- (Narrator) When dealing with the human body,
you have to talk about the immune system.
So first off, it's your body's defense mechanisms.
You have barriers.
Just flat out stops things from coming in.
Your skin is a great physical barrier.
Stomach acid, tears are great chemical barriers.
Your stomach has a very, very low pH.
A pH of maybe 2, or so. So it's very acidic.
It will simply destroy a lot of bacteria.
Tears, you're going to have different defensive mechanisms
in your tears that help to destroy bacteria.
Vomiting. You're saying, well hold on...vomiting?
A lot of times vomiting is caused by something
that is in the stomach, or in the GI tract,
the upper GI tract, that is going to be irritating.
It could be a toxin. It could be a bacteria.
But something your body wants to get out of there.
Then you have these things called non-specific
defense mechanisms.
Non-specific because it does not matter what triggers it.
Anything that causes a problem can trigger it.
Phagocytosis. That's when you have your defensive cells
eating other cells or particles.
So, phagocytosis is a cell eating.
Inflammation. If you ever had a cut, a bruise, a bump;
you know it swells up.
Inflammation is your body's defense mechanism to try
to help limit further injury or further infection.
But then we have some that are very, very specific.
You have antibodies and T cells.
Well, T cells are a derivative of one of your
white blood cells, they're coming from your lymphocytes.
The T cells are meant to cause an immune response.
They're meant to attack, destroy foreign particles.
Well antibodies, they're also coming from the lymphocyte.
Now it's not a direct path,
there's something else between.
But, the idea is, these antibodies
coming from the lymphocytes indirectly
are going to be able to recognize foreign objects.
Could be foreign pathogens, like bacteria or virus.
Could be foreign cells that just shouldn't be there.
So we have our antibodies and T cells.
They are specific because they only recognize
what they're programmed for.
The example for antibodies, think about...chicken pox.
If you ever had chicken pox, or if you didn't.
You might have had the chicken pox vaccine.
Well, once you've either had the vaccine or had chicken pox;
How often do you get it a second time?
Not typically, I mean some people will get it a second time.
But more often than not, once you get it, that's it.
It's because your body has recognized that virus.
Your body made antibodies to recognize the virus
and then it fights off the virus anytime it sees it.
These diseases could be caused by either living
or non-living organisms.
Now, these living organisms,
like bacteria, fungi, parasites,
any of those can cause a pathogenic infection.
Now bacteria, you've probably heard of.
They're one celled prokaryotes,
very basic, very simple organisms, things like Ecoli.
Fungi, or fungus,
unicellular and multicellular,
that means they could be one cell or many cells.
But they're eukaryotes, a little more complex.
Could be a parasite or parasites even, plural.
Again, unicellular, one cell or multicellular, many.
So any of these. bacteria, fungi,
or parasites can cause infection.
But there's also nonliving particles.
You have viruses and prions.
Now a virus is not living, because without a host,
a virus cannot survive.
The way a virus typically replicates, or duplicates,
is by injecting its DNA into a living cell,
letting the living cell perform the action.
Prions, well they're even smaller than viruses.
They're tiny particles
that when ingested into the system,
either eaten, it can be have a drink, it could be
simply inhaled, unfortunately.
They potentially could cause pretty severe infections.
So we have both living and nonliving
that can both cause a pathogenic infection.
Here's looking at the left hand side is a eukaryotic cell.
If you notice, a eukaryotic cell has a nucleus.
It has all these different particles around it:
your endoplasmic reticulum, your golgi apparatus,
your mitochondria.
All the organelles.
But in comparison, look how small
the bacterium is next to the eukaryotic cell.
And the bacteria, all you're seeing:
cell wall, DNA, ribosome,
plasma membrane.
It's pretty small and pretty basic.
But even smaller and more basic, are going to be a virus.
So for the virus, it's a tiny little dot
in comparison to a larger, eukaryotic cell.
So we have our viruses,
bacteria that are typical animal
cells with a eukaryotic cell.
All right, so back to these bacteria.
We mentioned they're prokaryotic, single-celled.
Just one cell. You might found a clump of thousands of them.
But each one is its own organism,
with a ton of different ways to grow and reproduce.
You can find bacteria living in
thermal vents in the bottom of the ocean.
You kind find them living in the coldest
reaches of a mountain peak.
You can find them pretty much anywhere.
It adapted to live in almost any environment.
Now infections, we're looking at pneumonia,
tonsillitis, tuberculosis, botulism,
toxic shock syndrome,
syphilis, Lyme disease, and the list goes on and on.
