Okay. So let’s take a look
at what’s in our environment
and what will influence
our genetic expressions.
So genetically based behavioral
variation in a natural population
is influenced by three things.
One, the environment.
That, we’ve discussed.
The second is experiences.
So what were experiences that are
experiences that we’ve had in the past
will actually have an impact
on our behavioral variation.
And the third really
important factor is social,
I would even lump in cultural factors
into shaping these genetic changes.
Okay. Let’s look at human
How do we grow over time?
Right down to the point where we’re
just a little sperm swimming around
and we make that
we start to grow, divide, and become the
ultimate super happy baby that comes out.
So at conception, the female has
an ovum and the male has a sperm,
so the ovum would refer to the egg, and
the gametes fuse to form a zygote.
The zygote then contains
all the genetic material
it's going to need to develop into a human.
So that’s where you’re getting the genetic
information from your mom and your dad.
So during the prenatal stage,
development is influenced by
genetic and environmental factors.
So the genetic is pretty
You’re getting the genetic
information from your folks,
but the environmental
factors play a huge role.
This can include a lot
of different things.
This can include the actual local
micro environment that you’re in,
so what the mother is consuming,
smoking, drinking, drugs, what she eats,
as well as the state
that she’s in.
So if your mother is completely stressed
and has continued to stay stressed,
this might influence
So, a lot of different things to consider.
And then outside of that
we even look at what are
some of the environmental
so the air that we have, the toxins in the
air, in our food, our water, our soil.
All of these things can have a
huge impact upon development.
Now, while you’re in there and
you’re growing and developing
and turning into that amazing baby,
you’re separated by something
called the placenta.
So the placenta transfers
nutrients and oxygen to the fetus
and takes away garbage
waste and carbon dioxide.
So it’s this kind of a
protective shell, if you’d like,
and it has this really important process,
and all of this is done through
the exchange of blood.
So the placenta is very much connected,
interconnected with the
blood supply of the mother.
So if you look at the image
here you’ll notice the red
and you’ll notice the blue and
the intertwining of everything.
That are the blood vessels of the growing
and developing fetus in the placenta
and the mother.
So high interconnectivity and
allows for this exchange.
Now, a lot of people misconceive
that name of placental barrier
and they believe that it’s something that’s
keeping all bad things
out and all toxins out,
but we now understand or we have
understood for quite some time now
that the placental barrier
actually is not a barrier at all.
It’s more of a geographical
divide really if anything,
and whatever the mother consumes,
anything that enters her blood -- alcohol,
drugs, caffeine, nicotine, heroin --
anything she’s consuming
that enters the blood
is exchanged with the
blood of the fetus.
So there’s no barrier,
there’s no protection.
Whatever the mother is experiencing,
the child is experiencing
and this leads back to our
point of environment.
So whatever environment she’s creating for
the child will impact the development.
So whatever she consumes is shared
by the child, the unborn child.
Okay. So as a baby is born and develops,
we have different stages of development,
and now we’re going to look
at the motor development.
So stage one is called
and this is just a very primitive Eevee
like little animal-like movements
where the baby just kind of,
without real obvious control,
is just kind of doing these little
wailing of the arms and legs.
So this involuntary movement
is used to initiate
and get the whole process of the
neuromuscular system intact.
You do things like the palmar
grasp where, you know,
you can put your finger or
something in front of the
baby and just instinctively
will go and grab that.
So again, that’s the mind teaching
itself these complex movements
as I need to go here, I need to
grab this thing and squeeze it.
Reflexes and learning to inhibit
the reflexes begin to develop.
So the child starts to learn reflexes
and learning to inhibit other reflexes,
so things like those involuntary movements,
it learns to maybe control some of those.
So the baby starts to
develop and understands
it’s not okay to just
constantly be moving your arms.
You want to have your arms sort of at rest
and you want to initiate
movement as required
and that needs to happen
by you sort of turning off
some of these
And we get to rudimentary movement.
This is where you find your
first voluntary movements --
crawling, walking, grabbing
a toy, grabbing a spoon --
these are first coordinated movements,
and this is dictated by genetics.
So this is innate
This isn’t something that
they typically learn
so, you know, a child comes out
and that they just by themselves
start to try to crawl,
walk, grab things.
You’re not sitting there,
“Okay, little baby,
I know you don’t understand me or English
but this is how you grab a ball.”
They don’t really get that.
And then stage three is
and this is now they’ve gotten a little bit
older or around two to seven years old
and the child learns to manipulate
their body through actions.
Now they’re really starting to get their
body to understand coordinated movement.
They’re much more coordinated and less
clumsy and not falling all the time,
and it’s highly influenced
by the environment.
So the more you’re engaged with the
child, the more they’re playing,
the more they’re
interacting with others,
so social interaction is extremely huge
in developing fundamental movement.
Next we get to specialized movement
and now we’re getting into
sort of the adolescent years.
We learn to combine fundamental movements
and apply them to specific tasks.
So, there’s a transitional substage
where a combination of movements occur,
and the application
stage where conscious
decision to apply skills
to specific activities.
So there is some learning involved
and there’s some application,
and this is where you can see
that a small child doesn’t
have the cognitive abilities
to really make that connection
and as you get older, a little bit smarter
you’re able to get into this stage.
And then the final stage is
that lifelong application stage
is the catchall for sort
of adolescents onwards
and this is where you really refine your
movements and you get much much better,
and this goes more to the learning
style of behavior versus the innate.
So adolescence is a transitional period
between childhood and adulthood,
I think we all understand that,
and I think what some of the important
parts are what happens to the brain.
So we know that in the
brain during this
developmental phase you
have cell proliferation.
So, especially, and what that refers to is
cell development within the prefrontal
lobes and the limbic system,
two systems that we’ve talked about
quite a bit in these courses.
Prefrontal cortex, prefrontal lobes
deal with executive function,
emotion, reasoning, behavior.
Limbic system is involved
with the arousal activation,
reinforcing behaviors with the dopamine
release or the dopamine reward pathway.
So kind of stuff that’s really,
really important as you get older
and you start to develop,
especially at that adolescent age.
You also get to this process
of synaptic pruning
and this, like the name implies,
you consider pruning a plant or
cutting dead leaves and branches off
and that’s exactly what happens,
is initially we’re actually
born with a sea of connections
but they’re not all necessary.
And so your brain realizes
that this network
has not fired much versus this
one which is firing a lot,
so I don’t really need a lot of
those unnecessary connections,
and so it actually goes
in and removes them.
So it does it through a process
called atrophy or pruning
where they kind of descend and
those connections pull back.
And there are some really cool videos
you can catch online or read in books
and they show the
process of attachment.
So it’s going to show a neuron sending out
some of its dendrite to make a synapse
and over time because
there’s no stimulation
there it actually withdraws
or shrinks into nothing
or it goes back into
being a little nub.
So really, really kind of cool stuff.
And then the last thing that happens in
adolescence is the process of myelination
and you remember at the top
of this earlier module
we talked about synaptic transmission
and salutatory conduction
and how myelination increases
the conduction speed.
And so we understand that in adolescence
the degree of myelination increases
and this strengthens
and it improves transmission of
the electric chemical signal.
So this covers a
lot of information
and at this point I
hope you understand
the organization of the
central nervous system,
we understand the synaptic transmission,
and we understand some of the
factors that modulate our behavior.