- [Voiceover] Here I'm looking at different parts,
different things in the body, with feedback,
so we talk about those body systems
and the cavities that can fit with them,
but how does your heart know
to speed up or slow down?
How does your body know to sweat because you're hot?
All these are feedback loops.
Basically what a feedback loop is,
there's either a positive or a negative feedback loop.
In this case we're looking at the negative feedback.
In the case of a negative feedback, there's a stimulus.
Something is happening that is not to norm.
For example, if you walk outside in the middle of winter,
and it's zero degrees out, you're not going to feel warm,
you're going to feel cold.
It's that cold temperature
that's going to trigger receptors in your body,
thermal receptors,
so that's the stimulus.
The stimulus with the cold.
Then sensor are the receptors.
They then will go and control an effector,
which will be your body shivering,
because you're going to want to warm up,
so pretty much your body is controlled mostly
by negative feedback loops,
and these negative feedback loops are always the same way,
they're always the same four basic parts,
stimulus, a sensor that picks up the stimulus,
a control mechanism that will make a change in your body,
and that causes an effect to put you back to normal.
I've already used a great example
is going to be temperature.
It doesn't matter if it's hot or cold.
I give you an example of cold, on the screen here,
you can see hot,
but always something is going away from the normal,
and this whole negative feedback
is trying to maintain homeostasis.
Homeostasis is what your body's trying to do.
It' trying to stay at a set level,
so you're not trying to get too warm or too cold.
You want to say at a comfortable level,
but sometimes there's also positive feedback loops
in your body.
The example shown here is normal childbirth.
When it's time for birth,
the body will initiate a positive feedback loop
so what'll happen here,
is as the body is getting ready to give birth,
oxytocin, a hormone is being carried in the blood stream.
The oxytocin will initiate uterine contractions.
As the uterine contractions continue
and the baby's head pushes against the cervix more,
more and more oxytocin keeps getting released.
More oxytocin means more contractions,
and it's like constant feedback.
The stronger the contraction, the more oxytocin.
The more oxytocin, the stronger the contraction.
It'll eventually cease and stop, once the baby is born.
Then, after that's done, it can return back
to normal homeostasis, but as long as the positive feedback
is going, it'll keep changing away from the normal,
to cause this positive response.
In this case you might say contractions are positive,
but the ultimate result childbirth, is a positive response,
but the body itself for all we know about,
we know a lot and so much
because of all the different medical imaging,
and technology we have.
I mean X-Rays have come a long way.
An X-Ray now can show hairline fractures.
It can show great detail in the bones,
but when they first started,
it was a very rudimentary, very crude way
of taking a radioactive isotope in a box,
and putting a hand or a limb over it,
with extra paper on the other side.
It wasn't even.
It wasn controlled.
It wasn't anything like the images you can see today,
so medical imaging has come a long way to help out.
It's not just X-Rays, you have CT scans.
You can go in for MRIs,
you have even PET scans,
and finally ultrasounds,
can be used for a huge range of things.
It's not just ultrasound for pregnancy,
but ultrasound can be used for other
different aspects as well.
They can monitor different glands,
like a thyroid gland can be monitored through ultrasounds,
so there's tons of various medical imaging
that can help see different aspects of our body,
from the heart tissue, bone, to the very soft tissue,
blood flow, or brain tissue,
so there's a lot of things that are going on with our body,
but also they've seen around society.