? A vaccine containing an inactive form of a pathogen can give you the disease.
False. The pathogen is inactive or weakened so cannot cause illness, but its antigens still trigger an immune response.
Why is a booster dose of a vaccine given some time after the first dose?
It causes a secondary response, producing more antibodies and more memory lymphocytes, so immunity lasts longer.