None of these are overly pleasant.
Probably, of course this sounds really bad,
but one of the more mild versions here is tonsillitis.
Any of the rest of them can get pretty severe,
pretty quickly.
All by these tiny, single-celled bacteria.
More often than not, though, all of these
can be treated by antibiotics.
Now the trick with antibiotics is to
one, make sure it is a bacteria.
Because a virus, antibiotics doesn't make a difference.
But two, it'd be great if they could figure out,
okay which antibiotic will be functional
against this particular bacteria.
So you know that the antibiotic will work,
not just kill off all your normal flora
or your normal bacteria, leaving the pathogenic one
to get larger and proliferate.
Well, if you think about antibiotics and viruses
don't forget they usually don't work.
They're very, very small.
Tiny little thing, much smaller than a bacteria.
Now I put them under the nonliving category earlier
but there technically is debate
of whether they're living or non.
The reason that it goes non usually,
not living, is because it cannot
reproduce without a host cell.
That means a virus by itself cannot make more viruses.
Also, a virus will not have any metabolic activity.
So living, nonliving? It's up for debate.
A lot of them are heading more toward
the nonliving currently.
Structure of viruses, DNA or RNA?
You will not have both.
And this DNA, or the RNA, within a virus
is surrounded by this protein coat,
it's meant to keep it safe
and keep it contained all in the one place.
Viruses can cause things like AIDS, HIV- AIDS.
Hepatitis, encephalitis, rabies,
influenza,
colds, warts, chicken pox
and there's more than that.
What all these share in common, though,
is they all can be confected and caused by a virus.
How about these prions?
Now prions, a lot of time you've never heard of.
They pop up every so often, but more often than not,
they're not really talked about.
Prions are actually just protein.
Its normal brain proteins
that just don't quite fold properly.
So they turn into these little, tiny particles.
And once they're misfolded or turned the wrong way,
then it become self-propagating.
So once there's a couple of them
they make more and more and more.
Now all this protein that's around is not helping anything.
This excess protein debris
can actually fill, disable,
and potentially destroy any cell it comes in contact with.
And here's the scariest part...
Prions cannot be cooked away. You can't kill them.
Freezing. Doesn't do a thing.
They just stay there because they are nonliving.
Drying. You can try to dry out
the particles as much as you want.
But it's not living. No metabolic activity.
So really drying, freezing, cooking.
None of these have any impact on getting rid of prions.
So bovine spongiform encephalitis,
better known as "mad cow disease", is caused by a prion.
That's why countries are being so
cautious when they go through the whole buy process.
If you're buying beef from a country
that has found to contain prions,
a lot of times they'll shut down all sales in that country.
Visible fact they're not wanting to introduce
the prions into the current market.
This goes for Canada, the US, Britain, any of the countries.
We also have Creutzfeldt-Jakob disease.
Another prionic-based disease.
So both these are based on those mutant proteins
just building up and causing problems.
Now that we've gone through the
different types of pathogens,
let's figure out how they are transmitted,
how they pass along.
Well transmitability is how easy that pathogen
can go from person-to-person.
It could be in a handshake.
It could be someone sneezing and
the particles are floating around.
So there's different types of transmission.
There's respiratory, your breathing.
When you sneeze, you cough and all of a sudden,
the particles are floating around.
It could be fecal to oral transmission.
You're thinking, hold on, that's just wrong.
Well, fecal to oral.
How do you know where all the fecal matter is in the world?
The fecal matter has to be filtered out at some point.
It goes back into the ground and is reused as nitrogen.
So it's not saying direct fecal necessarily,
but it could be in some roundabout way.
It could've been from some animal
that decided to have a problem right in your garden.
So this whole fecal-oral sounds disgusting.
But, it's one of the biggest reasons
why you wash your hands after going to the bathroom.
Testing doorknobs and bathrooms,
you'd be amazed at how much it shows up
on those doorknobs what's there.
Body fluids. These are things from
tears, to blood, to saliva,
to any other fluid coming forth from the body.
Virulence is the damage it can infect.
Some of the high virulence means
it'll influct a lot of damage, very quickly.
An example is the Ebola virus
The Ebola virus
can inflict a ton of damage
within the first 24 hours,
if not potentially kill the person within the 24 hours.
Something with a lower virulence could be the common cold.
You might have it for a day or two
and not even know it, until it builds up enough.
Once it builds up, a couple of days later,
a lot of times, you're back up and moving.
No major problems.
So transmitability, mode of transmission
and virulence.