The body's non-specific barriers, what white blood cells actually do, and how vaccination produces immunity without causing the disease.
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1.Name the four non-specific defence systems of the human body.
The skin, the nose, the trachea and bronchi, and the stomach.
2.How does the skin defend against pathogens?
It acts as a physical barrier, produces antimicrobial secretions, and forms scabs to seal cuts.
3.How does the nose defend against pathogens?
Hairs and mucus trap particles containing pathogens before they reach the lungs.
4.How do the trachea and bronchi defend against pathogens?
They secrete mucus which traps pathogens, and cilia waft the mucus up to the back of the throat where it is swallowed.
5.How does the stomach defend against pathogens?
It produces hydrochloric acid, which kills pathogens in the mucus and in food.
6.State the three ways white blood cells defend the body.
Phagocytosis, producing antibodies, and producing antitoxins.
7.What is phagocytosis?
A white blood cell engulfs a pathogen and digests it.
8.What are antibodies?
Proteins produced by white blood cells that are specific to one pathogen and mark it out to be destroyed.
9.What are antitoxins?
Proteins produced by white blood cells that neutralise the toxins released by bacteria.
10.What is an antigen?
A molecule on the surface of a pathogen that the immune system recognises as foreign.
11.Why is an antibody specific to one pathogen?
It has a shape complementary to the antigens on that particular pathogen, so it will not fit any other.
12.What happens during vaccination?
Small quantities of dead or inactive forms of a pathogen are put into the body.
13.How does vaccination make you immune?
The white blood cells produce antibodies against the antigens. If the live pathogen enters later, they produce the correct antibodies quickly and in large numbers, so you do not become ill.
14.Why does a vaccine not usually give you the disease?
The pathogen in the vaccine is dead or has been inactivated, so it cannot reproduce and cause illness.
15.What is herd immunity?
If a large enough proportion of the population is vaccinated, the pathogen cannot spread easily, so even unvaccinated people are unlikely to catch it.
16.Give an advantage of vaccination.
It has controlled many communicable diseases that were once common, and widespread vaccination helps prevent epidemics.
17.Give a disadvantage of vaccination.
It is not always completely effective, and occasionally a person has a bad reaction to a vaccine.
18.Why do you usually not catch the same disease twice?
Memory white blood cells remain in the body and produce the right antibodies rapidly if that pathogen returns.
19.Describe the difference between the first and second response to a pathogen.
The first response is slow and produces few antibodies. The second is much faster and produces far more, so symptoms do not develop.
20.Why is a new flu vaccine needed each year?
The influenza virus changes, so the antibodies produced against last year's strain no longer recognise it.
21.Why do doctors recommend vaccinating young children?
Their immune systems have not met these pathogens before, and several of the diseases are most dangerous in young children.
22.What is the difference between a specific and a non-specific defence?
Non-specific defences such as skin and mucus block all pathogens equally. The specific immune response makes antibodies matched to one particular pathogen.
23.Why does a cut becoming infected suggest the skin has been breached?
The skin is the main physical barrier. If it is broken, pathogens can enter the tissue underneath directly.
24.Why might someone with a damaged immune system get ill more often?
They cannot produce enough white blood cells or antibodies, so pathogens that a healthy person would destroy are able to multiply.
25.What is an epidemic?
When a communicable disease spreads rapidly through a large number of people in an area.
26.Why does smoking damage the trachea defence system?
Smoke paralyses and destroys the cilia, so mucus with trapped pathogens is not moved out of the lungs.
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