Defence Against Disease [2] (Biology GCSE)

Uploaded by freeeschool on 04.09.2012

GCSE Biology – Defence Against Disease 2
Hello! Welcome to the second video on Defence Against Disease and in this video, we are
going to particularly look at Vaccination.
To help us understand what vaccination is, here is just a recap of what was in the previous
video about Defence Against Disease and how the body defends itself against disease.
Here, we have a white blood cell and we said that all pathogens or all microbes have this
little structure on the surface of their bodies or cell membranes and it is called an antigen.
That antigen is different for different pathogens. What the white blood cells can do is produce
these antibodies which will actually fit the shape of these antigens like so and that can
help destroy these microbes that might enter the body. Now, we can use that in a useful
way by producing what we call vaccination.
Here is a young man who is being vaccinated and will probably be interesting just to see
what’ actually inside this vaccine here. If we enlarge that there, if we were to then
take a little look inside to see what’s in here, magnify that, what you would see
inside there are microbes that we are defending ourselves against. This is the particular
disease that we are defending ourselves against. This is the microbe or the pathogen that causes
that disease and you notice that it has antigens like every other microbe. But what also is
quite important to note is that this microbe is actually either dead or very weakened.
If it is dead, while it can actually reproduce and cause any damage in the body, the antigens
are still there on its surface. If we have this dead or very weakened microbe, and we
inject that into the body of somebody, the microbe can’t actually do the damage itself,
but what it can do is cause the body to produce antibodies. So the white blood cells produce antibodies. The antibodies for this
particular microbe, if we have a look, the antibodies for this one would actually be
this kind of shape, so that it could fit on the antigens. Once the white blood cells have
made this particular antibody, what happens is that there is what we call memory cells
and they remember the particular kind of antibody that’s required to destroy this microbe.
If the real microbe enters your body, before the antigen can cause a disease, the body
can react very, very quickly and produce the antibodies that will kill it.
It is probably worth looking at that graph that looks something like this. You might
come across something like this in an exam or in class or something. What we got here
is a graph that shows the level of antibodies present inside the body over time. This time
could be days or weeks, but here, we have the point where the vaccination is given,
instantly when the vaccination is given, the levels of antibodies rise but this vaccination,
remember, is the dead or the weakened virus, so it’s very easily gotten rid off and the
antibodies that are produced are reduced in the blood, but if you come across the actual
disease, what we have here is a secondary response.
This is the primary response and this is the secondary response. You can see, the secondary
response is quicker and you can see that more antibodies are produced. That means that the
body can fight off this disease much more quickly and much more effectively than if
you have never met it before. It doesn’t give that disease time to get hold or actually
cause any kind of severe problems inside the body.
That’s a quick summary and overview of how vaccination works and you need to know the
details at that light in this video.
[end of audio – 04:30] GCSE Biology – Defence Against Disease 2