Human Physiological Development – Biological Bases of Behavior (PSY, BIO)

00:01 Okay. So let’s take a look at what’s in our environment and what will influence our genetic expressions.

00:06 So genetically based behavioral variation in a natural population is influenced by three things.

00:10 One, the environment.

00:11 That, we’ve discussed.

00:13 The second is experiences.

00:15 So what were experiences that are experiences that we’ve had in the past will actually have an impact on our behavioral variation.

00:22 And the third really important factor is social, I would even lump in cultural factors into shaping these genetic changes.

00:31 Okay. Let’s look at human physiological development.

00:35 How do we grow over time? Right down to the point where we’re just a little sperm swimming around and we make that initial connection, we start to grow, divide, and become the ultimate super happy baby that comes out.

00:46 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.

00:57 The zygote then contains all the genetic material it's going to need to develop into a human.

01:01 So that’s where you’re getting the genetic information from your mom and your dad.

01:05 So during the prenatal stage, development is influenced by genetic and environmental factors.

01:10 So the genetic is pretty straightforward, right? You’re getting the genetic information from your folks, but the environmental factors play a huge role.

01:18 This can include a lot of different things.

01:20 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.

01:31 So if your mother is completely stressed and has continued to stay stressed, this might influence that environment.

01:38 So, a lot of different things to consider.

01:40 And then outside of that we even look at what are some of the environmental environmental factors, so the air that we have, the toxins in the air, in our food, our water, our soil.

01:50 All of these things can have a huge impact upon development.

01:56 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.

02:05 So the placenta transfers nutrients and oxygen to the fetus and takes away garbage waste and carbon dioxide.

02:11 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.

02:21 So the placenta is very much connected, interconnected with the blood supply of the mother.

02:27 So if you look at the image here you’ll notice the red and you’ll notice the blue and the intertwining of everything.

02:33 That are the blood vessels of the growing and developing fetus in the placenta and the mother.

02:40 So high interconnectivity and allows for this exchange.

02:43 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.

03:01 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.

03:17 So there’s no barrier, there’s no protection.

03:19 Whatever the mother is experiencing, the child is experiencing and this leads back to our point of environment.

03:24 So whatever environment she’s creating for the child will impact the development.

03:28 So whatever she consumes is shared by the child, the unborn child.

03:34 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.

03:40 So stage one is called reflexive movements 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.

03:53 So this involuntary movement is used to initiate and get the whole process of the neuromuscular system intact.

04:02 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.

04:09 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.

04:16 Reflexes and learning to inhibit the reflexes begin to develop.

04:21 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.

04:30 So the baby starts to develop and understands it’s not okay to just constantly be moving your arms.

04:36 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 involuntary movements.

04:45 And we get to rudimentary movement.

04:46 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.

04:56 So this is innate or preprogrammed.

04:58 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.

05:06 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.

05:13 And then stage three is fundamental movement 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.

05:20 Now they’re really starting to get their body to understand coordinated movement.

05:24 They’re much more coordinated and less clumsy and not falling all the time, and it’s highly influenced by the environment.

05:30 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.

05:40 Next we get to specialized movement and now we’re getting into sort of the adolescent years.

05:45 We learn to combine fundamental movements and apply them to specific tasks.

05:49 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.

05:57 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.

06:09 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.

06:25 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.

06:35 So we know that in the brain during this developmental phase you have cell proliferation.

06:40 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.

06:50 Prefrontal cortex, prefrontal lobes deal with executive function, emotion, reasoning, behavior.

06:57 Limbic system is involved with the arousal activation, reinforcing behaviors with the dopamine release or the dopamine reward pathway.

07:05 So kind of stuff that’s really, really important as you get older and you start to develop, especially at that adolescent age.

07:10 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.

07:26 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.

07:39 So it does it through a process called atrophy or pruning where they kind of descend and those connections pull back.

07:45 And there are some really cool videos you can catch online or read in books and they show the process of attachment.

07:52 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.

08:04 So really, really kind of cool stuff.

08:06 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.

08:19 And so we understand that in adolescence the degree of myelination increases and this strengthens synaptic connections and it improves transmission of the electric chemical signal.

08:32 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.